Rpms drop when coasting to a stop
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From: Coeur D’Alene, ID
Rpms drop when coasting to a stop
Hello
i have a 2008 manual 2.3L 4x2 ranger without AC and I’m having idleing problems: After it’s warm when I push in the clutch to coast to a stop the rpms drop to about 500 then surge back to 750 and stay there. This doesn’t happen every time; it usually happens when I’m coasting to a stop after driving at a constant speed or when the rpms are high and I push the clutch in. And sometimes the rpms are a little high and move around a bit then settle at 750. The truck seems to run well otherwise. Good power, no hesitation, no misfire as far as I can tell.
I replaced the alternator, starter, and battery cos they went bad, but before they did there was no idle trouble. The alternator was the last thing I did and just after replacing it I degreased and washed the engine compartment at the self serve car wash cos it was really dirty in there from oil undercoating; after I did that I noticed the trouble. Since this problem started I replaced the air filter and cleaned theair box, the MAF (which didn’t seem too dirty) and the IAC (which was significantly dirtier).
I’ve read that this may be “normal”. I just bought this truck so I don’t have a lot of history with it. Should I not worry about it? Maybe replace IAC? The guy at O’Riely mentiond something about a part in the clutch but I can’t remember what he said. Any insight would be greatly appreciated. Thanks
i have a 2008 manual 2.3L 4x2 ranger without AC and I’m having idleing problems: After it’s warm when I push in the clutch to coast to a stop the rpms drop to about 500 then surge back to 750 and stay there. This doesn’t happen every time; it usually happens when I’m coasting to a stop after driving at a constant speed or when the rpms are high and I push the clutch in. And sometimes the rpms are a little high and move around a bit then settle at 750. The truck seems to run well otherwise. Good power, no hesitation, no misfire as far as I can tell.
I replaced the alternator, starter, and battery cos they went bad, but before they did there was no idle trouble. The alternator was the last thing I did and just after replacing it I degreased and washed the engine compartment at the self serve car wash cos it was really dirty in there from oil undercoating; after I did that I noticed the trouble. Since this problem started I replaced the air filter and cleaned theair box, the MAF (which didn’t seem too dirty) and the IAC (which was significantly dirtier).
I’ve read that this may be “normal”. I just bought this truck so I don’t have a lot of history with it. Should I not worry about it? Maybe replace IAC? The guy at O’Riely mentiond something about a part in the clutch but I can’t remember what he said. Any insight would be greatly appreciated. Thanks
Welcome to the forum
"Normally" the idle should stay high, above 1,000rpm, when clutch is pressed in and speedometer is above 5mph, its an emissions thing
Emissions are less at 1,000rpm than at 700rpm because idle requires a Richer fuel mix to prevent overheating in the cylinders.
Yes, the IAC Valve is what the computer uses to control RPMs under 1,500.
It is a controlled air leak past the throttle plate, kinda like opening throttle plate a little more or less to set RPM.
And its very accurate, +/- 3rpm
IAC Valve is also used at Cold Start, part of the Choke setting.
At cold start RPMs should be 1,100 or so then slowly come down as coolant/engine warms up.
If thats working then not sure IAC Valve would be the problem
You can remove IAC Valve then plug in its 2 wire connector
Turn on the key, engine off
IAC Valve should open all the way for starting
Unplug its wires and it should close all the way
Plug wires back in, repeat as you see fit to make sure it is not sticking any where
You can also clean it while its out
"Normally" the idle should stay high, above 1,000rpm, when clutch is pressed in and speedometer is above 5mph, its an emissions thing
Emissions are less at 1,000rpm than at 700rpm because idle requires a Richer fuel mix to prevent overheating in the cylinders.
Yes, the IAC Valve is what the computer uses to control RPMs under 1,500.
It is a controlled air leak past the throttle plate, kinda like opening throttle plate a little more or less to set RPM.
And its very accurate, +/- 3rpm
IAC Valve is also used at Cold Start, part of the Choke setting.
At cold start RPMs should be 1,100 or so then slowly come down as coolant/engine warms up.
If thats working then not sure IAC Valve would be the problem
You can remove IAC Valve then plug in its 2 wire connector
Turn on the key, engine off
IAC Valve should open all the way for starting
Unplug its wires and it should close all the way
Plug wires back in, repeat as you see fit to make sure it is not sticking any where
You can also clean it while its out
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