Jump to content
CaddyInfo Cadillac Forum

Northstar...could it be my headgasket?


Recommended Posts

I really hate for my first topic post on here to be about a problem I am having, but well, I'm running out of places to turn to. I have a 1994 Eldorado with the 4.6 Northstar. I love this car sooo very much. :D I'm pretty savvy when it comes to cars, so I know when something isn't right, and about 3 weeks ago I noticed it was starting to idle a little higher than normal when I started it. I didn't think too much at first (I live in NY and it's cold) but as days went on the idle went from about 900rpm to about 1200rpm when i started it. Then it started doing it not only while it was idling, but while it was driving as well, sometimes revving as high as 3,000 before dropping to normal. I wouldn't even have to hit the gas to get it up to 30mph most of the time. I ran the OBD and the only relevant code that came up was for the MAP sensor. (the other was the ABS, but i am already aware of that) I had to wait a few days to get the sensor changed...I didn't drive it while i was waiting...i'm not dumb. After I got it changed it was running like a brand new car.....for a few days. Then the erratic idling started again. I tried a few other things...cleaning the EGR valve, disconnecting the cruise control (maybe it was turning on/off by itself?), fiddling with the idle air control (with professional assistance) all to no avail. Couldn't find any other vacuum leaks at all.

At a loss for an explanation I gave up for a little while. While sitting around pondering/looking for another solution, one of the tires got really low, so I decided to drive it to the gas station to fill it (I didn't want a bad tire to top off all else) and as I'm pulling into the gas station I hear a knocking sound from under the hood, followed by a chugging, pulsing feeling...I know this sound...the sound of a motor with no oil getting ready to seize or throw a rod. I check the oil, it's fine. :huh: Down about a quart maybe, but hey, it's a Northstar, it happens. I check the temperature gauge, and it's at 212. It's never run higher than 208 on me before, so I checked the coolant. The reservoir was bone dry, so i filled it about halfway, then called my mechanic (my brother). He put a quart of oil in it, started it, floored it, and it ran fine...not so much as a tick.

2 days later I go to start it to move it so I could shovel the driveway. It was ping-pong idling...back and forth from 1,000 to 4,000, then died. I start it again and it idles perfect at 600 for about 10 seconds, then dies without warning. I call my brother again.... He shows up and gets it to stay running by starting it and holding his foot on the gas then drives it to his shop. It's a 10 minute drive and it was 12 degrees outside. By the time we got there the car's temp was at 222 and there was coolant spewing from the overflow hose on the tank. I squeezed the upper rad hose and there was no pressure at all...felt like it was full of air.

We checked the oil and it was fine (wasn't foamy). There was no "false boiling" in the coolant tank. Can't tell if there is white smoke coming from the exhaust because I live in NY and it's so cold right now that everyone has white smoke coming from their exhaust, lol. I have to wait until the weekend to have a coolant system compression check done on it.

I apologize for this post being so long, really. I hope this isn't a head gasket issue, but the couple of mechanics I have talked to around here say the erratic idling, loss of power, loss of coolant and running hotter than normal are all signs that it could be, and I've exhausted anything else I can think of. :( I have never overheated it. I won't let it get over 230. I'll shut it off first. I want to keep this car around for a while. Any input or advice is greatly appreciated.

Oh, I forgot to mention, it also seems to take forever to cool off. I had parked it for the night and the temp was at 205, and when I went out the next morning to start it the temp gauge said it was still 101...keep in mind, it's been in the range of 10-20 degrees outside here lately.

Edited by CarlaValentine

big4870885.jpg

Link to comment
Share on other sites


  • Replies 133
  • Created
  • Last Reply

Top Posters In This Topic

I had some problems with my Northstar when it would go from 500 rpm to 1500 rpm at idle and even when driving! Removed,cleaned and regreased the idle control motor fixed this problem! If your oil is fine and theres no "boiling" in the coolant reservoir it shouldnt be the headgasket! Have you checked for codes?

