Intermittent Idle problem in '86 5000QT

It sounds like you are familiar with the ISV system and have established that it is functioning correctly. Therefore my guess is that you have a vacuum leak that is somewhat intermittent (those are the most fun).

Have you tried the T44Q back yard vacuum test?

- Engine idling: pull oil dip stick - engine should falter and begin to run rough.

- Replace dip stick.

- Remove oil filler cap - engine should die.

If not you have a vacuum leak.

First place to look is the Michelenman hose (fr> Hello,

more regular. Some idle adjustments a couple of months

removed) but won't start for a couple of minutes if the

and most of the time succeeds but for the last two

and then I can't start it for a couple of minutes. If

problem. Then today I drove the car for a couple of hours

smoothly and I never sense a loss of power. I've gone

idle stabilization valve (engine dies when I disconnect

the various ignition parts have been replaced. All

Columbia and it passed like a new car (so said the

not the oxygen sensor.

start fine when put in gear when moving....)

Hi Tony,

Yes

Yes

Yes

need to remove it to check carefully for cracks on the

other possible lines. Don't forget the decel valve in

problem it can be disconnected with little effect on

I will check those, I noticed one of the lines was plugged. Also, when I squeeze what you call the Michelin Man hose the engine falters or dies if squeezed stronger, that's normal, right? (it's being choked of air?)

Thank you very much Tony for your help, it gives me something to go at. I took it to a known Audi fuel injection expert and he couldn't figure it out, I suppose if I threw money at it then he could probably solve, but the car is basically worthless (market wise), so I guess I'll try to figure it out myself, it's more fun that way. =)

cp

Also,

it is functioning correctly.

Not too familliar. In this case, how would I know that the ISV is OK? (engine dies when unplugged?.....)

cp

The fact that the engine dies when you unplug the ISV indicates that it is operating. this includes the ISV itself, the wiring, the ISV controller, temp sensor and closed idle switch on the throttle body (which tells the controller to operate the ISV).

I think that what you indicated in your other email is a strong clue to the problem. You said that the engine falters and dies when you squeeze the MM hose. I don't think that is due to the compression but rather that the offending split in the the bottom of the hose is opening and creating a vacuum leak. Replacing the MM may be the fix.

Check the on line sites for a replacement:

I am not sure if these ship to Canada but worth a try.

cp wrote:

it is functioning correctly.

dies when unplugged?.....)

Yeah, so I figured =)

closed idle switch on the throttle body (which tells

problem. You said that the engine falters and dies

rather that the offending split in the the bottom

Will take a look, thank you (again) Tony!

cp

Tony, the MM hose fixed the problem! I owe you big time, stop by for a beer when in Vancouver! =)

There was a 2cm rip in the bottom part of the hose, now the car drives great, didn't know it had that much power, at round 5000rpm, for a heavy car it takes off like a pocket rocket! =)

THANKS! cp

it is functioning correctly. Therefore my guess is

need to remove it to check carefully for cracks on the

other possible lines. Don't forget the decel valve in

problem it can be disconnected with little effect on

more regular. Some idle adjustments a couple of

again gradually.

removed) but won't start for a couple of minutes if the

and most of the time succeeds but for the last two

and then I can't start it for a couple of minutes.

problem. Then today I drove the car for a couple of

very smoothly and I never sense a loss of power. I've

the idle stabilization valve (engine dies when I

already). All the various ignition parts have been

in British Columbia and it passed like a new car (so

probably not the oxygen sensor.

start fine when put in gear when moving....)

Good to hear you got it corrected and have now discovered the potential of these great engines. I'll be sure to collect the beer when in the neighborhood. It couldn't be more than 1,200 miles from Minneapolis :-)

Enjoy the ride.

T> Tony, the MM hose fixed the problem! I owe you big time, stop by for a beer

when in Vancouver! =)

didn't know it had that much power, at round 5000rpm,

it is functioning correctly. Therefore my guess is

need to remove it to check carefully for cracks on the

other possible lines. Don't forget the decel valve in

problem it can be disconnected with little effect on

more regular. Some idle adjustments a couple of

again gradually.

removed) but won't start for a couple of minutes if the

and most of the time succeeds but for the last two

and then I can't start it for a couple of minutes.

problem. Then today I drove the car for a couple of

very smoothly and I never sense a loss of power. I've

the idle stabilization valve (engine dies when I

already). All the various ignition parts have been

in British Columbia and it passed like a new car (so

probably not the oxygen sensor.

start fine when put in gear when moving....)

these great engines.

Yes, didn't think a little engine like that would haul a heavy car this "lightly"! =)

For five cyls, the engine doesn't even move a bit when idling

than 1,200 miles from Minneapolis :-)

=) should be a nice ride on the I90, email me cplas at telus dot net if ever in town =)

Fer sure!

cp