Engine starts chugging and will stall out

Hi,

This could be a few things. The engine coolant temperature sensor can cause this, an engine vacuum leak and so on. I want to start by checking for diagnostic trouble codes so we aren't guessing.

Here is a link that explains how to retrieve codes. This has an OBD1 system and it doesn't require a scan tool to check. All that is needed is a short jumper wire or even a paper clip. Follow this link and let me know the results.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

and

https://www.2carpros.com/articles/engine-stalls

Let me know.

Joe

I'm not showing any error codes.

Hi,

Check to see if there are any vacuum leaks. Here is a link that explains how it is done. Also, if there are no leaks, we will need to make sure the catalytic converter isn't partially plugged and causing issues at idle when warm. You could remove the O2 sensor before the cat to see if that makes a difference.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

One other question. When this happens, if you place it in neutral, does the idle return to normal or will it still stall?

Let me know what you find.

Joe

The O2 sensor before that catalytic converter was the one I replaced. Can I just unplug it to test it or do I need to take it out? Also, the truck will stall and shut off in neutral or in gear. If I'm not pressing on the gas it will shut off.

Hi.

Remove it so there is an additional location for the exhaust to vent from. This will reduce back pressure if the converter is plugged. Simply because of the size of the sensor port being small, it won't make things perfect. However, if the converter is the issue, you should be able to tell a difference.

Let me know.

Joe

I did find a broken boot on the vacuum tube that goes to the PCV valve. I replaced it and it didn't fix the issue. I was reading the directions in the link and where is the throttle bore gasket? If it makes any difference I can smell the exhaust much more like the truck is running rich.

The throttle bore gasket, it is between the throttle bore an the intake. See pic 1.

If the gasket is leaking, that would create a lean mixture. The idea that you smell fuel would indicate a rich fuel mixture. Have you checked fuel pump pressure to see if it is high?

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Let me know.
Joe

The fuel filter and pump were one thing I thought about. I got a pressure test kit and a new fuel filter. I will test the pressure and replace the fuel filter tomorrow. Also I have read some about maybe the distributor causing this issue?

It could be related to the ignition control module. If it is failing, it can cause issues with both ignition and injection timing.

Okay, I once I started messing with the distributor I noticed the cap was full of carbon and the magnets were covered in rust. I replaced the distributor and it runs great. It is still missing a little bit tho. Will the truck computer catch up and work it out or do I still need to replace something else?

The computer may be going through a relearn process. If it continues, see if you can find codes.

Let me know, and I'm glad to hear it's going for you.

Take care,
Joe

Also, when I first start my truck it idles pretty high and doesn't go down once it's warmed up but once I put it in gear and start driving it will settle to a normal idle rpm. Could this also be a computer relearning issue too?

Absolutely. How many miles have you put on it since it has been running? It honestly shouldn't take too long for the relearn to happen.

Joe

Maybe 6 miles.

Okay. Drive it more. In addition to miles, speed, times started, and so on all play a part in the relearn. Try it for a couple days and let me know if it doesn't change.

Take care,
Joe

I took it out today and got it up to highway speeds. It chugged some when I first started it but it seemed to fix itself. The truck ran great but I got a "service engine soon" light. I checked the code and it was 32 and saw it was the EGR valve. I had that same code once before and the next time I drove it it went away. Seems to only come on when I go at highway speeds.

You may have an issue with the EGR hanging up or even a vacuum issue. Have you done any work on it? Let me know that and if you have an electric shift transmission or not. See pic 1.

Joe

I have not done any work on the EGR but I did pull a lot of the vacuum lines off to inspect them and make sure they were okay when trying to fix the other issue. I don't know how to find out if i have an electric shift transmission.

Hello, I'm Danny.

Just here to add my 2 cents. I've attached a picture of the location of the EGR valve and cleaning instructions if this helps. I've owned a few 88-98 K1500's. The EGR is behind the throttle body near firewall.If it's too far gone you can replace. As far as your transmission it is more likely to be the 700R4 which is non-electronic. We can confirm with your VIN - the vehicle identification number.Attached my K1500's below.Hope this helps and thanks again for using 2CarPros.

I know from past, and present transmission issues, that my transmission is a 4L60E. I will also get on with cleaning my EGR valve. Thank you

You're welcome!

Keep us updated after cleaning the EGR to see if the symptom persists.Thanks again for using 2CarPros.

