89 Jimmy 350 TBI Misses when cold

[redstinger]

Does the same damn thing everyday. I have to climb a moderate hill on my way out of the neighborhood about a block from my house, and it's like its running on 7 cyl, laboring up the hill...I give it more gas and it picks up steam like the 8th cyl just kicked in, and accelerates briskly up the hill. Then about 5 blocks later, another hill, low power, hit the gas past 1/2 throttle, smooths out and power back. Then while sitting at the stoplight, brief millisecond miss, like someone flickered the ign key off and on real fast. You actually feel the engine shake for a tenth of a sec, then after truck warms up, runs great, no missing, runs on cyl all the time. In the last 5k miles I've replaced plugs, wires, cap/rotor,fuel injectors, swapped in adj fuel reg, fuel is 15psi. Still does it. It never did this before the tuneup, so maybe cracked spark plug?? Any ideas?

 

[1BEATK5]

check and make sure the wires are on the plugs and cap all the way then
i would look carefully at every plug. cracked porcelin during shipping or installation is common. i think you will find the problem with a close visual inspection of the secondary ignition system

 

[Code3K5]

make sure the plug wires are correct. My guess.... no.5 and no.7 spark plug wires are swapped

 

[redstinger]

plugs and wires are all new. fuel injection system is all new too. 17 psi fuel pressue. The issue seems to be getting worse. Problem seemed to go away after warmup but now it happens even after warmup, still intermittent though....cutting in and out. Ignition module?? Coil?? Any ideas?

 

[redstinger]

Update!! Just replaced ignition module...problem still there. Really starting to pull my hair out here.

 

[Mountain_man]

Did you get around to checking the #5 and 7 wires? Otherwise check the wiring.

 

[redstinger]

Did you get around to checking the #5 and 7 wires? Otherwise check the wiring.

I did, they are correct. I would think that would cause a consistent miss anyway...my condition only occurs during the first several minutes of driving when the truck is cold. After reaching operating temp it goes away.

 

[63chevyll]

Sounds like a bad plug, or cap maybe.

The plug can be temp effected.

What plug did you put in.....

 

[redstinger]

I put in the ACDelco plugs

 

[Mountain_man]

Well you could also be dealing with a gasket leak. If you have a leak in the tbi or headers, manifolds, intake or any of these places it could be needing to warm up so the gaskets swell and stop the leak mostly. I'd start with exhaust leaks and such to make sure. Then obviously check the other gaskets.

 

[redstinger]

now it is starting to stall out when pulling out into traffic. And sometimes it dies after starting...and hard to restart. I'm going to try a new coil and see if that cures it. one bad spark plug would not cause stalling and hard starting I don't think. The coil looks pretty old, its an aftermarket accel coil installed by previous owner

 

[redstinger]

Update

replaced coil, problem fixed!!! No missing or stumbles, smooth idle, pulls hard up hills when cold, hot, etc...now maybe I'll get better than 10mpg also!!