cold start misfire

[winterset]

Exhaust passages for these cylinders might have a restriction. - when the EGR kicks in, the restriction is lessened. I know one symptom for a plugged cat is misfire, but you only have these symptoms when the engine is cold, so I suspect it's something that changes once the engine warms up. Maybe the work you did opening up the EGR passages will take a little while to clean out the internal exhaust passages?

[rockfangd]

Would it be safe to seafoam it? I have used it on many vehicles but have heard not so good things on using it on the northstar

[Cadillac Jim]

Try reversing the two plug wires that go to coil 1. If the miss follows the coil output, it's the coil. If it doesn't, then it's the wire.

[KHE]

Would it be safe to seafoam it? I have used it on many vehicles but have heard not so good things on using it on the northstar

I would not recommend that - if it pools in the intake and then gulps it down, it will hydrolock and blow out the crankcase.

Check the plugs on the misfiring cylinders - they may have lost the platinum pad on the ground electrode.

[winterset]

You might want to go the seafoam route. I think the trick to not blowing a hole thru the engine is after the soak, to disconnect the coil pack, and crank the engine - that way any puddles are dispersed.

I believe BBF had a thread recently where one of his lifters was scorched, and it wasnt moving properly causing a miss. I suspect you may have a similiar issue. - maybe yours is bound in a little carbon>

[rockfangd]

I wonder that also. I have had good luck with seafoam. I wish the Guru was still around for that question.

[rockfangd]

Ok I pulled the cylinder 1 and 3 plugs and both are clean, just like when I installed them.

What about the newer seafoam that is an aerosol that sprays into the throttle body rather than pouring into a vacumn line?

[winterset]

Before the seafoam, try putting 8oz of Marvel Mystery oil into a full gas tank, and next time you need to add oil, use MMO instead.

[rockfangd]

Before the seafoam, try putting 8oz of Marvel Mystery oil into a full gas tank, and next time you need to add oil, use MMO instead.

I took your advice and put 1.25 quarts in the engine and 8oz in the tank. I have never run anything in my Cadillacs other than chevron techron due to being not recommended but I am up for trying anything.

I am a strong believer of the marvel oil. I have run it in all of my vehicles with good results.

I hope for the best that it helps.

I have gone 300 miles since I cleaned the top half and today took a strong smell in the coolant jug. Its clean and has no smell of exhaust

[rockfangd]

Well guys. It is doing it worse than ever, also has a new symptom. When you start it and attempt your first moderate acceleration it feels like there is no power and then all of a sudden it takes off.

Even if it sits for 35 minutes-1 hour it does it. Still not throwing any codes, and no coolant loss. I swear it smells like raw gas in the exhaust. Why just the 2 cylinders though is what I cant figure out?

Hoe can it run so good after the spell? I went 150 miles this week and it is just not getting any better

[KevinW]

Maybe the injector drivers for #1 and #3 are performing erratically until they warm-up to some degree. Do you have a scope? Spare PCM?

[Cadillac Jim]

If you are smelling gas in the exhaust when it does this, the problem is pretty likely ignition. Things that won't throw codes include cross-arcing or arcing to ground plug wires (my personal favorite), arcing in the spark plug well (bad spark plug boot with oil or condensation on it), or loose or bad spark plugs. Bad coils and bad connections on the coils and ignition module are rare.

One thing I have heard of causing exactly that is a bad ground on the ignition module. There are two, and it will seem to be fine with one of them off, most of the time.

[rockfangd]

If you are smelling gas in the exhaust when it does this, the problem is pretty likely ignition. Things that won't throw codes include cross-arcing or arcing to ground plug wires (my personal favorite), arcing in the spark plug well (bad spark plug boot with oil or condensation on it), or loose or bad spark plugs. Bad coils and bad connections on the coils and ignition module are rare.

One thing I have heard of causing exactly that is a bad ground on the ignition module. There are two, and it will seem to be fine with one of them off, most of the time.

Thank you Jim. The only thing that is leading me away from it being a spark issue is because it disappears. I would think if it was cross arcing it would do it while driving also. I recently replaced the plug wires, and there is no oil in the plug wells. Thank god. I was almost sold on a leaking injector, but found nothing. Is it too much of a coincidence to be those 2 cylinders? 1 and 3 and 1 being the worst and 3 being less

[Cadillac Jim]

Actually the thing about plug wire arcing is that if it isn't bad it tends to go away when the engine heats up and all the condensation moisture is out of the area under the beauty cover. Perhaps a quick way to find it is, just before you go to bed, pull the beauty cover, start the car, and get out and see if you can hear or see the arcing.

[rockfangd]

Ok I will try it tonight

[KHE]

It would be interesting to see what the compression readings are.

[rockfangd]

Ok so last night I fired it up when it was dark and watched under the hood. Problem was as usual but no arcing or anything abnormal from the plugs/wires

This morning it was severe enough to finally trip the check engine light. Code p0300. multiple cylinder misfire. It is the first time it has actually thrown a code. Drove it like usual and like always after about 2 minutes it was running perfect.

Tonight it did the usual but did not trip the light, I did notice 2 things though. The pcv valve is noisy on the rear cam cover. (is this normal) I realize it means it is working but is it supposed to constantly rattle?

