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Idle hunting issue
I have been having an issue pop up recently now and then but not consistently. Sometimes my idle will surge from 1000 to 2000 as if I have a disconnected MAP sensor. Other times it will idle high at around 1200-1300. When I step on the clutch the idle drops down to 1000 for a second but then back to 1200-1300.Any other time it idles normall at around 1k.
I've checked for boost leaks and just cleaned my IAC valve last summer so I don't think those are the problem. Is the first butterfly closest to the front of the car in the throttle body suppose to be closed all the way? It seems to be open a little bit in the closed position. *Should mention that I am getting no codes |
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I doubt your secondary throttle (the one for the oem traction control system) is related. This butterfly should be fully open most of the time, except when your traction control system is triggered. |
Yah I've been leaning towards a small boost leak. I had a boost leak awhile ago where one of the accordion style rubber pipes above the turbos was loose but I fixed that.
I had my exhaust from the turbo manifold back removed last year to look at removing the stock cats but didn't do anything with it and just put it back on. I don't think an exhaust leak there would be causing this though. I guess I'll rig up one of those homemade boost leak testers and check my IAC just to be sure. The thing is if I keep my foot steady on the pedal under boost, my boost gauge stays constant and doesn't drop off. *edit: Did another visual inspection today and found a couple hoses with small cracks on the ends of them at the EGCV VSV and a some above the turbos. Going to look at replacing them although they don't seem to be leaking. I give the car a cold start and it idles at around 900 which is good, but after it warms up the idle goes up to 1100-1200. I take it for a drive to test my boost pressures and am getting around 8 psi from turbo1 until turbo2 kicks in at 4000 RPM and my boost pressure goes up to 14 psi. I did add some fuel injection cleaner last time I got gas but that wouldn't increase my idle 200 RPM would it? |
possibly if ur injectors were clogging and that cleaned them mabey ur getting higher rpm cuz o more fuel! =D
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What would cause my cold starts to not idle high at all? Right now my cold starts the same as hot starts and idle at 900 instead of over 1k like it should. The IAC is used after it warms up right? Or do I have that backwards.
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After more troubleshooting I'm still stuck at the same spot with a cold start idle around 500-750.
*Cleaned idle air control valve and even opened up the inside of the stepper motor which was clean. Checked the stepper motors bearings and that the spring was good. Did resistance checks on the IACV and they were reading 20.5 ohms. *Checked coolant temp sensor resistance when cold and it was 2.1k ohm *Cleaned air intake temp sensor and checked the reading on it when cold, it was 2.3k ohm *Checked my coolant by measuring the voltage between the negative of the battery and the coolant at the rad cap. It read 0.13 vdc, 0.1-0.5 is supposed to be good. Is there anything else I can try? I'm not completely sure it isn't the motor on the IACV but buying a new one just to test is $300+ :( Also really hoping it isn't the ECU on its way out. *edit. After resetting the ECU and having to keep it from stalling by hold the accelerator in a bit, I managed to get it to idle by itself at 500 RPM. I went for a drive and then let it sit for a couple hours. Tried to start it up later and was having a hard time, it was turning over fine but wouldn't start. It eventually started and revved up to 2300 RPM and started to hunt from 1k to 2k again like it was a couple of weeks ago. I'm really thinking the IACV is bad. |
Pulled all my spark plugs today, and they were all soot black so I cleaned them with a wire brush and some brake cleaner (they are iridiums with less then 10k on them).
I tested my intercooler piping with a homemade boost tester and it wasn't leaking. Took the car for a drive after resetting the ECU. It started up cold at 2500 RPM and slowly came back down to around 1800. While driving I noticed when the clutch is pushed in the revs bounce from 1000 to 2000 continulously. (An ongoing problem that comes and goes that i've been trying to solve) Come back to the house and right before I shut it down the MIL and CEL come on. I shut it off thinking that I will have a code that will point me in the right direction. Put my paper clip in and turn the key and my CEL light isn't flashing just on solid with my "SLIP Cont off" light flashing. 30 mins later I try to check the codes and the CEL light is flashing steady telling me there is no codes. I start looking into my electrical system checking the plugs at the ECU which look fine, they are tight and none of the pins are bent. (The car is pretty much stock) Upon looking at the large bundle of wires that come through the firewall from the ECU I find this. http://img594.imageshack.us/img594/4527/img0623u.jpg There four wires (3 black and red stripe one and 1 thicker black one all spliced into one black and red wire and also another 2 wires spliced into 1 where the blue electrical tape is. That's not standard I'm assuming? I had a greddy emanage ultimate that I used to have hooked up only for the speed limit removal and speedo adjustment for bigger rims. I disconnected it awhile ago trying to eliminate possible problems while troubleshooting but it wasn't the problem. I'm thinking I could hook it back up and use it to datalog some data to troubleshoot with although I've never used that datalogging part of the EMU, hoping its straight forward. Anyone have any ideas? After looking at some electrical diagrams, I'm starting to think I have some grounding problems. |
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Yah removed the tape today and there are crimp connectors and all the wires are red striped black wires which are grounds i believe? I don't know why it is the way it is though.
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Regarding the wire colors in the harness, it's best to refer to the TSRM: http://www.mkiv.com/manual/1995_elec...ual/index.html |
No the crimps were all metal and seemed very secure. I have seen mentions of some splices in some factory wiring diagrams so maybe they are normal.
After some more testing my recent problem of the CEL and MIL coming on after driving for awhile has got me thinking it could be something as simple as the O2 sensor on the way out. It seems to always come on after driving for about 15 minutes after the car has warmed up a bit. It still doesn't explain why when I check for codes it says there are none, or the trac off light flashes and my CEL doesn't even blink. The car definately runs rich when this happens. Ox1 reads above 0.9v, exhaust smells almost like straight gasoline. Can oxygen sensors work bad when warmed up but fine when cold? I always pegged them as a failing unit. |
I think the crimps are labeled on this picture as "E24" splices.
http://www.mkiv.com/manual/1995_elec...95elec_088.JPG |
At long last I traced all my problems to a bad battery. It had never been below 12 vdc when I checked it but after doing some testing, I found that it wouldn't hold a charge much past 12.15 volts. If you charged it up to around 12.7 volts with a charger and hooked a multi meter up to it with nothing else connected you could watch the voltage drop and in about 10 minutes it was at 12.05. It would never drop below 12 volts so I never thought much of it until this test.
Replaced it with a new battery and after a test drive the voltage is reading 12.9 and not dropping. Roughly 1 volt makes all the difference in the world after factoring in the resistance of the wires. |
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I haven't done as much extensive testing as I would have liked yet since I got hit with a down pour. However starting the engine from a cold start gave me 1300 RPM while it warmed up and then dropped down to 900 RPM when the engine had reached operating temperature. So I do in fact now have a working cold start system.
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Updating this since it's been fixed for awhile now. The problem came back and after looking inside my ECU found some burnt components, most likely from the time I boosted my car awhile ago when my battery died. At least that's what I think caused it. I got a second hand ECU from England to replace it. Really hard to find a JDM ECU around here.
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