Errrrc Posted August 6, 2016 Share Posted August 6, 2016 I have a 95 ej22 conversion in a volkswagen. It had been running fine and i can't quite remember when it started but when the engine comes up to temp it'll idle down to about 850 then Rev up to around 2k then slowly die down to 850 then back down. Ive been told it should idle at 750 and i can tweak the throttle to idle steady just undwr 1000 but thats just masking the problem. I replaced the iacv with a tested used part. Twice. Nothing. I have a small vacuum leak at my brake booster but I have plugged it at the engine with no change. Tested the tps and the signal voltage is in the range it should be according to FSM. I've yet to pull the timing cover to see if I skipped a tooth but it runs like a dream when it's not idling so I think the timing is fine. Unplugging tps makes it idle high yet steady. Unplugging iacv same thing. Unplugging maf makes it stall and knock sensor makes it slightly less intense but it still hunts. I occasionally get the code p0106 manifold pressure absolute but the solenoid seems to be in working order. When I unplug the o2 sensor I don't get a code which is weird. The sensor in the cat is the one that came with the car the one before the cat is aftermarket. I'm at a loss here except I think the ecu thinks it's going to stall so it revs up to compensate but I can't figure out what is actually causing it. Quote Link to comment Share on other sites More sharing options...
Natedoc808 Posted August 6, 2016 Share Posted August 6, 2016 Clean MAF? No misfire code? MAP sensor good? Is the IACV housing clean/clear? Quote Link to comment Share on other sites More sharing options...
Errrrc Posted August 6, 2016 Author Share Posted August 6, 2016 I got a misfire code once but it went away when I replaced plugs and wires. I have been getting map sensor code. Iacv is in great condition new gasket cleaned with deform etc.. I'll try and test out the map sensor or perhaps try a new one but I've never heard of them going bad so not sure if that's the problem. Any insight as to why I get no o2 sensor code when disconnecting o2 sensor? Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted August 6, 2016 Share Posted August 6, 2016 What do you mean by "tweak the throttle"? Have you adjusted the throttle stop screw on the throttle body? That's a big no-no. If its a 95 are you running OBD1 or OBD2? Quote Link to comment Share on other sites More sharing options...
Errrrc Posted August 6, 2016 Author Share Posted August 6, 2016 I've adjusted the nut on the throttle cable and it's obd2 Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted August 6, 2016 Share Posted August 6, 2016 Ok, can't do that either. Throttle cable has to have some slack in it. If the throttle plate is held open the airflow through the throttle body will not be correct for the ECU to set and maintain idle speed. It can also push the TPS signal out of range. Loosen the cable and make sure the throttle plate closes all the way. There should be about 1/8" of slack in the cable. Also be sure the cruise control cable has slack as well if you have cruise installed. After that use a voltmeter to check voltage on the center wire of the TPS. Use a paper clip to back-probe the connector. Voltage should be 0.50-0.55v. If voltage is out of range loosen the screws on the TPS and adjust slightly until the voltage is within that range. After that, disconnect the battery negative for a few minutes to reset the ECU. Reconnect the battery and start the engine, DO NOT use the throttle to control idle speed. Let the ECU control idle and make its own adjustments. If the engine stalls simply turn the key off and restart. Let the engine warm up to normal operating temp. If you still have an idle problem after this, its due to either a vacuum leak, or some other sensor being out of range. Quote Link to comment Share on other sites More sharing options...
Errrrc Posted August 6, 2016 Author Share Posted August 6, 2016 Adjusted throttle cable as per your instructions. Check and double checked for vacuum leaks. I did find a hose on the map switch off but not sure how long it had been off. Also having trouble finding an accurate comprehend able vacuum diagram for my particular year and motor but I'm pretty sure it's hooked up. My only other thought is maybe I need to let the speed sensor register by driving it a bit. I'm hesitant to pulp my timing covers since my heat shield bolts onto it and I have to pull my whole exhaust to get at it but that might be the next logical step considering it was running fine then at some point after a 500 mile trip it started doing this. Does it sound like it might be a timing issue? Quote Link to comment Share on other sites More sharing options...
Natedoc808 Posted August 7, 2016 Share Posted August 7, 2016 Fairtax has it pretty nailed down per how to make sure you aren't giving yourself a false positive due to improperly adjusted cables. If you are concerned about timing to that degree I would break out the timing light (you have a VW so you have plenty of experience with one of these) and double check it as it is simple enough. Timing is rarely an issue with these more modern engines compared to what your twinkie was running before so try not to want to go there as soon as there is rough running; i use dto drive a 64 dart so I know the urge. THis is more likely an air/fuel mixture issue from the sound of it. Plus with regard to timing, remember that spark advance is determined by the ECM and not a distributor so unless you skipped a notch then if the timing is off it's due to compensation by the ECM for inaccurate input from the sensors (MAF, MAP, TPS, CPS, etc). Quote Link to comment Share on other sites More sharing options...
Errrrc Posted August 9, 2016 Author Share Posted August 9, 2016 Do you think that the fact that when I pull my o2 sensor it doesn't throw and o2 sensor code is indicitive that maybe my o2 sensors are junk? Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted August 9, 2016 Share Posted August 9, 2016 No, the computer wont set a code for an O2 sensor right away. Seems odd, but that's just how they're programmed on the early OBD2 cars. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.