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89 jimmy with timing and transmission issues :(

the_blaze

the_blaze

Nightmare / Plan B
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Hey,
@ashman and I are helping a brand new k5 owner with an 89 jimmy that he just picked up. It has some weird issues we cant figure out.

(1989 gmc jimmy, new gas tank, new fuel pump and sender, new fuel filter, new spark plugs, new wires, clean throttle body and injectors)

1. We think something is weird with the timing, we unhook the computer wire and try to set the base timing anywhere from zero to 10 and it just dies. If we set the base timing at 32 it seems ok but runs poorly when the computer is connected. next issue that might be the same issue...

2. When you get it running if you bump the throttle it dies. Sometimes it backfires a little, sometimes it just majorly hesitates, if you go really slow it will rev up ok.

3. The transmission will not shift out of 1st, seems to have enough fluid, and we tried adjusting the tv cable but it didnt do anything....

4. Basically any load and it stalls,
Have to put it in 4 low to move it around.


Any ideas? (Note: we pulled the cat tonight just to see if maybe that was plugged and part of the issue. No success but it sounds cooler )

@ashman correct me if i got anything wrong or forgot anything.
 
If it’s an unknown truck start at the basics. I’d assume all tranny problems are motor related until you have the motor seemingly right.

I’d start with minimum a compression test and I’d want a leakdown test, also check make sure all spark plug wires are intact and firing in correct order. Visually inspect the spark plugs, and verify fuel pressure is up to snuff.
 
Is the CEL working (comes on briefly at startup)? Is it throwing any codes?
Also check hoses for vacuum leaks by spraying carb cleaner around them and listening for rom’s to change.
 
It does sound like the timing may be way retarded....might be weak spark too,a dying coil or pick up coil can make an engine run gutless and pop back thru the intake intermittently...

The transmission ,if it only has reverse and first gear,and will not upshift into second or third,and it doesn't seem to be slipping in first gear ,it is probably the govenor --it has a nylon gear that is driven by the tail shaft and sometimes they'll scallop out and lose contact with the tail shaft and not spin it--no spin,the valve in it wont open and it wont upsift..
My '81 G-10 van had that symptom when I bought it in 1990 for $500 with a "blown tranny"..a guy who ran a transmission shop who was a customer at the parts store I worked at told me what to look for,it was simple,there is a tin cover with a spring clip on the passenger side of the transmission--take off the clip (its like the one on older master cylinders),and the govenor slides out--nothing should "fall in" or anything,so you don't have to be worried about that..

The nylon gear on the govenor looked like an apple after you eat all around it..its supposed to have nice straight teeth..
You can buy just the gear at a dealer,put you have to dork around driving the pin out without damaging the govenor and its a fairly intricate part..

I got a govenor at a junkyard from another TH350 rather than mess with the gear on the original one..and popped it in and the tranny shifted perfect again..
The govenor controls what speed it upshifts at,and one from a similar transmission may be calibrated a little different due to higher or lower gearing in the differentials,and tire sizes--but usually they are close enough to your original,if not you can tweak the weights and springs in it to alter the upshift speed..
 
Also, when you put it on tdc, don’t rely on the timing mark. It may have spun. Pull the #1 plug and bump the engine till it puffs your finger off the hole.
Then manually turn the engine in the correct direction till the piston is physically at tdc. You can feel it with a straw or something you won’t scratch the piston with. Then you can verify your timing mark on the balancer is correct and check your rotor is pointing at #1 on rotor.
 
Fastereddie said:
Also, when you put it on tdc, don’t rely on the timing mark. It may have spun. Pull the #1 plug and bump the engine till it puffs your finger off the hole.
Then manually turn the engine in the correct direction till the piston is physically at tdc. You can feel it with a straw or something you won’t scratch the piston with. Then you can verify your timing mark on the balancer is correct and check your rotor is pointing at #1 on rotor.
Click to expand...

I would agree. It sounds like the distributor is not in correctly to start with. Get the timing correct, and the rest of the problems will fall in line.
 
Thanks for the input guys. @Fullerton is new to trucks, and I'm new to TBI.

@rampage it is throwing a code. We need to get ahold of a obd1 reader to check it out.

@diesel4me I think you might be right about the governor. That describes the symptoms pretty well.

@Fastereddie we will verify TDC next time we are working on it for sure.
 
Thanks for all the feedback! this gives us something to look into.
 
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