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Idle surging

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I have a 94 Camaro racecar with a LT1 small block chevy I am struggling to identify an issue. At idle I get significant surging once the car has warmed up and is in closed loop. When I take it out on the track I will get misfires under high load (5th gear and 5,000 RPM). At the end of a long day it will cut out completely and not refire until it has fully cooled.

So far I have:

- measured fuel pressure which is reading 31-32 at idle and 40s at WOT per the stock parameters

- fogged the intake with no visible vacuum leaks

- checked all spark plug wire connections

- Checked grounds

- Checked exhaust manifolds for leaks

- Replaced my MAP sensor

I've attached my HP Tuners log. I'm pretty new to all this but it seems like there is an asymmetry in my bank1/bank 2 fuel trims that is consistent each time I test and the MAP seems to fluctuate strangely.

Any advice would be greatly appreciated

Attached Files


Regarding the misfires worsen with prolonged use, I would look at the ignition side of things first. In particular ignition coils.


Just to confirm, which gen' "LT1" is this - sometimes the earlier "LT-1" is also written as "LT1"?

If the former, the OEM coil, or HEI, is weak at higher rpm, and upgrading is a must.

If the later, as seems to be the case, how have you got the fuelling routed, if it's looped, and the rails, fittings, etc are a little undersized for the requirements, you will get a pressure drop along, and between, the fuel rails.

Thanks guys!

I have the newer “LT1” which predated the LS1 in the 90s. I upgraded the ignition from the Optispark to coil packs which are all new. My fuel pressure sensor is at the rail.

Any thoughts on how I could troubleshoot ignition vs. fuel related issues? Is the asymmetry in fuel trim suggest an issue on the fuel side?


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