Rough Idle/Stall when in Reverse
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Rough Idle/Stall when in Reverse
I’ve got a 1995 Ford F-150 XL with the L-6 300 with just over 215000 miles. I think it’s got the E40D transmission. We bought it a year ago mostly to just have a old farm truck but also to have something to tinker with. I’m no mechanic but I can turn a wrench and I love to tinker.
About the first of this year the truck started not idling well when in gear sometimes even stalling. It seems to be worse in reverse but it also happens in drive also. It starts fine and when in gear with a little throttle it seems to run fine. It also idles fine in park or neutral. Seems like as soon as the transmission adds load it’s starving for fuel and air. It’s a 1995 so it has the older obd1 under the hood but I’m not getting a check engine light. My mechanic put his scanner on it and ran it through it’s paces multiple times and wasn’t able read any faults or codes. After he drove it he confirmed what I was thinking. The IACV wasn’t opening correctly and suggested I just replace it. I did this and it made no difference. When it does run in gear or reverse at idle with my foot on the brake it feels like it’s searching for the right setting, speeding then slowing. I don’t have a tach so I don’t have specifics on the RPM. I hope to have a new timing light this week that reads RPM too I’m anxious to see what it’s idling at. It feels just a little high.
Ive also checked the tps by backprobing and it seems to be responding correctly. I tried backprobing the MAP sensor but the discovered it’s signal is frequency not voltage. It does seem to be doing something, when I disconnect vacuum at idle in park the engine starts running very rough and dies. This puzzled me since signal voltage didn’t change but now makes sense since it’s frequency.
I’ve also checked the EGR valve. When I draw vacuum on it at idle the engine dies so it’s not stuck closed. The vac solenoid didn’t check ok so I did replace that but it made no difference.
I changed plugs which were in bad shape with no improvement. I’m going to replace plug wires and check timing but I don’t hold out any hope for those since it runs ok (I.e. doesn’t die) everywhere except at idle when in gear.
It really feels like for some reason the IACV is not being told the right thing to do. Maybe a sensor.
Where do I go from here?
About the first of this year the truck started not idling well when in gear sometimes even stalling. It seems to be worse in reverse but it also happens in drive also. It starts fine and when in gear with a little throttle it seems to run fine. It also idles fine in park or neutral. Seems like as soon as the transmission adds load it’s starving for fuel and air. It’s a 1995 so it has the older obd1 under the hood but I’m not getting a check engine light. My mechanic put his scanner on it and ran it through it’s paces multiple times and wasn’t able read any faults or codes. After he drove it he confirmed what I was thinking. The IACV wasn’t opening correctly and suggested I just replace it. I did this and it made no difference. When it does run in gear or reverse at idle with my foot on the brake it feels like it’s searching for the right setting, speeding then slowing. I don’t have a tach so I don’t have specifics on the RPM. I hope to have a new timing light this week that reads RPM too I’m anxious to see what it’s idling at. It feels just a little high.
Ive also checked the tps by backprobing and it seems to be responding correctly. I tried backprobing the MAP sensor but the discovered it’s signal is frequency not voltage. It does seem to be doing something, when I disconnect vacuum at idle in park the engine starts running very rough and dies. This puzzled me since signal voltage didn’t change but now makes sense since it’s frequency.
I’ve also checked the EGR valve. When I draw vacuum on it at idle the engine dies so it’s not stuck closed. The vac solenoid didn’t check ok so I did replace that but it made no difference.
I changed plugs which were in bad shape with no improvement. I’m going to replace plug wires and check timing but I don’t hold out any hope for those since it runs ok (I.e. doesn’t die) everywhere except at idle when in gear.
It really feels like for some reason the IACV is not being told the right thing to do. Maybe a sensor.
Where do I go from here?
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