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:

I had this on a 1996 Express van. Fix was simple yet took forever to find.

The hot wire on the battery, at least on the van, ran from the positive pole to a fuse box sort of thing on the other side of the engine compartment. This was more a box full of fuse able links than a real fuse box. Where the wire connected to this box was a single pole with a nut that screwed down on top to hold the wire.

The nut had come loose and the wire was not making good contact. I removed the wire, cleaned it and the pole, stuck it back together and the trouble vanished.

Hopefully this is all you are dealing with.

You put your finger on a problem with keeping these old vehicles running. There are all sorts of small items that can become corroded, loose, just less than optimally functional. I’ll look for the thing you speak of.

I found a post from 2015 on another site on this topic, he raised an interesting point that I hadn’t heard before. I’ll cut and paste about half of the post here:

https://www.vanning.com/threads/ubbthreads.php/topics/693506/all/help-with-my-g20-tbi-problems

I agree with the cut and paste post. Resistance through loose, dirty and/or damaged connections is FAR from good. Resistance goes up voltage goes down and sensors are sent incorrect values. This can turn into the "snowball effect".

Cleaning and tightening connections takes time but becomes more critical as our vehicles age.

Good luck!!!

Yeah, that was a lucky find wasn’t it? It’s the kind of thing I wish I’d had the insight to think of myself!

And since we know that fuel and other bits and pieces of the puzzle are allocated at ideally the right amounts at the right time based on those signals, can’t be good if those signals are faulty.

Holy shiite batpeople. Looks like it might’ve been the fuel filter as the main culprit. INSIDIOUS is clearly wrong about everything else but he was right about the fuel filter.

This has been a weird drama. I limped to the O’Reilly’s by the skin of my teeth when I first had the problem - put in plugs, cap n rotor, cables, and air filter in the parking lot. When I started it up was quite a bit better but not really 100% - the next day it was closer to 100%.

Then, the same drama a week later before I replaced the coil, I wasn’t limping as bad when I got to O’Reillys for that one, but limping. It ran better, but still funny, the next day it seemed almost ideal. Almost.

That was maybe four or five days ago. Today it started doing the missing and hesitation again. So I’m thinking OK, get over the sqeamishness of having gas drip on you, put in the fuel filter. I had a couple of paper towels to catch the dripping, suckers were dirty when I was done. I shook some more of the fuel out of the old filter, holy crap the paper towel got dirty. I’ve not seen that before.

All I can figure is that the tuning upgrade was badly needed and the two steps gave me enough power to fight the plugged filter. Strange.

I’m going to check all the other stuff anyway, the EGR, the idle valve. Going to clean the sensor contacts as recommended by the unknown poster of seven years ago.

LOL

Notice we don't hear much about this anymore? He is having too much fun tooling around with trouble free fuel delivery :D

Periodic Maintenance
 

I see this all the time : old fuel filters, often never having been changed since the vehicle was new .

My 2000 Ford Ranger Trucklet came to me with the original fuel filter, only 100,000 miles but you should change filters every 10,000 miles or five years as they get restricted and this back pressure kills the electric fuel pumps on modern vehicles .

I know they're not fun to change , Fords require a special tool that fits inside the ring retainer, guaranteed you'll get a gas bath no matter what, why I think so few ever get changed out .

This is one more reason no one wants to work on oldies ~ if you look there's always plenty of "Might As Wells" that need doing and the time alone no one wants to pay for.....

The average garage parts changer / $tealer "Mechanic" only wants to do the quickest flat rate job possible and on any oldie this ensures you'll be going back time after time.....

My brother doesn't like to "waste money" on anything that isn't broken so whenever his jalopy wheezes and rattles to a halt 2,500 miles from home guess who gets stuck fixing it on the road side in Glacier National or Yellowstone park, Death Valley, North Wyoming etc. ? .

Then do I ever get a "thanx Nate "? of course not, only 'that took a long time or wow that co$t a LOT ! " .

If that van isn't rusty and you like it, DON'T SELL IT ON ! .

Replace the little things, U-Joints, drive belts etc. and keep on enjoying your hopefully PAID FOR truck .

I paid $1500 for it about 12 years ago, I collected $1900 in insurance for a rounded crease put on one side. So I was on the plus side at that point.

An odd thing with this rig is how many of the bolts are metric. But not all of them. It’s a little bit maddening. Check this out:

The nut Holding the clamp/hanger was clearly metric. So I tried metric for The fuel filter nuts. 17 was too loose, 15 was too tight, am I said, I like many, does not have a 16 mm.

