Extremely rough idle
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Joined: Feb 2018
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From: Arlington, Tn
Extremely rough idle
Recently purchased 02 ranger 149k miles 3.0 FFV auto trans. Replaced, plugs, wires, coil pack, fuel filter. Idles really rough but no hesitation and smooths out considerably at higher RPM’s. Gas mileage is good, I get occasional cylinder misfie codes nothing else as far as codes. Have also run several cans of sea foam through it not much improvement. Seems to get worse once engine warms up.
Thread Starter
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Member
Joined: Feb 2018
Posts: 42
Likes: 3
From: Arlington, Tn
The strange thing about this issue is it starts out mild then gets to the point it feels like it’s idling on three cylinders. But if you bring the RPMs up past 1k it smoothes out considerably. But theres still a noticeable misfire or shudder. It’s dam strange.
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Joined: Jul 2016
Posts: 2,023
Likes: 44
From: BC Canada
Can't remember what years, but some (not all) had issues of the valve seats "pocketing" in the heads.
A compression test will tell you if you have that problem _ should be at 165 psi at least.
May also be a good idea to check your fuel pressure too at idle and while revving it.
There's a schrader valve on the fuel rail for this.
Pressure should hold at 65 psi, anything below 50 will give problems.
To check for vacuum leaks...
Have engine fully warmed up and wile it's idling, pull the connection off the IAC valve.
RPM' should drop to 500 or below _ it may even stall.
If it does any of these things, that's good.
With the IAC valve disconnected and it continues to idle normally or above 500 rpm, then you have a vacuum leak.
You may get a check engine light that will go away after 1 or 2 driving cycles that there is a fault with your IAC valve _ that's just from you disconnecting it.
A compression test will tell you if you have that problem _ should be at 165 psi at least.
May also be a good idea to check your fuel pressure too at idle and while revving it.
There's a schrader valve on the fuel rail for this.
Pressure should hold at 65 psi, anything below 50 will give problems.
To check for vacuum leaks...
Have engine fully warmed up and wile it's idling, pull the connection off the IAC valve.
RPM' should drop to 500 or below _ it may even stall.
If it does any of these things, that's good.
With the IAC valve disconnected and it continues to idle normally or above 500 rpm, then you have a vacuum leak.
You may get a check engine light that will go away after 1 or 2 driving cycles that there is a fault with your IAC valve _ that's just from you disconnecting it.
Last edited by Jeff R 1; Feb 6, 2018 at 10:45 AM.
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