Engine Cutting Out

[JimCT_9C1]

Sharing my experience with bad coolant temp sensor (CTS) on my 95 LT1 -
My CTS failed low (constant, not intermittent), but not failed to the point that a code was set.
Flooded out the engine - wouldn't run when warm. Could start it with flood clearing mode (throttle to floor, no fuel) but would flood out after running a few seconds. Pulled the CTS connector to cause a hard failure. Started and ran well enough with code set and no CTS to get me home.

Testing without the sensor in play (and thus wiring as well) may help narrow things down.
Note my experience was with LT1, so others can chime in on any differences to your application.

Hope this helps -
Jim

[NomakeWan]

To add to the above, Code 15 is triggered (at least on the 94~95 LT1) when the ECM detects CTS at -40F or lower for 2 seconds. On this application, that means CTS circuit at 100700 ohms or more (open circuit) for 2 seconds.

So if you're triggering Code 15, that means your CTS is intermittently reading essentially disconnected for 2 seconds or more. However, as Jim pointed out, it would be good to know what "temperature" is being reported for those times when Code 15 is not triggered as well. My bet is that it will read normal until Code 15 events happen, because the culprit is poor wiring causing a complete signal dropout.

[srgould41]

Thanks for the info Jim. I had black smoke coming out the exhaust when the engine lost power. The black smoke could be the ignition cutting out or a super rich condition. I would not think that the intermittent CTS would cause what I was experiencing, but thinking of your failure experience I am not so sure now. However, I was getting the intermittent check engine light all day without runability issues, so... Hmmm.

I recorded the CTS plug positions at the ECU so I can run a continuity test while wiggling the wires today after work. I have a new plug I could wire in if the wires at the plug are faulty. If the wires seem good a new CTS is cheap.

Sharing my experience with bad coolant temp sensor (CTS) on my 95 LT1 -
My CTS failed low (constant, not intermittent), but not failed to the point that a code was set.
Flooded out the engine - wouldn't run when warm. Could start it with flood clearing mode (throttle to floor, no fuel) but would flood out after running a few seconds. Pulled the CTS connector to cause a hard failure. Started and ran well enough with code set and no CTS to get me home.

Testing without the sensor in play (and thus wiring as well) may help narrow things down.
Note my experience was with LT1, so others can chime in on any differences to your application.

Hope this helps -
Jim

[tayto]

sounds like you don't have equipment to data log? if not try to jumper the terminals of the CTS together. start engine, within ~30 seconds you should get a code 14. If you do, the wiring to ecu should be ok and the sensor is most likely at fault.

TBI codes explained with troubleshooting flow charts:
http://www.gearhead-efi.com/gearhead...c/TBIcodes.pdf

[srgould41]

Hmmm. I like that idea as an extra troubleshooting step. I do have data logging capability as well as chip burning. I will try the idea you suggested though. Seems worth a shot just to prove I am getting what I expect. I'll probably try both open and closed to trigger each error.

On a positive note, I guess, I just finished testing the wires. I could not detect any issues in either the CTS or ICM wires. Wiggled like crazy everywhere I could and no change in continuity. Ordered a new CTS. ICM should be here Thursday. Ordered both the D1943A and the Police version D1984A. The D1943A will go in my onboard spares bin.

sounds like you don't have equipment to data log? if not try to jumper the terminals of the CTS together. start engine, within ~30 seconds you should get a code 14. If you do, the wiring to ecu should be ok and the sensor is most likely at fault.

TBI codes explained with troubleshooting flow charts:
http://www.gearhead-efi.com/gearhead...c/TBIcodes.pdf

[tayto]

D1984A is the "369" module
D1945A is the "048" module

369 is the one to get. apparently gm discontinued the 048, so i've always wonder if both Delco numbers are the same module but never had the time to check with a timing light.

if you datalog just follow the troubleshooting flow chart in the pdf. my method is if you only have a paper clip in your tool box...

EDIT: aside from regular tune up items, I usually consider the CTS part of a "tune up" item for TBI. usually for my own vehicle or if someone brings me something that has been neglected or not running right. Also consider the same for the O2 sensor, I usually upgrade to a heated O2 at this time.

[srgould41]

Thank you for the info.

D1984A is the "395" module
D1945A is the "048" module

395 is the one to get. apparently gm discontinued the 048, so i've always wonder if both Delco numbers are the same module but never had the time to check with a timing light.

if you datalog just follow the troubleshooting flow chart in the pdf. my method is if you only have a paper clip in your tool box...

EDIT: aside from regular tune up items, I usually consider the CTS part of a "tune up" item for TBI. usually for my own vehicle or if someone brings me something that has been neglected or not running right. Also consider the same for the O2 sensor, I usually upgrade to a heated O2 at this time.

[brian617]

The CTS is a common failure for a TBI engine. The cutting out you are experiencing is the huge amount off fuel being adding intermittently as the PCM sees an engine temp of -40* when the sensor fails. It is enough added fuel to stall the engine and cause the issues you are having. Ignition cut out issues are usually followed by exhaust backfire.