Roger

Roger Martinsen

Link to comment
Share on other sites

I Also had the same crazy idle symptoms as Roger with my 95 Seville N/S and changed my idle control actuator and that took care of that problem, I'm not sure of your other issues yet, but I had a 93 before this one and had a problem maybe once or twice a year where I had to keep the pedal to the floor to keep it running, but then shut it off and re-started it and then it was fine.

Link to comment
Share on other sites

The erratic idling sounds like a bad idle speed control motor. They go bad over time. The coolant should not spew out the surge tank at only 222 degrees. Are you sure you're not overfilling the surge tank? The proper full level is 2-1/2" below the lip on the filler neck. If you're over filling it, it could overflow out of the surge tank.

Remove the coolant line that runs between the throttle body area and the surge tank at the surge tank and have someone start the car. Coolant should flow out if the disconnected line. If not, there is a restriction in the line - most likely where it comes off the waterpump cover area.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

Link to comment
Share on other sites

well I ran out this morning and ran a check for codes (again) and the only thing coming up is

-open Map signal (history): I changed this already, just didn't clear the codes afterward...guess I should do that.

-intermittent map signal (history): see above

- front left wheel speed sensor continuity fault (current): changed wheel hub and had a wiring issue with the ABS unit...haven't taken care of it as I have bigger fish to fry at the moment.

I also started the car and let it warm up for a while. I checked the surge tank first to be sure there was coolant in it after the episode the other day, and I had to add to it. It was idling high (2500) for about a minute or two, then dropped to about 1000 and stayed there. Kept an eye on the temp gauge and warmed up from 35 to 209 in less than 10 minutes!! It's freezing out, how does that happen? Checked the surge tank overflow hose, and it wasn't spewing at all, and top hose had good pressure. Let it run a little longer. It got up to 234, then the temp dropped quickly down to 199 and stayed there. All the while the idle was bouncing all over the place, but the rad hose pressure stayed firm and no coolant spewed out at all. I don't believe I overfilled the coolant as I had only filled the surge tank halfway before it started spewing before. I'm starting to wonder if maybe I have a bad coolant temp sensor? But I figured that would show on a code check.

I think my next step will be to replace the idle air control unit and see how that pans out as far as the idling issue goes. As far as the coolant thing, I'm kinda new to these motors and am trying to learn as much as I can. I've heard that normal operating temp for them is 190-210. is this right? Before I started having issues mine typically ran about 208, no higher than 211 at a long idle.

big4870885.jpg

Link to comment
Share on other sites

I dont know where to start with this thread, its all over the place, the racing idle was covered above, that is your problem with that.

The 94 has a phenolic spacer and mouse holes in the EGR system has it ever been cleaned?

That 212 degree figure you noted after getting air is NOTHING at all, 212 is LOW and not a big deal, you are over sensitive, now if you said 260, I would say hmm yes that is high, but after you shut your engine off it will naturally rise and be higher on start up, during the summer I ofter see 240 on start up then it drops to 212 to 215. We have discussed before that the digital temp gage causes owners to be over sensitive

ONE QUART low in oil is NO BIG DEAL, stop worrying about that, not a factor at all, the engine was designed to run on 5 quarts, the extra two quarts are in there for HIGH-G cornering to stop the engine from sucking air, that was NOT your problem

The ranging idle from 1000 to 4000 needs to be figured out its probably due to the ISC motor, check that out, the 222 degree temp AGAIN is NO BIG DEAL, and its NOT an indication of trouble its NORMAL and probably due to the ranging idle you are having

222 should NOT cause coolant to flow from the tank, how old is the radiator cap? Replace it if its old, maybe its not holding pressure. after it released at the tank, squeezing the upper hose meant NOTHING, the pressure was released already.

If you want to eliminate the head gasket issue have a test done on the coolant to see if it has combustion by products in it by a radiator shop or buy the kit from NAPA. Sometimes if you have a bad head gasket you can smell exhaust in the coolant try smelling it

It seems that your temp sensor could be messed up, 101 in the morning seems to be a problem, I would change the temp sensor, mine will get low. Its possible that its inaccurate. A weirded out temp sensor can affect the cooling fans and closed loop operation....

By the way 230 degrees in the summer is NOT a problem, you are hyper sensitive about overheating.

Dont panic, pressurize your cooling system, check the coolant for combustion by products, smell the coolant, check the coolant for at least a 50/50 mix, check your cooling fan operation, change the cap and thermostat, check/replace the ISC motor (do you hear it clicking after your turn the engine off?). A racing engine can raise the temps above what you are used to...

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

I dont know where to start with this thread, its all over the place, the racing idle was covered above, that is your problem with that.

The 94 has a phenolic spacer and mouse holes in the EGR system has it ever been cleaned?

That 212 degree figure you noted after getting air is NOTHING at all, 212 is LOW and not a big deal, you are over sensitive, now if you said 260, I would say hmm yes that is high, but after you shut your engine off it will naturally rise and be higher on start up, during the summer I ofter see 240 on start up then it drops to 212 to 215. We have discussed before that the digital temp gage causes owners to be over sensitive

ONE QUART low in oil is NO BIG DEAL, stop worrying about that, not a factor at all, the engine was designed to run on 5 quarts, the extra two quarts are in there for HIGH-G cornering to stop the engine from sucking air, that was NOT your problem

The ranging idle from 1000 to 4000 needs to be figured out its probably due to the ISC motor, check that out, the 222 degree temp AGAIN is NO BIG DEAL, and its NOT an indication of trouble its NORMAL and probably due to the ranging idle you are having

222 should NOT cause coolant to flow from the tank, how old is the radiator cap? Replace it if its old, maybe its not holding pressure. after it released at the tank, squeezing the upper hose meant NOTHING, the pressure was released already.

If you want to eliminate the head gasket issue have a test done on the coolant to see if it has combustion by products in it by a radiator shop or buy the kit from NAPA. Sometimes if you have a bad head gasket you can smell exhaust in the coolant try smelling it

It seems that your temp sensor could be messed up, 101 in the morning seems to be a problem, I would change the temp sensor, mine will get low. Its possible that its inaccurate. A weirded out temp sensor can affect the cooling fans and closed loop operation....

By the way 230 degrees in the summer is NOT a problem, you are hyper sensitive about overheating.

Dont panic, pressurize your cooling system, check the coolant for combustion by products, smell the coolant, check the coolant for at least a 50/50 mix, check your cooling fan operation, change the cap and thermostat, check/replace the ISC motor (do you hear it clicking after your turn the engine off?). A racing engine can raise the temps above what you are used to...

Thanks. Maybe I am being a little oversensitive, but I really love this car, and I don't want ANYTHING really bad to go wrong with it, and the best cure for that, as we all know, is prevention. I'm not very familiar with these engines as I have only owned the car for 6 months....so I guess I'm a little paranoid. I just know something isn't right and it's hard to find anyone in my area that knows this motor enough to tell me what's going on with it. I'll try the advice I have been given, as this is a beautiful car and I'd really like to keep her running for as long as I possibly can. :D

big4870885.jpg

Link to comment
Share on other sites

Believe me, I understand.... My 96 is sitting in the driveway with bad head gaskets

Have patience, these engines have lots of places that coolant/coolant pressure can leak from and that can only be determined by doing a pressure test

Your main problem is the ISC motor, that needs to be fixed. You are not showing head gasket symptoms, just consider what the membership said above.

