Diagnosing an intermittent D-Jet problem..., Hesitation under load at 2800 RPM but only when cold... |
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Diagnosing an intermittent D-Jet problem..., Hesitation under load at 2800 RPM but only when cold... |
MikeInMunich |
Oct 10 2016, 02:46 AM
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#1
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Member Group: Members Posts: 392 Joined: 19-November 13 From: Munich, Germany Member No.: 16,674 Region Association: None |
Hi again from Munich!
Here are the details. But please see update from Feb. 5th below! I have a D-Jetronic intake. Under load and at about 2800 RPM Im experiencing an intermittent hesitation. Yesterday my son and I took the car out for a drive from Munich, towards Innsbruck and back and we ran into a bit of rain coming along the Aachensee (lake), and this hesitation got worse. Then I remembered the only other time I've had this car out with 100% humidity and that it wasn't running well on that day either, so this is apparently a clue. So what can this be? And why does it happen at all, even when it's not raining, albeit not as noticeably? Is there a cure? Experts / senior gurus out there, thank you for your time and sharing your knowledge and experience, in advance! With kind regards, Mike in Munich (IMG:style_emoticons/default/smilie_flagge6.gif) |
pbanders |
Dec 7 2016, 08:07 AM
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#2
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Senior Member Group: Members Posts: 939 Joined: 11-June 03 From: Phoenix, AZ Member No.: 805 |
Still sounds like an intermittent contact issue.
Sounds like you've ruled the CHT out. FWIW, I contort the $#%@ out of myself when checking the CHT connection to get into the engine compartment so I can make 100% sure that the female spade connector from the CHT is actually on the male connector inside the plastic insulator from the wiring harness - it is <extremely easy> to think it's on when it's actually jammed between the plastic and the male connector. Might be worth one more check. If it's not the CHT, I'd expand the search. First thing I'd do is find a glass-smooth section of road. Drive on it in the RPM range where you have the problem. Is the bucking still there? Now, drive on a rough section of road. Worse? An intermittent contact is suspect. If not, it's probably something else. If you think it's an intermittent contact, check the relay board connectors. Check the underside of the relay board to make sure the epoxy coating is still in place and there's no contact corrosion. Swap in new relays on the board for the power supply (74) and the fuel pump (75). Check the ECU connector. Check all of your ignition connectors - BTW, what kind of ignition setup do you have? Check your plug wires and make sure they're in good shapee and aren't loose at the plug connectors. Check your ignition switch. Check the fuel pump connector at the pump (I had a crappy one that caused problems years ago). Check the FI grounds in the back of the engine. What kind of shape is your wiring harness in? Most OEM harnesses I've seen have gotten pretty bad over the years. Some of the best money I ever spent on my car was buying a new harness from Jeff Bowlsby. Other than intermittent contact, look further at your ignition. Try swapping in a new distributor cap and rotor, and new plug wires. Try swapping your coil. Make sure that the ground strap inside of the distributor for the points plate isn't broken or frayed. Check your distributor shaft wobble and make sure it hasn't become excessive. Put a timing light on the car and see if your timing mark is stable. If you have aftermarket ignition like a Pertronix, Crane, or MSD, try swapping back to conventional points, condenser, and coil to see if that's the issue. As far as other components in the FI system, the pressure sensor is another possibility. Check my web page (sig below) for photos of the internals. It could be that at a specific part-load level it's hanging up, possibly due to contamination or to a broken component. Only way to really check this is to swap in a known good or NOS unit. Yes, the MPS is really expensive, but if you have a D-Jet car I strongly suggest that you have at least one or more spares on hand, just part of the price of owning a 40+ year-old car. I'm sure others will have some additional suggestions. You need to be methodical and eliminate possibilities one at a time. I'm sure our various ASE certified mechanics here in the forum will tell you that's how they're trained to do it. Good luck, you will find the problem and fix it. |
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