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misfire questions. Could use some advice.


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Hi all. My new to me Eldo has a misfire. Let me be more specific.

I bought the car 2 weeks ago and when I went to look at the car it misfired like crazy. The harder I drove it the better it ran. I think the gas was bad from car sitting for almost a year.

So anyway It runs much better now but still has a misfire. car shows p0300. scantool shows p0304.

So I ordered new delco plugs, COP wires, Today I pulled the front coil pack unit and I found something weird, there are several cracks throughout the unit. I did not notice any spark tracking from any of the cracks but it still worries me. I changed the plugs, and wires and reinstalled the coil pack unit. did not help any, same code and misfire, not bad feeling but enough to make the SES light flash.

The questions I have are

If the coil pack unit was bad could it possibly only misfire on one of the cylinders?

If it is still from bad gas could it still be on the one cylinder?

I wasnt sure if the intake coupler could be the culprit but I would think it would misfire on several cylinders, same for the intake gaskets.

I am not sure if I should just finish changing the plugs and wires then just try and drive it, or if I should go farther in trying to figure it out. I mainly just worry about damaging any of the cats.

Thanks all

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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On the coil bank cartridge...I have seen one cylinder failures...Actually...thats the only type of failure I've seen. Never seen the whole coil go bad.

I used to carry a tested spare in the trunk.

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The coil packs are over $200 on RockAuto. I would do a compression check and, if number 4 is low, run some top-end cleaner through it, or do the GM carbon-knock hard-core top end cleaning routine.

The 2002 FSM general advice on P0300, omitting the random misfire advice, includes:

  • Incorrect CKP system variation data - run re-learn of the crankshaft sensor calibration data. (not likely here)
  • The system grounds - since you have a P0304, check the grounds on the front coil pack.
  • Fuel injector - check for a bad connection or clogged injector, or a bad O-ring on the injector for number 4. (Techron???)
  • Contaminated fuel. (Uh, huh!)
  • Manifold leak next to the affected cylinder.

The FSM also says that visible cracks in the coil are reason enough to replace it.

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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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I had a single cylinder misfire and it turned out to be a crack in the boot on the coil,moisture got into the crack in the boot and caused the misfire.I would think a crack in the coil itself would cause a problem.

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I am thinking coil is bad also. I hooked up my scantool tonight and cylinder 4 is the only one misfiring. Just to be sure I have this right.

Even cylinders are on radiator side

odd are on firewall side

Is that correct. I am thinking the second one is cylinder 4. 2 being closest to crank and 8 being closest to waterpump.

Also weirdly enough, the more I run the car I now find the check engine light isnt flashing anymore but still comes on solid.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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1357

2468

#1 is firewall side, passenger side corner.

You can always swap the coil and see if the misfire moves. The coils are different colors..but they are technically identical.

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Going through the thread, here are the things that come to mind.

When you pull the plug for no. 4 to change it, it should look different from the others, probably darker. Sniff it and see if it smells of gas; if it does, you likely have a spark problem but if it doesn't then maybe you should check the injector.

The FSM says that an intake manifold leak at a particular intake port can cause a miss at idle on that cylinder.

In the 2002 FSM (yours is a 2001, I believe, but it should be the same as the 2002), the coil packs have one coil per plug and there is no "waste spark" for another cylinder as there was for the 1993-1999 model years. So you can't switch the wires for no. 1 and no. 4 and see if the miss moves to no. 1.

The FSM says to replace a coil that shows visible cracks. I would suggest a new (or good used) coil, and don't let the tech pour oil on it when you are getting oil changes!

I remember the miss on no. 8 problem I had with my 1997 ETC a year ago. Only at idle, no performance or fuel economy problem, but a P0300 and P0308, with the MIL light coming on after a few days. New plugs, wires, and coils did not change anything. Compression and leakdown tests showed it to be an intake valve. It turned out to be carbon from a recent backfire-on-start that kept an intake valve from closing completely. MAC called it, but I didn't figure it out in time and I had the urge for the CTS-V overpowering me, but a top-end treatment as I suggested in post #3 above almost certainly would have cured it. If a new coil doesn't do it, try a compression and leakdown test. And, remember, Northstars don't need valve jobs.

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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well wonderful news. I located a coil pack today. It is a rear one but all I could find,. It looks like new. Delphi Black. took 10 minutes to install and problem is completely gone. Engine runs so smooth you cant even tell it is running. Saved 150.00 too.

I am so happy thats all it was. I still have to get used to the AIR system. Never owned a car with it before. It keeps the rpms up around 1200 til it shuts off then drops down to normal. I am dwindling the problems one by one. Gas gauge is starting to work properly also since I keep adding fresh non ethanol gas. once full I have a bottle of chevron techron for the full tank

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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One of those little GM mysteries....the coil banks are identical...but are different colors.

