EJ22 misfire when shutting down

[fnlyfnd]

It's a 1996 2.2L. Here is the list of new parts in the past 2 months:

 

Exhaust (almost all, except the cats and o2 sensors, but no leaks anywhere)

Ignition coil

Spark plugs (today)

Timing was reset

Motor mounts

transmission mount

PCV valve and connecting hoses all cleaned

IAC cleaned

MAF cleaned

Axles and stuff, but this is unrelated

 

The timing has been off for a little while, but just discovered and fixed today! I was throwing a code for cylinder 1 + 3 misfires. The car now runs great and doesn't have the constant misfire it used too. It is a non-interference engine. When I replaced the spark plugs, the 2 that were misfiring were pretty black. When I peaked into those two cylinders they also looked pretty black.

 

I can hear the car misfire through the exhaust when I come down to idle from decelerating. Usually happens around 1,000rpm or so. The idle then smoothes out and I don't hear it misfire.

 

Also, the car will misfire badly when I turn the engine off. I will be at idle (of course) and then turn it off. It misfires loudly until total shut down.

 

What do you guys think?

 

I am going to run seafoam through the top of the engine and the gas tank tomorrow morning.....

[fnlyfnd]

Here is some interesting observations based on today.

I'll explain:

 

Sitting in my driveway, the car is in neutral

I hit the gas and bring it up to 3k or more

Let off the gas

**Engine seems to stumble right around 1,500rpm. I hear what sounds to be a misfire through the exhaust.**

Car hits idle and transition is smooth

Shut down the car and it misfires/stumbles which can be felt and heard through the exhaust easily

 

Could it be an exhaust leak pre-cat that is causing the stumble/misfire?

I'm pretty sure I have one based on the seafoam smoke

 

Seafoam of the day:

 

I added about 2/3 of a can of Seafoam through the pcv today. Follow procedure; I've done this a few times with other cars.

I turn the key off and the engine kept running for ~4seconds.

Why?

[johnceggleston]

are these mis - fires or back fires?

 

in the old days, backfires could be caused by a timing/ distributor problem or an exhaust leak. with the computer controlling the spark these days i think the timing being off COULD cause back fires. maybe leaks too. back fires a pretty rare on computer controlled engines.

 

i would recheck the timing marks.

 

if the car is idling, do you hear any exhaust leaks when you use a rag to plug the tail pipe?

 

isn't there a dollar bill trick at the tail pipe you can use to check for burn exhaust valves or something like that?

[Ricearu]

he may be associating gurgle pops in the exhaust.when my car pops in the exhaust i get giddy and downshift and engine brake to make it do it more! mmmmmmmaaaaaaaaaaaaaaaaaa-pa pa pa aaaaa paaaaa paaa:)

Edited June 29, 2011 by Ricearu

[BigMattyD]

It sounds like the engine is "dieseling" or continuing to run after shutoff due to hot spots in the combustion chamber, probably from the excessive carbon buildup in those 2 cylinders. That is why it would keep running for 4 seconds after you shut the engine off while the seafoam is in there. In this case, the seafoam is acting as fuel, and being ignited by the hot spots in the chamber till either the hot spots cool down, or the seafoam runs out.

 

Anyway, that's my thought.

[Rpm90001]

I agree on the dieseling, that's the only way it will run after the car is shut down. Sounds like carbon build up that is staying red hot acting as a spark plug. once the carbon is cleaned up that problem should go away. Make sure to do the full treatment of sea foam and follow the directions, you need to remove the carbon deposits. Just my opinion..