Chasing a Ghost in the Machine, It’s been a year and I thought I had it. Options

[mgphoto]

About a year ago my usually good running engine began to stumble, slight backfire through the exhaust, between 1000 to 3000 rpm. I first suspected an electrical fault, as I would shake wires in the engine compartment and the issue would be gone.
This happened several times with different wires. I decided to tin the ends of the wires attached to the positive battery terminal. This seemed to work, for a while.
I began testing other wires for the D-Jet, I had success with reattaching the TPS connector, for about a day.
I began following a post about a member who had trouble with his 123 dizzy, his issue was related to the D-Jet pulse producing erratic fuel delivery.
OK, spoke with the tech person at 123 in Europe, we could test it using an oscilloscope.
I have a small pocket unit that I can test it with. This past Sunday I decided would be a good time do the test.
My plan was to take the car out for a warm up drive, once around a freeway loop gets my oil temp needle to move.
After exiting the freeway, I stopped at a traffic light and the car stalled, I’m used to that happening sometimes as I have a lightened flywheel, but this was different, like I turned the key off.
I turned the key to restart the engine but it sounded like a rattling chain, I never heard that sound before. I tried the starter again, now it had the typical hot start problem, after a moment I got it to run but the idle was now at 3400 rpm.
Since I could control it I drove it home and began checking simple things like throttle cable, TPS loose, MPS held some vacuum using the suck test.
I’m going to take a closer look at the throttle body.
Anyone have their D-Jet idle jump to 3200 rpm and what was the reason?
Thanks,
Mike

[brant]

Return spring maybe

[76-914]

spot weld failure on the clutch cable tube? (IMG:style_emoticons/default/beerchug.gif)

[Dave_Darling]

A 3200 RPM idle is an air leak. A *BIG* one. Check for hoses that have come off the manifold, then check for hoses that have come off other stuff in the bay. Look down the throttle bore to see if the throttle plate is jammed open or is damaged. Then check for stuff like holes in the plenum or a split plenum.

There's a reasonable chance that you have multiple problems adding together...

--DD

[JeffBowlsby]

The MPS mouth suck test is completely irrelevant, the mouth can only generate about 10% of the vacuum pressure and MPS sees/needs.

Use a hand vacuum pump and check it with a gauge.

[pbanders]

Good advice from all. I've found that finding the cause of such issues by chasing the symptom is often unproductive. What's worked for me is to go through everything in the D-Jet system, the intake system, the ignition system, and the charging system. My page has diagnostics for the D-jet components, and there are other resources out there for doing the same with the ignition and charging systems. Mechanical and vacuum inspection of the physical components (e.g. throttle plate, linkage, hoses, proper routing, etc.). Only when you are sure all of this is in order, do you start chasing symptoms. One of my old mechanics (Bob Grigsby) told me that when he had customers come to him about a running or driveability issue, he'd listen to them, take down what they said. Then he'd go and do a series of inspections, adjustments, and procedures he did on every single car that came it. He said after he'd completed this process, almost every time the problem was fixed.