Welcome Visitor! Please take a few seconds and 
pacodiablo
Member
- Joined
- Aug 6, 2007
- Messages
- 392
- Reaction score
- 3
- Points
- 18
- Age
- 36
- Location
- Birmingham, AL
- Vehicle Year
-
2002
1994
- Make / Model
- Ford
- Engine Size
- 3.0 4.0
- Transmission
- Automatic
I have a 1994 4.0L manual 4WD that has a weird issue at idle.
When I let off the gas, RPM will often drop very low (below 500 RPM on the tach, almost to "0" at times), sometimes almost to the point of stalling. The truck never does stall, and seems to smooth out and idle normally or almost normally after anywhere from a second to 15+ seconds. It's not just a bad reading on the tach, RPM actually is dropping very low. The lights dim and the engine stumbles. If I accelerate before it has a chance to smooth out, it has difficulty and stumbles, but clears up quickly when it gets above 500 RPM.
Above 500 RPM, the truck runs perfect. Smooth as can be and plenty of power, no problems at all. This only happens as I am coming to a stop. Clutch in or out doesn't seem to make a difference. Brakes don't make a difference. It's letting off the gas that causes the problem.
The check engine light does usually come on when this happens. I am getting codes 212 and 232, for loss of ignition diagnostic monitor/SPOUT circuit grounded and EDIS coil 1, 2, 3, or 4 circuit fault. No other codes. The check engine light only comes on when the issue is occurring, and turns off as soon as the RPM stabilizes, so it seems to be directly related and not a secondary issue. I'm used to ignition issues being worse at higher engine speeds than at idle, but that's the only thing the computer is pointing to.
Plugs are recent Autolites, and I wouldn't think this would be a plug issue. Wires are older aftermarket, but I didn't see any issues when I did the plugs. The coil was replaced at some point before I got the truck in April of this year with an aftermarket one, and the connector for it was also replaced. No ignition issues prior to this.
The issue first showed up a little over a week ago, after it rained. At the time, I just assumed idle issue = throw an IAC valve at it. It acted up again after that briefly, but cleared up and was fine the couple of times I drove it after that on Sunday, probably 40-50 miles. It rained again this week while the truck was parked (I usually drive my 2002), but was pretty much fine when I drove it Thursday night. It had the low idle one time, but was fine for the other 20 or so miles I drove it. It sat Friday and Saturday, then acted up all day today, which I wasn't really expecting given how it drove on Thursday.
It got too dark out to do any further diagnosis, but any ideas of what I might be up against? I'm thinking maybe the ignition control module is taking a dump? I haven't looked at it to see if it's original. There is a small capacitor looking thing next to the coil that is definitely original. Could that be related to this? Maybe a grounding issue somewhere?
As mentioned, IAC valve is new and symptoms haven't really changed, they have just been intermittent, but much worse today. Plugs are newer Autolite platinums, wires are older but good. A/F is good. MAF is clean. Air intake duct work is good, throttle body is clean. No idea when the fuel filter was last changed, but this doesn't seem fuel related. The engine runs great aside from the RPM drop when coming to a stop.
Any ideas are appreciated. I think at this point my next step is to take the ignition control module out and get it tested.
When I let off the gas, RPM will often drop very low (below 500 RPM on the tach, almost to "0" at times), sometimes almost to the point of stalling. The truck never does stall, and seems to smooth out and idle normally or almost normally after anywhere from a second to 15+ seconds. It's not just a bad reading on the tach, RPM actually is dropping very low. The lights dim and the engine stumbles. If I accelerate before it has a chance to smooth out, it has difficulty and stumbles, but clears up quickly when it gets above 500 RPM.
Above 500 RPM, the truck runs perfect. Smooth as can be and plenty of power, no problems at all. This only happens as I am coming to a stop. Clutch in or out doesn't seem to make a difference. Brakes don't make a difference. It's letting off the gas that causes the problem.
The check engine light does usually come on when this happens. I am getting codes 212 and 232, for loss of ignition diagnostic monitor/SPOUT circuit grounded and EDIS coil 1, 2, 3, or 4 circuit fault. No other codes. The check engine light only comes on when the issue is occurring, and turns off as soon as the RPM stabilizes, so it seems to be directly related and not a secondary issue. I'm used to ignition issues being worse at higher engine speeds than at idle, but that's the only thing the computer is pointing to.
Plugs are recent Autolites, and I wouldn't think this would be a plug issue. Wires are older aftermarket, but I didn't see any issues when I did the plugs. The coil was replaced at some point before I got the truck in April of this year with an aftermarket one, and the connector for it was also replaced. No ignition issues prior to this.
The issue first showed up a little over a week ago, after it rained. At the time, I just assumed idle issue = throw an IAC valve at it. It acted up again after that briefly, but cleared up and was fine the couple of times I drove it after that on Sunday, probably 40-50 miles. It rained again this week while the truck was parked (I usually drive my 2002), but was pretty much fine when I drove it Thursday night. It had the low idle one time, but was fine for the other 20 or so miles I drove it. It sat Friday and Saturday, then acted up all day today, which I wasn't really expecting given how it drove on Thursday.
It got too dark out to do any further diagnosis, but any ideas of what I might be up against? I'm thinking maybe the ignition control module is taking a dump? I haven't looked at it to see if it's original. There is a small capacitor looking thing next to the coil that is definitely original. Could that be related to this? Maybe a grounding issue somewhere?
As mentioned, IAC valve is new and symptoms haven't really changed, they have just been intermittent, but much worse today. Plugs are newer Autolite platinums, wires are older but good. A/F is good. MAF is clean. Air intake duct work is good, throttle body is clean. No idea when the fuel filter was last changed, but this doesn't seem fuel related. The engine runs great aside from the RPM drop when coming to a stop.
Any ideas are appreciated. I think at this point my next step is to take the ignition control module out and get it tested.