See this thread for additional info/research and info on the phenolic spacer

http://caddyinfo.ipbhost.com/index.php?showtopic=5803

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

With regard to the front left speed sensor check to make sure that the wiring from the hub bearing is connected, something when work is done that wire gets left off or dislodged. The speed sensor is part of the front hub bearing

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

I did the hub bearing myself, aside from some help torquing it back on, and I made sure the plug was back on. That code was present on the car when I got it back in August, but I was aware of it needing a new wheel bearing so I figured that was the issue. Put a new hub in and it was fine for a few weeks, then it kicked out again. I'm thinking maybe there is a bad ground somewhere, or a corroded wire or something of the sort. It hasn't been a major issue for me so I haven't put much time into it. I'm going to have the front end apart soon for new brakes so I will take a look at the wiring then.

As for the EGR system...I was mistaken in my first post in saying it had been cleaned. It hasn't. My brother was going to take the EGR valve off and clean it but he said it has a lead gasket and that I would need a new one before it could be put back on because the lead one would most likely crumble when it gets pulled off. I have called a few places around here and the only way I can get a new one is to order it factory direct, and I have to wait until Monday to get it. So now I have to sit here waiting on 2 parts...EGR gasket and Idle Air Control unit, the second of which I haven't even been able to find yet. No one around here has it, or can even order it. So if anyone has a lead on that, it would be appreciated.

I feel so stupid about all of this, but I guess it's better to have a few small things wrong than one giant thing (head gasket) as is hopefully my case. I apologize for being a pain in the @$$ to any of you.

big4870885.jpg

Link to comment
Share on other sites

The 94 has an extensive and unusual EGR system that needs cleaning every 100K miles, it involves cleaning the phenolic spacer and mouse holes, that was eliminated as of 96. Its a dirty and time consuming job, one of my prior links includes a thread by SCOTTY, that describes it... The EGR valve itself is not the full story..

And its NOT the IDLE AIR CONTROL UNIT, its called the ISC, or Idle Speed Control motor, or ISC MOTOR, I think someone posted a terrific thread on cleaning and adjusting it.. and diagnosing it. The NStar did not use an Idle Air Valve till 96

Make sure the wheel speed sensor is making a GOOD connection and that the connector is not corroded

Don't worry about asking questions, this engine is very different and you will need to relearn everything

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

I did the hub bearing myself, aside from some help torquing it back on, and I made sure the plug was back on. That code was present on the car when I got it back in August, but I was aware of it needing a new wheel bearing so I figured that was the issue. Put a new hub in and it was fine for a few weeks, then it kicked out again. I'm thinking maybe there is a bad ground somewhere, or a corroded wire or something of the sort. It hasn't been a major issue for me so I haven't put much time into it. I'm going to have the front end apart soon for new brakes so I will take a look at the wiring then.

As for the EGR system...I was mistaken in my first post in saying it had been cleaned. It hasn't. My brother was going to take the EGR valve off and clean it but he said it has a lead gasket and that I would need a new one before it could be put back on because the lead one would most likely crumble when it gets pulled off. I have called a few places around here and the only way I can get a new one is to order it factory direct, and I have to wait until Monday to get it. So now I have to sit here waiting on 2 parts...EGR gasket and Idle Air Control unit, the second of which I haven't even been able to find yet. No one around here has it, or can even order it. So if anyone has a lead on that, it would be appreciated.

I feel so stupid about all of this, but I guess it's better to have a few small things wrong than one giant thing (head gasket) as is hopefully my case. I apologize for being a pain in the @$$ to any of you.

As far as the IAC/ISC as far as I can remember in 94 they are the same thing part wise. go here: http://www.rockauto.com/catalog/raframecatalog.php

They have been the cheapest place to buy good quality parts that I have found online. As far as the EGR gasket, mine did not fall apart when I removed the EGR on my 94 Concours. I actually reused it, then replaced it later just for piece of mind. As far as the coolant, I do not think the fans kick on until the cooland reaches 225. You said the coolant dropped from 234 to 199, that is good it shows your fans and the thermostat are working.

Edited by PAUL T
Link to comment
Share on other sites

I really appreciate all the input and advice I have received thus far. Here is my plan of action...