Danny-

Okay, I have put about 175 miles on the truck. Now when I start it it almost seems to be missing. If I shift it into gear it will almost chug out and shut off. If I shift back to park or neutral it won't go back to normal until I let off the brake. After 5 minutes or so everything seems to even out and I have no issues after that. Even restarting it it will run fine. The issue starts if I let it sit and let it cool down.

Hi,

Does releasing the brake seem to clear things up for you? The power brake booster could have a vacuum leak. The brake booster is behind the master cylinder.

There will be a large vacuum hose running to it. I attached a pic I found on the net and circled where the vacuum hose will connect. Make sure nothing is leaking at that point.

Joe

How do I check for a vacuum leak there?

First, try moving the vacuum hose around to see if you hear a hissing. Do this with the engine running. If nothing shows up, here is a link that explains how to find an engine vacuum leak. You can use this procedure to check:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know if this helps.

Joe

I can't find any vacuum leaks but now it chugs and sputters when I first start the truck but after warming up everything smooths out and it's fine. It's the exact opposite problem I had when I started.

Have you rechecked for codes? Is it possible to record what it's doing and upload it for me to see? Also, when this happens, is there any smoke from the exhaust (black specifically)?

Let me know.
Joe

No black smoke and I haven't checked for any codes, but the check engine light is not on either.

Sorry the video isn't louder. I don't have exhaust on my truck so I though there wouldn't be any trouble hearing it. There did a not one time I gave it has to keep it from shutting off before it leveled out and drove without issue.

Hi,

I really can't hear it, but noticed the temperature gauge is off. Do you have access to a live data scan tool? If the engine coolant temp is sending a radical signal, it won't set the check engine light but will cause issues with the air/fuel ratio. That can cause issues.

Let me know.
Joe

Where could I buy the live scan tool?

Hello again.

You can find Actron or Innova brand scanners at most auto parts stores like Pep Boys, AutoZone, O'Reilly's, etc. You might want to see if you can borrow one first from a friend otherwise they range from $50.00 to $350.00 at parts stores. Hope this helps and keep us updated.Thanks again for using 2CarPros.

Danny-

Truck still stalling and running poorly. I've installed new fuel pump,tank,lines,sender,filter,sock,and ignition module. Computer states all is in perimeters! What could be causing this issue? I'm at a complete loss!!! Trucks problem persist.

When was the last tune up? Have you checked for vacuum leaks? catalytic converter? Any trouble codes in the computer?

Tune up was about 10 weeks ago. No codes in computer. New exhaust and cats installed. And no leaks that i could find. I had new exhaust installed and problem began shortly after. I scanned with SnapOn scanner and all was in perimeters. 02 was functional and good???

The fuel injectors could be failing or dirty. Try running a high quality fuel system cleaner through the system.
The best one to get is BG44K, but is hard to find and you will have to check service stations or car dealerships in the parts department to find it. The other good one is Sea Foam.
Run two cans of either one or you can do a direct pour into the engine using the brake booster vacuum line as your entrance to pur it into the engine. If you choose to pour it directly into the vacuum line leading into the intake manifold, there are a few things to know;

Do not rev the engine during the entire cleaning process.
It will create a great deal of smoke from the exhaust for several minutes. So, don't do it where you might irritate your neighbors who have their windows open.
Idle the vehicle until the smoke from exhaust clears and only use one can to do this.
Do not repeat this direct poor method for a while.
Performance changes may take a little bit of driving as many deposits will be loosened from parts and have to flush through sytem until the true results can be fealt.
You may need to replace the engine oil soon after cleaning as so many deposits will be removed, it tends to make the oil dirty.
You can still run a can in the tank, just don't run two cans of cleaner via the direct pour methed. It can overheat catalytic converters and O2 snesors if this is done.

I will try that. Can a fuel pressure regulator suddenly fail or is it gradual. No codes. Assumingthere is a delivery prob.

They can go fast or slow.

Truck starts and runs for a while then dies with no warning. Will not start up again without pouring gas into TBI. What could be the cause. I have changed fuel pump. fuel pump relay, fuel filter, spark plugs, wires, cap and rotor and still having the same problem. Please help.

Welcome, It's hard to get pointed in the right direction without knowing if your loosing spark or fuel, first, or something else? If your loosing spark, a possibility is pick-up coil or worn out distributor.