1993 k3500 with 350 tbi, issues starting in cold weather (below 35 degrees)

[JB 93]

I just purchased this truck back in the spring and it has ran great all summer. but now that it is cooling off it has had issues when trying to warm up. it is idling rough, missing, and sometimes stalls out. to restart i have to throttle it some to open it up. I have replaced fuel filter, fuel pump, egr valve, iac valve, coolant temp sensor, throttle body gaskets, fuel injection pressure regulator rebuild, and injector o rings. I swapped the map sensor out and tested that as well, no help. the fuel air mix is just off when cold starting, once it warms up everything smoothes out. any ideas thank you.

 

[evilunclegrimace]

Have you hooked it to a scanner yet? Some data will help with diagnosing the problem. See if the CTS is giving a correct temp. What about tune up parts? Have you looked at the inside of the distributor cap to see if it is corroded? checked your plugs?

 

[1997]

seems like a similar issue to mine ----
and others in this thread https://www.gmt400.com/threads/surging-idle-on-cold-start.55381/

wow that's alot of parts, i know it's not listed, but did you change the O2 sensor?

 

[Supercharged111]

My 88 was always a bit cold blooded once it got down in the teens. I'd have to give it some throttle to start it and keep it running for the first 5-10 seconds. After that it wouldn't stall, but was a bit cold blooded for the first minute or so. Yours sounds worse, but don't be surprised if it's never great in the cold.

 

[Nad_Yvalhosert]

I had the exact problem with my '88 5.7. Scan tool showed coolant at -40°. New CTS fixed it.

Scan, look at the datastream, find the erroneous pid

 

[1997]

I had the exact problem with my '88 5.7. Scan tool showed coolant at -40°. New CTS fixed it.

Scan, look at the datastream, find the erroneous pid

interesting, scanner says my IAT is -40, coolant temp changes with run time as expected.

 

[1997]

My 88 was always a bit cold blooded once it got down in the teens. I'd have to give it some throttle to start it and keep it running for the first 5-10 seconds. After that it wouldn't stall, but was a bit cold blooded for the first minute or so. Yours sounds worse, but don't be surprised if it's never great in the cold.

i've had the 95 since 96, never had this issue until this year, and it used to be colder,,

 

[Schurkey]

interesting, scanner says my IAT is -40, coolant temp changes with run time as expected.

Seems to me that TBI engines don't have an IAT sensor, so the computer may read that open circuit as "Forty Below". The "quick check" for coolant and other temp sensors--they should read ambient temperature or very close when checked after the engine is fully cooled-off. But the sensor has to exist for the test to be valid.

My '88 started and ran SEAMLESSLY hot or cold or anywhere in-between, up to the point where I swapped heads and intake manifold for aftermarket stuff. It still starts fine, but has some issues as it warms up, although it's better since I jacked-up the fuel pressure.

 

[Nad_Yvalhosert]

i've had the 95 since 96, never had this issue until this year, and it used to be colder,,

Yup, sensors wear out over time. And a 26 year old anything is gonna start having parts wear out.
My temp sensor was original from '88, so no surprise to me. Thankfully it was stil available, and cheap to replace.

 

[1997]

Seems to me that TBI engines don't have an IAT sensor, so the computer may read that open circuit as "Forty Below". The "quick check" for coolant and other temp sensors--they should read ambient temperature or very close when checked after the engine is fully cooled-off. But the sensor has to exist for the test to be valid.

My '88 started and ran SEAMLESSLY hot or cold or anywhere in-between, up to the point where I swapped heads and intake manifold for aftermarket stuff. It still starts fine, but has some issues as it warms up, although it's better since I jacked-up the fuel pressure.

google agrees , no IAT sensor on this TBI engine, think you're correct about the scanner -40 number, since it never changes, thx .