Fuching DJet issues *SOLVED*, Running out of things to try |
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Fuching DJet issues *SOLVED*, Running out of things to try |
rjames |
Jun 12 2019, 12:19 AM
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#1
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I'm made of metal Group: Members Posts: 3,922 Joined: 24-July 05 From: Shoreline, WA Member No.: 4,467 Region Association: Pacific Northwest |
Last summer all of a sudden my car wouldn’t stay running. If I could get it started the idle would hunt and the car would die unless I kept on the gas. Lack of power at times. All somewhat erratic.
Found that the MPS wouldn’t hold vacuum. Replaced the bad mps with a known good one. Car idles high when cold (higher than I think it should ~1600 rpm) so AAR is good, then when it warms up idle hunts from ~900rpm to the point where it almost dies unless I open the throttle body bleed screw quite a bit and turn the ECU knob just a few clicks away from full clockwise. So I did the following hoping to fix the issue: Replaced all vac hoses including intake runner to plenum hoses. New intakecrunner gaskets Verified plenum isn’t leaking New throttle body gasket Installed NOS throttle body Rebuilt the distributor New condenser Rebuilt injectors and flow tested New fuel lines Fuel pump is less than 2 years old Set timing and dwell with advance disconnected New CHT (resistance reads 1.7 w/engine off @70 degrees in the garage) Calibrated the TPS, even unplugged it to take it out of the equation, didn’t change anything. ECU matches the MPS (both correct part #s for a ‘75 2.0) Tried a known good ECU from a ‘74, no change. Feels like the MPS needs to be calibrated...but then again, these are all the same symptoms I had with the old bad mps. Replacement mps is from a Jeff B and was tested, but I haven’t retested it to see if it’s holding vacuum. (Don’t have the necessary tool, but maybe that’s the next step) Help! What am I missing? |
rjames |
Jun 21 2019, 03:55 PM
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#2
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I'm made of metal Group: Members Posts: 3,922 Joined: 24-July 05 From: Shoreline, WA Member No.: 4,467 Region Association: Pacific Northwest |
AAR is good.
Eschewing vacuum leaks for a second… Questions about the distributor operation under current conditions. Bare with me… My distributor vacuum canister is bad- but will hold vacuum for a second. So the advance plates move with retard line connected (retards timing/slows idle) but because the canister leaks, the advance plates return to their resting position quickly even though vacuum is still applied. This would explain why the RPMs drop to the correct RPM when the line is hooked up (retard is applied) and why the idle doesn’t hold steady (canister can’t hold vacuum; timing doesn’t stay retarded), but not why the idle drops to almost 0 RPM, vs going up when the timing is no longer being retarded. Shouldn’t the idle go up well past 1000 RPM when the canister stops holding vacuum? (retard not applied anymore, timing is advanced), especially if there was a vacuum leak? If there was a vacuum leak, why would it even drop to the correct idle speed when I first hook up the vacuum line? Wouldn’t it always remain higher than ‘normal’? My AFR reads full lean when the idle drops to almost 0, and the idle drops when the distributor canister can’t hold (retard) vacuum. The engine almost dies, and then retard vacuum is available again (canister diaphragm is 'reset' and holds vacuum for a second) , RPMs go up, and then the dance repeats itself. Could the distributor be directly or indirectly responsible for the drop in idle when it can’t hold vacuum for retard? Is there a way I can rule the distributor out of the equation besides installing a new one? |
914sgofast2 |
Jun 21 2019, 07:42 PM
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#3
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Senior Member Group: Members Posts: 613 Joined: 10-May 13 From: El Dorado Hills, CA Member No.: 15,855 Region Association: None |
Sounds like the source of your vacuum leak is the bad distributor advance/retard can. Put another one on the dizzy that will hold a vacuum on both the advance and retard ports, and your problem should be solved. Djets are extremely sensitive to fantom vacuum leaks.
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