Those with: erratic idle, TCS lights, and surging
04-03-2007, 02:20 PM
#1
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Those with: erratic idle, TCS lights, and surging This is what I experienced in the past couple weeks and finally figured it out.
I'm posting this because a few people in my other thread had the same symptoms and didn't know what it was.
It appears that when your TPS (Throttle Position Sensor) goes out it will affect the IAC (idle air control), TCS (traction control system) and it will make the PCM go to a Speed Density Tune(SDT). In some cases you will get "NO" SES light. I never had one show up at all ever. I replaced the IAC and it did nothing. My friend scanned it this weekend and it did show the TPS was not working, or whatever the computer says, I wasn't looking at it. I replaced the the TPS today ($36.95 at Advance Auto, part number 7793651) and the engine and everything else is perfect again.
When the PCM goes to Speed Density Tune you can unplug the TPS and the car will still run just fine. Mine was unplugged for two days and the engine ran normally. The only thing that sucks while in SDT is cold start, it will idle erratically and you MUST pedal the throttle for the first minute or so to keep it running until it warms up, than it will idle by itslef. Also, sometimes when you come to a stop at a light or stop sign it will surge up and down.
Also, for a 2-3 days during this period, the transmission would rev higher than normal in each gear before the shift came, hitting pretty hard during casual driving. That went away by itself.
Hope it helps someone.
.
I'm posting this because a few people in my other thread had the same symptoms and didn't know what it was.
It appears that when your TPS (Throttle Position Sensor) goes out it will affect the IAC (idle air control), TCS (traction control system) and it will make the PCM go to a Speed Density Tune(SDT). In some cases you will get "NO" SES light. I never had one show up at all ever. I replaced the IAC and it did nothing. My friend scanned it this weekend and it did show the TPS was not working, or whatever the computer says, I wasn't looking at it. I replaced the the TPS today ($36.95 at Advance Auto, part number 7793651) and the engine and everything else is perfect again.
When the PCM goes to Speed Density Tune you can unplug the TPS and the car will still run just fine. Mine was unplugged for two days and the engine ran normally. The only thing that sucks while in SDT is cold start, it will idle erratically and you MUST pedal the throttle for the first minute or so to keep it running until it warms up, than it will idle by itslef. Also, sometimes when you come to a stop at a light or stop sign it will surge up and down.
Also, for a 2-3 days during this period, the transmission would rev higher than normal in each gear before the shift came, hitting pretty hard during casual driving. That went away by itself.
Hope it helps someone.
.
05-04-2007, 07:48 AM
#2
I'm having the same problems as you stated. When did you start having the problems? I just did a h/c and 90/90 install and it ran fine on the dyno and drove home fine but the TCS light was on. Went to take the car out lastnight and play and it wouldn't idle for crap and would die when I stopped and when coasting down the road. In park it wold idle around 980rpm, but in drive it would surge from 500-1500rpm. I'm searching and there are different posts saying its the TPS or its the MAF table in the tune causing the problem. Please help!!!