2.9 idle issue

[GKM007]

My 2.9 run great except for a slight hiccup at idle when warm. This is not something I notice when it is cold.

I have done a full tune up and oil change, also ran a full bottle of Redline cleaner through. I had a unidentified tick that has stopped. I do not know if it was a lifter or a injector making noise but between the fresh Castrol Oil and Redline it has quite.

Once the truck warms up is when this hiccup happens. I will come up to a light the truck will idle down to the 850-900 range and about 2-3 seconds later it will start. If you bop the throttle rpms go up (obviously) and then it will settle back to idle and 2-3 seconds again it will start. It does not die during this either

Rpms do not not seem to drop when this happens. Best way I can describe it is it feels like a cam is installed, but I doubt it. Also it isn't a consist type of lope that you would find with a cam. Sometimes it is a heavier hiccup than others. It almost feels like a miss?

Things I have done:
Plugs/wires/cap/rotor/oil/fuel cleaner/air filter/fuel filter/timing set to 12 and running 89 octane.

Any ideas on what this could be? Other than the idle this things run good and pulls hard on acceleration.

 

[Mr. Tarkanian]

My 2.9 run great except for a slight hiccup at idle when warm. This is not something I notice when it is cold.

I have done a full tune up and oil change, also ran a full bottle of Redline cleaner through. I had a unidentified tick that has stopped. I do not know if it was a lifter or a injector making noise but between the fresh Castrol Oil and Redline it has quite.

Once the truck warms up is when this hiccup happens. I will come up to a light the truck will idle down to the 850-900 range and about 2-3 seconds later it will start. If you bop the throttle rpms go up (obviously) and then it will settle back to idle and 2-3 seconds again it will start. It does not die during this either

Rpms do not not seem to drop when this happens. Best way I can describe it is it feels like a cam is installed, but I doubt it. Also it isn't a consist type of lope that you would find with a cam. Sometimes it is a heavier hiccup than others. It almost feels like a miss?

Things I have done:
Plugs/wires/cap/rotor/oil/fuel cleaner/air filter/fuel filter/timing set to 12 and running 89 octane.

Any ideas on what this could be? Other than the idle this things run good and pulls hard on acceleration.

Possibly your TFI Distributor module? They are usually affected by heat. Just a guess.

 

[GKM007]

I have checked on that and it seems pretty new.

Anyone else have any ideas?

 

[sjr53]

My rough idle problems have been a leaking fuel pressure regulator that allows engine vacuum to suck fuel from the regulator into the upper intake. Pull the vacuum line at the FPR and if it is wet, replace the FPR. Apparently the FPR doesn't like ethanol. I've gone through 2 and know of others with the same problem. If this is the case, you will notice the engine restarts much faster after putting a new FPR on it.