I finally got my truck running OK, but it has a weird idle issue I've been trying to fix.
I can't get the idle screw to lower the idle past about 1250ish once its warmed up.
I replaced the o-ring on the idle screw and put teflon tape on the threads. The TPS has been ohmed and adjusted properly, I cleaned out the throttle body and adjusted the stop screw properly, I've tested my computer against a known good computer. I tested/ohmed the VAFM, it seems to be functioning properly.
I checked the coolant hoses to/from the IACV for obstructions and found none.
I checked replaced all the vacuum lines with new hose, and then tested with propane for any vacuum leaks and found none.
Timing is set to ~10° when engine is retarded from diag box, and it advances properly per the FSM
I checked the power and ground signals to injectors. All good.
When I blip the throttle, the engine revs up appropriately, and then when the RPM's drop, it acts like it wants to die... if I tap the throttle it resumes its previous high idle. If I turn the engine off, it is difficult-ish to start again once its warmed up. I have to give it some gas and try for a while. Or let the engine cool and it'll fire right up again.
It fires right up when cold. Idles high to warm up, then lowers the idle like it should... sort of
-coil is new
-ignitor is new
-plugs are new and gapped properly
-dizzy cap and button are new
-temp sensor is new
-starter is new
-batter is new
It's driving me nuts that I can't seem to figure it out.
EDIT: I'm leaning towards it being the IACV or VAFM, but I dont want to replace either one randomly. I dont like throwing parts at a problem or wasting money.
I can't get the idle screw to lower the idle past about 1250ish once its warmed up.
I replaced the o-ring on the idle screw and put teflon tape on the threads. The TPS has been ohmed and adjusted properly, I cleaned out the throttle body and adjusted the stop screw properly, I've tested my computer against a known good computer. I tested/ohmed the VAFM, it seems to be functioning properly.
I checked the coolant hoses to/from the IACV for obstructions and found none.
I checked replaced all the vacuum lines with new hose, and then tested with propane for any vacuum leaks and found none.
Timing is set to ~10° when engine is retarded from diag box, and it advances properly per the FSM
I checked the power and ground signals to injectors. All good.
When I blip the throttle, the engine revs up appropriately, and then when the RPM's drop, it acts like it wants to die... if I tap the throttle it resumes its previous high idle. If I turn the engine off, it is difficult-ish to start again once its warmed up. I have to give it some gas and try for a while. Or let the engine cool and it'll fire right up again.
It fires right up when cold. Idles high to warm up, then lowers the idle like it should... sort of
-coil is new
-ignitor is new
-plugs are new and gapped properly
-dizzy cap and button are new
-temp sensor is new
-starter is new
-batter is new
It's driving me nuts that I can't seem to figure it out.
EDIT: I'm leaning towards it being the IACV or VAFM, but I dont want to replace either one randomly. I dont like throwing parts at a problem or wasting money.
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