D1 stalling (loss of Idle) issue

[Tom109]

Looking for insight to solve an idle/stalling issue on our 1996 D1. It runs excellent under power, but once warmed-up and closed throttle the RPMs drop to zero. I replaced the IACV but problem persists. I've checked/replaced vacuum lines, but have not entirely ruled-out a vacuum leak. I'm told the following could be potential causes:
A. Faulty MAF idle bypass
B. Clogged flame trap
C. Throttle position sensor
D. Crank Position Sensor

Since the truck runs great, aside from stalling, I'm hesitant to believe it's C or D, but open to be proved wrong. Any suggestions for the next step? Anyone have a functional MAF they are willing to loan (for a possible sale)?

Need to get this thing back to safe driver status ASAP!!!

Regards,
Tom P.

[Frank84]

Try simply unhooking the wires from the MAF and see what that does (assuming you have a code reader to clear the code it will likely throw).

I'm not as familiar with the 1996-1999 DI, but a DII will go into a default program and often run much better with the the MAF disconnected if it is faulty.

[parovertech]

If you replace tha iac, you need to set the base idle with a T4 to have it run correctly.

[Tom109]

Frank - I'll try a test drive or two with/with-out the MAF connected.

Parvotech - Anyone in the club have access to T4?

Tom P.

[parovertech]

I have one, i am in kennett square.

[Tom109]

Does this sound like a case of T4 base idle adjustment and I'm good to go? How involved is the process? Have any time available this month?

Tom P.

[parovertech]

To me it does, but without seeing the car its hard to tell. I could make time this month,

[rvrsrvc]

Tom, on the top of throttle body housing, there is a approximately 1/2" circular plug that covers the base idle adjustment screw. (Sometimes, the plug gets removed for adjustment but doesnt get refit, so it may just be a port now.)
If the seal is still there, you could drill a hole, run a self-tapper into it and work it out with a pair of pliers on the screw. (I have a small slide hammer that does the trick, but not something everybody has in their tool kit!)
The adjustment screw requires a 3/16" allen key to turn it.
I would recommend spraying some sort of lube, WD 40 will work, into the opening as the adjustment screw is sealed with an o-ring. Keep track of how far you turn it. Counterclock wise allows more air into the by-pass, raising RPM. I would limit my exploratory to no more than a full turn. After that, something else needs attention.

This is relatively temporary- it should be adjusted to a spec that is available through a scan tool like Jon's T4 or my Autologic.

[Tom109]

Thanks for all the input. I have not, and do not want to mess with the idle adjustment screw. I'll manually fine tune the IACV this weekend. I think I can solve this way...

Tom P.

[Tom109]

Anyone have a known "good" MAF (to fit a 1996 D1) that I can borrow to troubleshoot my Disco?

I'm about 90% sure it's down to the MAF, but hesitant to throw $200 at it unless I'm sure...

Tom P.