OK, posted this problem about 8 months ago but was unable to get it resolved. Here goes again... Car runs beautiful, most of the time. Out of the blue, it will start to idle rough and hunt (RPM's increase and decrease continuously), sometimes it dies, but most of the time the idle control will kick in and keep the RPM's up. Does it while cold and hot, open loop and closed loop. While parked and driving down the road. Yes, it still drives while the problem is there, but at a serious loss of power. Then it'll start running fine again. It can go a week or a minute between events. I've captured the event using an AutoXray but everything looks fine except the idle speed. I am thinking an intermittently grounded or broken wire but without it staying more than ten or fifteen seconds at a time, it makes it difficult to troubleshoot. Does anyone have any suggestions as to where to begin looking. ANY and ALL suggestions would be appreciated. Mods that I know have been done: Speed Chip, Shift Kit. Bought it like this so I don't know when it started. Thanks for the inputs!

 

Just pulled the Superchip out and put the original back in unmolested. It was an ADS Superchip. Go figure. Drove great for about thirty minutes tonight. I'll update tomorrow.

 

it could be your TPS is out of adjustment or needs to be replaced, i would also try some throttle body cleaner, that helped my idle problems.

 

My car also has the exact same symptoms. My first guess was that it might be the TPS but I'm not sure how you adjust it. Can anyone tell me?? It's a 91 TBI

 

yeah, check the technical articles, i think there's one on there about how to adjust it, if you can't find it, let me know and i'll give you the link.

 

Day two with no problems. Also changed the thermostat today. It had a 160 degree in it. Probably for the chip that is now gone. If I get the problem back I will do the IAC and TPS adjustments. Thanks.

 

Day three and four... Good so far!!

 

One more thing to consider, when I bought my car, it had a similar problem. Ren fine sometimes would not idle properly occasionally, most notable right after any WOT event. Changed the EGR valve and the problem was cured. You might want to at least check the EGR, if not replace it (especially if it is original).
Good Luck
Norm

 

Thanks. I still have had no problems with it since I pulled the chip. I did have to replace the EGR vavlve on my 92 RS also but it also had a Check Engine light. I will take a look at it tonight.