strange misfire

[bis_1315m]

Alright this is driving me crazy so for a while now my car has had a little cough at low rpms or when I enter boost but nothing super bad I tried to find the cause but couldn't so I just let it be so about a month or two later I noticed it slowly got worst to the point that it takes me like 1min to reach highway speeds sputtering the whole way.

So first thing I did was do a boost leak test but found nothing except air was coming out of my dipstick and so was oil and a pretty good bit to.

Next I checked electrical connections found nothing, no engine codes or nothing.

Next I checked spark plugs and one had a crack in the insulator so bought new ones and still the drives horrible so I decide to check the spark plug wires they were pretty worn and there resistances were off so I bought new ones and still did not solve the problem.

So I had an extra set of coils laying around and an extra afm so installed both. Still didn't help at all.

So I brought out my ohm meter and started testing every electronic component and everything checked from what I know. I checked coils, ignitor, afm.

So then did a compression test and this is what I got,
135, 130, 125, 140, 150, 152 so are these real low and could this be the problem.

Oh and my mods are fmic,2.5 in piping, hks bov, 60-1ct 6lbs of boost, walbro 12v mod, intake and that's it.

So any help or suggestions would be greatly appreciated.

Thanks
Michael

 

[xzeror]

if im not mistaken there was something like your compression shouldnt vary more than 15 in each cylinder? correct me if im wrong :s

 

[gaboonviper85]

You did a boost leak test wrong...(didn't unhook the pcv) could have blew out your oil seals and cause a huge headache

 

[bis_1315m]

Damn really I blocked the PCV goin to the intake pipe but not the throttle body.

So that's wrong right.

Thanks

---------- Post added at 09:35 PM ---------- Previous post was at 09:29 PM ----------

Oh and when you say oil seal do you mean the rear main seal or what

 

[Supraflymk3]

test your o2 sensor

 

[gaboonviper85]

because you didn't block the throttle port you just pumped compressed air into the block which can push out you rear main, front main, oil pump shaft, and cam seals...

Not a smart move but an honest mistake.

 

[Fubar231]

because you didn't block the throttle port you just pumped compressed air into the block which can push out you rear main, front main, oil pump shaft, and cam seals...

Not a smart move but an honest mistake.

if you pop the oil cap your fine. youll hear a deep wooshing out of it but its real noticable difference between that and a boost leak

 

[bis_1315m]

Alright ill try another boost leak test today.

But if I do not find the problem what should I check next.

Thanks
Michael

 

[suprasixteen]

idk if you fixed the problem but i think that because it took so long to develop that it is probably something mechicanal like an injector clogging or something along those lines

 

[metaphysico]

Compressions varying that much could be the cause of the problem. If it does it at idle try to kill one cylinder at a time to see if you can fine which one is doing it, pull the wires from the coils one at a time using pliers that are grounded so you dont shock the piss out of yourself. If you have a miss and when you pull each wire all of them make a difference to performance then you dont have a dead cyl just one or some that are under performing. If you pull off one that has say 150 psi and it has a larger effect on the engine than pulling one that was at say 130 then you know the cyl at 130 is not pulling its weight and time to find out what is making low compression.

Also DTC is industry standard for automotive most of us say it without thinking about it.

 

[keshigomu]

hm i have a similar problem. have u checked your timing or vaccum?

 

[Nick M]

hm i have a similar problem. have u checked your timing or vaccum?

He has a mechanical problem with his engine. A retest of compession and a vacuum test would do him some good. I wouldn't be suprsised if he had a huge vacuum leak like you suggest, saw it, put the hose back, and now drives ok to him. So he hasn't been back. That wouldn't suprise me.

test your o2 sensor

Irrelevant. It will make your cat not work as well, and can deteriorate steady cruise MPG. That is it.