Greetings, All
I've lurked this forum for quite some time, never had a whole lot of problems with my own truck, but now I need some help.
My truck is an all original 1989 C1500 with the 5.7 and 700r4 auto trans. It's just about to hit 124k miles and was maintained exceptionally by the previous owner, with maintenance records from the very day he drove it off the lot. I have continued this record.
The problem started with a coolant leak, back passenger side of the intake, this infamous heater core fitting had failed. When i tried to remove it, of course, it broke, requiring me to remove the intake to remove the rapidly disintegrating "metal" piece that remained. I've done this before on my project cars, and in fact just swapped the factory intake for a performance one on my El Comino the week prior, but had never done so on a TBI engine. It wasn't a huge problem getting the job done, and the truck ran fine for a couple of weeks there-after. This, I think, is not the source of the problem, just something that happened shortly before my current problem arose.
About a week prior to my current problem I decided to put some new mufflers on the truck, I tired of the glass packs that where on it. Went to the muffler shop, had them installed, no problems. A couple days later, at work, coming back from lunch the truck nearly died at a stop light, and then ran poorly there after. On the way home it bucked and shook like crazy, no odd noises or anything like that, just shaking very bad at part throttle.
I believed that I didn't have the timing set 100% correct, as I didn't have a timing light, but the lines on the distributor and intake had all lined up when I reinstalled it after taking the intake off. So I ordered up a timing light and got that set, this did not solve the problem, so I hit my service manual up and pulled codes, 33 and 34, pointing to MAP sensor. Tested the MAP sensor, and it checked out fine, put a known good one on, same thing. Cleaned the EGR valve, testing the TPS, cleaned the IAC, installed a new distributor, wires, coil, checked the plugs, they're iridium and are clean.
I've set timing to 0 degrees with the wire disconnected, and then at my father's recommendation, 2, 4, and 8 degrees before and after TDC, with no change in how the engine runs. It runs fine at highway speeds, but you let off the gas it stumbles, tries to die at stop lights but only just after stopping, once it recovers it runs fine at idle, till you have to let off the gas again. Sitting in park or neutral with my foot lightly on the gas it acts like it's flooding out or getting too much gas and surges badly.
So I started poking around and noticed I left this plug
unplugged. but I cannot seem to find what it plugs in to.
I stopped by the dealership to see if they could direct me to what it goes in to, but they where unable to find anything either. The wire color is pink or purple.
It it not energized with the key off, but reads voltage with the key on. I believe it runs to some sensor, but cannot seem to find out what one.
Finally, throughout all my testing and part swapping, I read the codes again, after clearing them and driving it for a bit to see if it will set another code, and the only code I have now is code 34.
Any help would be appreciated, this is my only vehicle with a working AC and it's summer time in Texas!
I've lurked this forum for quite some time, never had a whole lot of problems with my own truck, but now I need some help.
My truck is an all original 1989 C1500 with the 5.7 and 700r4 auto trans. It's just about to hit 124k miles and was maintained exceptionally by the previous owner, with maintenance records from the very day he drove it off the lot. I have continued this record.
The problem started with a coolant leak, back passenger side of the intake, this infamous heater core fitting had failed. When i tried to remove it, of course, it broke, requiring me to remove the intake to remove the rapidly disintegrating "metal" piece that remained. I've done this before on my project cars, and in fact just swapped the factory intake for a performance one on my El Comino the week prior, but had never done so on a TBI engine. It wasn't a huge problem getting the job done, and the truck ran fine for a couple of weeks there-after. This, I think, is not the source of the problem, just something that happened shortly before my current problem arose.
About a week prior to my current problem I decided to put some new mufflers on the truck, I tired of the glass packs that where on it. Went to the muffler shop, had them installed, no problems. A couple days later, at work, coming back from lunch the truck nearly died at a stop light, and then ran poorly there after. On the way home it bucked and shook like crazy, no odd noises or anything like that, just shaking very bad at part throttle.
I believed that I didn't have the timing set 100% correct, as I didn't have a timing light, but the lines on the distributor and intake had all lined up when I reinstalled it after taking the intake off. So I ordered up a timing light and got that set, this did not solve the problem, so I hit my service manual up and pulled codes, 33 and 34, pointing to MAP sensor. Tested the MAP sensor, and it checked out fine, put a known good one on, same thing. Cleaned the EGR valve, testing the TPS, cleaned the IAC, installed a new distributor, wires, coil, checked the plugs, they're iridium and are clean.
I've set timing to 0 degrees with the wire disconnected, and then at my father's recommendation, 2, 4, and 8 degrees before and after TDC, with no change in how the engine runs. It runs fine at highway speeds, but you let off the gas it stumbles, tries to die at stop lights but only just after stopping, once it recovers it runs fine at idle, till you have to let off the gas again. Sitting in park or neutral with my foot lightly on the gas it acts like it's flooding out or getting too much gas and surges badly.
So I started poking around and noticed I left this plug
You must be registered for see images attach
unplugged. but I cannot seem to find what it plugs in to.
I stopped by the dealership to see if they could direct me to what it goes in to, but they where unable to find anything either. The wire color is pink or purple.
You must be registered for see images attach
It it not energized with the key off, but reads voltage with the key on. I believe it runs to some sensor, but cannot seem to find out what one.
Finally, throughout all my testing and part swapping, I read the codes again, after clearing them and driving it for a bit to see if it will set another code, and the only code I have now is code 34.
Any help would be appreciated, this is my only vehicle with a working AC and it's summer time in Texas!
