: 2000 Deville Misfire



postman2000
01-31-11, 04:37 PM
I am posting this here because i cannot fogure out how to start a new post..does anyone know what could cause a 2000 deville to misfire on cylinders 3 and 4 at the same time.. got a code p0300.. checked with my snap on scanner and found 3 and 4 misfiring..they do not share the same coil pack.. so its a mystery to me.. Also it does not do it all the time..sometimes it will run ok..then the check engine light starts blinking and it runs like crap.. thanks....Charlie

Submariner409
01-31-11, 07:00 PM
I am posting this here because i cannot fogure out how to start a new post..does anyone know what could cause a 2000 deville to misfire on cylinders 3 and 4 at the same time.. got a code p0300.. checked with my snap on scanner and found 3 and 4 misfiring..they do not share the same coil pack.. so its a mystery to me.. Also it does not do it all the time..sometimes it will run ok..then the check engine light starts blinking and it runs like crap.. thanks....Charlie

To start a new thread go back to the main Northstar Performance page and click on the tab "New Thread".

Misfires can be caused, on our 2000+ engines, by bad coil cassettes, bad ICM (identical for left and right, in the coil cassette leg), bad plugs, carbon tracked plug boots.

Please ask a Moderator to move this - it will only serve to hijack the OP's thread.

97EldoCoupe
01-31-11, 07:34 PM
As Sub said, that could be two coil cassettes in need of replacement, a plug, (boots are not too likely but it does happen, or fuel injectors. If you need injectors I have plenty of new OEM ones.

postman2000
01-31-11, 08:00 PM
Hey Jake, how are ya? How is everyone else too... Hey i have some other info about the problem.. It appears that these cylinders only misfire after car has sat for an hour or so or more. It will misfire until car warms up and then goes away.. I replaced the front coil cassette in december 2009, so i dont think that the coil is the problem..And it would be weird for both to go at the same exact time.. How hard of a job is it to do the injectors on this car? I was thinking maybe an intake manifold gasket, but i think these motors have individual gaskets..not sure of that though.. Any insight from fellow forum members would be of great help and much appreciated.. I thank you guys for all of your knowledge and time.. Tomorrows my birthday..I should have known something was gonna happen.. when my ignition coil went it was on christmas eve.. I dont think my car likes me very much..lol.. Thanks...Charlie

Submariner409
01-31-11, 08:29 PM
I DO NOT like the statement: "only misfire after the car has sat for an hour or so......."

Gotta ask this - Is the engine losing coolant but no leak is apparent ??

postman2000
01-31-11, 09:05 PM
Hey Sub, The Engine does lose coolant..but i know where that leak is.. i was thinking about that dreaded thing myself.. But i had the headgaskets done in 07/09.. So i am leaning in a different direction... just hope i figure this out soon.. I have spent alot of money repairing this car since i had it...just hoping i can catch a break on this one...Charlie

97EldoCoupe
01-31-11, 10:03 PM
Hey Charlie happy birthday my friend :) :thumbsup: -

We will get to the root of this and I am still expecting a visit from you someday-

Ok now be careful if you have leaking injectors (have seen quite a few 00+ fail) and they fill a cylinder full of fuel, the engine will be toast the next time you go to start it up. A misfire after you shut the car down and leave it for a while - injector leaks off slowly, drains the fuel rail, the cylinder has a problem trying to burn off all this extra fuel.

Best and easiest way to test injector leakdown? Raise the fuel rail off the intake, leave all injectors in the rail, have someone turn the key to "run" to pressurize the rail. Watch for any injectors that are dripping fuel, even if very little.

I have seen a few engines destroyed by leaking injectors. The trick is to catch it ahead of time; and it seems as though you are. If you want a really good deal on 8 brand new, give me a call tomorrow. I don't know how many I have here in Ontario but I will check as soon as Ponyboyt's 99 is back in his hands. Replace them all and be done with it.

I'm not going to say for sure it's your injectors but from what you're telling me; without being there in person; I'm going to take an educated guess and say betcha that's your problem.

Ranger
01-31-11, 11:09 PM
Post moved to New Thread and cleaned up to view as new thread.

Submariner409
02-01-11, 08:58 AM
Hey Sub, The Engine does lose coolant..but i know where that leak is.. i was thinking about that dreaded thing myself.. But i had the headgaskets done in 07/09.. So i am leaning in a different direction... just hope i figure this out soon.. I have spent alot of money repairing this car since i had it...just hoping i can catch a break on this one...Charlie

OK - Now start looking for fuel leaks - injectors, pressure regulator, (and this is a stretch) fuel pressure itself - if the fuel pump is weak that can cause some weird hard-start conditions.

postman2000
02-01-11, 03:56 PM
Thanks everyone, I will start by checking the fuel pressure and then maybe swap out the regulator.. go from there...

Ranger
02-01-11, 09:13 PM
Don't throw parts at it. Pull the vacuum line off the FPR at idle. If there is no gas leaking from the nipple, it's good. If it ain't broke, don't fix it.

postman2000
02-05-11, 01:11 AM
Very weird, car has not misfired since that day. I have been waiting for it to happen again. But its been a few days and no misfire... rather strange.. Hey Sub, i heard 2 million fish died over in maryland.. Do the locals think its natural causes like the media is saying?

Submariner409
02-05-11, 10:58 AM
Very weird, car has not misfired since that day. I have been waiting for it to happen again. But its been a few days and no misfire... rather strange.. Hey Sub, i heard 2 million fish died over in maryland.. Do the locals think its natural causes like the media is saying?

Hmmmmmmmm.....................Haven't had the TV on for days - need to take a look.

NHRATA01
02-11-11, 02:19 PM
I'd pull the plugs first, and see what the affected ones look like, ie are they fouled?

My '03 developed a miss, one of the coils on the cassette went bad. Thank you GM for designing the coils into a single $250 cassette instead of $40 individual units...

Ranger
02-11-11, 02:56 PM
I agree, but unfortunately when the engineers design these things I'd bet that cost or ease of replacement parts is not part of they're criteria.

postman2000
02-13-11, 11:25 PM
Yes, I might take out the plugs. The weather is supposed to be a little warmer this week.. The back coil cassette is a little annoying to get out.. You have to remove the A.I.R check valve.. I will get a new gasket for that thing when i take it apart.. I will keep you posted on whats going on...Hasnt misfired in about a week... But i could feel a very slight miss when i rev the engine a little bit...But its nothing like it was doing the other day...

Submariner409
02-14-11, 08:49 AM
rev the engine a little bit..[B]

Not that you got to it, but remember that these critters have a 4,000rpm rev limiter with the stick in N or P.

postman2000
02-14-11, 01:16 PM
Thanks Sub, yes I am aware of the redline.. I was about 2000 rpms...