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The coil bank problem could be due to two suppliers, and they are trying to use 50% of each one... or perhaps they think the engine looks better with a black coil at the back... or perhaps they have two bins in engine assembly and a decision was made on the line to use parts from one supplier at one point in assembly and the other supplier in another point in assembly...

Congratulations on getting the car back in shape with a minimum of cost. Where do you get non-ethanol gas??? I found a web site, Pure Gas:

http://pure-gas.org

I've checked out some of the gas stations that they mention and find that most sell "racing fuel" in 5-gallon cans at exorbitant prices. The best bet is to go to a local small airport and buy 100 octane low-lead aviation gas at about $6.25 per gallon. There is a web site that compares prices and gives the prices for 100LL and Jet A fuel at most airports on a query:

http://www.100ll.com/

One of the reasons that a GM car will idle fast for a few seconds is to light off the cat, AIR pump or no AIR pump. As your CAT gets the cobwebs out, this period should become shorter and eventually be unnoticeable like the other cars that you have driven.

If the gas gauge is becoming unstuck, then there may be no problems at all once the cobwebs are out of the car. I would use Techroline in the first two or three tanks if there is that much goo in the bottom of the tank, just to make sure that it's all gone before you stop adding Techroline.

If the miss is gone and the car drives well, and you have changed the oil and coolant and checked out everything else, and all the codes are gone, and the tires and brakes are good to go, now might be a good time to buy two or three bottles of Techroline and take a 500-mile drive. When you get home, you will have a limbered-up, trouble-free daily driver.

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'm sure it's a cosmetic reason for having 2 different colors.

That said, it does add some cost to the manufacturing process. Also, it's not value added.

Now...2 different part numbers. 2 different part numbers to inventory..2 different part numbers in the dealership computer system. Dealer tells you...'I have 6 black ones...But I would have to order you a silver one..'

You need 2 footprints on the factory floor for storing 2 different coils. 2 different racks at the point-of-use.

Guy unloading the semis has to keep track of how many of each are coming in.

Very short list. I bet you could easily save $1 per car by using the same color coils. At Cadillac...must be no big deal. It is a $40k+ car.

At (what used to be..) Saturn, you would be a hero.

I would be very surprised if Toyota would do this.

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well car still has other issues.

List follows.

trans leak by abs pump but it is not the lines at the radiator.

All brakes need servicing

tires.

vats bypass

good wash

coolant and tranny fluid change.

Both door panels are horrible, I personally think they were a poor design and are too cheap for the weight of the doors. Every one I have seen is broken. on the driver side anyway, this one is so bad that the master switches wont even stay in place.

One thing at a time I guess

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Yes, the door panels on the Eldorados could have been firmer. There are only two large screws that hold it to the door frame, and they tend to work loose if not tightened properly, and it seems that most body shops and even GM techs don't tighten them properly. So, the first time anybody goes in there, the panel begins to loosen. This can be easily dealt with by asking any body shop and many detailing shops to tighten the door panels. If you have a good relationship with a GM dealer and are going to them for service, ask the service manager if that is a good thing to ask of their tech.

But the switches mounting to the door panel is another matter. Those should *not* get loose. Either they were not properly re-installed when somebody worked on them or they are damaged. That is NOT a common problem with Eldorados.

If you service the brakes, try to do it yourself. If you have it done, be sure and specify the parts. There are economy $13 brake rotors that will work on your Cadillac but I am loath to think of what the brakes would be like if you try to pull the speed down from 125 mph to 65 mph when the radar detector goes off. And most mechanics will order brake rotors before they even see the car. I recommend PowerStop brake kits; they require a break-in that must be done on a road with a 50 mph speed limit and no one to get behind you while you repeatedly apply the brakes firmly to heat them up, but the feel and action is superior, and you need not fear downgrading the OEM brakes. If you don't like drilled and slotted rotors, pick your parts on Rock Auto or other reliable source and either provide them or specify them to your mechanic.

GM may or may not have separate part numbers for the front and rear coil packs. On my 1997, which has four coils (sold a year ago though), each of the coils has a cylinder number embossed on each plug wire connection. All the AC/Delco coils for that model have the same part number, and you better keep track or have a good manual because there are no cylinder numbers on replacement coils.

I wish I could say something about the tranny leak but "in the front near the ABS pump" doesn't tell me enough. Some of the other guys here may see something familiar to them, but I suspect that we need more information. If you can get under the car, try to find the damp component; wipe everything clean and look again after driving the car if you can. It may be something simple, like a little spillage when the tranny was topped off after servicing or prep for sale. But look at the fittings and hoses for the transmission cooler, and the pan and side gaskets - in fact you might check and see if all the bolts and fittings are tight while you are looking at them.

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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thanks for the detailed response.

The door panel is pulling away from the door and it is breaking between the handle where you pull the door closed and the master switch area.

If you ask GM for the 2 cylinder coils I believe they only offer unmarked ones. I think as for the brakes I am going to try to run the current brakes (but service them) and later replace the fronts then the rears.

