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Rough idle AND weird acceleration

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88BB8B

Proven Member
179
18
Oct 14, 2016
Coldstream, BC_Canada
Hey guys. My car is having some really weird symptoms, I can't find anybody with the exact same problem. A bit ago the car started to idle kinda rough, but it didn't really bother me, and it ran fine when throttle was applied. More recently a new issue which I think is related has started. When I press the throttle gently to accelerate, the car feels like its being held back. It will build boost, but run really poorly, sputtering and whatnot, and it will hardly accelerate, until a certain threshold, then it "kicks" and begins accelerating like it should and running like it should. This only happens under light throttle, WOT the thing goes normally. It is gradually getting worse, and i'm starting to get worried. It's difficult to cruise through town. I have to give it blips of WOT for it to "kick" and run properly as I accelerate from a light.

My ideas are that it could be, for some reason, running with very retarded timing when this happens. I have also heard of similar issues, and it seemed to be fixed by changing the injectors and fuel pump, but those were also associated with a rich running condition, which I cannot verify in my case. Please help, fuel, timing and engine management are not my forte with these cars.
 
I second that boost leak test. I recently just got my 2g together it wouldn’t hold an idle(would die) and turned out to be a big leak from Intake mani to head gap due to a washer I forgot about.
 
Save yourself a lot of time and a major headache by first doing a fuel pressure test as to rule out fueling as your issue but from experience your car runs like it has a problem with low fuel pressure and yes timing would be pulled as the computer senses knock so yes the timing would be retarded and yes the response would be lazy not to mention sense there is an absence of the proper fueling mixture you car is running dangerous lean and yes knock would be present effectively pulling timing and pulling power out of it. Lack of fuel definately doesn't make your car run rich. Hook up the fuel pressure gauge and verify against the specs for your vehicle at least anywhere from 35psi to as high as-50psi at idle depending on the manufacter specs with the vacuum source disconnected and connected is the most common testing procedure used diagnose the condition of the pump itself which with the symptoms you're describing I believe to be the source of your issues. Even with a boost leak or leaks the car would still be super super rich as the is more fuel present then air to atomize said amount of fuel therefore causing the hesitation and stumbling condition experienced when this condition occurs.
 
It isn't a boost leak. It has gotten better over the last day or two, and it isn't an all the time thing, only a sometimes thing, and it NEVER happens under full boost or full throttle. Only under light throttle up to 11PSI max. I just can't see that being a boost leak.

I will check the fuel pressure, that's definitely a good idea. If it isn't the fuel pump, then would injectors be a good place to go next?
 
I've ordered a fuel pressure gauge. I'll know more when it arrives. I also did something risky and unplugged the knock sensor (only for a 3 minute drive) it didn't change the problem at all. Which makes me think the car is just running pig rich.

Any ideas on what could cause it to intermittently run super rich?

Could a single stuck open injector cause these snyptoms? Or a bad MAF? Or a bad O2 sensor maybe?
 
It appears it was the knock sensor. Or rather the connector. I unplugged it, then plugged it back in and now it runs perfectly. I didn't know a fault knock sensor connection would cause it to run so rich.
 
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