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: 3,910 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? |
BeatNavy |
Jun 12 2019, 06:00 AM
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#2
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Certified Professional Scapegoat Group: Members Posts: 2,924 Joined: 26-February 14 From: Easton, MD Member No.: 17,042 Region Association: MidAtlantic Region |
Based on hunting idle it sounds like you're running too lean. That would be first suspect, but you should try to identify the broad root cause and then narrow down from there. What can you do to test if it's fuel delivery (too lean or too rich) and not something else like ignition, charging system, or vacuum? I assume you don't have a wideband O2 sensor. Have you tried unplugging the T1 (ambient air) sensor to see if that has an effect?
You've done a lot, but I would also recommend: 1. Verifying fuel pressure. 2. Inspecting/cleaning PCV valve. 3. Inspecting wiring harness for cracks, shorts, cleaning grounds, etc |
rjames |
Jun 12 2019, 11:13 AM
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#3
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I'm made of metal Group: Members Posts: 3,910 Joined: 24-July 05 From: Shoreline, WA Member No.: 4,467 Region Association: Pacific Northwest |
Based on hunting idle it sounds like you're running too lean. That would be first suspect, but you should try to identify the broad root cause and then narrow down from there. What can you do to test if it's fuel delivery (too lean or too rich) and not something else like ignition, charging system, or vacuum? I assume you don't have a wideband O2 sensor. Have you tried unplugging the T1 (ambient air) sensor to see if that has an effect? You've done a lot, but I would also recommend: 1. Verifying fuel pressure. 2. Inspecting/cleaning PCV valve. 3. Inspecting wiring harness for cracks, shorts, cleaning grounds, etc No PCV on ‘75 or ‘76 year cars- the hoses are connected directly to the air filter housing. What is the T1/ambient air sensor located? |
BeatNavy |
Jun 12 2019, 02:33 PM
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#4
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Certified Professional Scapegoat Group: Members Posts: 2,924 Joined: 26-February 14 From: Easton, MD Member No.: 17,042 Region Association: MidAtlantic Region |
What is the T1/ambient air sensor located? It's inserted into the top of the plenum and has a 2-wire connector on it. Disconnecting the connector opens the circuit, and ECU interprets that as the coldest possible ambient air temp and enrichens the mixture somewhat to compensate. Not nearly as much as CHT, but enough to normally notice a difference. Definitely verify fuel pressure. |
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