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Old 04-08-2004, 08:31 AM   #1
powerlabs
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Default Car stalls in idle, won't go over 4000RPM, can someone help?

Hi guys, hope someone here has had a similar problem and can help me out...
I was driving up a steep road yesterday during a storm and hit a *major* bump that I didn't see. I hit it hard enough that my radar detector flew off the windshield. Then as I was parking the car I noticed that every time the engine idled (when in neutral, pushing the clutch in, etc) it would run very rough (500RPM range) and stall. It also won't go over 4000RPM when I give it gas. I searched through the forums and saw that people have experienced this from blown MAFs (this is a 1999 Impreza 2.5RS) and blown O2 sensors. My MAF was replaced during the recall and I get readings from it through my S-AFC, so I don't *think* that is the problem. Also, no CEL yet. Any ideas what it could be? O2 sensor? Something else? Could the bump have damaged something (I looked under the car and it looks OK except for some major scratches under my front bumper)? The car now runs okayish (some minor bogging at times) when I give it gas up to 4000RPM, then it hits fuel cut (its in "limp mode", I presume).
For what its worth, mods are: borla headers and catback, UR pulley, Rallitek "J" tube intake, S-AFC. I also have recently opened up the vent covers on the hood.
I really hope someone can help me with this; I need to drive to Chicago this weekend (a 600 mile drive) and I don't think I can make it with the car running like this.
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Old 04-08-2004, 09:05 AM   #2
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seems like you should get a CEL? hmmm...

OK, if the MAF is unplugged on a working car I think the ECU WILL go in limp mode. So you could try unplugging yours and if there is NO difference - probably the MAF.

Also, you could try resetting your ECU.

Don't overlook the possibility of timing belt being off 1 or 2 teeth - not likely but maybe just coincidental with the bump you took.

let us know what you find out OK?
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Old 04-08-2004, 11:08 AM   #3
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GOod luck and let me know what you find out please. I'm having the SAME exact problem but I never hit a bump. I do believe it has something to do with your Mass Air Flow Sensor. You may have damaged it and now you're in limp mode. I have yet to find a sensor that works properly, so I can't tell if that is, in fact, the problem.

I've heard that it can be caused by a bad Camshaft Positioning Sensor or a Crankshaft Sensor...but I've replaced both of these and it's not the problem either.

I Definitely think you have to replace you MAF sensor. It's probably not unplugged, and if you unplug it entirely, your car will stall out a lot. I first started having the Rev Limiter / limp mode problem when I took my car for a diagnostic at a dealer and the plugged in my MAF sensor (I didn't know it was unplugged, but the car was okay). SInce then I've had the problem, but haven't taken the cash to replace the MAF.

//marcus
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Old 04-08-2004, 12:27 PM   #4
powerlabs
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I agree it definitely sounds like a MAF, but as far as I know when those go bad they throw a CEL and also as I said I can read the voltage from my MAF through the S-AFC and it looks normal... I think it may be the O2 sensor since those supposedly don't give a CEL (am I right here?) when they go bad...
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Old 04-08-2004, 10:14 PM   #5
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Did you examine the car underneath really well? maybe you dented the cat and now it's acting like a clogged cat?
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Old 04-09-2004, 01:48 AM   #6
marcus12
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1 Lucky Texan could be right there...I went to have my heat shield welded (had some rattle spots) and the guy said my cat may need to be replaced...

Cat stinks too...could be clogged, etc...


//marcus
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Old 04-09-2004, 08:45 AM   #7
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I went to drive the car today and it seems normal... Accelerates to redline, idles at 700RPM +-30RPM when warm... Today I have to drive 600 miles with it and I'm worried that the problem will return... Crap! Any ideas why it would have acted up like that and got back to normal?
Thanks for all the replies so far BTW I looked under the car and it looks like the only thing that was hit was the tow hook.
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Old 04-09-2004, 10:46 AM   #8
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maybe the cat "coughed up its hairball?"

I'm looking for a new cat since I think mine's rotten...

glad to hear it's back to "normal"

//marcus
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Old 04-09-2004, 11:34 AM   #9
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I bet that your air filter became waterlogged and when you pushed the motor harder it was sucking too much water through the filter and was choking your motor.

It fits with the facts that you were in a major storm, and removed the vent covers allowing lots of water to hit your filter and that now your car is running fine. If this is what happened and nothing happened at the time your motor should be fine. I have my right vent cover removed to feed my cold air box setup and actually experienced something like this during an extremely wet snow storm we had. I took the filter off, dried and my car was normal again. I will be getting a MRT side scoop vent soon so that it covers the vent vertically but still allows water in. After that I want to do a reverse scoop for the main hood vent.
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Old 04-09-2004, 04:03 PM   #10
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Interesting theory. I thought about it, but I figured it'd take *way* too much water to do that, plus the filter is oil soaked...
But if it happens again we'll know. I will keep you all posted
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Old 04-12-2004, 05:50 PM   #11
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Default Mystery solved!

Compressed was right; the car was running fine, drove 800 miles with it this weekend without any problems at all. Then went into a car wash. After the wash the car threw a CEL, hesitated, bogged down and stalled. I had to remove the filter (which was soaked) to be able to drive home. I guess removing the vent covers was not such a great idea after all
Now this makes me wonder; wouldn't a CAI such as INJEN have the exact same problem every time you drove through rain???
Thanks for all the help! I also seem to be having a big problem with my shifter... Since you guys are so knowledgeable, coul someone take a look at my post and shed some light as to what might be wrong? The post is at http://forums.nasioc.com/forums/show...hreadid=538749
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Old 04-13-2004, 01:05 PM   #12
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Yeah, it sure sounded like that is what happened to you. At least you know what caused it now. I'm looking to get the MRT vent scoop to avoid this issue but still get some air for the intake.

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Old 04-14-2004, 11:53 AM   #13
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Check all your vaccum hoses on the air intake, in case one slipped off a little.
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Old 04-14-2004, 12:26 PM   #14
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Quote:
Originally posted by maciek
Check all your vaccum hoses on the air intake, in case one slipped off a little.
Did you miss the post where he was able to pinpoint the cause?
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