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TBI problems please help

D

DesertDueler2

1/2 ton status
Joined
Dec 25, 2004
Posts
132
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Location
Chandler, AZ
My truck had a missfire under load. It would do it from a stop or when making a turn. I was checking things to see what it could be. First thing I did was replace the fuel filter. It was dirty but not that bad. It didnt fix the problem. I was told to check the coil. I replaced the coil and it didnt change anything. However I did notice the dist. was loose, so I checked the timing. It was off about 10-15 degrees. So I figured that has to be the problem. I disconnected the brown wire to set timming correctly. I set it at 0 like it says, and the truck runs fine with the wire disconnected(check engine light is on now due to the wire being disconnected). When I plug the wire back in it runs rough, stalls, surges, and even has a hard time starting up(acts like timing is too high). I disconnect the wire and it hard starts, then cleans out and runs good. The only problem is it detonates under load(like if the timing is too high, but I know the comuter is in limp mode so it wont adjust the timing properly). What do you guys think it is? I also tried replacing the map sensor. Any help is greatly apriciated as I am going to the lake this weekend.

Dan
 
What's the timing do with the brown wire connected? Is it stable or does it jump around?

Did you inspect the distributor internals and see if it's in good working order?

Good visual inspection of the entire engine bay?
 
It wont really stay running long enough to check with the wire hooked up. When it did once it did jump around, but I think mostly becasue of the engine not staying at the same rpm(it would jup up and down a 200-300 rpms). Everythin under the hood looks good(connections, vacuum lines etc). I will pull the cap and take a look.

Dan
 
Dist looks good. No oil and no carbon tracking. Everythin still looks tight as well. I do have a spare module I can swap in if you think that might be the problem. What else could it be?

Dan
 
I bought one of those $30 code checkers at Autozone...I hear that a paper clip across the terminals works too. I'd give that a shot. It figured out a sensor problem I was havin'...paid for itself right there!
 
I have a code reader, but the problem is no codes, so nothing to read:mad: I tried a good module and quess what? still the same thing. Next I am going to try the EST and the ECM. Could the knock sensor add timing? I know its job is to take away timing, but when it goes bad could it add timing. I am getting almost 20 degrees of timing at idle when the wire is plugged in. It wont stay running lond. I tjump between 20 and 10. It drops to 10 to keep it running, then jumps back to 18-20

Dan
 
20* at idle is probably correct. If it can't hold that, something is wrong.

Typically high advance means smooth idle. With an ECM GM could control timing enough to get the best (well, for factory) timing in all situations.
 
I posted over at 3rd gen, so we will se if someone else can help. It just seems that it is stuck with alot of timing becasue of it runnning for probably a long time with the dist retarted. So the computer or a sensor had to adjust for it, and now its stuck, I just cant figure out which one(at least I hope this is the problem)

Dan
 
Couple of things to try.
You could try resetting the computer by disconnecting the - batt cable for 5 minutes then reconnecting. If that doesnt work it could be the magnetic pickup coil. It is located inside the dist it is the round thing that encircles the shaft with 2 wires usually green and white or yellow. Disconnect the 2 wire plug coming from it and put an ohm meter between and read the coil.
Should have 500-1500 ohms. If out of those specs replace it. You have to pull the dist to replace.
 
Well I finally got it fixed. It was the timing off. The previous owner put on the wrong balancer so when I was timing it straight up it was off:eek1: Luckly I had a timing pointer laying around to put on it to time it. All better now:laugh:

Dan
 
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