TOO MANY REVS!!!!

[facemaze]

Just finally got my truck up and running off the blocks after a four month saga. I swapped rear main seal, clutch, flywheel, exhaust gasket and differential.

my issue is that,

when I put the clutch in revs spike close to 2000. When I engage the accelerated and release everything returns to normal. Until I get over 2000 rpm in gear, then I can release the accelerater and the truck will not slow on its own but will slowly increase speed. When coming to a stop with the stick in neutral, the truck will spike to 3000 before coming back to right above 1000 for a stationary idle.

I am taking my foot off the gas when I put in the clutch. I have no cruise control. I use a K&N air filter. When I swapped the diff, I used my newer abs sensor from my old diff on the new one.

the truck was running great with no issues after the work. The problem arose after spending 30 minutes on the freeway at 65mph

 

[Uncle Gump]

Check for vacuum leaks...

 

[facemaze]

Check for vacuum leaks...

Carb spray?

 

[Uncle Gump]

I use propane...

You can also google smoke testing. I've never done it that way but a bunch of people do.

 

[facemaze]

Propane?!? Really?!?!? Cool

 

[Uncle Gump]

I took and old torch head and took the actual head off. The slipped a hose onto the stem. I can point it exactly where I want it.

Remember to keep the tank upright... or you will get liquid propane.

 

[facemaze]

And you listen for the spike in revs like the carb spray?

 

[Uncle Gump]

yes... you find a leak you will notice a perceptible change in engine RPM

 

[facemaze]

yes... you find a leak you will notice a perceptible change in engine RPM

Thanks. Got an extra tank and I don’t have to buy spray!!

 

[RonD]

Warm up the engine and let it idle
Unplug the 2 wire connector on the IAC Valve, idle should drop to 500rpm, barely running, or engine may even stall, either is GOOD
If RPMs do not drop then you have a vacuum leak somewhere or IAC Valve is dirty or defective

If RPMs do drop then Computer is setting the high RPMs for some reason, usually "thinks" engine is overheating

 

[facemaze]

Warm up the engine and let it idle
Unplug the 2 wire connector on the IAC Valve, idle should drop to 500rpm, barely running, or engine may even stall, either is GOOD
If RPMs do not drop then you have a vacuum leak somewhere or IAC Valve is dirty or defective

If RPMs do drop then Computer is setting the high RPMs for some reason

Just to be clear, “warm up” is normal operating temp or just above C?

 

[RonD]

Temp just below 1/2, so normal operating temp, above 1/3rd is usually OK for the test

That's because computer is running Choke mode(high idle, Rich fuel mix) until coolant temp is above 150degF, operating temp is 185degF or so

 

[facemaze]

I removed the IAC connecter and it dropped to 500. I also found a small leak. Plugged it but it still sounds like a leak somewhere.

 

[facemaze]

Temp just below 1/2, so normal operating temp, above 1/3rd is usually OK for the test

That's because computer is running Choke mode(high idle, Rich fuel mix) until coolant temp is above 150degF, operating temp is 185degF or so

ok. I unplugged the iac connector. It dropped to 500rpm. Plugged the hole and cleaned throttle valve.

to it for a test drive. Problem still persists. When I push the clutch in the rpm rise and hold even if stopped. Then at a random moment the rpms drop to 1100 for a minute or so before falling to a normal idle of 800 or so. If I’m in 1-3 gear and let my foot of the gas, the truck continues to move as if I hadn’t taken my foot off. 4-5 gear will drop in mph but it seems less than it was.

I saw somewhere that the abs could be the issue. Idk

 

[RonD]

Does speedometer work?

Starting in the 1990's manual transmission software was added to the computer to hold RPMs high(not increase them) when your speed is above 5MPH and you are shifting gears, its an emissions thing
If you hold clutch pedal down then after 5 to 10 seconds the RPMs should drop to 1,100 or so, and if under 5MPH then RPMs should drop to warm idle, 800rpms or so

Since you have no vacuum leak then its the computer doing this
You can unplug IAC Valve again then go for a drive to confirm this, as IAC Valve is the only way computer has to control RPMs
If it behaves "normally" then you have the culprit, the computer

I would unhook either battery cable for 5min, then reattach and see if original software reboots correctly

Its possible there is now a "glitch" in the software causing this now, if you Call a Ford Dealer they can look up the VIN and see if there is a software update for your computer
I know there were some for the 3.0ls in the early 2000's for high idle and wandering RPM issues
Its not a "recall" issue so you would have to pay to have new software loaded

If you have or can get an OBD2 reader so you can see engine temp from the CHT(cylinder head temp) sensor, it could also be the culprit
The 2.3l duratec CHT sensors were known issues, if its reading HOT then computer will increase coolant circulation by increasing the RPMs of the water pump, so engine RPMs, lol