Intermittent misfire issue

1998 ISUZU HOMBRE
141,000 MILES • 2.2L • 4 CYL • 2WD • MANUAL
Avatar
DEELHEAD
  • MEMBER
  • 1 POST
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?
Sep 11, 2021 at 8:29 PM
Advertisement
Avatar
JACOBANDNICKOLAS
  • CERTIFIED EXPERT
  • 110,175 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

Sep 12, 2021 at 8:18 PM