I agree!..
when mine went bad I replace it with a 2 wire. it came with the pigtail.

Remember if the pigtail is disconnected from the sensor and you go to test the CTS with a volt meter you won't get any voltage since its not connected.

With your key on and pigtail disconnected you should read almost 5 volts between the pigtail and ground.

 

With key on and pigtail disconnected I read 0 volts between pigtail and ground. I get a higher voltage when key is off !!!

I'll go through the troubleshooting chart in my FSM and take the measurements at the ecm connector... I'm starting to believe that my ecm is bad.

 

Hi qws,

Well, I replaced the CTS, the fuel pump relay (wire conducters were actually touching each other) and put in a new fuel pump and measuring a steady 13psi...

I still have a rough idle... twhen running winaldl, readings are still weird with the voltage at 24.9, map at 184, IAC's at 80, etc...

I'm starting to believe that I have a bad ECM... How else would I be getting these readings,,, especially the battery at 24.9 (when my voltmeter and instrument panel are telkling me 13.1 - 13.4V) !!!???!!!???


I don't know if I'm going in the wrong direction....

 

Anyone ??
Joey

 

Hi Joey....wish I was responding with a solution for you, but unfortunately, what I am responding with is I am having a rough idle problem on my '84 as well. Problem here is it wasn't idling rough until I took it to a "reputable" garage with cooling fan issues, which were resolved BUT now, I have this rough idle, especially when I turn on the a/c. When I went back to the garage, the mechanic skirted the issue and said it was running rough when I brought it in, which it wasn't because I would have mentioned that when I took it in for the cooling fan issue....Anyway, I can't help but think the mechanic "hot wired" or "jury rigged" the fan to turn on at expense of something else....So, I need an order of things myself where to start........Mechanic blew me off, so I'm going to see what I can do with help from this site.......HELP!!!!!!!!!!

 

What have you done to your car try and resolve the problem so far ??

 

Hi Joey....after taking the car back to the "reputable" garage, with now a cruise control that won't hold under load and the car loping/rough idleing (wasn't doing any of those before) here is what they did: Changed out spark plug wires, and spark plugs; Couple frayed electrical wires repaired; replace fuel filter; found/repaired split vacuum line to cruise control (wonder how that happened? crazy2; Replaced O2 sensor. That is what's been done so far. I have the car in MY garage now, figure I would start looking for possible vacuum leak somewhere. What do you think? CTS hasn't been changed either. Thanks!

 

Hi NMVetteman.... Before replacing parts, did they change the fan switch mounted at the compressor and the fan switch mounted between cyllinders 6 and 8 ??? What did they tell you had resolved the fan cooling issue ??

I could tell you that in my case one of the things that drastically improved my idle was when I replaced the CTS as I had a short and the connector was totally melted...talk about a rough idle.
Another thing that improved the idle a little more was when I replaced the intake manifold and toplid gaskets, including cleaning the throttle bodies and replacing all their respective gaskets as well as the fuel regulator.

 

Hi Joey...When I first took the Vette in with the cooling fan issues, here is what they did: Diagnosis showed a bad cooling fan relay, which was replaced. They also replaced a cooling fan thermal switch and installed a new pigtail harness. It was when I went and picked up the car I noticed right off the bat (hind-site tells me I should have turned around and taken the car back right then and there) the car had this loping/rough idle. Needed the car the next day, so I just went home and headed out on my trip the next day. It was then I noticed the cruise control wouldn't hold under load and the loping/rough idle seemed to get worse when I was at a stop sign and turn the a/c on..So, are you saying there are 2 of these cooling fan switches? I have the car in my garage now. Am going through checking the best I can for vacuum leaks, tightening up bolts on the intake, took off the egr and cleaned it out (it seems to hold vacuum ok), cleaned pvc, and cleaning out throttle bodies. I ordered a new CTS, will be here in the morning, and will change it out. Gotta tell ya, the old one "appears" to be ok, no signs of melted wires or damage. I'll let you know what happens. Thanks for all your help.

 

Hi Joey.....I removed the EGR, cleaned it out, tested ok, re-installed. Installed new CTS. Tightened all bolts on top around throttle bodies, the throttle bodies themselves, checked for vacuum leaks as well as I could, cleaned PVC, cleaned throttle bodies.......and the car still has an obvious loping/rough idle..........runs good on hiway, but that idle thing has got me confused. I have not contacted the garage who did the work to ask them just exactly what they did to make the fan turn on. Just showed me the work order and parts they changed out. Headed out for a few days, taking the vette with me. Let me know of any other suggestions you may have. Thanks.

 

man if I haven't just gone through something similar myself with a "specialist shop" and truth be told I wish I understood half of the technical language you guys are using. I miss the older simpler days....lol. I was having spark loss and the shop recomended a D.U.I. ignition coil kit and module, of course I payed for the parts and only the module made it's way into my car and the rest of the parts who knows I forced a refund. My car now of course idles rough when in traffic and dies when I let of the throttle, it acts like it is loading up on to much (not enough spark at this point perhaps) so now I am trying to find out which is the better coil for a daily driver, it seems some of the coils out there loose power at idle. Any ideas folks I sure could use some after my recent dealings with that shop I'd say it is safe to say I don't trust them and I shall never grace their front door again