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91 F-150 idle lope. The horror continues

Still trying to get a new engine running correctly (5.0). Idle SOMETIMES lopes between nearly dying and 1200. Going down the road it's surging.

MAP sensor is checked as good, and the TPS, ACT, O2, EGR, knock, IAC, coolant sensors are all NEW!

Today it failed emissions miserably.

I have no idea where to go from here on what is virtually a completely new engine including sensors.

And of course checking for vacuum leaks was the first thing done. I'm

98% sure that's not a problem.

I could use some ideas on where to go.

The only code was a 334 which was resolved at the EVP.

Thanks

Reply to
Coyote
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Does the exhaust smell rich or blow black smoke? What's it running for fuel pressure? What's the timing set at? Bob

Reply to
Bob

check for EGR valve hose going directly to intake vacuum

I've seen this before on 302's after engine swaps

Reply to
TransSurgeon

Yup... that will cause a serious lope all right and it's old enough it might not set a code. Even if it's hooked up right it could be stuck open. I usually spray a little water on the steel tube between the exhaust manifold and EGR, if it sizzles there is a problem. Bob

Reply to
Bob

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