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Discussion Starter · #1 ·
Alright guys so its been a hell of a time ever since I got my motor back together my car has had a really rough idle and I just thought it was because of the cams so I adjusted the idle up a bit to 1200rpm at idle it was very happy there for a few days after I got the car back together. An then a few days later at cold start it would wanna stall and not stay running on a cold start or at a idle when I would come to a redlight. So I did some research and came to the conclusion that my MAF sensor was bad so I did a little test and unplugged the MAF car started right up no hesitation you plug the MAF in the car would immediately run rough and proceed to stall. So moving forward to today I got a new MAF sensor same exact problem the car runs like crap with it plugged in and wont stay running but the minute I unplug it it will run just fine. I am completely stumped at this point I've spent a fair amount of timing scratching my head looking for any possible reason and I just cant seem to figure this out... Anyone have any help or words of wisdom??
 

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Hmm, that's usually a good sign of a intake leak. How did you check? I typically spray ether around and see if the idle changes.

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Discussion Starter · #6 ·
I've checked several times I've sprayed around with carb cleaner to see if there would be a change in idle and nothing.. I've gone over all the vacuum lines a million times everything seems super secure.. All the vacuum lines are brand new. I've checked the FMIC couplers a million times I just don't see what it could be because everything about this motor is brand new its a fully built motor that was down for 6 months and carefully put back together.. When it is idling it isn't pulling vacuum it is sitting at 0 on the boost gauge. which would indicate a huge vacuum leak but I've checked EVERYTHING. When I have the MAF unplugged it idles happy and pulls a solid vacuum of -6/-7 on the boost gauge :confused:
 

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I'm thinking. I had a leak I didn't detect at the turbo inlet, and again at the tgv valves. Do you have a stock inlet?

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Discussion Starter · #8 ·
No I just bought a brand new Forced Performance 84mm turbo inlet. The only thing I'm still considering that might be not hooked up proper is my EWG hoses. I have a cobb 3 port and went on their website and followed their EWG diagram.
 

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Discussion Starter · #9 ·
I find it weird that it wont pull any vacuum when the MAF is plugged in, but when the MAF is unplugged it pulls a normal vacuum. I know its not a bad MAF cuz I just bought a brand new one today plugged it in with the same results as the old one.
 

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I've checked several times for leaks and everything looks perfect as far as leaks..

Did you pressurize the entire system to about 20psi and it held pressure with no hissing noises?


What to your fuel trims look like?

What injectors are you running? It's a long shot, but I had a similar issue and it turned out one (or more) of the injectors I had (Dontwerks 1300s) was bad.. I went through four sets of those injectors and never got a full working set. It would run alright with an ECU reset, but if you tried to add more fuel in the tune it would just get leaner, and since it was lean to begin with, as soon as it started to learn the fuel trims and try to richen it up it would get more and more lean until the trims were maxed out and it ran like crap. If I unplugged the front O2 sensor after a fresh reset (disabling learning) it would stay drivable.
 

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Alright guys so its been a hell of a time ever since I got my motor back together my car has had a really rough idle and I just thought it was because of the cams so I adjusted the idle up a bit to 1200rpm at idle it was very happy there for a few days after I got the car back together. An then a few days later at cold start it would wanna stall and not stay running on a cold start or at a idle when I would come to a redlight. So I did some research and came to the conclusion that my MAF sensor was bad so I did a little test and unplugged the MAF car started right up no hesitation you plug the MAF in the car would immediately run rough and proceed to stall. So moving forward to today I got a new MAF sensor same exact problem the car runs like crap with it plugged in and wont stay running but the minute I unplug it it will run just fine. I am completely stumped at this point I've spent a fair amount of timing scratching my head looking for any possible reason and I just cant seem to figure this out... Anyone have any help or words of wisdom??
ive definitely had to deal with the MAF sensor before. From what I've seen the MAF sensor will get dirty and it will read wrong so the car runs too rich and stalls out. Have someone stand behind the car when starting and if it pours black smoke it's most likely the MAF. The connector for the MAF sensor on the intake could be bad. Some aftermarket intakes have plug connectors that get dirty as well causing false MAF readings. What intake do you have? It seems You just have to find where the connection is bad at.
 
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