I have a 1994 5.8 f150. Fresh rebuild on the engine and it ran great for about a month. Now it has a really rough idle occasionally and it will all but die. It does not want to take fuel but if I put it to the floor it will come out of it at about full throttle. Bad MAP sensor? Its not throwing any codes for the MAP. Ideas?

 

Is it throwing ANY codes?

 

Only code it is throwing is Excessive TC slippage. Nothing on the from the engine.

 

bump

 

Id do a fuel pressure test as it sounds like a pump issue.

 

I guess I should have said I did test that and its fine. Im going to look over the vacuum lines to make sure they are all good and intact. But I'm leaning towards the sensor due to the fact at cruise it does fine it just will idle rough and not want to take fuel. But its not throwing codes and thats what had me wondering.

 

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Did you replace any other sensors in the rebuild? is the idle erratic or just rough?

 

The best way to describe it is it's a hard stumble. The engine will shake in the motor mounts it idles so rough. IAC was replaced without any change. Smog was removed and so was egr. But after further research EGR will be going back on it. Like I said it ran for about a month without issue. Not throwing any engine hard codes. Self test via computer will kick off before it finishes for whatever reason. Injectors were cleaned
With all new ignition components. As also previously stated if it put it to the floor it will hesitate a second then come out of it and of course it would jump to recline pretty easily if I held it there. Good fuel pressure and it's holding great vacuum. Like 24 at idle if I remember correctly.