IACV issues

[orangeaccord]

Hey,

I'm new here... hopefully I can get some help from someone on this.

I have a 1992 Accord LX 5MT with 210,110 miles. The engine was replaced at about 120,000 mi after the guy who owned it before me threw a rod through the block. I don't know the engine type as it has no stamp. I assume that it was replaced with either an F22A1 or F22A4 as the stock intake mani had no bypass valves on it.

Anyways.

Just changed the timing belt/balancer shafts belt and replaced the pulleys associated with them. Had trouble getting it started, turned out i didn't have the PGM ground connected to the body. Originally, I thought I had incorrectly timed it, so I removed the head to check for valve damage. There was no damage, so I polished the bottom of the head and replaced the Head Gasket and the Exhaust Mani gasket. Since I had the intake mani off, I decided to do the F22A6 intake mani swap. I headed over to the junkyard and picked one up for 22 bucks. Also picked up PT6 computer to replace the stock PT3 so I could run the intake manifold valves. Replaced gaskets, installed manifold, ran vacuum lines and wired up IAB box on the bottom of the mani to the computer and dizzy. Then I put everything else back together.
Started the car. First thing I noticed was an unusually high cool idle ~2000 rpm. Allowed to run a bit longer to reach warm idle where it settled at 1100 rpm (still too high). The car then started eratically idling between 1100-2000 rpm. Checked all vacuum connections and they were good. CEL came on shortly afterwards. Pulled codes and got 12 and 14- EGR Lift Valve Circuit malfunction and IACV circuit malfunction.
Eh, EGR valve code was a fluke, the connector on the EGR valve was loose. Fixed.
IACV is still a problem. When it is connected, the car idles erratically between 1100-2000 rpm. When disconnected, the car either sits at a smooth idle around 1200 rpm or jumps quickly between 1100-1200 rpm.
Voltage to IACV is about 14.93 volts . IACV reads resistance at 0.01 ohms. Voltage at battery is around 14.93 volts . The IACV is getting coolant. I've tried two different IACVs with no luck.



Very weird stuff going on here. Does anyone have any idea what the problem is?


Thanks,

Sean
OrangeAccord

[orangeaccord]

I also apologize if this has been gone over before. If so, point me to a thread that might help me.
I appreciate it!

[Ghostyman]

I had the same issue and it was a clogged coolant passage in the valve. I took the valve off the manifold and cleaned it very well. I had no problems after that. It was a long time ago and I don't 100% remember if it was the IACV but it was attached to the manifold and cleaning it solved the oscillating idle problem completely.

[orangeaccord]

I checked to see if there was any blockage, but the pipes were free and clear.
I hooked up the extra IAC just to see if the motor on it would run, but nothing happened.

[bobbycos]

you are sure all your vaccuum lines are tight and properly routed.

sounding like you have a vaccuum leak in the system.

mine will jump between 800-2k when i tap the throttle,but settle down to 8

when you swapped the IACV, did you use new rubber gaskets between it and the manifold?

[orangeaccord]

Bobby- no, I didn't change the rubber seal on it. I used the one that was already on it.

Yesterday I went out and replaced the FITV with a spare one I had laying around from my intake swap. I tightened up the spring really good before installing. It has helped a little bit, but confused me more if it makes sense.
The idle surge doesn't go from 1100-2000 anymore, more like 1100-1500 now. Sometimes when I start it it will surge at first and then settle at about 1200, other times it will surge into about 1800 for cold idle and then settle at 1500. The check engine light hasn't come back on since I swapped the FITV.

[orangeaccord]

Today I got fed up with it and siliconed the IACV. Well, obviously it wasn't the seal on the IACV because i'm still having issues.

Also, IACV appears to be working correctly. 13 ohms resistance, getting power, no CEL.
FITV I assume is working correctly, unless somehow I ended up with two bad ones.

I'll try adjusting the idle speed I guess.
Any other ideas?

[rollinjoy]

Try bleeding your coolant and adjusting your idle. I have been having this problem since my swap. i even replaced all my vaccuum lines and switched out my FITV and IACV. still idles bad. Good luck.

[king_cobra]

IACV is still a problem. When it is connected, the car idles erratically between 1100-2000 rpm. When disconnected, the car either sits at a smooth idle around 1200 rpm or jumps quickly between 1100-1200 rpm.
Voltage to IACV is about 14.93 volts . IACV reads resistance at 0.01 ohms. Voltage at battery is around 14.93 volts . The IACV is getting coolant. I've tried two different IACVs with no luck.

you have a bad IACV. testing it is a waste of time since its a stepper motor. the other 2 IACV's are also probably bad. test one that you know that works for sure (swap one from a friend or something). this is a VERY common problem. I went through 4 of these in my car since i bought it. all same problem, all used. GL!

