Hard Misfire

[Mullet Bullet]

ok, car has sat for about a week while parts were on order to replace the oil pan gasket and p/s hose leaks. fired it up this morning and moved it in the driveway so i could work on it.

replaced the pan gasket and buttoned it all back up. started the car to let it warm up so i could drive it on some errands i had to run. fired up and idled for about 2 minutes then stalled and wouldn't restart.

left it at home for a few hours. went out just now and it fired right up and idles strong. i can rev it up if i ease into the the throttle but if you stab it is stumbled and misfires very hard.

car ran perfect for the last few months that ive had it until now. any idea's?

[Jaxx_]

are you sure you didn't touch anything else?

where was it sitting while you were waiting for parts? (i might be useful for diagnosis if something has failed because of environment)

[Mullet Bullet]

only things that were disconnected were the ground wire and the oil level sensor. both are still connected.

car sat outside just like it always does in my driveway. weather has been near freezing for a few weeks now.

[jlevie]

left it at home for a few hours. went out just now and it fired right up and idles strong. i can rev it up if i ease into the the throttle but if you stab it is stumbled and misfires very hard.

That is almost always caused by intake leaks. Replacing the pan gasket means disturbing the engine in some way, which can result in intake leaks.

Have a shop do a smoke test on the intake and repair as indicated.

[Mullet Bullet]

But with a vacuum leak the idle would also be higher were it's still rock solid were it's always been.

[jlevie]

Not necessarily. That depends on the size of the leak and the condition of the ICV.

Other causes are possible, but until it is certain that there are no intake leaks it is pointless to investigate those.

[Mullet Bullet]

the only vacuum leak that could be there would be from the oil pan gasket. im going to crawl under the car tomorrow and check the gasket to make sure its in the proper place all the way around.

its just odd, ive never seen a vacuum leak cause a misfire under no load. but i will check it out.

[Kershaw]

if it's big enough, it can definitely cause a misfire.

[Mullet Bullet]

huh i am going to get under the car tomorrow and check it out. but if thats the case its kinda funny since the old pan gasket was literally falling out and half the pan bolts were not even finger tight but the car ran fine before lol.

we shall see what ends up tomorrow.

[Mullet Bullet]

finished redoing the oil pan gasket, misfire is still there. fire the car up and it idle's fine, drove it down the street and it started missing hard again with more then 25% throttle or so. parked it and left it idling and went to put the tools away in the garage. started missing at idle then stalled. now it won't restart again.

ive got a spare DME that i will toss in later but i have a feeling its fuel delivery. i think the original fuel pump with 215K on it is finally kicking the bucket.

just went and did a stop test and it came back 1444

[Jaxx_]

i dont know the stomp test 1444 or any others...


but are you getting spark? throw some starter fluid there if you are and see if it fires.

[Mullet Bullet]

it will fire right up as long as its cold, once the car starts to warm up it won't run for shit. it does have a new coolant temp sensor.

[Jaxx_]

it will fire right up as long as its cold, once the car starts to warm up it won't run for shit. it does have a new coolant temp sensor.

open the hood and see if it fixes the problem.

you might have a bad ignition coil that is getting heat soaked or something.

if having the hood open DOES seem to help (whether it takes longer or never happens at all) then you need to start heat soaking components BEFORE you start the motor to see what causes it to run shitty.


edit: and what I mean by opening the hood is leave the hood open when you cold start it and time how long it takes for it to start running shitty. if it takes longer for the symptoms to appear as compared to the usual hood closed scenario, this is a clue.

[Mullet Bullet]

I understand what you mean by heat soak, I will give that a try. But honestly the car won't stay running long enough to even get the hood warm to the touch, mind you it's been in the low to mid 30's for that few weeks

[Jaxx_]

I understand what you mean by heat soak, I will give that a try. But honestly the car won't stay running long enough to even get the hood warm to the touch, mind you it's been in the low to mid 30's for that few weeks

well, if this test doesn't yield anything it's probably related to fuel.

I had a hard time thinking that your oil pan gasket would cause this.