twocross

I have a '92 VX hatch with the wonderful idle surge that we all love. My latest attempt at diagnosing the idle surging (at operating temp.) led me to the MAP sensor. As soon as idle began surging I unplugged the MAP sensor, and the idle stopped surging. I plugged the connector back onto the MAP sensor and all "seems" fine now with idle, no surging. The CEL came on of course, and displayed the code 3 for the MAP sensor.
Now what do I do? This isn't the correct way to solve an idle issue, so what do I check next?

Former User

Reset the ECU and then check whether the idle problem continues and any codes pop up.

CivicxTree754

+1 on the above statement. Also if you ever have the idle surge again an effective way to check for leaks ( if that was the case) would be to spray throttle cleaner around and see if the idle surges which would point you to the leak.

twocross

I reset the ECU, no CEL codes come up, and idle continues to surge. I do get the 5 volt reference to the sensor. I have sprayed very carefully around all mechanical and vacuum components of the intake manifold (IM) and throttle body(TB) with no change in engine rpm. Also, new gaskets on IM and TB.
I have tried 3 different MAP sensors that are for the '92 VX 1.5 and same result as I described earlier.
Connected with no CEL codes=idle surge / disconnected, then reconnected with code 3=no idle surge.

Former User

Clean the FITV and IACV.

blackedEk

what he said^^

if there is still surging, check the volt specs on the tps sensor with a digital multimeter

should be .5 at closed throttle
and 4.5 at wide open throttle

twocross

Cleaned both, IACV and FITV, replaced all vacuum lines, bled coolant per manual method. The MAP sensor still is a issue for me, because it shouldn't have positively effected the idle while having a code display.
Any thing else to check, O2 sensor? Exhaust leaks?

Former User

Be careful concluding that the MAP sensor is at fault based on your test result. Unplugging the MAP sensor causes the engine to go into pre-programmed limp mode, which ignores inputs from engine sensors.

When the engine is having the idle problem, remove the air intake system and then use your finger to cover the port leading to either the IACV or FITV. Does covering one of these ports eliminate the idle surge?

fleabag

This!

twocross

At operating temperature, and after the idle begins its surging. I take the air cleaner off and cover the lower air port in the TB, which is connected to the FITV, and no change in idle, doesn't effect the idle surge. Next, I cover the hole in the upper air port, which goes to the IACV, and the engine wants to stall and die. I can feather the air port with my index finger and can "control" the idle. Control meaning that I can make the idle speed go down by covering the hole. The surging nearly goes away completely and the idle speed lowers also as I feather this upper air port with index finger.
Idle speed is effected from covering the top air port is a yes. Is the IACV motor worn out or stuck open?
Thanks to all of you contributors to my thread.

Former User

Your test result suggests that you:

1) Use the service manual procedure to set the base idle speed (see FAQs sticky).

If (1) doesn't help:

2) Measure the resistance of the ECT sensor.

3) Measure the TPS output voltage at closed throttle.

jakl

what steps would you go though if plugging the IACV port in the TB stops the idle surge in the given situation?

Former User

Same as I posted above and also clean the IACV.

Hot2Dth

Have you tried replacing the IACV and or FIACV. That sounds like your issue if covering either one of those holes stops the surging.

freddyfingers

I had this same problem a while back. Spent a good month trying to pinpoint the problem to no avail. Checked everything you could possibly check yet the idle surge still came back sometimes it would be good for a few days but would always come back.

When we ran the CEL, it said the IACV was the problem.
So cleaned the original IACV which still looked brand new. Installed it and reset the ECU problem solved parked the car overnight and same issue. So purchased a used/new IACV from the junkyard and same thing as above happened parked overnight and the idle surge was back.

Ended up being the ECU in my case purchased a used/new one from the junkyard for $80 problem solved!

whitey

Im having trouble with the same thing...

I have a 92 hatch with a bard gsr. I changed the head gasket, had the head resurfaced, new intake manifold gasket, new tb gasket, new IACV. After all said and done it still throws two cels, 10 and 14. Any suggestions?

twocross

I completed the three suggestions from RonJ, and my results are as follows:

1) At operating temp I followed the manual's procedure for setting base idle. With 2p connector unplugged the idle was approx. (approx. meaning +/- 50 rpm) 600 rpm. The idle adjuster on throttle body was/is threaded in all the way in, thus not allowing me to lower idle speed per manuals procedure. Once the code was cleared, and engine was operating at temperature and under electrical load the idle speed was approx. 1500 rpm.
*Base idle speed setting was unable to be set per manual's specifications, so I tested the two other components that RonJ listed.

