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Post by Exo81 on Mar 30, 2015 22:29:26 GMT
I'm at a loss here. I have had the motor running well for a few months and have driven it around the neighborhood several times all with no issues. In preparations to get DMV blessings I was doing the final tidying up of the wiring harness. Not cutting anymore out just making it neat with tape, split tube, securing, etc. After I finished the car won't idle. Starts great and if I hit the throttle no issue. But if I let the motor run on its own it drops below 800rpm and will either flat line immediately or sputter below 500rpms for a few seconds then die.
I checked to make sure the ECU is plugged in securely, all grounds are good, AFM and air ducts secure with no air leaks, no vacuum leaks and all plugs properly fitted. Still no idle. I removed all the tape and tube covers looking for a frayed or rubbing wire. Nothing there. I have not done anything with the idle setting as it was running perfectly before so it should not have unscrewed itself while sitting still.
Today, I did a slight tighten of the throttle cable. At 900rpms it fine. Slacking it out to 800rpms it dies. Any idea what I'm missing?
Bill
1992 1.6 |
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Post by Toed64 on Mar 31, 2015 10:20:01 GMT
I had a Nissan heap that did something similar - it was far too rich at idle and the culprit was the MAF sensor.
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Post by gwnwar on Apr 1, 2015 18:05:13 GMT
Exo81.. You don't adjust the idle by tightening the gas cable.. Adjust cable so you can move it up/down 1/8".
Adjust idle by jumping Grd and Ten in dia box then adjust idle screw in throttle body..850 +/- 50 rpms..
This is same pins to jump when setting timing.. Did you check the rubber cap on the vac port on the rear of the intake manifold that is used for cars with auto transmissions. it is down low pointing towards firewall..
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Post by Exo81 on Apr 2, 2015 14:48:35 GMT
RESOLVED! Dashpot was gunked up and misaligned. No idea how that happened as I didn't twist the mount and it took a fair amount of effort to straighten so bumping it wouldn't bend the mount. Cleaned it, straightened it and put in a few drops of oil to lube it and all is good again.
Because the dashpot was not allowing the butterfly to return to the "idle" position, the TPS was telling the ECU that the throttle was open and therefore not to run the idle sequence. Now that the dashpot is correctly aligned and lubed it allows the butterfly to fully close and therefore the correct signal is now being sent to the ECU.
Sad part is now I have to re-tape everything I opened up trying to figure this out. Turns out it wasn't wiring at all it just showed up when I finished making the harness look neat.
And yes, I let the throttle cable back out. I only drew it tighter to keep the motor running without the need for me to do so manually while I tried to diagnose the issue. When trying to get the TPS to read in idle position I actually removed the throttle cable to make sure it wasn't binding even though I had slack in the cable. Fortunately this only cost me time and not money.
Now it's time to get back to making this DMV ready. |
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