Quickie lesson for anyone We might not know how to transpose these things, not trying to insult anyone’s intelligence, but I was sort of a math whiz:

You only need to remember the number 25.4. Divide millimeters by 25.4 to get inches. Surprisingly that number is accurate to about five places, Here is the actual number:

25.39998

The reverse is to multiply inches by 25.4. Here is a sample problem:

I was curious what the SAE was for 16 mm, maybe I would get lucky. I divided 16 mm by 25.4 and got 0.629921. Multiply that by 16 and you’ll know how many sixteenths you have, in this case: 10.08, which is as accurate as you need. IOW, 5/8 will be too small of a wrench by a tiny amount. Turns out the 5/8 wrench open end would just barely slip over the nut, it was an annoyingly difficult fit at many points.

But my crescent wrench was so huge I’m lucky the 5/8 wrench worked.

Last time I dealt with one of those wonky fuel filters I came to the conclusion that they were not made for a particular wrench size in either metric or english, but that they were a tweener and you could get some wrench from either set to work even if a tad oversized. Or there was a third system of sizes that I haven't met yet :)

I replaced the fuel filter on my Express van as it seemed like the natural problem. It didn't help but it didn't hurt and needed doing.

When running down one of these weird problems you do catch up on a bunch of maintaining you sometimes overlook.

yea ... NOPE. It really is 25.40. You must have arrived there by doing a reciprocal of an approximation to 0.03937007874015748031496062992126. Or some other sloppy conversion you met somewhere. Didn't your ma warn you about staying away from sloppy? Don't argue. Just accept this. Ask the other engineers if you must. Or open your calculator function. Carry on

Mathmatics.....
 

I told him to take off his shoes, that mostly works for me.....

Any maintenance done yourself that reduces the chance of a road breakdown. Tends to be cheap in comparison. Or extends the useful lifespan of a vehicle.

I really go over an older vehicle before putting it in service.

Bad news chief. 25.39998 and 25.40 are essentially the same number.

My truck had been running great since the fuel filter change. Today it started hesitating again. Very strange. I’m going to have to get busy and clean the contacts on the sensors as outlined in the cut and paste above.

Yet still not "actual number" :)

Any chance you got a bunch of crud in your tank and/or lines? Long ago I noticed some crud coming out of the line when I disconnected the filter.

I put a pail on the line and bumped the pump ( key on for second) . unreal grey sludge came out in the first cup of gas. then clear.

Try it and let us know.

Dirty Fuel
 

THIS - it never ceases to amaze me how bad fuel from the pump can be ~

There was a time when fuel full of debris wasn't common but those days are long gone .

This is why I insist upon adding clear / translucent filters some where in the system, you cannot do this with modern fuel injection systems .

TWO YEARS AGO I cautioned my brother to change the intake screen in his 1987 300SDL, it packed up tight and stalled the car last weekend.....

I’m starting to wonder if the engine is past his pull date. It’s been putting out some gray smoke at start up for some time. When I first had the trouble two or three weeks ago, I limped into an O’Reillys by the skin of my teeth, it was barely moving. I put in plugs, cap and rotor, cables and air filter and it ran way better, but still not 100% great. The symptoms came back, I put in a coil, again it ran a lot better but not ideal. There was some improvement with the new fuel filter, but again not perfect. In my experience, a clogged filter reduces performance at the high end, does not make for hesitation and missing at the low end.

Now the symptoms are back, I put in a new EGR plus solenoid a few days ago, very little improvement.

My mechanic pulled off the vacuum line and played with it and said it seemed the EGR was stuck open. There’s a little ring of felt-like substance inside of it, it was falling out as I took it out. So I suspect it was indeed bad.

I’m wondering if the recurring symptoms are basically the plugs becoming fouled again by the blow by. About three years ago I ran at way low on oil one time accidentally, barely showed on the dipstick. Who knows, maybe I did some damage, and it does have 175K, and is 33 years old.

A new motor is not out of the question, one decision would be to stick with 5.0 or go to 5.7. I understand it usually doesn’t have much effect on MPG.

Have a good mechanic check it out before considering changing the engine. If you work at it every day. You can often identify problems you have seen a lot of before.

Sounds like you did and he did find one problem. He might locate the real one since that is repaired. What did he think the ignition spark looked like?
Good mechanics develop intuitive skills. Even more so in the old days where they were not paid for diagnostic time.

This guy is pretty good. He hasn’t had it in his possession to look at it yet. We’re talking about doing that on Monday. But yes, you’re absolutely right, I’m not going to replace the engine on a hunch.

It almost behaves like that’s what’s going on. But some of the evidence contradicts that. After I gave it the tuneup - plugs, cap n rotor, cables, air filter - it ran much better for a week. And it barely ran before that. Why would the fuel supply suddenly be better for a week?

But one thing is certain, it did run better the evening I put in the fuel filter.

If a fuel filter changed it for a bit I wouldnt change the engine. Get a compression check first. Im leaning towards a bad fuel pump.