2) The ECT is brand spanking new, however, the coolant fan relay tested as bad, so I have a relay arriving Friday. So as not to overheat engine, the ECT connector has a jumper to keep coolant fan operating while engine is running. Coolant has been bled per manual's procedure already.

3) TPS at closed throttle position tested at an output of 0.46 V. With a smooth transition to fully open throttle position tested at an output of 4.5 V.

Diagnosing is now my middle name. Anxiously awaiting further (and much appreciated) instructions.
Thanks all.

fleabag

lol... when you had the check engine code for the IACV, did you actually clear the code on the ECU? You can't just disconnect the battery, you actually have to use an OBD-II device in order to clear the code of the IACV. Otherwise the ECU won't know to start using the IACV again and will continue to think the IACV is broken. What did you do with the old ECU?

twocross

The factory repair manual instructs to remove the 7.5 V ECU back up fuse. That has worked for me in the past with clearing codes. Are you saying that that method isn't correct?

twocross

I completed the three suggestions from RonJ, and my results are as follows:

1) At operating temp I followed the manual's procedure for setting base idle. With 2p connector unplugged the idle was approx. (approx. meaning +/- 50 rpm) 600 rpm. The idle adjuster on throttle body was/is threaded in all the way in, thus not allowing me to lower idle speed per manuals procedure. Once the code was cleared, and engine was operating at temperature and under electrical load the idle speed was approx. 1500 rpm.
*Base idle speed setting was unable to be set per manual's specifications, so I tested the two other components that RonJ listed.

Any ideas why I can't set the base idle speed? Is it related to coolant fan relay, that will be replaced when it arrives in my mail box?
Related to IACV? Plugging the air port to IACV from TB has the engine want to stall and die.

jakl

bump, did you fix the problem? im having similar troubles with mine.

fleabag

On an OBD-II car, you've got to use an OBD-II reader.. Frankly, anyone serious about working on an OBD-II car should get a reader as doing diagnosis and fixing the car and reading other engine parameters becomes 11xty billion times easier. There are some measurements you just can't pickup with stock instrumentation that you can pickup with an OBD-II reader.. When I saw that my car was idling at 670rpm when warm from a cold start, not driven but then would magically idle between 670 and 750rpm when the engine was recently driven, that lead to me looking around the engine bay and discovering that I had a cracked exhaust manifold, leaking in fresh air and also screwing with the o2 sensor ground, causing the computer to go into fail safe mode. The car had no check engine codes and passed smog in this condition but it's things like this that make me be thankful for having an OBD-II device. The change of 670 and 750rpm is so small that it simply doesn't show up on the tachometer. I also used it to diagnose my sticking IACV and to make sure that all of my sensors weren't giving erroneous readings.

With all of that said, this does not apply to you because you have an OBD-I car and so the procedure to reset the ecu by removing that fuse is absolutely correct. Do you have a copy of the service manual? Idle troubleshooting procedures should all be in there and there should be a flow chart on dealing with it.

twocross

I have not solved the idle riddle yet. I have bled the coolant many times and I don't have any bubbles coming out of the top of the radiator, where the cap threads in, at all. In order to eliminate the possibility of air in coolant I am considering taking the car to a shop for them to do a coolant flush/fill. Shouldn't that then eliminate the doubt of air if it is done professionally with proper tools? The thermostat is new (replaced months ago), and I get hot air coming out of vents when car is at operating temp.

I will figure this out if it is the last thing I do.

fleabag

Have you replaced the PCV valve and the vacuum hoses going from it to the manifold? When you disconnect the IACV electrical plugs, how is the idle affected? On the 92-95 civics, IIRC it's ok to disconnect the IACV but on the 96-00 Civic CX/DX/LX civics, they have a three wire IACV and diagnostics of the IACV is not possible via disconnecting the IACV. Assuming the FITV and IACV aren't the issue, the only other explanation would be a vacuum leak.

twocross

I have replaced the PCV valve and have checked the vacuum lines, and double checked with diagram in manual. I got a hold of a IACV from a VX with out a idle surge problem. I have not yet installed it though.