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| mgphoto |
Feb 10 2026, 11:46 AM
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"If there is a mistake it will find me" ![]() ![]() ![]() Group: Members Posts: 1,431 Joined: 1-April 09 From: Los Angeles, CA Member No.: 10,225 Region Association: Southern California |
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 |
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| pbanders |
Feb 11 2026, 01:42 PM
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Senior Member ![]() ![]() ![]() Group: Members Posts: 990 Joined: 11-June 03 From: Scottsdale, AZ Member No.: 805 Region Association: Southwest Region |
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. Only then would he chase the symptoms.
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mgphoto Chasing a Ghost in the Machine Feb 10 2026, 11:46 AM
brant Return spring maybe Feb 10 2026, 11:50 AM
76-914 spot weld failure on the clutch cable tube? :beer2... Feb 10 2026, 12:14 PM
Dave_Darling A 3200 RPM idle is an air leak. A *BIG* one. Che... Feb 11 2026, 01:28 AM
JeffBowlsby The MPS mouth suck test is completely irrelevant, ... Feb 11 2026, 08:42 AM
mgphoto Big air leak!
Major clue, going to check it in... Feb 12 2026, 09:41 PM
mgphoto Ok, I’ve gotten this far.
I removed the air filt... Mar 9 2026, 12:32 PM
914sgofast2 I would suspect your AAR valve has gone bad and ne... Mar 9 2026, 12:47 PM
emerygt350 that t that the pcv goes to on a 73 is often the c... Mar 9 2026, 12:47 PM
bkrantz Is starter spray (ether) still a thing? Spray thi... Mar 9 2026, 06:50 PM
76-914 Disconnect everything from the vacuum side except ... Mar 9 2026, 09:10 PM
mgphoto Don’t see the AAR as the issue as it hasn’t wo... Mar 11 2026, 06:04 PM
emerygt350
Don’t see the AAR as the issue as it hasn’t w... Mar 12 2026, 09:40 AM
mgphoto
Don’t see the AAR as the issue as it hasn’t ... Mar 12 2026, 01:25 PM
rjames Check the Plenum too. They rust out from the insid... Mar 12 2026, 09:48 PM
jim_hoyland I had an air leak caused from a faulty 3-way conne... Mar 13 2026, 05:56 AM
mgphoto Ok, I pulled the hoses on the plenum, there is a r... Mar 16 2026, 01:14 PM
rjames
Ok, I pulled the hoses on the plenum, there is a ... Mar 17 2026, 04:47 PM![]() ![]() |
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