I am supposed to bring the car to my brother's shop on friday for a coolant system compression test, which I think I will still do just to be safe about the head gasket thing. It is seeming much less likely though that that is my problem. Plus it will help determine if there is a leak somewhere else in the cooling system which I can then deal with.

While I am there, I am going to have him take the ISC motor off, clean it, adjust it, put it back on and see if that helps with the idle problem. He has access to r&r specs for pretty much anything where he works, so I am pretty sure he can do that.

Regardless of whether that works or not, I am going to order the new gasket for the EGR valve, and have him do a cleanup on the EGR system and double check for vacuum leaks.

If after both of these are done, the idling is still a problem, I will get a new ISC motor and put it in.

Also I will replace the coolant temp sensor, as that seems like it could be an issue.

I'm a little tight on money right now, so all this might take me a week or so to get done, but I promise I will keep everyone up to date on my progress. With a little luck, and hopefully not too much money I will have her back up and running like new real soon.

If anyone has any other suggestions they would like to add, feel free to do so. And thanks again. I feel much more convinced now that it ISN"T my head gasket(s) that is the issue here.

big4870885.jpg

Link to comment
Share on other sites

I really appreciate all the input and advice I have received thus far. Here is my plan of action...

I am supposed to bring the car to my brother's shop on friday for a coolant system compression test, which I think I will still do just to be safe about the head gasket thing. It is seeming much less likely though that that is my problem. Plus it will help determine if there is a leak somewhere else in the cooling system which I can then deal with.

While I am there, I am going to have him take the ISC motor off, clean it, adjust it, put it back on and see if that helps with the idle problem. He has access to r&r specs for pretty much anything where he works, so I am pretty sure he can do that.

Regardless of whether that works or not, I am going to order the new gasket for the EGR valve, and have him do a cleanup on the EGR system and double check for vacuum leaks.

If after both of these are done, the idling is still a problem, I will get a new ISC motor and put it in.

Also I will replace the coolant temp sensor, as that seems like it could be an issue.

I'm a little tight on money right now, so all this might take me a week or so to get done, but I promise I will keep everyone up to date on my progress. With a little luck, and hopefully not too much money I will have her back up and running like new real soon.

If anyone has any other suggestions they would like to add, feel free to do so. And thanks again. I feel much more convinced now that it ISN"T my head gasket(s) that is the issue here.

When cleaning the ISC, make sure to clean the closed throttle switch contacts. Most often, that is the cause of the problems with the ISC.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

Link to comment
Share on other sites

This took some time to find, but here is a tutorial showing how to clean the ISC motor by Barry94

http://caddyinfo.ipbhost.com/index.php?showtopic=7605

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

This took some time to find, but here is a tutorial showing how to clean the ISC motor by Barry94

http://caddyinfo.ipbhost.com/index.php?showtopic=7605

thank you very much. I will be sure to print this out and bring it with me to the shop as a reference. It always helps to be able to see what you are doing before you actually have to do it.

big4870885.jpg

Link to comment
Share on other sites

The one thing that concerns me the most is the loss of coolant. You need to figure out if it is leaking internally or externally. Common external leak points are the surge tank and the radiator side tanks and are certainly a possibility at that age.

Link to comment
Share on other sites

The one thing that concerns me the most is the loss of coolant. You need to figure out if it is leaking internally or externally. Common external leak points are the surge tank and the radiator side tanks and are certainly a possibility at that age.

This is why I am going to go ahead with the coolant system compression/pressure check tomorrow, just in case. If there is a leak somewhere, I am sure it will show. I've started it a couple times in the last 2 days and so far haven't lost any more coolant...so we'll see what happens.

big4870885.jpg

Link to comment
Share on other sites

Well, I figured I would let everyone know how everything went with my car today.

