89' Project Civic
d16a6/d16y8 "mini-me"
Wait a second, is your car a manual?.
hunting idle issues.
- Thread starter hal9000
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hal9000
New Member
It's somewhere else in the thread I think; but the car came from the factory as an '88 DX Auto. I converted it to manual with a trans and ecu swap and some very minor wiring changes reverse lights and neutral lockout.
Since this problem basically started immediately after the swap, I'm guessing that I either missed something with the wiring, or the new ecu is bad. I haven't swapped ecu's yet, and nobody seems to be able to confirm for sure the wiring differences, but at this point I have covered just about every other possibility that it could be.
The only things I haven't tested, cleaned, replaced, or otheerwise serviced are the fuel pump/relay (which shouldn't be causing this problem in the first place) and the O2 sensor (which I just haven't got around to).
Since this problem basically started immediately after the swap, I'm guessing that I either missed something with the wiring, or the new ecu is bad. I haven't swapped ecu's yet, and nobody seems to be able to confirm for sure the wiring differences, but at this point I have covered just about every other possibility that it could be.
The only things I haven't tested, cleaned, replaced, or otheerwise serviced are the fuel pump/relay (which shouldn't be causing this problem in the first place) and the O2 sensor (which I just haven't got around to).
89' Project Civic
d16a6/d16y8 "mini-me"
My best advice would be switch to the PM5 for 1.5l engines -or- PM6 for 1.6l engines. I hope that helps. Your maps are probably incorrect and that is why this is happening. Think about it, an auto engine would rev to about 2,000rpm and shift. Well your trying to get it past that but cannot because your maps are off. So try that out and let me know.
89' Project Civic
d16a6/d16y8 "mini-me"
My suggestion would be, do not pay over $10 for a PM5 -or- $20 for a PM6.
hal9000
New Member
Both the auto ecu the car came with and the manual ecu I bought for it (Bench test included, $5 btw) are PM5 Ecus.
I confirmed this afternoon that swapping back to the auto ecu has no effect on the problem. The only additional hint I can give at this time is that it definitely appears to be temperature or altitude related. The problem got far worse while I was in Phoenix (77 deg F) than it is here in Flagstaff (45 deg F). When I first pulled off the highway in Flagstaff, it was behaving like it did in phoenix (High idle at around 2400-2800... blip the throttle and it drops and starts to hunt between 1000-1500 rpm). But after stopping and re-starting the engine a few times, it settled back into what it normally does here in flag (High idle around 1400-1800, blip the throttle and it'll drop to near 750 and usually be stable).
I've also checked the O2 sensor and it appears fine.
Could it be a tach sensor issue?
I confirmed this afternoon that swapping back to the auto ecu has no effect on the problem. The only additional hint I can give at this time is that it definitely appears to be temperature or altitude related. The problem got far worse while I was in Phoenix (77 deg F) than it is here in Flagstaff (45 deg F). When I first pulled off the highway in Flagstaff, it was behaving like it did in phoenix (High idle at around 2400-2800... blip the throttle and it drops and starts to hunt between 1000-1500 rpm). But after stopping and re-starting the engine a few times, it settled back into what it normally does here in flag (High idle around 1400-1800, blip the throttle and it'll drop to near 750 and usually be stable).
I've also checked the O2 sensor and it appears fine.
Could it be a tach sensor issue?
hal9000
New Member
Well, still no solution. Last weekend I checked the TPS on an ocilliscope and found out it was bad. After replacing and re-adjusting it, the symptoms changed, but didn't go away. Now the car idles high when cold, but when 100% warmed up, it pulses between 1000-1500 rpm at idle. I tried re-adjusting the base idle the other day, but with the ICV disconnected, could only get the idle down to 750. When ICV was reconnected and the ecu cleared, the pulsing came right back.
The only thing that stands out right now is that even though the temp sensors were in range, when I disconnect the Air temp sensor, it hardly makes a difference to the idle. Can somebody else with a DPFI car pull the plug on their air temp sensor to see if it makes a difference? Maybe there's a problem with that circuit....
The only thing that stands out right now is that even though the temp sensors were in range, when I disconnect the Air temp sensor, it hardly makes a difference to the idle. Can somebody else with a DPFI car pull the plug on their air temp sensor to see if it makes a difference? Maybe there's a problem with that circuit....
