‘95 4.3 – W engine – Engine dies while driving – Problem solved

[DelCoch]

‘95 Jimmy 4.3 - W engine with 125K miles. I’m the original owner and it has no after market anything on it. A new Bosch fuel pump was installed 5K ago during regular maintenance and new plugs, plug wires, cap, and rotor installed about 1K ago.

About 500 miles ago the engine started dieing while driving down the highway. However it would re-start by itself before coming to a stop. When driving on the hwy and taching 2K (about 60-65 mph) the engine would die and as the tach needle started dropping the engine would re-start by the time the tack needle reached zero. It would do this about every 50 miles or so during a 100 mile trip. When the engine would die, there were no idiot lights that came on as it would re-start before losing oil pressure, etc.

After a couple hundred miles of this it got worse and the engine started dieing when at an idle while warming up in cold weather. Another couple hundred miles and it started dieing when stopping at traffic lights, but would always re-start immediately. On my last 50 mile trip it got to the point where it wouldn’t start right back up, and would backfire up through the intake. After leaving it sit for a few minutes it would start up again. Then, it got to the point it would only run on the hwy when the engine was under a load, like when going up hill. When going down hill the engine would die and not re-start before coming to a stop.

Thus, it now came time for some trouble shooting. No codes were set and the SES light had never come on. The fuel pressure test was right on specs, and it had good spark. In fact it would start and idle for several minutes. I’m now thinking the distributor cap may be arching inside, as towards the last when it was real bad, it was backfiring up through the intake when trying to re-start. So, as I’m taking the screws out of the distributor cap to remove it, I accidentally drop my ¼ inch torx socket and extension down between the distributor and the firewall. It didn’t fall all the way to the ground, or even to the skid plate. I believe it landed on top of the transmission and rolled up under the body down behind the firewall. Since there is not much space between the top of the transmission and the body, I couldn’t see or feel in there from the top or from underneath. The space is so tight that I couldn’t even get a magnetic pick-up tool in there to search for it. After about an hour I finally gave up on trying to retrieve the torx socket and extension and just left them in there; they will probably fall out one day and stick in my rear tire.

Anyway, I go ahead and remove the distributor cap and it looks ok. Now, I’m thinking there must be a problem with the central port injectors, the spiders, or the fuel pressure regulator leaking. Thus I set about taking the upper intake off. I disconnect all the wiring connectors and remove all brackets, etc, that are attached to the top of the intake. As I remove the coil, which is mounted on the side of the intake on this engine, the 12V wiring harness that connects to the coil just falls off, not secured by the plastic snap clamp like it should be. Now, I’m thinking, “Hey this just might be the problem”. So, I put everything back together, making sure the 12V supply to the coil is secure. It started up and seems to be running ok on my latest 50 trip. Apparently, when I replaced the plug wires I had removed the coil to give me more space to work and the 12V supply to the coil didn’t get re-attached all the way.

I thought I would pass this on as it’s something to keep in mind when trouble shooting. Especially if someone else has done a tune up before the vehicle comes to you.

[MT-2500]

Thanks for letting us know what you found.
And yes a lose or bad wiring will give you fits.
And check the wiring circuit is one of the first steps in many repair procedures.
And the key word in many code repair checks.
Glad you found the problem.
MT