1SIKAP1

So my mech did a compression test on my 2000 s2k with 189k mi on the engine, im having missfire with no codes on idle only, he also swapped my plugs. the results are 195/185/185/180 on a cold engine. he said the plug on cylinder 1 look the worst assuming that none look pretty good with that comment. Im gonna put my car on a dyno and tune it with a vafc2 to fix the running rich issue associated with ap1's, he said I might need to rebuild the cylinder heads. no sure what to do from this point, coils? rebuild head? should i waste my money on a tune? i already have a vafc2 w/harness? your thoughts are apreciated.

s2000maniac

According to billman, mis fire at idle is caused by burnt exhaust/intake valve. Have the mechanic do a leak down test.

BUT my buddy was having the same issue and the problem was dirty/bad fuel injectors.

1SIKAP1

Yea my mech also noted it could be bad injectors, I use lucas inj cleaner regularly and it seems to help? If it is the exhaust valves how hard is that to fix?

boyguan

Numbers low but look good. Check for something else

steven975

The numbers are consistent, and it is a cold engine.

1SIKAP1

I was very happy with the compression numbers after 189k, missfire is probably 90% gone after new plugs,small missfire randomly at idle,im gonna send my injectors to get clean and if that doesnt help probably save up for a head rebuild, i,ve cleaned the iacv, replaced the map sensor twice and cleaned the throttle body, air pump seems to be working fine, another clue is that when the air pump is on the engine doesnt missfire, once it turns off it would start, its very weird to me. Thanks for the feed back fellas, please keep the ideas coming for i am no mechanic and need all the help i can get.

MR.T

you're supposed to test compression with a warm motor, though your numbers do look great as far as consistency. having the injectors cleaned is probably not a bad idea, but i think you're just throwing money at it. before you go through all that trouble, and definitely before you get a new head, do as already suggested and get a leak down test done. this will show and hopefully pinpoint problems with the head..

do us a favor and get the dtc's from your mechanic and post them. is it a cylinder specific misfire?? has the car ever been over revved? it's an easy job to pull the valve cover and check for cracked retainers.


edit: sorry, didn't see where it said "no codes" if you have any s2k buddies you could try stealing a set of coil packs to swap out.

1SIKAP1

Actually some codes came up about 16 mo ago and never came back, it was cylinder 2 misfire, mult misfire, and random misfire

MR.T

If it were me I'd

1. bum a set of coil packs from someone, or buy used if you can Get'em cheap enough.

2. Pull the valve cover and check for cracked retainers.

3. Then do a leak down test since it involved pulling the vc anyways.

At least that's the order I would go, those will cover most of the foundation of basic misfire diagnostics.


I don't know a thing about the vafc, so if someone does maybe they can chime in. I would highly suspect something with that if everything else checks out ok.

1SIKAP1

Billman please chime in.Update!!... So I took it to raceline to get the vafc2 tuned, when he starts to play with the settings he notices the missfire, he starts messing with the settings and tells me to notice that when he adjusts a certain setting on the vafc the misfiring stops, I asked which setting it was and he said he was messing with the fuel setting, when it was at +40 missfire would go away and but very very slowly start coming back, almost non existent. Then he would put it back to zero and it started misfiring like crazy, he said I needed to rebuild my head, and not to tune till I fixed my head, he quoted me 1100 including parts. Could it be my ecu?? Or is it the head??... Help!?!