omg B16 Idle Problem

RonJ

Banned
At this point, I don't see a problem with the resistances or voltages. The last items to check are that the IACV, TPS, and ECT sensor wires are pinned correctly to the ECU. If those are fine, then the problem may be with the ECU chip or tune. The last resort would be to swap your ECU with a known good one.
 

1991civicb16

Guest
RonJ said:
At this point, I don't see a problem with the resistances or voltages. The last items to check are that the IACV, TPS, and ECT sensor wires are pinned correctly to the ECU. If those are fine, then the problem may be with the ECU chip or tune. The last resort would be to swap your ECU with a known good one.
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If i removed the chip could the engine still run on a regular P28 ecu? If not what kinda ECU's would be compatible with my car so when i go to the wrecking yard i know what to look for.
 


RonJ

Banned
No you should not remove the chip because the P28 itself won't run your B16 engine properly. If you want to stick with the OBD1 set up you have, the chipped P28 is the way to go, though there may be other compatible OBD1 ECUs that I don't know about. You should post a thread in the ClubCivic and Honda-Tech Tuning subforums to ask tuning experts whether there is a way for you to check whether your chipped ECU has been tuned to make the idle speed run high and, if so, how to fix it. Be sure to summarize your set up and what you've done up to this point.
 

RonJ

Banned
Have you already tried adjusting the idle speed?

 


RonJ

Banned
With the new IACV installed and the engine fully warmed up, what would you estimate the idle speed to be with the IACV plugged in versus unplugged? And when unplugged, does the idle fluctuation stop?
 

1991civicb16

Guest
RonJ said:
With the new IACV installed and the engine fully warmed up, what would estimate the idle speed is with the IACV plugged in versus unplugged? And when unplugged, does idle fluctuation stop?
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I can try that i know that when i was checking the Resistance i forgot to plug that back in and the car would not start without throttle and it died but that was cold i will try it....
 

RonJ

Banned
1991civicb16 said:
I can try that i know that when i was checking the Resistance i forgot to plug that back in and the car would not start without throttle and it died but that was cold i will try it....
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Yeah, warm the engine up fully and while it is idling, unplug the IACV. What is the idle speed and idle behavior before and after unplugging the IACV?
 

1991civicb16

Guest
RonJ said:
Yeah, warm the engine up fully and while it is idling, unplug the IACV. What is the idle speed and idle behavior before and after unplugging the IACV?
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I did and the idle dropped down to 500 rpms and stayed steady the car did almost die though at first. I found someone selling a p72 obd1 close to my house you think that would work with my car?
 

RonJ

Banned
1991civicb16 said:
I found someone selling a p72 obd1 close to my house you think that would work with my car?
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Hold off on buying an ECU. I don't want to see you waste your money.

I did and the idle dropped down to 500 rpms and stayed steady the car did almost die though at first.
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What was the speed and behavior of the idle prior to unplugging the IACV?

With the engine warmed up and idling, again unplug the IACV as you did above to get the 500 rpm idle speed. Now slowly turn the idle screw on the throttle body in an attempt to further lower the idle speed until the engine almost dies but doesn't. At this point, turn the engine off, plug the IACV connector back in, and then remove the 7.5A hood Back Up fuse for 3 or more minutes to reset the ECU. Then reinsert the fuse and restart the engine to see whether there is any improvement in the idle speed.
 

1991civicb16

Guest
RonJ said:
Hold off on buying an ECU. I don't want to see you waste your money.



What was the speed and behavior of the idle prior to unplugging the IACV?

With the engine warmed up and idling, again unplug the IACV as you did above to get the 500 rpm idle speed. Now slowly turn the idle screw on the throttle body in an attempt to further lower the idle speed until the engine almost dies but doesn't. At this point, turn the engine off, plug the IACV connector back in, and then remove the 7.5A hood Back Up fuse for 3 or more minutes to reset the ECU. Then reinsert the fuse and restart the engine to see whether there is any improvement in the idle speed.
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The 500 idle speed is with the idle screw already screwed in all the way and unplugged. Prior to me pulling the plug it was at 1,000 rpms it was not roaming at the time though it picks and chooses when to roam. It dont always roam but it will if you are driving it around. Also can i just pull the ecu fuse or does it need to be that one?
 

