I've been tinkering around with a cold start problem in my 1987 Camaro with a EFI 383 and custom PROM.

I keep my car in the garage and it is air conditioned. One thing I noticed is that at cold starts at 67F, the Tuner Pro readout is showing coolant temperature to be 82F.

I checked the resistance of the sensor and it shows 3600 ohms at 67F. That seems to be right on according to the chart. I haven't checked at operating temp.

At operating temperature, Tuner Pro is showing coolant temperature to be in the 185 range. I have a 180 T-stat and prom burned for lower temps. So It seems to be showing good temp.

If the ECM is actually seeing 82F temp at 67F temp, that could be messing up the cold starts?

 

See if these attachments help.

 

Which sensor are you checking? There are 2 the ecm sees iirc for the 87s, unless you have deleted the coldstart inj setup

 

My car has done same thing. Figure it must be a bad ground or bad connecter. I unplugged sensor and put a paperclip in the plug and car starts up in closed loop but Runs fine once I give it a few pats on.the gas pedal. I have to dig a lil more into it and fix it but for now it's running perfect other than a lil cold natured. Mine was signaling to ECM the car was running hot and sending it into limp mode when it would reach about 205. ECM was giving me crazy high temps through the scantool.and I knew that wasn't right being i.Had two gauges checking out ok.

 

Was this ever solved?

 

No, I forgot about it and the car is in storage for the winter.

 

Yes, this will make the car hard to start. I had this exact problem with my -88 GTA several years ago. Car is stock, 1227165 ECU.

I had cold start problems, and smelly exhaust among several other problems. I bought a ALDL to USB cable, and when I tried it out for the first time the car was in winter storage in my rented spot in a cold garage. The car had been sitting unstarted all winter, and it was 6 degrees Celsius (~43 F) outside and in the garage. I connected the ALDL cable and opened WinALDL to see the live data, and the coolant temp sensor was at 30 degrees Celsius (~86 F)...

I started taking measurements, the CTS resistance was okay (also replaced earlier due to looking like ****, so was also fairly new). After measuring the 5V voltage going to several sensors on the engine to only about 2V I realized the ECU 5V-circuit was broken. So I replaced the ECU and the problem was solved.

 

Good info!!!! Thanks for sharing