Rough idle and SES light
12-22-2007, 11:09 AM
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Rough idle and SES light Well here's the problem whenever I start the car and let it warm up for about 2 minutes it starts to have a rough idle as it bounces from about 700 back to 1000 rpms. Also driving it is the same way it seems to limp down the road, then after about another 2-5 minutes the SES light comes on and the problem goes away and the cooling fans kick on,and stay on. until I stop and shut it off then the problem repeats once I start it back up. I have had people tell me maybe one of my o2 sensors went bad, could this be true? Since the guy at the shop had to rewire them to extend them to the headers I could see that happening.Im really not to sure at this point any ideas?
12-22-2007, 11:40 AM
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Chris,
Few thoughts:
1) If you have an SES light, that means there is a code stored in the PCM. If you go have the PCM scanned for diagnostic trouble codes, it will tell you exactly what is wrong. That's far better than people guessing over the internet. Though, I think the first thing I'd check is the MAF, since it seems to run ok when the SES is on. ([Edit] FYI -- the high-speed fans are rigged to turn on with any SES light.)
2) As for the oxygen sensors, did they actually cut into the factory wiring, or the wiring of the sensor itself? You're right to be concerned -- the oxygen sensors rapidly fluctuate from 100mV~900mV, signifying a lean and rich condition, respectively. It's a sensitive system, and any faults in the wiring can wreak havoc on your fuel trim. The oxygen sensor wiring supposedly has a waxy coating, which makes it difficult to get a good electrical connection when splicing. Instead, we usually use "02 extensions" (about $25 each from places such as ThunderRacing) which are simply plug-n-play, and they work great.
However, if there's a problem with the oxygen sensors, I'm not sure if the PCM resorts back to a different method of fueling. It should theoretically set a code if the block learns reach 108 or 160, but I don't otherwise see how the car would run better when the SES is lit.
Anyway, get the codes pulled if you can, and post them here.
Few thoughts:
1) If you have an SES light, that means there is a code stored in the PCM. If you go have the PCM scanned for diagnostic trouble codes, it will tell you exactly what is wrong. That's far better than people guessing over the internet. Though, I think the first thing I'd check is the MAF, since it seems to run ok when the SES is on. ([Edit] FYI -- the high-speed fans are rigged to turn on with any SES light.)
2) As for the oxygen sensors, did they actually cut into the factory wiring, or the wiring of the sensor itself? You're right to be concerned -- the oxygen sensors rapidly fluctuate from 100mV~900mV, signifying a lean and rich condition, respectively. It's a sensitive system, and any faults in the wiring can wreak havoc on your fuel trim. The oxygen sensor wiring supposedly has a waxy coating, which makes it difficult to get a good electrical connection when splicing. Instead, we usually use "02 extensions" (about $25 each from places such as ThunderRacing) which are simply plug-n-play, and they work great.
However, if there's a problem with the oxygen sensors, I'm not sure if the PCM resorts back to a different method of fueling. It should theoretically set a code if the block learns reach 108 or 160, but I don't otherwise see how the car would run better when the SES is lit.
Anyway, get the codes pulled if you can, and post them here.
Last edited by Alex94TAGT; 12-22-2007 at 11:48 AM.
