Weird engine trouble with my Chevy van
 

About 10 days ago, I started having severe missing and lurching in my van, a 1989 Chevy with a 5.0 liter. I had been needing to call my mechanic with an issue about my SDL so while I had him on the line I picked his brain on the Chev. He asked me when was the last time I did a tuneup. It dawned on me it had probably been 20 to 30,000 miles ago.

So I put in plugs, new cables, cap and rotor, and air filter. It miraculously started running much better. I’ve never had so dramatic a change from a tuneup, but then again I used to do them more regularly.

Then last night it started displaying the same symptoms again. And me all WTF? It’s more than the missing of a single cylinder, the whole engine loses power for a second, then regains it for a moment.

It occurred to me that a few times in the last year I have left the ignition key on for a spell w/o the engine running. Years ago on some other gasser I burnt a coil out in that fashion.

I did a search for symptoms of a bad coil, and it sounds a little bit like what I have going on, these especially:

#3 – Engine Misfiring.
#4 – Vehicle Stalling.
#5 – Engine Jerking, Rough idling, Poor Power.

I’m wondering if the tuneup cleaned up enough trouble to enable the faltering coil to have a bit more life. Even when it started running much better after the tuneup, it did not seem 100%.

It has 173k, I’ve owned it for about 50,000 of those, probably still the original coil.

Coil is cheap. Upgrade to a Hi po. Fuel filter?

Also inspect the distributor base plate for cracks, especially around the screws. You prolly would have noticed that with the new cap swap.

Oh wait! This is a GM.... HA !

If the distributor has a vacuum advance unplug the vacuum hose and see if the lurching goes away. If yes it's degraded wires on the distributor pole piece.

Good luck!!!

Good advice. I’ll put in the fuel filter later today, they didn’t have one on the shelf at the auto parts store last night.

I’m also thinking a fuel pump would be a good idea, given that it’s so damn hard to access, and I know I’ve never replaced it, it’s a bit shocking, but this might be the original fuel pump. You need to lower the fuel tank to do it.

The bizarre thing in all of this is that every change I’ve made has resulted in better performance but the hesitation thing is still there. Yesterday I put in a new stock GM coil. It’s an odd shaped thing, it’s not the big cylindrical item you commonly see. Would be a lot of work to attach anything other than the stock item. It ran noticeably better, but still not perfect. Wasn’t very many weeks ago that I was astounded at how well the engine was running. Apparently I had some deferred maintenance items coming due.

Thanks! I like this whole truck, a new engine might be called for one day, but I would prefer to put that off for a while.

A few years ago I had a horrible stalling problem. I had to put it in neutral and rev the engine somewhat at stop lights and stop signs or it would die. Trying to reverse to get into a better parking situation was an ordeal. One foot on the gas and one on the brake. I did everything I could think of, I finally took it to my mechanic buddy who is pretty sharp, he found that the distributor itself was bad. I had already put on new cap and rotor, but the thing had incredible internal friction.

That sounds like the idle air control valve. Those get gunked.

The stalling could be an EGR valve sticking partially open creating a vacuum leak.

The stalling of a few years ago was greatly improved by the new distributor. What it’s doing now is not the same thing, the engine rarely dies, it just hesitates on acceleration. Or, I should say that it did.

I really don’t get it, I put in the new coil day before yesterday and it ran better, but some of the problems were still there, some hesitation definitely. I got in it the next morning and it ran great, problems virtually gone. Now and then I’ll detect a tiny amount. But it is incredibly better.

I’m going to look at the other things you mention because I have been coasting with this engine for too long, not really paying attention to details that needed it. I’ve had it for about 10 years and 50,000 miles, just now discovered where the fuel filter is. Not good. I will put one of those and a fuel pump in soon. I’m trying to find the best fuel pump to use, don’t want to be lowering the tank again, unless maybe I put in a new engine someday.

Not sure you should do the pump unless you have indication it is needed.

Lots of distributor problems with many GM engines.

Is this carbureted or injected? What weight/series?
Does it have a computer?

89 prolly TBI, but cmac will tell us eventually. They had HEI ignition sys which ATE caps rotors and plugs. I switched to Hi po caps and rotors , upgraded the wires and went Bosch platinum plugs.

Yes, it is TBI. I bought a rebuild kit and did that some years back. I’ve often wondered if I did everything just right.

As for computer, it’s got something because you can do a stomp test to pull codes whenever you get a test engine light warning. There is a multi port little jack receptacle under the dash, you hotwire the top two on the right and then you get flashing of the check engine light, I’m sure most all of you have seen it, will send out a code number in that fashion.

It’s a tough one on the fuel pump, the old “if it ain’t broke don’t fix it“ principle. OTOH, I’m thinking 175K, it’s 33 years old, I know the fuel pumps in my Beemers would have failed by now. I still haven’t put in the fuel filter, I need to do that soon. Performance has been much improved, crisis mode is over, but something is not quite right.

Yup dirty sticky or bad IAC or EGR valve.

Good luck!!!

I’ll check it out. I hope you’re right, I will definitely give you props if you are.
:beerchug: