Mechanics

'92 GM 3.1 V6 TBI. LUNGES AT AROUND 1500RPM.

1992 Isuzu Rodeo • 6 cylinder 4WD Manual •

'92 Rodeo GM 3.1 V6 TBI. Lunges at around 1500RPM.

I was checking timing today it is 10* BTDC at 700 - 800RPM. After I reconnected the EST bypass wire, I was seeing how it advanced the timing in relation to RPMs. From 700 to about 1500 it stayed dead on 10 degrees BTDC. At about 1500 it suddenly jumped to 13 degrees then slowly advanced as I accelerated the engine further. If I backed of the throttle it jumped back to 10. There was no smooth advance in the timing from 10 degrees to 13. I have also been told that with the EST reconnected it should not be at 10* but advanced beyond that at idle.

Could this be causing the lurching I experience when driving?

Am I right in thinking that the timing should advance smoothly with acceleration?

If this ain't right then what's wrong?
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Rodeo joe
July 22, 2011.



No, I don't think that it should jump like that. The problem could be in a vacuum sensor (MAP) or the throttle position sensor. My guess is that one of them has an issue that causes its output voltage to spike around 1500 to 1600 RPM. Use a multimeter to test them.

Rivermikerat
Jul 22, 2011.