I just finished an LS Swap into my 1981 El Camino. I have a lot to say so I will hopefully cover all the bases. It has an engine from a 2001 Yukon (5.3) that is completely stock internals and stock rebuilt 4l60e. I have a Holley mid mount kit along with a LS6 intake manifold and a few other cosmetic things that look nice on top of the engine. Stock emissions equipment is also gone on the engine. The stock PCM out of the truck was sent off and reprogrammed for my car and the unnecessary wiring was removed to make it a standalone PCM now. So the whole thong is mostly stock other than cosmetic upgrades to make it look nicer. Currently it just has exhaust manifolds like the OEM ones but from Hooker Headers and then an extended pipe down to where the catalytic converters connect to. So right now it is just essentially header dumped with the first o2 sensros plugged in and screwed into the exhaust and the rears are just hanging there since I do not have the cats in yet as I need to drive to the exhaust shop. It is a long intro but I just want the build to be as clear as possible to the state it is in.
Now for my actual problem. It has a really low idle at about 350-400 RPM and the throttle is not super responsive while trying to accelerate. The transmission also is not shifting properly, upshifting is fine and does do it but just not that well. Then most of the time it just wont downshift and I am left leaving a stop in 3rd gear. The voltage reading on the dash is also high at about 16V, I think this could be separate from the other issues but let me know if it is maybe connected. As for the other issues I feel like they are connected to one problem. Does it seem like the low idle and trans not shifting sound like it could be connected? Especially with the throttle not super responsive I don’t know if a sensor or possible vacuum leak could cause the PCM to not know what to do with the transmission. I might be able to get access to a scan tool to check these sensors.
So for the next steps
1. If it’s a vacuum leak could this cause the trans to act up if the car is running lean because of the added air.
2. My TPS could be bad or installed improperly since the throttle is not responsive and the trans doesn’t shift properly.
3. For just the low idle, what are some common causes of that? Anything that would be some easy first tests.
4. I check the TCC wire and it has supply voltage at resting position and then goes to open at a brake pedal press so it functions. And it does down shift sometimes so I believe it is working. I will say it is just one wire from the PCM to my stock TCC wire in the car off the pigtail that used to connect to the old computer so could I maybe need a more modern TCC switch?
5. It fires right up and doesn’t almost die on startup but it’s just low idle, I haven’t done any testing and I just wanted some second opinions before I go digging into the thing trying to find where the problem is. TPS is my biggest red flag that brings all those issues together but any help will be appreciated!
I would also like to note that its first test drive was yesterday to the gas station just outside my neighborhood and once turned off it goes back to 1st and then just doesn’t want to downshift once driving. Today I did a run in my neighborhood and it did ok at lower speeds only but once I turned on the road and got speed and then went back to a stop it hadn’t downshifted. Thank you to those who can help!
Now for my actual problem. It has a really low idle at about 350-400 RPM and the throttle is not super responsive while trying to accelerate. The transmission also is not shifting properly, upshifting is fine and does do it but just not that well. Then most of the time it just wont downshift and I am left leaving a stop in 3rd gear. The voltage reading on the dash is also high at about 16V, I think this could be separate from the other issues but let me know if it is maybe connected. As for the other issues I feel like they are connected to one problem. Does it seem like the low idle and trans not shifting sound like it could be connected? Especially with the throttle not super responsive I don’t know if a sensor or possible vacuum leak could cause the PCM to not know what to do with the transmission. I might be able to get access to a scan tool to check these sensors.
So for the next steps
1. If it’s a vacuum leak could this cause the trans to act up if the car is running lean because of the added air.
2. My TPS could be bad or installed improperly since the throttle is not responsive and the trans doesn’t shift properly.
3. For just the low idle, what are some common causes of that? Anything that would be some easy first tests.
4. I check the TCC wire and it has supply voltage at resting position and then goes to open at a brake pedal press so it functions. And it does down shift sometimes so I believe it is working. I will say it is just one wire from the PCM to my stock TCC wire in the car off the pigtail that used to connect to the old computer so could I maybe need a more modern TCC switch?
5. It fires right up and doesn’t almost die on startup but it’s just low idle, I haven’t done any testing and I just wanted some second opinions before I go digging into the thing trying to find where the problem is. TPS is my biggest red flag that brings all those issues together but any help will be appreciated!
I would also like to note that its first test drive was yesterday to the gas station just outside my neighborhood and once turned off it goes back to 1st and then just doesn’t want to downshift once driving. Today I did a run in my neighborhood and it did ok at lower speeds only but once I turned on the road and got speed and then went back to a stop it hadn’t downshifted. Thank you to those who can help!
