94 3.0L - Low power, rough idle
#1
08-17-2010, 01:30 PM
94 3.0L - Low power, rough idle
But here's the skinny...
This 94 was given to me. It has been sitting for nearly a year and the guy just wanted it off his property. It's in fine condition except for this low power situation.
You can floor it from a stop and it not accelerate very fast. It does 0-35 in about 25 seconds. It sounds as if it is missing or out of time. It sometimes backfires into the intake under load like when I pull in my inclined driveway
Here's what has been done so far.
NEW - cap, rotor, wires, plugs (Autolite AP104), fuel filter, O2 sensors, air filter, fresh fuel.
CLEANED - MAF, IAC, no vacuum leaks detected, battery was dead has been charged to 13V.
The fuel pump appears new and the screen is not clogged. And I ran fuel pressure test today and it is well within the specs of 30-40psi.
The cat has been gutted (not by me. I just verified it yesterday.) The muffler is not clogged.
I ran all KOEO & KOER tests using the check engine light. 411 & 543 came up.
411 (R) Idle speed system not controlling idle properly (generally idle too high)
Odd because the computer raised the idle. It's fairly low when in gear.
543 (O) Fuel pump monitor circuit shows no power (M) (Service 556 code first if present) Fuel pump relay or battery power feed was open.
I think this is a memory code. Not sure how to clear it.
It starts right up with no issues. And when cold runs and sounds perfect. It's just when it drops out of "warm up mode" that there is what sounds like a miss. Revs drop fairly low when warm and you drop it in gear. Acts like it is missing when you step on the gas.
Questions:
Why would it run/sound fine when in high idle but not when the idle drops to normal?
Could there be an intake leak? Are these 3.0L prone to that?
I keep thinking it's a head gasket but I have no tell-tell signs of a bad head gasket.
This 94 was given to me. It has been sitting for nearly a year and the guy just wanted it off his property. It's in fine condition except for this low power situation.
You can floor it from a stop and it not accelerate very fast. It does 0-35 in about 25 seconds. It sounds as if it is missing or out of time. It sometimes backfires into the intake under load like when I pull in my inclined driveway
Here's what has been done so far.
NEW - cap, rotor, wires, plugs (Autolite AP104), fuel filter, O2 sensors, air filter, fresh fuel.
CLEANED - MAF, IAC, no vacuum leaks detected, battery was dead has been charged to 13V.
The fuel pump appears new and the screen is not clogged. And I ran fuel pressure test today and it is well within the specs of 30-40psi.
The cat has been gutted (not by me. I just verified it yesterday.) The muffler is not clogged.
I ran all KOEO & KOER tests using the check engine light. 411 & 543 came up.
411 (R) Idle speed system not controlling idle properly (generally idle too high)
Odd because the computer raised the idle. It's fairly low when in gear.
543 (O) Fuel pump monitor circuit shows no power (M) (Service 556 code first if present) Fuel pump relay or battery power feed was open.
I think this is a memory code. Not sure how to clear it.
It starts right up with no issues. And when cold runs and sounds perfect. It's just when it drops out of "warm up mode" that there is what sounds like a miss. Revs drop fairly low when warm and you drop it in gear. Acts like it is missing when you step on the gas.
Questions:
Why would it run/sound fine when in high idle but not when the idle drops to normal?
Could there be an intake leak? Are these 3.0L prone to that?
I keep thinking it's a head gasket but I have no tell-tell signs of a bad head gasket.
#2
08-18-2010, 04:20 PM
Did you check the timing? I've heard of the distributor shaft gear wearing down on the older 3.0L OHV motors, causing timing problems and even a no-start condition. See: https://www.ford-trucks.com/forums/9...d-battery.html
It could also be a flaky ignition module.
On the fuel side, I'd also consider dirty/clogged injectors.
It could also be a flaky ignition module.
On the fuel side, I'd also consider dirty/clogged injectors.
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