The 1991 F150 XLT Lariat (5.8l, 2x4 E4OD) has come up with another challenge for me...

Today I started her, and she started HARD. Cranked & cranked: Would not start until I tapped the gas- and then BOY did she start... See ran her cold idle up to 2500, and would not drop down!

Temperature is cooler and damp today: every other time, she's started right up, and then idled nicely at 950-1000...

Oh- and the "Check Engine" light is now off.

HELP!?

Ideas?

Thanks!
Scott

 

Pull the codes to see what is stored. High idle can be a few things, ACT, IAC, O2, vacuum leaks.

 

The codes I pulled were 53 & 94- now the check engine light is out! I will see if it has anything more, but is just not faulting...

Thanks!
Scott

PS- One thing I did was to replace the beat looking vacuum lines on the sensor going to the canister on the right front of the engine compartment... The one right up next to the throttle body... Wonder if that is doing something? But it didn't give any problem the day I did it...

 

Replace your tps (code 53), it's causing 94

 

Could that be why the engine is hi idle so badly?

 

Well, I just started her up after finishing the work I was doing today, and she is BACK to NORMAL... And the check engine light is back... I didn't do ANYTHING- except let her sit with the hood open for several hours, and redo the front brakes... Hmmm...

Scott

 

You have an intermittently working TPS, those are cheap and easy to replace. Make sure you get the best quality one you can find, the cheaply made ones will really just end up costing you more in the long run.

The TPS is used by the PCM to determine where your foot is on the gas pedal...how far down. If your foot is all the way down, your PCM knows to give more fuel (your year doesn't measure air, it approximates air flow based on TPS). If the PCM is getting a faulty signal from the TPS, it will adjust fuel and cause this behavior. Just sayin'.

 

So that's what the codes add up to? Cool- I'll swap one in tomorrow, and see what happens... I know the 53 code was a TPS issue: but it is causing the 94 (CCC solenoid in trans.) code? Didn't know they'd do that- but if so- great! Means I don't have to tear into the transmission...

Scott

 

Actaully, I need to take a step back. Earlier when I told you about code 53 I looked that one up and I thought I knew what code 94 was, but I was mistaken. You need to see if the code 94 is a O or R code, see here - Ford EEC-IV/OBD2 OBD Trouble Codes ?

It would make sense if it's an R code considering code 53, so they MAY be related. If it is an R code, that is related to the smog pump but can also be reported due to the idle issue by code 53

 

According to the Ford Engine/Emissions-Diagnosis 1991 Shop Manual, the 94 is an "O" code- Convertor Clutch Control (CCC) solenoid circuit failure (53 is an o/c- TPS above maximum voltage)

Is it still possible the TPS is the issue? I haven't had a chance to shoot the wiring yet & check the voltage in/out.

Scott

 

You can ignore the fact an R code exists but you might want to pay attention to it. An R code is a much different problem than a O code. You had better hope you have an R code, the O code might be a bit harder and more expensive to fix.

 

Should I still replace the TPS?

Scott

 

I installed a new TPS... I also cleaned out the throttle body as I had it apart: the backs of the throttle plates were very cruddy... I cleaned some oil out of the intake area behind the throttle plates: I wonder what could be causing it...I pulled the battery cables to clear the memory, and fired her up- NO Check Engine light! I ran her for a few minutes, and nothing came up! (The RAS light did not return YET, either...)

See how she goes tomorrow, after I finish the brake overhaul...

Scott