Weird Idle

[system-f]

I finally fixed many major problems with my 88 LXI, but it still has a funky idling problem.

I set the idle right around 800rpm with the A/C off and everything is good. I get in the car the next morning and drive to work and the idle has gone back up to around 1200 rpm?!?! Is there something I am not doing? Do you have to put the ECU into a mode on the 88 and 89s to set the idle like you do on 89 preludes? (jump wire to set idle)

Fast idle valve is good
I am replacing the ECU temp sensor
no vacuum leaks
IACV seems to be fine
Coolant level is good

[2oodoor]

very important/ two things you already mentioned
IAC valve can not "look ok" and could be your problem since it adjusts the air allowed in the mixture at idle.
Coolant sensor for ECU, pretty critical for the mixture as well

some people have dissassembled the IAC and cleaned it up, but if the little motor and pintle inside are shot, that will not help any.
If you adjust the idle screw factory preset, you probably can expect wierd idle if the original problem still exists. I don't think these Accords have Idle learn like an Obd 1 or 2 .

[system-f]

IAC valve can not "look ok" and could be your problem since it adjusts the air allowed in the mixture at idle.

Agreed, but I never said it looked ok, I said it seems fine.

I cleaned the fast idle valve and IACV with carb cleaner and now I am getting a rolling idle between 1k and 1.5k rpm. I am pretty sure the fast idle valve is shot due to the rolling idle. Sometimes the idle doesn't roll it hangs at 1.5k rpm then climbs slowly to 1.7k rpm then suddenly drops back down to 1k rpm and goes back into a roll between 1k - 1.5k rpm.

[2oodoor]

sorry<wrong choice of words

You mean "hunting" idle? when you say rolling?
Try bleeding the air out of your coolant, make sure your egr valve isn't causing a slight invisible vacuum leak.
If you manually adjusted the screw too much either way, it could be out of range for the IAC. Hope this helps at least some. When you turn on the AC what does it do then?

[2oodoor]

Clean your throttle plates too. According to Snap On you do pull the ECM fuse to reset on Accords.

[system-f]

I bled the coolant before the first post which I was hoping would help, but didn't.

Okay, so pull the ECM fuse, I haven't done that..



The car does idle up when the a/c is turned on and when an electrical load is applied so that seems to be working good. Today the idle was rolling on and off. I am going to put something inbetween the fast idle valve and the manifold to block it off as a test.


Thanks for the input so far.

[LX-incredible]

I had the same problem setting it around 800. Moving it back down solved the problem. I couldn't handle the vibration so I moved it up in the 900-1k range. Worked fine aside from the rolling idle within 5 minutes of startup at low speeds. Pulling the ECM fuse only resulted in temporary relief of the problem when set at 800... Or you could just change the motor mounts. :)

[system-f]

After blocking off the fast idle valve I pulled the ECU fuse and set the idle and for a day everything was great. Yesterday when I went to work the car started idling at 1200-1500 rpm again and later in the evening it even started to roll between 1000 and 1500 rpm. Maybe the EACV is bad? I am going to go to the yard today and pick a couple of valves up...this is my 3rd 3g and throwing parts at the problem can sometimes be cheaper considering the yards in my area. Ideas?

[2oodoor]

still can't help but think it is coolant related, what degree thermostat are you using? any thermo control vacuum switches on yours?

[system-f]

I thought about it being coolant related and cannot rule that out though I wonder if it is possible for the coolant-dependent part of the EACV to fail? There are no thermo vacuum switches on mine. In fact the only two items I can see that have anything to do with idle are the EACV and Fast idle valve, both of which accept coolant. I might as well grab a temp sensor for the ECU while I am at the yard.

This car feels like it was a junkyard car someone put back together. The title is clean but it is the first 3g I have ever had where the problems were fixed by replacing electrical modules. Example: dash lights didn't work and the dimmer module was dead. I have no idea what to think about this car, it is strange yet has only 122k miles and compression is great. I guess I will just continue to fix the problems and drive it.

[system-f]

One thing I failed to mention:

On 88s and 89s there are two electrical thermo sensors right next to each other. one, on the timing belt side has a 19mm nut and a tan connector. On my car this one is good, but the green connector is plugged into it.

The other, on the thermostat side has a green connector and on my car this one is dead.

So, the green connector is hooked to the Tan thermosensor and the tan connector is hooked to nothing.

At the junk yard I got the green and tan sensors and both look new. I will replace them later today.

[2oodoor]

don't forget to unhook the battery before you energize with the new parts in.

[system-f]

As you all know the water comes from before the t-stat to the fast idle valve, through the throttle body then through the EACV and back to the water pump suction under the intake.

As it turns out the passage through the throttle body is blocked allowing litle to no water through. Does anyone know if the water through the throttle body does anything other than help to heat incoming air? If not I am going to bypass it and see if this solves my problems....I knew when I was at the yard I should have grabbed a throttle body!!! darnit!

[system-f]

It seems like nothing I did fixed the problem and then I looked at the idle speed adjustment screw and it looks like it has actually backed out?!?!?! I did notice that it is very lose. After fixing the water flow problem I pulled the ECU fuse set the idle and put some silicone on the idle speed screw to see if it is moving.

I did figure out that the second electro themo sensor on the thermostat side with the larger 22mm nut is actually an on/off switch for the condenser fan when the engine is very hot after shut off. I noticed that my condenser fan never came on after the vehicle was shut off as it did on previous Hondas in the HOT Texas summer. After replacing the switch the condenser fan now cycles on as appropriate after the vehicle is completely shut off.

[Oldblueaccord]

Two things I would also look at is our throttle cable must have some slack at idle and I would make sure there is not air trapped in the lines going to the EACV. Loosening the clamps and pushing on the hose should let the air out.



wp

[system-f]

The throttle cable is VERY loose, plenty of slack. I bled the coolant system and it looks good. I drove the car today and the idle remained the same. I think the main problem was with the idle screw coming lose. So far so good, thanks for your help...now on to the power steering repair. Has anyone ever seen the two bolts parrallel to the block in the power steering bracket in the head and block shear out the outside section bolt holes??? I have for the first time. Now it is time to fabricate a new power steering pump bracket or replace the entire engine :thumbdn: