94 GMC Jimmy! Surges and dies.

[gs1344]

Engine starts surging and then would die. Impossible to restart. After a day it would fire and run for a few miles. A local small shop changed the Spider Assem, Nut kit, EGR, Fuel pump again, Fuel filter, cam sensor, fuel cuttoff switch(?). No error codes! It ran for about 1 month and now the same thing again ..... any thoughts or anyone seen this before?

[gs1344]

More info, strong spark at plug. Fuel pump is running with good pressure.

[94 Jimmy]

I had a similar problem, it was worst at idle, of course it was the Central Port Injector(CPI, Spider). Changing that many parts without knowing which one was at fault makes it hard to determine which might have been bad out of the box.
Is the problem worse at idle or while driving, low power crusing or high power acceleration. How about plugs, what are their condition, carboned up on one side and not the other? Are the plug wires new, I've seen them break down internally and melt the plastic center conductor which can make for weak or nonexistant spark.

Check out: http://www.asashop.org/autoinc/feb2000/techtotech.htm

This will give you some infor about the CPI and fuel pressure.
Good luck, let us know what you fine.
94

[gs1344]

Thanks for the info. New plugs, wires, ignition parts, I can not think of anything that has not been changed except the brain. Catlytic, O2's, relays, and all the others I listed asnd more ..... Engine starts, then no acceleration after a few minutes of running. High RPM, Low RPM doesn't matter. It surges like it wants to die then picks up again and repeats surging. After about 5 minutes and no more than 30 mph it will die and then you have to wait for a few hours to restart. I limped it to a NAPA Service Center and told them to figure it out, I've had it, but "IF" they are successful I will post what they found. Maybe it will help someone else as this is apparently a very common problem with the 4.3 If they can't get it, it will find a permanent parking place at my house.

Thanks!

[maxwedge]

Typical of a failing fuel pump or clogged fuel filter.

[gs1344]

I agree that is what is sounds like but it has a new fuel pump assembly, Fuel pressure switch, and filter also. They have changed out all the $$$$$ things it will probably end up being a $2 part.

[gs1344]

Well they think they found it or they are 99.7% sure. I have no idea why they are leaving a .3% margin of error. They found that the surging/dieing can be stopped by moving, pulling, kinking the wire harness that runs from the Brain to the CPI unit. With the ECM connected to the diagnostic machine you can see the readings go erratic and stop by moving the cable around. Even though they checked connections at both ends, The plan is to change the harness. They believe it is a heat over time issue with the wires. A connector I can believe, but we shall see over time and a few miles driven. I hope that .3% is included in the warranty, you need one with the 4.3L W engine!

[gs1344]

FYI to all with this problem. Before you spend a lot of money changing the Spider Assembly (unless you smell raw fuel), check this wire harness and the wires going to the CPI. If your 4.3 is surging and dies, you may be able to move this harness around while the engine is running and make the engine die. I have been chasing this problem for months. GM sells a pigtail, harness replacement kit and it FIXED THE PROBLEM!!! The truck is running like new. Good luck to all.