So, the roommate's WRX is acting up. We're not sure exactly what's going on with it, but it's goofy as all get out. Here are the symptoms. Mind you, it only happens when it's warm/hot outside. Cool nights, the car is fine. It also only acts up after the car warms up. It also only acts up when accelerating in any forward gear. I drove it for about 5 minutes and it immediately started acting up. Anything above 3k RPM, the car gets jerky and stutters. The RPM needle bounces all over the place and the car acts like it wants to stall out. Things we've done/replaced so far. Cleaned MAF changed oil new PCV valve seafoamed the car new spark plugs The problem was before all this was done. My thoughts are it might be something in the turbo. it's an 03 WRX wagon with 86,000 miles on it. Could it be pulling timing? The car is bone stock otherwise. Nothing aftermarket on it. NO CEL. That's what gets me. HELP!
It was those or a flopping cock - take your pick! The rest was in the laundry... And yeah - drove about 350 miles yesterday in the mountains and it was a cool day - raining part of the day, just cool the rest of the day and there was minimal to no problems... There was a little bit of stutter occasionally going around a sharp turn and up the mountain but nothing that made me worry about not making it the rest of the way... On Friday I could barely get above 2000 RPMs before it stuttered extremely badly... There were times where I was wondering if I was going to make it. So so far the guesses are Fuel Pump and Coil Packs - any other ideas? Is there any way to determine which of the two is more likely? Also - can someone explain why it would only affect the car when it was hot? I don't see why the Fuel Pump or Coil Packs would only act up when it was hot... Here's the list of things I've compiled from doing additional research... Possibly bad O2 sensor Possibly bad Crank Sensor Possibly bad Coil Packs Possibly stuck/dirty injector I still need to run Seafoam through the vacuum line into the engine, it's only been through the oil & gas tank... Again - is there any way to figure out which of the above 4 issues it really is? And damn...I really miss the "Fuel + Fire == It runs" engines...*sigh* Thanks guys!
really strange that it wouldn't throw a code, at least a misfire code. I wouldn't think a 20 degree change in ambient air temp would cause a coilpack or fuel issue, but I could be wrong. I think the MAF would be the most affected by temperature fluctuations
Not sure how it would affect things in this case, but on a lot of cars those issues would point to a bad 02 sensor. That would normally throw a check engine light, though. Does the car happen to have EM that causes it to ignore any codes the 02 sensor might be throwing out? Not sure this is a plausible theory... but it's just a thought.
I know I'm going to take some flack for this one, but try the grounding mod on his car. His car does have enough miles on it to where the stock grounds could be corroded, check them. Maybe try swapping MAFs and 02 sensors with another WRX to see if those make a difference. You could even swap coilpacks, those are a pretty easy swap.
Warning: This is left field.... On my '03 S2000 the MAF sensor on top of the intake was coming loose, causing a similar jerking/cutoff feeling over X rpms and at X% trottle. For a while it appeared to be temp related. Swapping MAF's, while logical, didn't work because it was a design flaw of the connectors. Finally figured out you could zip-tie the MAF sensor to the connector. Honda also promptly released a TSB for a new MAF sensor with a built-in zip-tie based off our design! It was a little more intermitant than your's but it was a similar enough symptom that I decided to mention this. Good luck!
I'm leaning towards a possible bad coil pack/s. Find someone with known good coil packs and see if they will let you swap and try that. It's a quick job to swap them out.
i think you might have a vacuum leak. when i put the wrong intake manifold on my old civic(who know 99 and 98 manifolds could be so different on the same engine) it did the same thing, for a while it was cool, but then it seemed all over the place stuttering but still running somehow. if you get some carb cleaner and spray it around where you might think you have a leak and it shuts off thats your leak. with a car with that many miles its a good bet some simple hose has popped off or fallen apart. (but with the problems you have noticed it would be a major piece though) good luck.