Fuel Filters & E.G.R. Valves.....
 

I'd remove the EGR valve proper and hand clean it ~ so often they get gunked or carboned up and cause weird running problems .

If there's a bunch of crud in the fuel tank you may have allowed it to run better until the new filter began to get blocked .

I know removing the tank isn't fun but sometimes the fuel intake screen gets slowly restricted.....

Sounds like you're close to getting it done, don't be in any hurry to increase the engine displacement, gasoline isn't going to drop in price any time soon .

Have you tested the O2 sensors? Might even be cheap enough to just replace.

Plenty of diagnostics you can do...test fuel pressure, test O2 voltage, check vacuum at idle, pull the plugs and check for fouling, test for vac leaks, etc. Not sure if you can bench test those old TBI injectors bur st 175k they might be giving up too.

I did a quick skim of the thread, does this issue happen all the time or only cold/warm?

Yes, a compression check of course before even thinking of changing it. I’m speculating wildly. The symptoms in the way it’s reacted to various improvements is just mind boggling, it doesn’t make any sense. I also wonder about the fuel pump. I’ve Red speculation that Bad valve seats could be leaving to the smoke on start up, not sure how much all of these things would foul the plugs.

I’m going to ask the mechanic about a fuel pressure check. This is where my shadetree mechanic ass is limited. I’ve never done a fuel pressure check, I don’t know how, and I don’t have the equipment. I’m sure it’s not that tough, but the learning curve just gets massively steep sometimes.

Get a quote on valve seal replacement as well.

The old in for a penny, in for a pound thing is rearing it’s head. I’m wondering if a new fuel pump and cleaning the tank while it’s out would be good. I don’t have a good facility to do a lot of the stuff at present. I’ve got enough work on the table such that it makes more sense for me to spend my time on my speciality and pay the mechanic to fix the rig. He knows so much more than I do and has the shop for it. He rebuilt the tranny on this thing and it runs fantastic.

Like I said, in for a penny, in for a pound. I heard an account of one of these things totally cherried out, asking price $60K. This one is still halfway solid. I get purchase offers all the time.

Yup. If the compression is good, my guess is doing the heads is all that’s needed in the rebuild category.

My former neighbor, the outstanding welder, thinks the intake manifold gaskets might be aged out as well. I tried the old brake cleaner spray test, didn’t get any action from that.

Could will be the complete renewal of the TBI is called for as well.

It happens warm or cold. I forgot to mention that I swapped in a 02 sensor a few days ago. Holy crap that was an ordeal. On top of everything else, I need to get it smogged to renew my tabs. I bought the sensor, I went to the mechanic for the smog, the same guy also smogs (from the verb “to smog“). He loaned me his Snap-on 22 mm to put it in on the street. Using both arms I could barely get the damn thing to move for about 3/4ths of the extraction. Putting the new one in only slightly easier. Somehow I emerged relatively unscathed. He told me that he’s seen them so badly seized that he had to cut the nipple out and weld in a new socket.

I had read that a bad O2 sensor would lead to hesitation issues. The new one had no effect, but I’m pretty sure the old one was aging out anyway. I am wondering about vacuum issues as well.

When I first saw the symptoms 2 to 3 weeks ago, I limped into an O’Reillys and put in plugs, cap and rotor, cables, and air filter in the parking lot. I always have a set of tools with me. The old plugs looked pretty bad, and it ran 90% better. It’s been a strange experience, hopefully I’ll get some valuable lessons from it.

I haven’t had the new plugs out for a looksee yet, I’m thinking to take one or two out later today.

He did ask about warm cold ...

About the IM gasket The 5L gm's of that era had a corrosion issue with the gasket. I think the Olds 307 was the worst. I think they were aluminum? And that manifested in a coolant leak into the valley and cylinders. any coolant loss? IIRC the corrosion/leaks were usually at the rear on the driver side of the motor.

Is the engine light on? Pulled any codes?

Well, yes he did ask about it and I answered. The problem is about equally bad warm or cold.

Funny you should mention, there has been a persistent coolant issue that I cannot solve. I put in a new radiator a few years back, my mechanic found a couple of freeze plugs that were in bad shape and leaking, and yet there is still a slow leak. It never goes terminal, but I have to top the damn thing off. I have wondered a few times if I’m a nut job for keeping this running.

The only intake manifold gasket I’ve changed in my storied career was on one of my BMW E30 325i units. That was a tricky job, but it did the trick. It was going into loping at low rpm, I would be herky-jerking around turns.

The only code in all of this has been 43, knock sensor error. I checked it out, the line was pulled off, I put it back on, still got the code. I have a new sensor, I didn’t have the right socket to take it out. Will be a PITA to get out. No indication of knocking.