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cold start misfire


rockfangd

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If the fuel system is all GO and you have a misfire, look at the ignition. But, you have no P030x codes?

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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none at all. I have debated on replacing the coil packs and control module but dont want to waste the money for nothing.

I am going to service the egr valve, throttle body, and MAF anyway while I have it down. Maybe I will find something.

GM FAN FOREVER

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I just checked my 1997 FSM, and a P0101 that has been set since the key was turned ON will suppress the P030x codes. I think that there is something sneaky in the P0101 check list that is eluding you. Like a hairline crack in the big rubber seal between the throttle body and the manifold that opens up when the engine moves but you can't see or hear when the car is in neutral.

If you smell gas in the exhaust after a hard start in the morning, you have gas leaking down into the intake overnight. There are two ways that I know of for that to happen: fuel injectors, which you have just eliminated, and FPR diaphram leaks. A new FPR is not *always* a good FPR. I would take off the beauty cover and check the new FPR.

FYI, from the FSM page 6-426, the complete list of codes that will suppress the P030x codes is P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0340 and P0502. The P030x codes will not be set if you are moving over 45 mph, or if the EBTCM is sending a "rough road" signal (the PCM detects misses and assigns them to particular cylinders by detecting crankshaft rotation irregularities).

When enough misses are detected so that the PCM declares possible harm to the cat if things continue, it asks the EBTCM about "rough road" conditions. A missing "rough road" signal from the EBTCM through the Class 2 network will throw a P1380 and the P030x will still appear, and the MIL will turn on.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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The misfire code will not indicate which cylinder is misfiring - all that will be displayed is the PCM P0300 code for that vintage of car.

If it were mine, I'd get a TECH-2 hooked up to it and monitor the misfire counts per cylinder and see what cylinder is causing the issue. Cheaper than throwing parts at it.

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

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I will hook up mine. I have a Determinator. I will have to record the parameters from startup and see what happens.

I dont know if I mentioned this but it has never once attempted to stall and starts every time

GM FAN FOREVER

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Ok here is what I have done as of today. I hooked up my fuel gauge and cycled the key a few times.

Fuel pressure is 45 psi. I left the key on for about 5 minutes with the rail pulled up. No leakage at all.

I then pulled the rail completely and replaced the upper seals, lower seals, and clips. Found nothing obvious to throw a red flag.

Removed the egr valve, Pretty clean but I cleaned it anyway.

I removed the MAF sensor. Looks clean.

Tomorrow I am going to remove the throttle body and spacer, clean both and the egr pipe. Reinstall everything and run it. If the MAF sensor code comes back I will replace it. If cold start misfire persists I will hook up the scantool and see if it can catch something the onboard system may not.

I am hoping this helps.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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If the fuel line is 45 psi without turning the key off and on several times, the fuel pump is OK. If the fuel pressure holds for several minutes without discernible leak-down, your injectors and FPR are great.

I think you will find something when you take off the throttle body.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Ok Let the hole get deeper. I found 3 red flags and am surprised.

1. The egr tube that bolts to the TB spacer. When I removed the tube I found that the port in the spacer was 99% closed. you could barely get the tip of a small screwdriver through it. Also I broke the bolt off in the crossover housing that holds the lower portion of the egr tube.

2. Even if the fuel regulator was unhooked it wouldnt make a difference because the spacer and the throat of the intake had at least 1/8" of solid carbon all around them. The port to the fuel pressure regfulator was plugged shut completely.(Note the port is tiny and this could be very common of a problem for others).

3. I could be wrong but there was a pool of oil in the bottom of the intake. It looked clean like fairly fresh oil. This is something I dont know what to do or if I have to worry about.

Here is where I am at at this point. I am going to pull the intake and clean it, replace the intake gaskets, and reassemble everything.

The reason why I am surprised with what I found is because

I only run non ethanol premium fuel

I run chevron Techron twice a year

I change the oil regularly

This car does not see idle time and I drive it hard.

I think this has stemmed from previous ownership and was just too far to clean it out. I have only ever cleaned out the throttle body and egr since I bought this car.. This is a true cadillac because even with all that I found it still ran good and had good power. It never has really gotten good gas mileage though, I am all ears on opinions

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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The FPR regulates the fuel pressure between the rail and the intake manifold - the pressure across the fuel injectors - so that the pulse width at the injectors needed to provide a given amount of gas does not change with vacuum. Without that, when you do a sudden movement of the accelerator, the vacuum drops and you get too little fuel until the PCM "sees" the lean mixture at the oxygen sensors and corrects. If the vacuum line to the FPR isn't working, this could be your stumble.

I would clean the oil out of the manifold and not worry about it. This is probably from the PCV and, if you have a good PCV valve and don't have a lot of blow-by, it won't happen again. Note that the cylinders have only 51.8 cc volume (1997 FSM, p. 6-11) and that is the amount of liquid in any one cylinder that it takes to hydrolock it. If the oil is below the manifold in the valley where the starter is, just clean it out; it can't hurt anything there.

LIke you, I always ran top-tier premium gas in my 1997 ETC. Unlike you, I never had a problem with the top end until I got the miss around March 1 of this year. That miss was eventually attributed to coughing back combustion chamber goop into the intake; MAC said at the time that this is the most likely suspect when you have a sudden miss or low compression on one cylinder. My throttle body was clean. Car had no codes other than P0300/P0308, except for one P1380. According to the FSM, you can get a P1380 when the PCM is trying to throw a P0300 on a rough road, which is what was happening when the MIL came on that time. I have no idea where all the carbon in the intake came from, unless it's the EGR.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I wouldn't worry about the inside of the intake - I seem to recall the guru stating that was normal - something about the heavy deposits from the fuel.

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

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I think that carbon from the EGR might be a function of oil consumption, the type of oil used, and perhaps whether the car was driven on the road much or otherwise "cleaned out" from time to time. I always used synthetic oil, which is known to keep engines cleaner over time.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I think that carbon from the EGR might be a function of oil consumption, the type of oil used, and perhaps whether the car was driven on the road much or otherwise "cleaned out" from time to time. I always used synthetic oil, which is known to keep engines cleaner over time.

If you maintain this kind of AVERAGE speed over a 200 mile distance... does it help to keep the engine clean ??

.

.

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lol. the answer is yes to that.

Also I only run 7 quarts and never over in both of my caddys. I never overfill.

See I think this stemmed from previous owners because it had egr issues and the TB was plugged when I bought it, but I just never went any farther til now. If it wasnt for the cold start miss I wouldnt have found what I did.

I dont see my Seville ever having this issue. It is all fresh and I drive like the above post. No city driving in that car

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Ok update.

I have good news and surprising news.I got the broken bolt drilled out and retapped for the egr tube.

I removed the intake and the lower ports came out excellent. Look like new

I found a mouse nest in the valley. This was a first for me as I have never seen one in a northstar before. It was very old and it looked like stuffed animal stuffing. No damaged wires whatsoever. Cleaned right out.

And anyone who says the starter location is ridiculous is stupid(sorry). I think that is the best place to put a starter, especially here in NY. It still looks good with no rust or corrosion.

I have had many people badmouth the starter location on Cadillacs and to me it makes them unprofessional.

So all I am waiting on is the intake gaskets and I can reassemble everything. I am keeping my fingers and toes crossed that it works out. I love my Deville and dont want to think about retiring it, After all 200k is not even broken in yet for the old horse

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I agree that Texas Jim is unlikely to have cobweb problems with his Cadillac.

I agree with rockfangd about the location of the starter. It's protected and has zero envelope extension on the powertrain, and the high-current battery cable is well protected from mischief or shorting from road debris under the intake manifold. The intake manifold is so easy to pull, and the rest is so easy to service, that I do believe in putting the starter in the valley of an OHC engine, so long as it can fit between the heads with the manifold off.

I've heard a complaint about the alternator being on the bottom and hard to service, but if you drive the car up on ramps you can get right to it from underneath, making me wonder what the objection there is to ease of access.

In point of fact, everything I see about a Cadillac seems to be very well thought out and carefully done. There is one area that vexes me as a lifelong DIY guy for light maintenance (and occasional heavier work) is that the FWD Northstars need to have the cradle dropped for an awful lot of things. That is easy if you have a lift and a transmission jack, and the J 28457-A Engine Support Fixture, the J 39580 Universal Engine Support Table, or an engine stand. Air tools and other shop equipment are good to have around too. This keeps the engine/transaxle compartment compact and the flat rate manual numbers down, and lowers the cost of the warranty that is layered on the manufacturing cost of a new car, but it is an issue with the occasional DIY guy.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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And anyone who says the starter location is ridiculous is stupid(sorry). I think that is the best place to put a starter, especially here in NY. It still looks good with no rust or corrosion.

I have had many people badmouth the starter location on Cadillacs and to me it makes them unprofessional.

