In trying to diagnose my TPI cold start issues (takes 3-6 key cranks to fire up) I checked my scantool for the CTS reading when cold....the car has sat for 3-4 days and the temperature is 60 degrees out but the scantool reads 100. Is this normal or correct? Would this contribute to a hard start when cold?

 

That doesn't sound right in any scale. You need to know if the scan tool returns degrees F or degrees C. After sitting for days, the scan tool should report the same temperature that the IAT (or maybe MAT)sensor does. These should both pretty much match the outside temperature.

 

It reads in F.....I figured it should read the same as the exterior temp. This may sound dumb but what is the method to test resistance of the sensor? I have a cheapie multimeter but I never was real keen on testing wires, etc.

 

Well I swapped out the ECM with my spare and the CTS readings are different as well as TPS readings, which have been another issue and hopefully explains the lack of performance off the line.

Car was kinda warm and read 117 with the old ECM and 110 with the replacement. TPS would read only up to 1 with the old and 5 with the replacement via the ScanTool but accurate at the sensor. I'm glad this appears to of fixed it rather than a wiring gremlin but I haven't tested the car enough yet to be certain. When cold today the CTS read 69, the temp outside and it started with one longer crank, not repeated attempts .

 

I have this exact same problem. CTS reads 30-50 degress higher than actual temp and TPS is correct at idle and only goes to 1.41V at WOT, if back probed it reads correct.
Did the ECM resolve this issue or did you find anything else after this? TIA

 

The fact that a different ECM moved all the readings closer to sanity tells me that you're headed in the right direction. ECM "learns" how to start the engine and hold a stable idle over time so give it a few cycles before you decide if it's "fixed" or not. When you swapped ECMs it started from ground zero, so give it a chance to do it's thing.

 

I haven't found anything else since realizing my old ECM was giving false CTS/TPS readings, the car performs much better and the cold starts are no longer a PITA. I hope to "test" it by taking it to the local 1/4 track this fall yet, last year it did a paltry but consitent 15.01, when I think with the motor/car, while mild, should run a low 14 in its current configuration.

 

Cool, thanks for the reply, I am getting a new ECM tomorrow then. I am excited to see what happens once it is changed, I am hoping it really feels like a 350 should. I have been chasing this for going on two years now, I never had anything to tell me it may be a bad ECM until I got my scanner as saw this post. Since my CTS and TPS are doing the same thing that has got to be it. There is alot to be said about non-computer controlled cars!!!!

 

Cool...let us know how it turns out. I chased my problem for awhile too, really frustrating. I should of thought of it sooner but better late than never I guess. Those sensors giving bad readings can really hold back the engine . Still think there is more of my engine to be put to the ground but the only thing I can think of now is my PROM being adjusted regarding timing tables and one source I've heard thinks the 305 ESC and knock sensors could throw things off too, being that its a 350.

 

I will let you know what happens. I don't know much about the ESC but I know on the 305 vs 350 knock sensors that they respond to different frequencies. Not sure the exact effect other than if the 305 freq keeps counting when it should not for a 350 you could be losing some timing. Emissions standards are holding my car back

 

All I can say is..... "WOW, so that is the difference between a 305 TPI and 350 TPI". The ECM was definitely it. I guess it has been bad since I have owned the car. Wish I would have got the scanner 2 years ago. Would have saved me alot of frustration. It immediately started reading the TPS and CTS correctly, startup was like it should be and the throttle response is amazing. I am so glad I didn't get rid of this car. Thank you a bunch, I can't tell you how relieving this is.

 

Glad that solved the issue! I was pretty excited when I found those problems and had a good spare ECM on hand to fix it.

 

Yes, I am pretty excited myself. It is like a new car. At least just about every part on it is new now Ü