Dies in gear when throttle applied

[92GMCK2500]

Cheers @1990Z71Swede

Also, thanks @Schurkey !

 

[92GMCK2500]

Data stream is a wonderful thing. I believe it should be mandated that the driver can call up the data stream on the center console without any special tools or paywall. My Holley Sniper shows datastream on the handheld, and already I've been able to diagnose two failures just my looking at it.

That's cool. BTW, how do you find the sniper? I'm interested but have concerns with reliability.

 

[Erik the Awful]

Reliability is an issue. I've had to replace the TPS and the O2 sensor, and readjust the throttle blades because they were sticking. The data stream is how I diagnosed the TPS and O2 sensor. The sensors just quit reporting and it was immediately obvious on the Sniper's "gauges".

Holley Sniper EFI FR550-510 Holley Sniper EFI Self-Tuning Kit - Shiny - Factory Refurbished

The Sniper EFI Factory refurbish process starts by stripping a used or blemish Sniper EFI throttle body down to the bare casting. From there, our highly trained factory refurbish technicians flow the original fuel injectors. If any injectors fail to meet our flow standards they are replaced with...

www.holley.com

 

[92GMCK2500]

Reporting back on this. Haven't had the time dig into the harness nor ECM. Too many life things going on at the moment.

HOWEVER, some good news. I took the truck on some shake down runs. It drives ok, not perfect of course, but ok. I even loaded up the camper & drove to our summer camping spot without too much hassle. It's about a 30 min drive.

Truck warns up to op temp. CTS reads as it should. This is what I noticed on the drive, I was reading the scan tool along the way:

- Commanded desired idle rpm is 1000 rpm regardless of gear, or driving conditions. If I turn engine off, then restart it goes to 600-650 rpm, which seems more appropriate.
- The actual rpm at idle, in gear matches desired idle speed. However, in P/N is idles at 1500-1800 rpm. After the truck has been driven it slowly drops but only to about 1200 rpm.
- At the same time as this is happening, the IAC steps are 155. Really high. Spec is 5-30 steps at 525 RPM.
- Furthermore, regardless of gear, or driving conditions, IAC steps are always pegged at 155. Even cruising, 0% throttle, no AC, no lights or other loads. IAC reads 155.

Would this explain the high rpm at idle or high commanded desired rpm?

Another theory, could the ECM be opening the IAC Valve more, to add air, to try balance the rich fuel condition due to the Code 15, low coolant temp, aka add fuel?

What do the block learn numbers mean?

Ok my brain hurts. I'll see if anyone has anything to add. Cheers

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[Schurkey]

Truck warns up to op temp. CTS reads as it should. This is what I noticed on the drive, I was reading the scan tool along the way:

- Commanded desired idle rpm is 1000 rpm regardless of gear, or driving conditions. If I turn engine off, then restart it goes to 600-650 rpm, which seems more appropriate.
- The actual rpm at idle, in gear matches desired idle speed. However, in P/N is idles at 1500-1800 rpm. After the truck has been driven it slowly drops but only to about 1200 rpm.
- At the same time as this is happening, the IAC steps are 155. Really high. Spec is 5-30 steps at 525 RPM.
- Furthermore, regardless of gear, or driving conditions, IAC steps are always pegged at 155. Even cruising, 0% throttle, no AC, no lights or other loads. IAC reads 155.

Would this explain the high rpm at idle or high commanded desired rpm?

IAC at 155 is going to lead to high idle speed. Question is "why is the IAC commanded to 155?" Does the IAC actually work?

Another theory, could the ECM be opening the IAC Valve more, to add air, to try balance the rich fuel condition due to the Code 15, low coolant temp, aka add fuel?

I wouldn't expect so. if the fueling is too rich, it should adjust the fuel trims, not add more air. I don't know why you have a Code 15 for low coolant temp, when you say the coolant temp is good.

What do the block learn numbers mean?

"Integrator" is short-term fuel trim.
"Block Learn" is long-term fuel trim.

For both, the mid-point, "no correction" is 128. Your photo shows block learn at 119--lean command. The computer has reduced the amount of fuel delivered compared to what it was programmed to deliver, by 9 numbers. Having reduced the long-term fuel trim, it then feels it need to add one number to the short-term trim. Sorta like reducing the fuel trim by 8 1/2 rather than 9 numbers.

 

[1990Z71Swede]

I dont think it is possible to have Code 15 with "CTS reading correctly" at the same time. thats weird. Code 15 is probably related to the demanded 1000 Rpm Idle. But it does not seem to be able to control, (not even trying actually) Idle Rpm, not sure why but the most obvious reasons would be a vaccuum leak or faulty IAC, in that order. The fact that it ends up at 1000Rpm in gear is just the converter lugging it down, the IAC at 155 all the time means the ECM is not trying to control Idle speed, not sure why, again maybe Related to code 15, as in it thinks the engine is cold, maybe not -40 any more since it starts but still not right.

Also, the ECM leaning out could point towards an Erroneous CT reading, in the way that the ECM is in the Fuel map block for a Coldish engine while in fact the engine is a lot closer to operating temps, where the engine needs less fuel. For that to be the case though the ECM would have to be in Closed loop, that is the only way for it to detect the Rich running, that again points towards CTS reading too low but not really cold, because i think it does not go into closed loop until the engine has warmed up some.

 

[Schurkey]

Clear the code, see if it comes back.

 

[92GMCK2500]

Clear the code, see if it comes back.

Will do.

 

[92GMCK2500]

When I follow the scanner, the CTS reading starts at ambient temp, then slowly warms up in 5*C increments until it reaches 90*C (194*F) when the thermostat opens. I have not seen the CTS higher than this temp, yet. This is what I am calling '"the CTS reading correctly".

However, please note, the actual voltage at the CT sensor is only 3.75V with KOEO, not the 5V spec the FSM calls for. As we've already gathered there is a problem in the 410 CKT wiring, I just haven't got off my a$$ to investigate further thus far.

I can't say for sure whether the IAC is working correct or not. It appears not. It is a newer Standard Motor Products piece with new pigtail. I was reading up, there is a IAC Valve reset procedure.

I'll try this plus clear the trouble codes using the scanner & see what happens for a starter...

Cheers again fellas.

 

[92GMCK2500]

I dont think it is possible to have Code 15 with "CTS reading correctly" at the same time. thats weird. Code 15 is probably related to the demanded 1000 Rpm Idle. But it does not seem to be able to control, (not even trying actually) Idle Rpm, not sure why but the most obvious reasons would be a vaccuum leak or faulty IAC, in that order. The fact that it ends up at 1000Rpm in gear is just the converter lugging it down, the IAC at 155 all the time means the ECM is not trying to control Idle speed, not sure why, again maybe Related to code 15, as in it thinks the engine is cold, maybe not -40 any more since it starts but still not right.

Also, the ECM leaning out could point towards an Erroneous CT reading, in the way that the ECM is in the Fuel map block for a Coldish engine while in fact the engine is a lot closer to operating temps, where the engine needs less fuel. For that to be the case though the ECM would have to be in Closed loop, that is the only way for it to detect the Rich running, that again points towards CTS reading too low but not really cold, because i think it does not go into closed loop until the engine has warmed up some.

Your onto something here and again I feel it is the 410 CKT wiring as we've discussed.

I did double check for Vacuum leaks & found nothing. Used carb cleaner spray method, propane gas method & listened carefully through a hose method. Didn't register any vac leaks. IAC could be faulty.

Anyone know how to test these?