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1991 GMC Suburban 5.7 700R4 trans. New distributor, wires, coil, spark plugs, IAC, and battery. When the new distributor was install the timing was set to 0 degrees TDC with the pink unplugged. The truck is stock as far as I know but it doesn't idle correctly. I think the TPS is out of range and it looks like the IAC count to high. But here is the file from the first run with OBD1 cable hooked up to my laptop.
Any suggestion are welcome, Brian.
Are you sure you unplugged the proper connector? Every GM OBD1 I have set timing on was a tan/black wire.
I really can't remember the color of the wire right now, but I remember it was a single wire below the brake booster. I thought it was pink in color but it might have been brown. I do remember unplugging the wire and setting the timing to 0 degrees TDC and then plugging it back in and watching the timing marks jump all over the place. The Suburban was stalling when you came to a stop and sometimes would not start. So troubleshooting the problem and found out the distributor rectifier was the problem. I made sure to mark the old distributor before taking it out and when I installed the new one put it back in the same position but when I check the timing it was way off. Since the new distributor has been installed the truck always starts and even runs better than before and is getting better fuel mileage.
Thanks, Brian.
Edit: Not sure what the magnets on the distributor are called but that was the problem with the truck stalling and not starting at times. After a new distributor the truck always starts and runs fine but it surges at idle.
usually the check engine light will appear with the timming advance wire disconnected
Yes the check engine light came on when the wire was disconnected. I disconnected the battery after the timing was set and connected the wire back. Then connected the battery back and check the timing again and the timing mark was moving.
One big problem even when newer is the base gaskets for the TBI. I would start with the basics first. The base timing check, a leak down test or compression test, then check for vacuum leaks, even if it meant tracking down a smoke machine from a local tech. A good check of the basics can keep you from running in circles. So many times a customer would come in almost belligerent that they just know they have a "computer problem" and it ended up being something very easy and basic. All they got to do was pay me to check stuff they should have checked in the first hour of their work.
Tomorrow I'll take a look at the timing again and check for vacuum leaks. When I changed the spark plugs they all looked pretty good except one was oil fouled just a little.
It's entirely up to you, but "looking at the plugs" is not a compression check or a leak down test. This is what I was talking about. It may be a hassle, but a diagnosis is only as good as its foundation. If you skip the basics or don't check them properly then you could be correct in your guess and save yourself an hour or two, or you could end up chasing your tail for weeks because you hoped it was good and it was not. A leaking valve will not usually foul the plug, but it will show with a leakdown test and most likely show with a compression test if its bad enough. The typical scenario from a shops perspective is the customer thinks they know, try to fix it and by the time it gets to us there are a lot of new parts on the engine that may or may not be installed correctly. The customer is now upset with all the money they flushed and the basics have not been checked properly. It was not always the simple stuff, you could gamble, but you don't know unless you are very methodical in your approach to the problem. Just a little info, to try to help you out.Quote:
Originally Posted by SlowGrind