Also noted coolant is a little low, not low enough to throw the message. Maybe it is because I checked it while it was running, but I would think it wouldnt make a difference.

Tomorrow I am going to try something different, I am going to relieve the cooling system pressure after I drive it and see if it does it on the next cold startup. If it doesnt then it must be coolant related.

It doesnt smoke alot on startup but if it is minor then it may not be as easily notable. I have seen quite a few that are ingesting coolant and they smoke white like crazy.

I dont have a compression tester but I will look into it.

[KHE]

Have you put a Tech-2 scanner on it to see what cylinder(s) are misfiring?

[rockfangd]

yes. I posted them here. in this thread. page 5 or 6. Cylinder 1 misfires constant, cylinder 3 misfires but not as bad. The numbers are in the other reply

[Cadillac Jim]

If the PCV vale is noisy, that may be a smoking gun. If it is clicking with half-engine rotation speed (a double-click, if you have two cylinders), it may be a leaking intake valve causing vacuum pulsations. If so, you may have something as simple as a sticking intake valve, something I have painful recent experience with. Perhaps a top-end clean-out would do the trick. The dealers have at lest two, a de-carbonizing and a ring-unstuck one, and they are similar. They involve getting a solvent solution into the top end through the plug holes or through a vacuum line of an idling engine (very, very carefully - hydrolock hazard!) and letting it sit in the cylinders for up to two hours. I'll look for the TSB if you want to go that route. You may want to look at simpler, less ticklish aftermarket procedures that work in similar ways.

I wouldn't jump on the dreaded head gasket at all. Yes, you can get a miss on two adjacent rear corner cylinders with a blown head gasket, particularly on a cold start in the morning. On a Northstar, this is one of the late-stage symptoms, and by that time you will have sudden overheating whenever you climb a hill, consistent and large coolant loss, bubbles in the surge tank with a strong exhaust smell all the time, and a strong coolant smell in the exhaust when you start the car in the morning. You have none of these.

This has gone on too long. We have been working with assumptions. The usual is that if you have a miss, it's spark, or it's gas. But sometimes it's a sticking valve, a sticking injector actuator, a loose wire on an injector, etc. We gotta get our eyes and ears open and get this.

[rockfangd]

Ok I have unfortunate news but at least I have something.

Last night I relieved the cooling system pressure when I got home and let it sit overnight. Today I had 0 misfires on startup. It ran beautiful. I know for 100% that it made a difference.

I was dreading it but had a feeling that it would tell me something. Today was the first time in a long time that it did not misfire on startup. Am I looking at headgasket problem. If it were it would be the rear head as the 2 cylinders are 1 and 3.

2 reasons why I dreaded the problem was when I hooked up my scantool and watched the misfire counts for cylinders 1/3/5. 1 missed alot, 3 missed less, 5 barely missed. All 3 cleared up after about 2 minutes.

I thank the member that posted about removing system pressure like I did. Maybe I have been mistaking the smell of gas as coolant on startup.

any input on the new update is highly appreciated

[KHE]

Go to Autozone and rent the block tester kit and test the coolant for combustion gasses.

[rockfangd]

It is definately coolant related.

This morning It had no misfiring.

This afternoon I did not relieve the pressure and it did it.

This afternoon I relieved the pressure after I drove it and same thing. No misfires at all. I will have to look into the kit but I hope I have enough in the reservoir to test it. It is kind of low and if I top it off I will have to wait.

also is it possible that exhaust gases are not getting into the coolant? As in the coolant is leaking in through the piston or intake side?

[Cadillac Jim]

Relieving the cooling system pressure sounds like MAC or KHE or Logan or another of the Caddyinfo regulars, and that's one I am going to remember.

Try the nose test. See if there is any coolant smell in the exhaust right after it does it, or any exhaust smell in the surge tank. If either is definitely there, would still get a leakdown test or test the coolant for exhaust by-products but if the nose knows, it knows.

[JohnnyG]

Ok I have unfortunate news but at least I have something.

Last night I relieved the cooling system pressure when I got home and let it sit overnight. Today I had 0 misfires on startup. It ran beautiful. I know for 100% that it made a difference.

I was dreading it but had a feeling that it would tell me something. Today was the first time in a long time that it did not misfire on startup. Am I looking at headgasket problem. If it were it would be the rear head as the 2 cylinders are 1 and 3.

2 reasons why I dreaded the problem was when I hooked up my scantool and watched the misfire counts for cylinders 1/3/5. 1 missed alot, 3 missed less, 5 barely missed. All 3 cleared up after about 2 minutes.

I thank the member that posted about removing system pressure like I did. Maybe I have been mistaking the smell of gas as coolant on startup.

any input on the new update is highly appreciated

I congratulate you on a very perceptive diagnostic procedure! I had not seen the previous post by the member that recommended relieving the pressure, or I would have congratulated him as well. Now, I would do this if it were my car. I would do that (relieve the pressure after a run) for a few days, maybe a week, then I would rent the block tester kit as KHE says. This delay will allow CO to build in the cooling system to a detectable level. Let's face it, you should have NO CO in your coolant on a tight engine. If any is then detected after that time, you will have a decision to make as to whether to repair the engine or replace the car. At this point I would call your issue more of a headgasket "seep" which would explain the lack of major symtoms normally associated with HG failure.