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EGR/misfire issue

Tiny
TMINER
  • MEMBER
  • 1998 CHEVROLET 1500
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 265,000 MILES
So I had a check engine light on but in the past it was on and would always go off without an issue due to an O2 sensor. I was driving and had a tremendous shudder start at a light. I went to Auto Zone (no I do not buy parts there) and they read out I had an EGR valve and random misfire issue. I cleaned the EGR valve of carbon and put it back on. The light went out temporarily and now has come back on. Unhooked the EGR valve and shudder at idle is still there. EGR should not be the problem at idle right? When I accelerate I have really bad shudder and at idle it shudders with or without EGR hooked up to electrical connection. I pulled the plugs and checked the wires and they all look okay for now but will need replacing eventually.

I tested the wires with an Ohmmeter. They all seem to be okay. The plugs had points for contacts not a flat surface. Should I replace all of them? I now think the cap and rotor may have been moved over. They look new.
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Sunday, March 18th, 2018 AT 1:07 PM

59 Replies

Tiny
ASEMASTER6371
  • MECHANIC
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Good morning.

Does the engine stall at idle? That will tell if the EGR is the issue.

As far as the shutter, do you mean misfire like and engine miss?

Roy
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Monday, March 19th, 2018 AT 2:07 AM
Tiny
TMINER
  • MEMBER
  • 49 POSTS
With the EGR connected or disconnected the engine runs the same and does not stall at idle or at another time.

I got a misfire code along with the EGR problem on the computer readout at AutoZone so that may be the real problem here but not sure what to check next.
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Monday, March 19th, 2018 AT 3:24 AM
Tiny
ASEMASTER6371
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Can you explain the shutter?
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Monday, March 19th, 2018 AT 3:33 AM
Tiny
TMINER
  • MEMBER
  • 49 POSTS
It is a consistent shudder and it is really bad under acceleration. When coasting or at idle it is not near as bad but still there. When I hit the throttle while in park it does it as well. It almost feels like someone is shaking the car. The engine appears to shake while I move the throttle under the hood.
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Monday, March 19th, 2018 AT 4:38 AM
Tiny
ASEMASTER6371
  • MECHANIC
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Okay.

It sounds like all the cylinders are not working.

How old are the ignition components? Plugs etc?

Also, a compression test would be a good start to be sure the engine is good.

Roy
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Monday, March 19th, 2018 AT 4:51 AM
Tiny
RENEE L
  • ADMIN
  • 1,260 POSTS
Hello TMINER,

If you decide to conduct the compression test yourself here is a link to an article from our site with written step by step instructions, pictures and video to guide you:
https://www.2carpros.com/articles/how-to-test-engine-compression

If you have any questions or need further advice please reply to your post and one of experts will be happy to help you.

Thank you for visting 2CarPros and have great rest of your day!

Renee
Admin
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Monday, March 19th, 2018 AT 11:18 AM
Tiny
TMINER
  • MEMBER
  • 49 POSTS
Roy the plugs and wires are old. They were on the engine that was put in my truck to replace the engine that was in my truck before it got melted by a family member towing a loaded trailer. The cap and rotor I believe are new. I was going to possibly get new plugs today as the wires are all okay I believe for now. The plugs are not much also.
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Monday, March 19th, 2018 AT 11:22 AM
Tiny
ASEMASTER6371
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That is a good start. Start with basics with the ignition parts.

Keep me updated.

Roy
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Monday, March 19th, 2018 AT 12:16 PM
Tiny
TMINER
  • MEMBER
  • 49 POSTS
New plugs helped some, wires did not. I now went back to O'reillys and have 13 unique codes. They are:
P0405 EGR Sensor A Circuit Low
P0302 cylinder 2 misfire
P0300 random multiple misfires
B1054
B1061
B1071
B1025
B1026
B1015
B1018
B1019
B1021
B1024

I am still leaning towards EGR because I'm getting exhaust fume smell. Maybe I should soak the pintle area in carb cleaner overnight? I know not to dunk the thing. The pintle error I had isn't there now though. The service engine soon light still flashes but usually only when I accelerate and I get the shake.
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Saturday, March 24th, 2018 AT 6:22 PM
Tiny
ASEMASTER6371
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Ok did you do a compression test while the plugs were out as I suggested?

If they are ok, the next step to check the injector.

