1991 Buick Regal 3.1L MPFI 'VIN T' Vacuum Harness R&R

STEPHEN.WOLFE

MEMBER
1991 BUICK REGAL

I think I've been here before, anyway, I successfully swapped my Vacuum harness.

The original problem was and kind of still is the engine will not idle on start, if you just barely feather the accellerator it will run. In about 3 - 5 minutes it will rough idle on its own. When the engine is completely up to running temperature it will idle almost smooth. However, a new problem has appeared since R&Ring the vacuum harness. It will now do a throttle burst every now and then.

So, in summary, cold engine no idle without assist and an occasional throttle burst.

What should I check now?

Thanks in advance!

4 Replies

CHEVY22

MECHANIC
1,375 POSTS

CHECK THE IAC (IDLE AIR CONTROL VALVE) LOACTED ON THE THROTTLE BODY, AND OF COURSE ALL ENGINE COMPARTMENT VACUUM LINES
LET US KNOW

JIM

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Monday, February 26th, 2007 AT 3:35 PM

STEPHEN.WOLFE

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3 POSTS

Jim, Thanks I'll check that this evening and let you know what I find out. Are there any particular resistance or voltages levels I should expect?

Also, yesterday evening I walked out cranked the car and it held the idle (although a little rough, kind of like pulsing) immediately. The ambient air temperature was 79 degrees F. This weekend when it wouldn't hold an idle the ambient air was 43 degrees F. OBTW, I live in Wesley Chapel FL (East Pasco county) so we have some pretty wide temperature swings this time of year.

Thanks again, and I'll let you know what I find out.

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Tuesday, February 27th, 2007 AT 6:41 AM

CHEVY22

MECHANIC
1,375 POSTS

Please do

thanks jim

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Tuesday, February 27th, 2007 AT 6:52 AM

STEPHEN.WOLFE

MEMBER
3 POSTS

I finally got around to checkingthe IAC valve last night. I took it off the throttle body and cleaned it up. Put it back on and there was no change in operating condition.

So, I do I know it it is the culprit or not? I replace the vacuum harness assembly and all other vacuum lines are in good shape.

The vehicle will now idle roughly now in park with some engine pulsing (low to medium throttle bursts).

What should I check now? Do you think I may have a low fuel pressure coming from the fuel pump, if so, I don't know how to verify the pressure.

I need suggestions, guys, I'm running out of ideas.

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Thursday, March 1st, 2007 AT 1:32 PM