 Surging and Unsettled Idel after MPS Rebuild, '74 2.0L D-Jet |
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| 914four |
 Oct 17 2016, 07:36 PM
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#1
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Senior Member  Group: Members Posts: 515 Joined: 4-March 07 From: Rainbow City, Alabama Member No.: 7,582 Region Association: South East States 
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Running down a bucking issue and found my MPS to be leaking. After rebuilding the MPS and verifying a good seal, everything went back together okay. When I started the car, the engine surged up and down and would not idle.
The electrical connector socket on the MPS does not appear to be keyed and using the diagram below from Clay's D-Jet troubleshooting guide it seems I may have plugged in the MPS wire incorrectly. I ohmed the wires from the ECU connector to the MPS socket and made sure the wires are in the order shown in the diagram. The wires look to be looping back from terminal 7 to 15 and 8 to 10 so that the socket could be plugged in either way and work correctly. Could plugging in the MPS wires incorrectly have damaged the ECU? If not, what should I be looking for that would cause the surging and lack of idle?  |
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| ChrisFoley |
Oct 18 2016, 11:32 AM
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I am Tangerine Racing Group: Members Posts: 7,986 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None
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Kelvin,
You have the adjustment tools. It may take no more than a small change to the center screw to bring the mixture into the proper range. The first step is to see if turning the mixture knob clockwise on the ecu improves the idle. If so, return it to the center position and back off the MPS center screw 1/8 turn at a time until the idle smooths out. You can do this with the engine running as long as you don't push in on the diaphragm with the tools. |
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| 914four |
Oct 19 2016, 09:17 PM
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#3
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Senior Member Group: Members Posts: 515 Joined: 4-March 07 From: Rainbow City, Alabama Member No.: 7,582 Region Association: South East States
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QUOTE(Racer Chris @ Oct 18 2016, 12:32 PM)  Kelvin, You have the adjustment tools. It may take no more than a small change to the center screw to bring the mixture into the proper range. The first step is to see if turning the mixture knob clockwise on the ecu improves the idle. If so, return it to the center position and back off the MPS center screw 1/8 turn at a time until the idle smooths out. You can do this with the engine running as long as you don't push in on the diaphragm with the tools. Chris, Thank you for the direction on the MPS. I was able to turn the ECU knob four turns clockwise and it stopped there. I started the engine and the idle settled down so I turned the ECU knob back to the original position. I adjusted the MPS center screw 1/8 turn counterclockwise but the surging came back. Ran out of time this evening but I'll try to adjust the center screw another 1/8 turn in the next day or so. Just wanted to give a quick update because I think you have me headed in the right direction. Thanks again, Kelvin |
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Posts in this topic
914four Surging and Unsettled Idel after MPS Rebuild Oct 17 2016, 07:36 PM
Rand It's lean. Which means vacuum leak somewhere a... Oct 17 2016, 07:39 PM pbanders You can't plug the MPS in incorrectly, you did... Oct 17 2016, 07:47 PM
914four
You can't plug the MPS in incorrectly, you di... Oct 17 2016, 08:13 PM Jeff Bowlsby The MPS may be calibrated too lean for your engine... Oct 17 2016, 10:26 PM pbanders
The MPS may be calibrated too lean for your engin... Oct 17 2016, 11:19 PM Philip W. I agree with all the above,
you are running lean-... Oct 18 2016, 06:33 AM pbanders
Jeff Bowlsby can check your MPS and set it to th... Oct 18 2016, 08:11 AM Bleyseng You are running too lean and need to use a AF mete... Oct 18 2016, 08:07 AM 914four Thank you all for the responses. I was able to ch... Oct 18 2016, 11:16 AM pbanders
Thank you for the direction on the MPS. I was ab... Oct 20 2016, 09:28 AM zambezi What would you recommend for a good tester to test... Oct 20 2016, 10:39 AM pbanders
What would you recommend for a good tester to tes... Oct 20 2016, 02:16 PM 914four Success!
I disassembled the MPS and added t... Oct 20 2016, 08:36 PM 914four So far I my car has been running smother than ever... Nov 3 2016, 06:24 PM pbanders
So far I my car has been running smother than eve... Nov 3 2016, 11:19 PM 914_teener Check your fuel pressure and TPS conditions first. Nov 3 2016, 07:08 PM lsintampa I chased a surge for over a year on my 2L (1975). ... Nov 21 2016, 07:55 AM R Shaff I know this is an old thread, but for anyone who w... Apr 2 2017, 05:00 PM Rand
I know this is an old thread, but for anyone who ... Apr 2 2017, 05:11 PM r_towle What kind of cigar? Apr 2 2017, 07:04 PM Tbrown4x4 A friend of mine built a smoke tester with a coffe... Apr 3 2017, 07:14 AM cary I built one with a new paint can. Worked great to ... Apr 3 2017, 07:53 AM |
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