I havent found the tranny leak yet. I did find the dipstick is dry and there are some drips on the ground. cannot see anything from under the hood. I am hoping it is something fairly easy.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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If the door panel is damaged, the cheapest thing to do might be to get a clean used one from a recycling yard. Failing that, finding a body shop good at interior work might be a tough proposition.

If the transmission leak doesn't leave spots on the garage floor, and the transmission fluid doesn't go down with time, it might be a seep that you can ignore. I would make sure that all the bolts and fittings are properly tightened up (check the torque specs and follow them).

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 have scouted door panels at my local yards for quite some time now and havent found a non broken one yet. most of them are screwed to the door(not original)

As for the tranny leak, it is leaving a puddle and there is nothing on the stick. I am not starting it until I top off the fluid.

The weather has been unpredictable like usual so I have not had much time to look at it.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I suppose this post is too late for the door panels on this post, but the dealers have a repair for the L shaped "clips" on the bottom of the panel. I would guess that they need attention before they become so loose as to let the center section tear away from the rest. I am not remembering well, there may be the same clips under the arm rest?

If you were to get salvage ones, you may want to repair any broken ones before using, Maybe someone will read this and save their panels.

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I have scouted door panels at my local yards for quite some time now and havent found a non broken one yet. most of them are screwed to the door(not original)

As for the tranny leak, it is leaving a puddle and there is nothing on the stick. I am not starting it until I top off the fluid.

The weather has been unpredictable like usual so I have not had much time to look at it.

When my daughter had hers I would check ebay regularly and no luck. New ones for around $300 I think.

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I have seen the boomerang looking clips. they glue them onto the door panel in the place of the clips that broke off, still a poor fix and they end up in the bottom of the door. I am watching a set on ebay now but they are both damaged and seller is asking 400 plus shipping.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Cadillac northstar heads do need valve jobs. I have seen a handful of burnt valves on 2000 engines and 6 broken valve springs. Do a compression test. You can see the pics on my ebay ad of trhe valve spring.

Brad Barczy

B & B automotive llc 46250

http://www.ebay.com/itm/Cadillac-Buick-Northstar-head-gasket-engine-repair-4-6-overhaul-rebuild-/171142290169?pt=Motors_Car_Truck_Parts_Accessories&hash=item27d8e01af9&vxp=mtr

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Cadillac northstar heads do need valve jobs. I have seen a handful of burnt valves on 2000 engines and 6 broken valve springs. Do a compression test. You can see the pics on my ebay ad of trhe valve spring.

Brad Barczy

B & B automotive llc 46250

http://www.ebay.com/itm/Cadillac-Buick-Northstar-head-gasket-engine-repair-4-6-overhaul-rebuild-/171142290169?pt=Motors_Car_Truck_Parts_Accessories&hash=item27d8e01af9&vxp=mtr

Yup, should have realized that a tech would read my post, and have a counterexample. I would venture to say that you would have a fine story to tell about how that broken valve spring came to be.

IMHO, broken valve springs on robust engines come about through prolonged or extreme valve float, where the lifters are "thrown" off the cam surface and bang back down on the closing ramp, sending shock waves rebounding back and forth through the valve spring. It's hard to do in a Northstar, because there is a rev limiter at 4500 RPM in neutral or drive, and the transmission will shift before it will let the engine go very far into the red zone, even if held down in low range. The red zone begins at 6250 RPM on the 1993-1999 Northstar, which is 133.5 mph with the 3.71 final drive ration and 159 mph with the 3.11 final drive ratio. The owner's manual for my 1997 ETC stated that the car would go 150 mph, which is 7025 RPM, and I have seen the tach wander almost that high on a full-throttle shift with no discernible signs of stress from the engine. So it would seem that the simplest way to overrev the engine is by running it overspeed on a dyno, or in a situation like running full throttle while stuck in snow with the rear wheels loose.

I'm not even going to discuss the idea of running an engine at high RPM with flat lifters (i.e. no oil in the hydraulic lifters, which means very high valve lash).

I guess the best way to reconcile all this is to ask if anyone ever needed a valve job on a Northstar that they had been driving for at least a year. If a tech knows of a Northstar engine that has been brought to him with head or valve problems, is there any information on how the car got that way?

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 have yet to hear of a valve problem with any northstar yet, and none of mine have. Thank you for the detailed response. I am confident that there is no valve problems with this eldo. I am sure it would show if there was

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Yeah, but you have to respect the viewpoint of a tech. If it can happen in this world, an experienced tech will see it sooner or later. This guy specializes in exchange Northstar engines.

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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Yeah, but you have to respect the viewpoint of a tech. If it can happen in this world, an experienced tech will see it sooner or later. This guy specializes in exchange Northstar engines.

I agree with that, but even agreeing, I will posit that it is very, very rare for a NorthStar to have valve issues.

In my 8 years of having NorthStars and being on two Cadillac forums, I don't recall anyone ever having to have a valve job done on a NorthStar.

I have owned Cadillacs for the last 34 years.

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