Hard to time

[snowball]

Hi all,

I just got my burb running. 1990 350 2wd, and I replaced the icm. I set it to 0. Started and it looked like it was 2 notches ahead and steady. I got on the road started to drive and after about a minute, she started to stumble. Giving her gas caused the truck to shake and stall.

Finally got her home and i looked at the timing again, and she was mostly at 0 but sometimes would jump a lot towards the right, maybe 20' and the whole engine was shacking A LOT!

Any thoughts would be greatly appreciated.

[snowball]

Pulled the codes and got a 33 and 42

[Corts60]

Assuming original TBI? How many miles on it? May be time for a timing chain and/or new distributor.

[Just call me Sean]

33 is MAP sensor, it won't run very well if that's bad. Make sure it's plugged in and the vacuum hose is still attached on both ends. 42 is EST, which you will get from disconnecting the bypass to set the timing. You have to clear the computer after setting the timing to clear the 42. If you did clear the computer, then the bypass might not be making a connection from corrosion.

[kwmech]

Originally Posted by Just call me Sean

. 42 is EST, which you will get from disconnecting the bypass to set the timing. If you did clear the computer, then the bypass might not be making a connection from corrosion.

I was going to ask if he even disconnected the timing bypass before he set the timing

[snowball]

1. Yes. bypass was disconnected. When I do this she runs VERY rough and stalls after about a minute.

2. I replaced the MAP sensor. Same problem

3. 350Miles total but I replaced the engine with a GM crate about 5 years ago. has 20k miles on it.

I'm going to test the TPS. Any other ideas?

[snowball]

nope. not the TPS

[Just call me Sean]

Did you hook up all the engine grounds?

[snowball]

Yup

[kwmech]

Any chance that the balancer has spun on the inner ring?

[snowball]

Anything is possible, but I took off the distributor cap, brought it to TDC and it lined up with the mark.

[kwmech]

Are you sure the piston was at top tdc or the line on the balancer lined up and the rotor was close. Just throwing it out there to see if anything sticks to help you out

[snowball]

yes

[kwmech]

How many miles on this. reason I ask is my 91 went through a very short similar issue then just quit altogether. First I noticed no fuel, 'cuz I didn't hear the fuel pump. My first thought was with 154k on the speedo the pump went out. Thumping the tank to get it to fire wasn't working. So I'm thinking pump went out. Further checking revealed no spark which I wasn't surprised. My search into the distributor revealed A LOT of rust. So I pulled the dist to clean it and freshen it up since it needed it anyways. Got it apart and the pick-up coil was toast. At that point I ordered a brand new dist from Jegs. Nice unit, machined from billet aluminum. Dropped it in and the 'burb fired right up and hasn't missed a lick since.

[snowball]

Lol

That's a loaded question. Truck has 359k miles but the motor was replaced with a crate 20k miles ago, but the distributor was transferred and that was replaced about 10 years ago

I guess that's the only thing left to replace?

[kwmech]

I still haven't replaced the fuel pump. Starts and drives just fine. I think all along was a bad pick-up coil and/or module. Part of the module on the tbi triggers the fuel pump relay

[snowball]

Props to you kwmech. New distributor and got her running. The old one had a huge wobble.

Thank you very much!!!