Intermittent misfire issue

Tiny
DEELHEAD
  • MEMBER
  • 1998 ISUZU HOMBRE
  • 2.2L
  • 4 CYL
  • 2WD
  • MANUAL
  • 141,000 MILES
Starts normal and idles smooth but as you drive and this is not constant but when you drive it acts like it's missing. If you step on it it goes away until you are at a steady speed. And again it doesn't do this all the time. It goes days with no issue and then out of the blue it starts to act up again. No check engine light! I have changed the fuel filter, EGR valve, 02 sensor TPS, air fuel sensor and cat. I just can't figure it out and it doesn't spit out a code for obd to tell me. I don't know what else it could be?
Saturday, September 11th, 2021 AT 8:29 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,145 POSTS
Hi,

This is a tough one because it isn't all the time. Have you checked for engine vacuum leaks and fuel pressure? Either could cause this.

Here are two links explaining how both are done:

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

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

Let me know. The idea that it goes away when you press the throttle seems like it is fuel-related. By chance, do you have a live data scan tool? If you do, can you let me know what the short-term fuel trims are?

I will watch for your reply.

Joe

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Sunday, September 12th, 2021 AT 8:18 PM

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