I've been dealing with the surging idle for a year-plus now. The only thing I haven't replaced is the IACV. I have however cleaned the heck out of it. But recently, my mechanic friend found some misadjustments and fixed those. I reset the ECU (yes, it's new). I started her up and she idled fine, even revved down on her own. I ran it for 5 minutes, it was beautiful. I went out a half hour later, started her up, she idled fine again ... until I started going. I started going and at the first stop sign, welcome back SURGE. I am trying to avoid the $230 IACV, but I am almost to the point of no other option. Two questions, could it be the TPS since it starts after I get going (it does it at start up now again)? Or somehow could it be related to the now non-working coolant temp sensor?

 

IACV/FITV/TB Cleaning thread

Drain and refill your coolant

I don't know why you'd replace your ECU and think it'll fix it - waste of money honestly.

There's also the idle adjustment **** at the top of the TB you can crank down (tighten) and see if that solves it.

There are PLENTY of threads on the topic you need to search.

 

Dude, I have done all those. I didn't say I replaced ECU to fix this problem. ECU had to be replaced for a number of other reasons. Idle adjustment won't help the surge.

My neighbor, a Honda mechanic, says the surge comes from the system shutting off the injectors because of a misread or bad information sent to ECU. Then when the idle falls too rapidly and too low, the system turns the injectors back on.

So rather than assume I haven't read the other threads, why don't you read mine? It says I cleaned the heck out of the IACV, so I must have read that thread. I asked two questions that I wanted input on, the TPS and the CTS.

 

Well and you didn't say you did all those in your post did you? I'm not going to assume what you have and haven't done. Reread your post - you talk about the issue and say you've reset your ECU (that's new) as if you replaced the ECU to help trouble shoot.

*edit* To clarify, you talk about the IACV but not the FITV or cleaning your throttle body, which is why I pointed that out.

And 99.9999999% of these threads no one HAS read those other threads.

And yes, the idle adjustment **** WILL help the surge - had to do it on my H - if you haven't played with it yet, please go out to your car and screw it all the way in.


And I would say your coolant temp sensor certainly is not helping the situation. If you haven't played with the FITV and have already bled your coolant and are free of bubbles and screwed the Idle Adjustment down then I'd be fixing that.

I wouldn't replace it until you did those other *minor* and cheap fixes.

 

All right, not going to argue semantics.

I will recheck the idle adjustment ****. Everything in the IACV, FITV and the like is new, except IACV (but it has been cleaned). I bled the coolant system a month ago, but will recheck that. I need to grab the CTS anyway, so why not. I cleaned the TB, but with 270k on her, it could be dirty again, it was 8k ago.

Will report back in AM.

 

Ah gotca

You have to understand it's the simple trouble shooting thing - when you call like an IT help desk you can say whatever you want but they still ask you if it's plugged in

Because half the time it isn't!

Also have you noticed anything in particular sets it off? AC being turned on/off or something along those lines?

 

Nothing in particular sets it off. My heat is on all the time (great in winter, sucks in summer).

I got a new temp sensor, gonna put it in tomorrow. This will give me another chance to bleed the coolant. Cranked the idle down today, and it really changed nothing ... that has me concerned.

LOL and I understand. I used to work for Apple Assistance Center. An old lady called and said she couldn't get her "CD thingy" to work. After a few entry level questions, found out she had a "square" CD. I explained that was the jewel case and the CD was the round disc inside.

 

I am havin the exact same problem in my 91! ive jumped through a few loops so far tryin to fix it. first i cleaned the injectors and throttle body because there was hesitation in the accelration as well as the surge. That really didnt help so i pulled a TPS from and junkyard and replaced it. now there is no hesitation in the pedal but the surge came back after about and hour of driving and the rpms never dropped below 1800. was i supposed to reset the ecu?? now im gonna try cleaning the IACV and see if that helps. any other suggestions?

 

Do as I have already. Make sure no vacuum leaks, clean/adjust FIT valve (good thread on here). Check throttle cable tension and idle adjustment screw. Make sure you have no air in cooling system. If you clean IACV, make sure you remove the O-rings before, cause they will swell.

 

Hopefully temp sensor takes care of it - was the idle adjustment screw out a couple threads?

*edit* As another thought, have you noticed leaking coolant anywhere? You *might* have cracked hoses allowing air to be taken into the system.

And square CD's are always my fav!

 

When summer comes you can reach in there between the firewall and engine, disconnect the cable, and turn that water valve off by hand.

 

Item 1
http://www.hondaautomotiveparts.com/...y5=WATER+VALVE

 

Idle screw was in but just in case I backed it off and tightened it again. That sensor is all locked up. Should be a 10-minute job, lol, but I am working on it as we speak.

And thanks for the heater tip, but I was getting used to the rolling summer sauna.

 

has the engine ever been rebuilt? becuase with alot of the hondas, they for some reason surge after being rebuilt and they still dont know why it only happens with hondas

 

WTF???

Where did you hear this from? If a lot of Honda engines are doing this around your area. I would say that it's time to find a new engine builder/ or install shop.

Yes I will agree that the surging idle is a very common problem with older Honda's. but that has nothing to do with a rebuilt engine. If it's surging after a rebuild that is usually a sign of something not put back properly.

Cooling system = Improperly working ECT sensor or low coolant/air bubble
Idle system = out of adjustment or IACV or FITV dirty/not working.
A vacuum leak = cracked hose or improper installation of gaskets.
Wiring or sensors = some people mix up the TPS and MAP sensors.or forget to plug sensors in at all.

 

Engine never rebuilt. Although it seems I may be doing that one piece at a time . Temp sensor installed, coolant purged/bled, ecu reset. No change. Thinking IACV is the only thing left.

TB is clean, IACV is clean, FITV is clean and tightened/adjusted. Idle is cranked down. Coolant has no air. CTS is new. No vacuum leaks.

I do have a question. The Chilton's book says idle should be around 500 with IACV disconnected. Is that accurate? Mine is at 1200-1300 with idle adjustment screw all the way in/tight.

 

You have a vacuum leak, alternate source of incoming air, if your idle is at 1200 with the IACV unplugged.

If you remove the intake tube you will see two ports on the inside of the throttle body. With the IACV unplugged there should be no suction/vacuum in the upper port. Put your finger / thumb over the port and see what happens.

Have you ever played around with or loosened the throttle stop screw? It's the little screw & nut located under the throttle rotor.

 

All right, here's what it was. The IACV was shot. Installed new one and now no surge and car idles at 850 rpm, 500 exactly with IACV disconnected.

 

 

Just an update, surge came back a week later, ending up replacing main relay and the surge is gone. Haven't had it since and that was over a year ago. Interesting.