[king_cobra]

also i'd suggest to pull the ECM fuse out (to reset it) after you swap the valve. running the car with the IACV unplugged may confuse it.

[orangeaccord]

Well if it weren't for the fact that the IACV was good before the swap, I might agree that it's no good.
Plus, testing resistance is what the Haynes manual says to do. idk. I'm gonna go out and try adjusting the idle today. I'll probably also test the Throttle Position Sensor, as it may be bad.

[johnl]

You could try experimentally disconnecting the IACV electrical connector to see if that cures the idle problem. The idle speed may drop, possibly a lot (even stall if the base idle speed is far enough out of spec), so you might need to adjust it at the throttle body.

Doing this will cause a CEL, and make on / off throttle behaviour harsh (the computer doesn't like the IACV to be disconected), but at least it will help isolate the problem to the IACV or not (i.e. it's a diagnostic measure, not a fix). If the IACV seems to be the problem, then I'd suggest blanking off the ports into / out of the IACV so that no air can pass through the IACV to the plenum.

Doing this (blocking airflow through the IACV) doesn't cause a CEL or harsh on / off throttle behaviour, but does mean the IACV can no longer adjust idle speed when auxilliary load is on the engine (AC, lights etc). I found that setting the base idle (which becomes 'the' idle with IACV disabled) on the high side of spec prevents idle rpm from dropping too far (when AC, lights etc are on), though idle rpm will still drop (just not quite into the zone that causes excessive engine vibration).

Disabling the IACV in this way will tend to improve gear shifts as well, because the IACV will no longer be affecting off throttle engine behaviour. On the overun, or any time the throttle plate is closed as when changing gear, the IACV briefly holds open to keep rpm higher, or at least causes the rpm to not drop as sharply as would be the case without this action from the IACV, this action being a pollution control measure. In some cases the IACV can even cause the off throttle rpm to momentarily jump a few hundred rpm (as when changing gears), which is really irritating.

This action of the IACV causes problems with gear shifting, keeping rpm from dropping fast enough for the next gear (unless the shift is done slowly), so you can get an irritating push in the back as you let the clutch pedal back out (because the rpm are too high for engaging that next gear), and can interfere with the accuracy of rev matching when downshifting. After disabling my IACV, gear shifts both up and down are much improved.

[Granite CB7]

^Yeah, I agree w/ John completely, I have my IACV blocked off b/c I thought it was acting up, but it wasn't. Left it blocked though, took alittle getting used to but I really do like it now. It's been blocked for almost a year now.

What I did was (really simple) I had an extra IACV, I traced it out on a piece of cardstock, marked the 2 bolt holes, cut it out and sandwiched it in place (as a gasket, but blank) Worked fine, it would def. get you back on your feet.

Alittle off subject but my final setup w/ be H plenum, a6 runners, no FITV, blocked IACV on plenum w/ no coolant running through it, will run IACV during winter.

Def. block the IACV and raise the idle, see how you like it. If the FITV is acting up, block that also to see if that's the problem too.

[orangeaccord]

I blocked the IACV as per your suggestion and it works great. My only problem is that the idle is around 1200 w/ no accessories and I can't make it go down anymore. It's all good though, I can live with it for now.
I love the sound of those bypass valves opening up when you really wind it up.

[johnl]

I'm not sure why the idle would now be at 1200, unless there was an air leak, or the throttle stop screw (the one at the cable on the throttle body) were adjusted incorrectly, i.e. too open (?). Maybe try adjusting the idle at the throttle stop, but keep track of the original position of the screw in case you need to reset it to that position (say if adjusting the throttle stop doesn't fix the problem).

Don't close the throttle plate all the way, it needs to be at least a little bit open because closing it too much may cause the plate to jam closed, i.e. the throttle body casting expands when warm, and when it cools down it can shrink around the edge of the throttle plate and 'grab' it.

Granite CB7, a cardboard 'blind gasket' will work, but over time may start to shred (exposed to fluctuating pos and neg pressure), bits of 'gasket' could concievably end up inside the IACV and block it open. I've used brass shim for my blanking plate, but drink can aluminium would work fine (using a bit of non hardening gasket goo isn't a bad idea).

I'd keep the FITV because it gives a high idle for a cold engine (this isn't the IACVs job, even though the IACV will 'step in' if the FITV ceases to work). However, the FITV doesn't need the coolant lines to operate correctly, it picks up the required heat (to close) from the warm engine bay air and conducted heat from the plenum. As with the IACV and throttle body, the coolant lines are only there to prevent icing up in sub zero temperatures.