Yes, I would soak the pindle in carb cleaner. Try that first

Roy
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Saturday, March 24th, 2018 AT 6:43 PM
Tiny
TMINER
  • MEMBER
  • 49 POSTS
I didn't see that you said you recommended to do that. I only saw it was something to maybe try. I'm sorry.

I will soak the pintle but do you think the EGR sensor A circuit low could be a bad EGR? Only trying to help.
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Saturday, March 24th, 2018 AT 6:46 PM
Tiny
ASEMASTER6371
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The pindles load up with carbon chunks and hold it open. It will then run lean and cause a misfire from a vacuum leak.

Roy
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Saturday, March 24th, 2018 AT 6:47 PM
Tiny
TMINER
  • MEMBER
  • 49 POSTS
Do you think the EGR caused a vacuum leak somewhere since it was caked with carbon?
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Saturday, March 24th, 2018 AT 6:50 PM
Tiny
ASEMASTER6371
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Yes, when the valve is open, that is a vacuum leak, a big one.

Roy
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Saturday, March 24th, 2018 AT 6:53 PM
Tiny
TMINER
  • MEMBER
  • 49 POSTS
Oh! I didn't know you meant the valve IS potentially the leak.

Do you assume the cylinder 2 issue could be the injector? Would that cause the running rough issue potentially?
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Saturday, March 24th, 2018 AT 7:12 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,462 POSTS
If the EGR is even partially open when it shouldn't be it will let inert exhaust gases into the engine and cause symptoms similar to but worse than a common vacuum leak. With a normal vacuum leak you get a lean fuel/air mix. Usually it will still ignite but you don't get the same amount of power. With the inert gas from the EGR you get a mix that doesn't ignite or only part of the fuel burns. Both will cause random misfires and loss of engine power as well as hard starting. The first thing I would do would be a top cylinder cleaning to break up as much carbon as possible. Next would be to pull the EGR and use a flexible brush and wire to clean carbon out of the passages in the intake. Then run it a bit with the EGR removed to blow out as much of what you loosened up out of the intake. Clean the EGR but be careful as you can damage them if you get aggressive. Order a screened EGR gasket (Kleen Screen or similar) and install it. Clear all of the codes and run it a bit to see what returns.

The EGR issue alone will cause rough running and misfires so it needs to be the first repair.

The B codes are all airbag and SRS related.
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Tuesday, March 27th, 2018 AT 8:37 AM
Tiny
TMINER
  • MEMBER
  • 49 POSTS
I kind of figured that, Steve. Thanks so much! I will try to get a screened gasket today. I soaked the EGR in throttle body spray and some more black came out. I'll drive without the valve on and go get the codes cleared first as well.

The flashing service engine soon light I was told meant I shouldn't drive the truck and another person told me it meant misfire.

CRC Motor treatment slowly through the brake booster hose while running is ok? The truck has O2 sensors and a cat converter.
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Tuesday, March 27th, 2018 AT 9:26 AM
Tiny
STEVE W.
  • MECHANIC
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Don't drive it with the valve off, scrub the passages and run it with the valve off just to blow out the chunks that come free. It will run like crap but you don't want to blow the carbon through the rest of the system if you can avoid it.

Flashing SEL/CEL actually means there is a problem that could damage the converter. There are a few things that can be, the primary one is a misfire as those dump raw fuel into the converter and they are not designed for that. It can easily cause them to burn out or glaze over inside.

I prefer seafoam or GM top cylinder cleaner as it seems to do a better job than most others.
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Tuesday, March 27th, 2018 AT 10:36 AM
Tiny
TMINER
  • MEMBER
  • 49 POSTS
After doing the top cylinder clean with Sea Foam it smoked bad. After driving it slightly hard it does run better but still hesitates under acceleration and shakes intermittently. I was going to let it soak overnight but then saw hydrolocking is a concern so I turned it on after about 2-3 hours of it hot soaking. The CEL no longer flashes but is still on. I didn't drive it far. I was considering clearing codes to see where we are. What do you think?

I got a regular EGR valve gasket as I would've had to order a screened one. I didn't put it on yet though. I guess I'm waiting to see if I need a new valve.
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Wednesday, March 28th, 2018 AT 5:34 AM
Tiny
ASEMASTER6371
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You could also try GM top engine cleaner. We use that all the top and it works great breaking up the carbon.

Roy
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Wednesday, March 28th, 2018 AT 6:34 AM

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