'90 RENIX Rough Idle

mecompco · Aug 13, 2008

'90 Wagoneer 4.0--Idle pulses from 300 to 500, more or less. If the small vac line from the fuel pressure regulator is removed and plugged, idle immediatly goes to a nice, steady 700 RPM. Would you agree that the regulator should be replaced? If not, and other ideas? Plugs, wires, dist cap/rotor, fuel filter and injectors have just been replaced.

Thanks!

jneary · Aug 13, 2008

does gas drip out of the regulator if it is unplugged

Muad'Dib · Aug 13, 2008

Id replace it even if it isnt leaking. Especially if your certain that you have no vacuum leaks. Now if you have a vacuum leak fix that first then see what happens.

mecompco · Aug 13, 2008

Gas does not seem to drip out of regulator whether plugged or unplugged.

I may have a vac leak--CC is intermittently unstable, but HVAC works in all positions. Could not a bad regulator be the source of the vac leak? Or should I look elsewhere? Thanks!

Oh, and a couple times the idle has gone right to 3K and stayed there upon startup. Shut down and restart and it is back to the 300-500 business.

Muad'Dib · Aug 14, 2008

mecompco said:
Gas does not seem to drip out of regulator whether plugged or unplugged.

I may have a vac leak--CC is intermittently unstable, but HVAC works in all positions. Could not a bad regulator be the source of the vac leak? Or should I look elsewhere? Thanks!

Oh, and a couple times the idle has gone right to 3K and stayed there upon startup. Shut down and restart and it is back to the 300-500 business.

Typical of a vacuum leak...

I think its very possible that you have a vacuum leak. When you unplug and cap off the vacuum line to the regulator your taking a small load off of the system possibly allowing the system to run as it should. Plug in the vacuum line, and spray carb cleaner (while the engine is running of course) directly on each section of vacuum line that you see. If the idle changes at all (hesitation etc included) then you have found a vacuum leak. Fix said leak and continue to make sure you have no more. Then you can determine if its actually the regulator or simply a vacuum leak. Im betting is the latter...

Dont forget that a sticky IAC can do the same things. Make sure you clean that puppy up also... In this instance however, since the problem is fixed when fooling with something vacuum related, that to me says hey... the problem is probably a vacuum related problem!

mecompco · Aug 14, 2008

Muad'Dib said:
Typical of a vacuum leak...

I think its very possible that you have a vacuum leak. When you unplug and cap off the vacuum line to the regulator your taking a small load off of the system possibly allowing the system to run as it should. Plug in the vacuum line, and spray carb cleaner (while the engine is running of course) directly on each section of vacuum line that you see. If the idle changes at all (hesitation etc included) then you have found a vacuum leak. Fix said leak and continue to make sure you have no more. Then you can determine if its actually the regulator or simply a vacuum leak. Im betting is the latter...

Dont forget that a sticky IAC can do the same things. Make sure you clean that puppy up also... In this instance however, since the problem is fixed when fooling with something vacuum related, that to me says hey... the problem is probably a vacuum related problem!

Thanks for the advice--will go on a vac leak hunt and check out the IAC.

'90 RENIX Rough Idle

mecompco

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jneary

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Muad'Dib

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mecompco

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Muad'Dib

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mecompco

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