bvaubel Posted February 5, 2005 Report Share Posted February 5, 2005 My 94 SLS has had an erratic RPM problem for the last two weeks. Last night I was sitting in a parking lot in Park with the engine running and the RPM's would vary between 1100 and 1500. Within a couple minutes I started overheating, it went to 240 when it usually stays right at 207. Smoke started to roll. As soon as I left the parking lot it cooled back down and stayed in the normal range as long as I was moving. As soon as I hit a stop light it started heating again. Darn thing wants to go 40 or 50 mph without touching the accelerator. My hunch is the cat convertor is plugged. Any ideas? Thanks, Brian Link to comment Share on other sites More sharing options...
adallak Posted February 5, 2005 Report Share Posted February 5, 2005 Your problem is rather under the hood than somewhere else. Idle speed control system would be the first thing to check out. Any codes? Are the cooling fans ok? The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
bvaubel Posted February 5, 2005 Author Report Share Posted February 5, 2005 Cooling fans are okay. No check engine light. Why would a fast idle make it overheat? Link to comment Share on other sites More sharing options...
bvaubel Posted February 5, 2005 Author Report Share Posted February 5, 2005 I went and checked the codes. No codes. Brian Link to comment Share on other sites More sharing options...
adallak Posted February 5, 2005 Report Share Posted February 5, 2005 Cooling fans are okay. No check engine light. Why would a fast idle make it overheat? The higher RPM the more heat produced by engine. The fans can handle the heat at 600 RPM but cannot at 1200 RPM I guess. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
bvaubel Posted February 5, 2005 Author Report Share Posted February 5, 2005 The next question is would ISC problems cause the PCM to set a code? Brian Link to comment Share on other sites More sharing options...
maremrak Posted February 5, 2005 Report Share Posted February 5, 2005 It could be many things involved. Did you do tune up at all? Did you recently change the coolant? It has to be changed every two years. I would work around idle speed control motor, throtle possition sensor, and also check EGR valve. Overheating could be because the fan is not turning on. It should be on when temp is over 235 if I remember correctly. 1960 Sedan De Ville (sold) 1970 Coupe De Ville (sold) 1987 Mazda RX-7 (sold) Link to comment Share on other sites More sharing options...
bvaubel Posted February 5, 2005 Author Report Share Posted February 5, 2005 I checked the fan when it was hot. It was working okay. I haven't done a tune up but I also haven't changed the coolant for some time. It would seem to me that any problems with ISC, TPS or EGT would throw a code. Brian Link to comment Share on other sites More sharing options...
cadillac_caddy_sts Posted February 5, 2005 Report Share Posted February 5, 2005 My car used to do the same thing! Excet for the overheating it never did that but the car would actually spin out when I put it in drive and took my foot off the brake it can be a very dangerous situation! I replaced my idle sensor and it never did it again! Its a tricky thing to replace though it took me and my dad almost 3 hours to take the old one out and replace it with a new one! Good luck! Defending Northstar perf a qtr mile at a time!!!! Link to comment Share on other sites More sharing options...
bvaubel Posted February 5, 2005 Author Report Share Posted February 5, 2005 Are those idle sensors high dollar? I assume that is a Cadillac only part. Brian Link to comment Share on other sites More sharing options...
cadillac_caddy_sts Posted February 5, 2005 Report Share Posted February 5, 2005 I don't know what the dealer charges I got myn off a parts car but there was also a local salvage yard near by that wanted 120 dollars canadian! You could check with the salvage yards near you and check the dealership see what they price it at! Defending Northstar perf a qtr mile at a time!!!! Link to comment Share on other sites More sharing options...
maremrak Posted February 5, 2005 Report Share Posted February 5, 2005 ISC should be around $100-$125. Get the original one, the others could not be adjusted with the hex. It is preatty easy to change it on my 95 STS. You would need to perform the TP Sensor/Idle Learn procedure after you install it. The procedure is explained in detail in the service manual. So, I guess, you either invest in a service manual, and do it yourself, or find the good mechanic to do it for you (and that's the scary part). 1960 Sedan De Ville (sold) 1970 Coupe De Ville (sold) 1987 Mazda RX-7 (sold) Link to comment Share on other sites More sharing options...
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