I had one heck of a time getting the car to start and stay running when I went to bring it to the shop. I'd start it and the idle was all over the place, and it just kept dying out on me. Finally I just said to heck with it, laid into the gas a bit, let off it, put it in gear, and drove. It stalled once on me on the way there at a red light, so I started it, did the same thing over again, and finally made it there in one piece.

After I got there:

-Checked the coolant system for leaks, and there were none, so everything looks good there. =)

-My brother took off the ISC motor and took it apart. Man that thing was a MESS! The gears had nearly NO grease on them, and the switch wasn't making contact at all. I wish I could have taken pictures, but I couldn't find my camera battery charger before I went. I apologize for that. He cleaned the switch with contact cleaner and a piece of paper...took about 12 swipes before it came out clean. Then he adjusted the gap so that the contacts actually touched when the actuator was closed like they were supposed to. Re-greased the gears, put it all back together, and put it back on the car.

-I ran the OBD to clear any prior computer codes, then started the car and let it run for a little while. It was idling at a perfect 600rpm and not once did it even try to stall!

-I ran the OBD the check for any trouble codes (just to be sure) and I get the ABS code that has been there for a while, and the Open MAP Signal code....I just changed the MAP sensor, and cleared the codes, so we started looking for a vacuum leak and found a broken hose. I'm not sure what it was on...I think it was attached to the brake booster. He put a new fitting on the end of it and re-connected it, then cleared the codes again. Now the only code reading is the ABS one, which I will deal with some other time.

-I started the car to leave, and it idled up to 1,500 for a few seconds then dropped right down to 600 where it stayed until I put it in drive. It's not trying to drive itself anymore, nor is it stalling out, and I took it on a pretty long drive on the way home. Got her out on the highway and opened her up a bit...and the temp never went above 213. I plan on replacing the ISC motor in the future, but for now I think this solution will do.

-During all this I have come to believe that I also have a clogged catalytic converter...as my exhaust smells pretty bad, so next on the list is a new cat and a cleanup of the EGR system to go along with it. I figure it best to do them both together.

It feels good to be able to drive my baby again!!!

Thanks again everyone for all your help, and as always, I will keep you posted!

big4870885.jpg

Link to comment
Share on other sites

Glad you got it fixed. A clogged cat doesnt cause a smell, it will sap power. Try taking your car for a long highway speed ride, a sunday ride. There is nothing better for these engines than a long high speed ride (60 to 75) for a couple of hours.

If you are smelling eggs, that is a rich mixture. Your FPR (fuel pressure regulator) is located in the intake so its hard to see if its leaking. What kind of smell do you smell?

Glad all is well

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

Glad you got it fixed. A clogged cat doesnt cause a smell, it will sap power. Try taking your car for a long highway speed ride, a sunday ride.

There is nothing better for these engines than a long high speed ride (60 to 75) for a couple of hours.

If you are smelling eggs, that is a rich mixture. Your FPR (fuel pressure regulator) is located in the intake so its hard to see if its leaking. What kind of smell do you smell?

Glad all is well

Mike,

If I wanted to do that...why should I drive so slow?

Some of the highways here in Texas (out west) have 80 MPH speed limits...and most people are going even faster than that.

:lol::lol::lol:

Just playing with you...I know that speed limits are much slower back East.

But, seriously, my car does like to get out on the highway and RUN. :D

I oblige it whenever I get a chance.

I don't want it to be unhappy. :D

Posted Image
Link to comment
Share on other sites

I believe there is supposed to be a gap between the ISC plunger and the throttle lever. Do a search on ISC or idle speed control as there is a ton of material in the archives. The adjustment procedure is in there.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

Link to comment
Share on other sites

I believe there is supposed to be a gap between the ISC plunger and the throttle lever. Do a search on ISC or idle speed control as there is a ton of material in the archives. The adjustment procedure is in there.

On a 4.9 engine the gap should be around 0.0300" (0.70 mm). Probably the same on a Northstar.

The saddest thing in life is wasted talent

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.



×
×
  • Create New...