Idles rough, misfire, loud and check engine light flashing

  • 1994 CHEVROLET 1500
  • 5.0L
  • V8
  • 2WD
  • 120,000 MILES
I it's been acting up lately at first I could get it to stop by taking the negative battery cable off and now that's not even working. It suddenly starts idling weird kinda high for a second and then low to where it will sometimes stall if you don't give it some gas. The engine sounds a lot louder than normal and one time the exhaust manifold was glowing red. That only happened once that I've noticed. It also will not shift once this starts happening. I can only go about 35 mph. I cleaned the EGR value and the EGR sensor valve is working properly. And if I unplug the map sensor while it's running the truck will shut down so I assume it working. It also seems like it's got more acceleration when this is happening also I'm not quite sure what to do or where to start. And it sometimes bogs at a higher rpm. Also the check engine light starts flashing rapidly.
Any idea what the problem could be?
Do you
have the same problem?
Monday, February 10th, 2020 AT 3:12 PM

1 Reply


Based on your description, it sounds like you have a plugged catalytic converter. The idea that the manifold was red hot tells me either the converter is plugged or you are dumping fuel.

Take a look through these two links. The first describes converter symptoms and the second how to check one.

Next, I would recommend checking fuel pressure to make sure it is within spec.

There is one other thing I would like you to do and that is check for diagnostic trouble codes. This vehicle has an OBD1 system. Here are the directions for retrieving the codes on your truck. All you need is a short jumper wire or even a paper clip.

Let me know if this helps or if you have other questions.

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Monday, February 10th, 2020 AT 3:37 PM

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