99 Jimmy DIED

Major Crisis - need HELP.

I am new to this forum, for this simple reason. My wife's 99 Jimmy (4.3L, 2WD) died on us recently, with no warning and no signs of what could be wrong. Driving home, it just simply died. The gas pedal went dead and the engine just cut out. There was no noise or engine light or smoke or anything. We got it off the highway and the engine would not start up again. It will crank and crank, but not start. I spent three whole days troubleshooting it and still cannot come up with anything. I checked the computer with a brand new OBD II scanner and it came up with no codes, though the service engine light is on when the key is in the on position, which is very strange to me. Next, I tried checking the ignition system. The throttle body will backfire every once in a while, and even with ether sprayed in, it won't fire. The spark plugs are firing very intermittently, almost no spark at all. I replaced the coil, the ignition module, and the crank shaft sensor, but no help at all. The distirbutor cap looks fine, no arcing or melted plastic, which led me to the timing. With the number 1 piston at top dead center, the cap is pointing right on top of the triangle on the distributor. I can turn the crank shaft pulley with a wrench and see the distributor move, so the shaft isn't twisted in two. There is little to no play in the chain either.

Next I took it to a GMC dealer here in Dallas, and they have had it for 3 days and cannot find the problem either. They suggested timing, but the timing checked out. They suggested a stuck valve, but I would think the engine would still run with just a stuck valve (and not die on the road instantaneously). Next they said bad gas, but did a gas test and came back with clean gas. Now they want to do a compression check, but I don't see how that helps that there is no spark getting to the chamber. They said the computer is communicating, but won't plug in a new one to verify that the computer is not the problem.

Any suggestions guys? Can the computer just die and still pass a communications test with the dealer's diagnostic machines? I don't want to replace the $250 computer if that is not the problem. And I don't want to tear out the front of the engine if the timing chain or cam chain is not the problem either.

Any help would be greatly appreciated, as 3 A.S.E. certified mechanics are stumped on this one.

Thanks in advance,
Damian

it sounds like the computer to me.

Ed

Now the dealer mechanic says that since the cap and rotor are not GM parts, that is the problem. He also said two cylinders have low compression (80%) and that is why is won't start. They also said the fuel pressure regulator is bad.

The car keeps 60 psi when the key is on, sure it bleeds off after you let it sit for a few hours, but that is normal.

The cap and rotor are ACDelco and have about 20,000 miles on them, with no signs of wear or failure AT ALL.

As for low compression, wouldn't the car still start, just run rough? And how does low compression change the fact that there is no spark to the plugs???

Dealerships are the most dishonest bunch of crooks I have ever dealt with. This is ridiculous!!!

Can anybody out there offer any kind of tips or sugggestions???

Can anybody out there offer any kind of tips or sugggestions???

It still sounds like the computer. None of those issues would prevent it from starting.

Ed

Well, the dealership said timing, so we took the timing chain cover off....and

TADA - the timing is fine! The chain looks good with very little slop...the gear looks perfect, very minimal wear for having 115,000 miles.

So, we asked for out money back from the dealer for the incorrect diagnosis and they told us that it was a stuck valve then, if the timing was correct.

Shady, shady people.

I hate to buy a new computer if it is not malfunctioning, but hell, I am out of ideas...and patience.

Thanks for your help Ed.

D

the cap and rotor would prevent it from starting had the same problem with mine

find a dealership that knows what they're doing. if you can find a competent mechanic with an oscilloscope and a tech 2 scan tool you get it fixed in no time. it's not good to throw parts at a problem but in this case i'd throw a cap/rotor, plugs& wires at it because they need to be replaced anyways. oh i just thought of another possibility. when the fuel pressure bleeds off it's leaking into the intake through the cpi. this will flood the engine and wash oil off the cylinder walls resulting in you guessed it low compression. i'd remove all the plugs, remove the fuel pump& ignition fuses, crank the engine over a few times, put a little bit of oil in each cylinder, crank it over a few more times then put the plugs in hook everything back up and it should flash right up. oh yeah the check engine light is supposed to be on with ignition on and engine off. good luck with this one!!

We don't really know what fixed the problem. The local GM dealer pulled out everything they could think of and ended up not replacing anything at all. When they put it all back together, she fired right up. It was the weirdest thing. And they didn't charge us for anything, which was very impressive.

Try just unplugging the computer and plugging it back in. Maybe replace the cap and rotor, just to be safe (or at least replace it with a new one to try out, then return the new one if that didn't help).

I have heard half a dozen guys with late 90's GM trucks or SUVs with the same problem. One guy sent his to 4 dealers before it started again...then it died on the way back home.

I trust my Ford car more than any GM or Chevy...