Hi all,
I have done a lot of reading on the forums here and FSM testing but I am a bit stuck. In short, the truck stalls out after I release the accelerator in drive or reverse. This sometimes happens in park as well. Generally, I will apply the accelerator and rev above 2000rpms, release, the rpms will drop below 500, the engine catches it about 50% of the time and returns it to normal idle around 650 and the other half it dips all the way down and stalls.
Relatedly, in April, I desmog’ed the truck but left the cats in it. I also replaced most of the vacuum lines, PCV, valve cover grommets, and thoroughly cleaned the valve cover which had a ton of white residue build up. Truck ran fine for a few days until I embarked on my next project which was replacing most of the rubber in the cooling system, the thermostat housing, water temp sensor, and cold start injector sensor (old one was sheered straight off and I didn’t know). I bypassed the oil cooler in this process too.
After this, I went to start the truck and it had a very low idle below 500 which was new. To address this, I replaced the TPS (and ended up having to replace the whole throttle assembly) and cleaned the ISC which was pretty dirty (This helped the base line idle.) and reset the baseline idle using the golden screw (ended up doing this about a dozen times to get it right). Verified the throttle cable has about 2mm of slack.
Since then, it started stalling after I release the accelerator but sounds much better while idling in park at least. I verified continuity and voltage of the AFM at the AFM and ECU (discovered it was not receiving 5v and fixed that - but did not test the AFM at idle or 3000rpm per FSM) verified the TPS is adjusted correctly and checked all voltages and continuity per the FSM. I am fairly certain I have no vacuum leaks but I am going to do a smoke test eventually. I also cleaned the engine grounds at the manifold and body.
Last time I checked, I am throwing codes:
21, 24, 28, 31, 41
Previous performed work in the last year that might be related: new fuel filter, new rubber refuel return lines, new charcoal canister, new spark plugs and wires, new battery leads and terminals, new starter, new NSS.
Where do I go from here? How can I systematically figure out what is happening without throwing parts at it. I am stumped. I am still suspecting something with the AFM.
Thanks!
I have done a lot of reading on the forums here and FSM testing but I am a bit stuck. In short, the truck stalls out after I release the accelerator in drive or reverse. This sometimes happens in park as well. Generally, I will apply the accelerator and rev above 2000rpms, release, the rpms will drop below 500, the engine catches it about 50% of the time and returns it to normal idle around 650 and the other half it dips all the way down and stalls.
Relatedly, in April, I desmog’ed the truck but left the cats in it. I also replaced most of the vacuum lines, PCV, valve cover grommets, and thoroughly cleaned the valve cover which had a ton of white residue build up. Truck ran fine for a few days until I embarked on my next project which was replacing most of the rubber in the cooling system, the thermostat housing, water temp sensor, and cold start injector sensor (old one was sheered straight off and I didn’t know). I bypassed the oil cooler in this process too.
After this, I went to start the truck and it had a very low idle below 500 which was new. To address this, I replaced the TPS (and ended up having to replace the whole throttle assembly) and cleaned the ISC which was pretty dirty (This helped the base line idle.) and reset the baseline idle using the golden screw (ended up doing this about a dozen times to get it right). Verified the throttle cable has about 2mm of slack.
Since then, it started stalling after I release the accelerator but sounds much better while idling in park at least. I verified continuity and voltage of the AFM at the AFM and ECU (discovered it was not receiving 5v and fixed that - but did not test the AFM at idle or 3000rpm per FSM) verified the TPS is adjusted correctly and checked all voltages and continuity per the FSM. I am fairly certain I have no vacuum leaks but I am going to do a smoke test eventually. I also cleaned the engine grounds at the manifold and body.
Last time I checked, I am throwing codes:
21, 24, 28, 31, 41
Previous performed work in the last year that might be related: new fuel filter, new rubber refuel return lines, new charcoal canister, new spark plugs and wires, new battery leads and terminals, new starter, new NSS.
Where do I go from here? How can I systematically figure out what is happening without throwing parts at it. I am stumped. I am still suspecting something with the AFM.
Thanks!