I also have had people ridicule the location of the starter in a Northstar engine. To me, they are ignorant - they equate the removal of the intake to a small block Chevy engine that would take a few hours to do. When I point out to the ignorant types that it is a 20 minute job to remove the intake, they do not believe me and I always say, "You think I'm making this up? I TIMED MYSELF when I did the headgaskets.". That usually shuts them up. If they still insist it is a stupid location for the starter, I go on to say that the location keeps the starter clean, cool, and dry, unlike a starter located in the traditional location next to a hot exhaust manifold. If they still keep the negative comments spewing, I just say, "Yeah - I guess you're right - I'd much rather be laying on my back under the car with crud falling in my eyes over standing up any day." then change the subject...LOL

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

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I just replaced the alternator on my Deville and it took me 1.5 hours taking my time.

I cleaned out the intake today. It looks all shiny and new. And I also figured out how to remove the blow out valve which is cake

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Well I am kind of excited. My gasket kit comes in today, I cant wait to get my Deville back up. Then I have to do front swaybar bushings and alignment. I still have that nasty clunk. I am hoping alignment shop will see something I am not.

I will post my results in a few days.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Update 8/10/13.

Today went very well. I took my time and reassembled everything.

To recap. what I did.

Intake gaskets

Throttle body and spacer gaskets

serviced all injectors

cleaned out intake, egr ports, coolant hoses and pipes, the bolt with the hole in it (had no blockage), egr valve.

replaced pcv valve

inspected all vacumn lines, plug wires

It fired right up but ran like crap for about 5 minutes. Smoking and all.

Test drove it and was amazed by the increase in power and acceleration. It spun the tires and the traction kicked in. I was not expecting that. It runs better than it did before for sure.

But the exhaust broke at the 4 bolt flange. It had been getting louder but broke today. So I brought it back home and repaired and bolted the flange. Also did the swaybar bushings while I was under there.

Tomorrow morning will be the true test as it will have sat overnight and will be a cold start.

I am praying it works out. I love this car and try to do anything to keep it going strong. I have driven quite a few cadillacs and still love this one the most. I love the 96.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Well unfortunate news. Problem is definately still there. Just as bad as always. Even if it sits for 2 hours it does it. This morning it did it for 2 blocks. I am bummed and there is no codes. I will have to hook up my scantool and hope for something. Is there a possibility it could be a headgasket problem before I put too much money and time into it. Places look at me weird when I ask for a combustion by product tester.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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You can get a good indication of whether the head gaskets are leaking with just your nose and a couple of shop rags. In the morning when the car is cold, take off the cap on the surge tank and sniff the coolant. If it does not have even a trace of exhaust odor, you are good, put the cap back on and start the car. After it runs for a few seconds, shut it off and go to the rear of the car and smell the exhaust. If there is not trace of a coolant smell, you are good.

If the car passes both tests, the head gaskets are almost certainly good. If it fails either smell test, you can get a coolant test as you say, or you can pressure test the cooling system.

But, a cold start misfire doesn't sound like a head gasket to me. It sounds like ignition problems. Most ignition problems won't throw a code, other than the P0300/P030n. If it is an ignition problem, you need a code reader that will get you the miss counts, which will tell you which cylinder is the culprit. Then, go over the coil (switch with another coil), wire (with the beauty cover off, see if you can hear an arc or, in the dark, see it), and spark plug.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I will try that tonight and drive it tomorrow.

I dont know if this helps but It held cooling system pressure for over 2 weeks. If it were leaking somewhere would it still have had pressure? whether internal or external

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Ok guys I hope this helps shed some light. I finally hooked up my scantool yesterday and it showed me what was going on. It stumps me even more though.

on a cold start

cylinder 1 misfires erratically bad

cylinder 3 misfires erratically but not half as bad

Cylinder 5 misfires once or twice.

here are the numbers for the misfire history on the 2 cylinders

Cylinder 1 4643 misfire history count

cylinder 3 544 misfire history count. You can clearly see this one is nowhere as bad as cylinder 1.

both cylinders misfire for a period of time varying on how long the car sits before startup.

I recorded the datastream and sure enough within 2 blocks yesterday all cylinders were showing 0 misfires and it was running excellent.

I did it today and same results. I pulled the plug wires and inspected the wires, and towers. Both look like new. And they are on seperate coilpacks.

I have been so busy lately I havent had the chance to pull the 2 plugs, but I did them last year due to this exact problem and all 8 were excellent. I thank you all for the help and I hope this can help explain things. It seems like one heck of a coincidence that it is those 2 cylinders, that is why I am so worried about possible head problem.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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