Surge at Idle

N

Nopedal

New Member
I'm getting a very bad idle surge (lope) when my 1999 Ranger 4.0 (cam in block) is in park or neutral (auto trans). Don't have the problem when in drive or reverse. It almost stalls at the low end and sometimes does.

I know it could be:
Fuel pump/sending unit
vacuum leak
Idle Air Control Solenoid (IAC)
Intake Air Temperature sensor
Throttle position sensor
Mas Air Flow (MAF) sensor
Worn cam shaft,
etc...etc...

By the way, it has new plugs and wires.

What is a knowledgeable persons first best guess?
Oh, and it also idles a little too slow.

Thanks,
Nopedal
 
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Been idling poorly for some time (year or more). Most likely I have a bad head gasket that is causing most of the problem (off and on). I've had a bleed down test done so looks pretty certain. In the mean time I used some additive to my antifreeze to postpone the inevitable. However, the really bad lope has only been going on for two to three weeks. I'm sure you're thinking I could have pulled something loose when I changed the plugs and wires, but that was about 12 weeks ago. Also, just checked that out a little while ago and all looks fine; no loose vacuum hoses or plug wires.

Also, the plugs have been gaped. Anyway, unless they were really off, seems a stretch that a gap issue would cause this problem given that it runs great when in drive. At least as long as I keep my coolant level low enough to stop a lot of pressure build up that then causes water to get shoved into my leaking head gasket.

I've moved my discussion over to the tech side for 6 cyl 4.0's.
 
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my truck was running perfect than i changed my plugs in hope of getting better mpg. they werent gapped properly and my truck has a rough idle now. i just need the time or money to gap mine or get new plugs.
 
Could be that a plug wire was slightly damaged during the plug change. Might try putting in a new set or getting the parts store to check any codes. Of course, it could be the gap, but unless it's way off, I'm thinking "not". But then again, I'm no expert on such things.

By the way, I went back to the "ford" brand when I changed mine; man what difference. I'd tried some other brands for the gas milage thing too, but never really got the performance I wanted.
 
Lope at Idle

I'm getting a very bad idle surge (lope) when my 1999 Ranger 4.0 (cam in block) is in park or neutral (auto trans). Don't have the problem when in drive or reverse. It almost stalls at the low end and sometimes does.

I know it could be:
Fuel pump/sending unit
vacuum leak
Idle Air Control Solenoid (IAC)
Intake Air Temperature sensor
Throttle position sensor
Mas Air Flow (MAF) sensor
Worn cam shaft,
etc...etc...

By the way, it has new plugs and wires.

What is a knowledgeable persons first best guess?
Oh, and it also idles a little too slow.

Thanks,
Nopedal
 
Been idling poorly for some time (year or more). Most likely I have a bad head gasket that is causing most of the problem (off and on). I've had a bleed down test done so looks pretty certain. In the mean time I used some additive to my antifreeze to postpone the inevitable. However, the really bad lope has only been going on for two to three weeks. I'm sure you're thinking I could have pulled something loose when I changed the plugs and wires, but that was about 12 weeks ago. Also, just checked that out a little while ago and all looks fine; no loose vacuum hoses or plug wires.

Also, the plugs have been gaped. Anyway, unless they were really off, seems a stretch that a gap issue would cause this problem given that it runs great when in drive. At least as long as I keep my coolant level low enough to stop a lot of pressure build up that then causes water to get shoved into my leaking head gasket.
 
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