RonJ

Banned
Edit -- sorry, I forgot you have a 91 Civic. Reset the ECU by removing the 10A Hazard fuse #34 for 3 or more minutes.



With the engine warmed up and idling at 500 rpm with the IACV unplugged, turn the idle screw in any direction it will turn to see whether the idle speed changes. Play around with the screw a little bit to see how the idle speed changes. When you find the point where the idle speed is as low as you can get it, turn the engine off, plug the IACV connector back in, and then remove the 10A Hazard fuse #34 fuse for 3 or more minutes to reset the ECU. Then reinsert the fuse and restart the engine to see whether there is any improvement in the idle speed.
 

bmxkills

New Member
Althought it does not make much sense, I'm still calling the TPS or throttlebody. LIke I said, my buddy had the same problem(s). We cleaned his IACV, tried about everything else in the book, the steps you listed, and checked the idle screw, made everything better, however, still had an unsteady highish idle. Eventually he got fed up, ordered a Blox TB with TPS, and everything was fixed. If you're like me/us, everything goes wrong, and you had a few minor problems...
 

1991civicb16

Guest
RonJ said:
Edit -- sorry, I forgot you have a 91 Civic. Reset the ECU by removing the 10A Hazard fuse #34 for 3 or more minutes.



With the engine warmed up and idling at 500 rpm with the IACV unplugged, turn the idle screw in any direction it will turn to see whether the idle speed changes. Play around with the screw a little bit to see how the idle speed changes. When you find the point where the idle speed is as low as you can get it, turn the engine off, plug the IACV connector back in, and then remove the 10A Hazard fuse #34 fuse for 3 or more minutes to reset the ECU. Then reinsert the fuse and restart the engine to see whether there is any improvement in the idle speed.
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That didn't work. its funny when the IACV is unplugged the idle is fine, i when i rev it it drops right back down to 500 and stays there, but when the IACV is plugged in the idle is at 1k and when i rev it it slowly comes down and when it initially gets to 1k it bounces up to 1.5k then slowly lowers down to 1k. Strange stuff.... So what you got for me now?
 

RonJ

Banned
^This test result is consistent with your others in saying that the problem stems from the IACV receiving improper signals from the ECU. This is generally caused by a faulty ECT sensor or TPS, but your tests suggest that this is not the case in this instance. As I said earlier, I think you should first verify that all IACV, TPS, and ECT sensor wires are properly pinned to the ECU. Also check whether the one IACV wire that runs between the IACV and ECU has a short. Do this test (looking for continuity to body ground) with the IACV and ECU connector unplugged.
 

1991civicb16

Guest
RonJ said:
^This test result is consistent with your others in saying that the problem stems from the IACV receiving improper signals from the ECU. This is generally caused by a faulty ECT sensor or TPS, but your tests suggest that this is not the case in this instance. As I said earlier, I think you should first verify that all IACV, TPS, and ECT sensor wires are properly pinned to the ECU. Also check whether the one IACV wire that runs between the IACV and ECU has a short. Do this test (looking for continuity to body ground) with the IACV and ECU connector unplugged.
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OK, with ECU and IACV Unplugged body ground to BLUE/Yellow is not getting a reading, and for the black yellow wire i got 84.1. I also did it with the ecu plugged in just incase u needed that and with ecu plugged in i got Black/yello 92.5 and blue/yellow 133.
 

RonJ

Banned
Yes, the Blu/Yel wire measurement indicates there is no short. The other measurements don't mean much.
 

1991civicb16

Guest
RonJ said:
Yes, the Blu/Yel wire measurement indicates there is no short. The other measurements don't mean much.
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So now you want me to check the pinning of the ecu then right? If the pinning was done wrong though wouldn't it throw a CEL?
 
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