ok heres my problem. i have a 1991 accord f22a1 automatic. my engine will idle cold at about 2000 rpm. after it warms up it will bounce from 1000 to 1500 constantly. it seems to go away after i get pissed off and smoke my tires and just haul *** till it gets to 4th gear. someone told me to check vaccum lines but they are good. i just recently did a full tune up, engine and trans. need help with this problem before i get pissed off and blow the engine.

thx for the help

 

You can do a search for my name and this very problem, its all over the archives, may come back soon with your fix for you.

standby.

That took 2 minutes even.

High Idle speed and Fluctuation troubleshooting

Leaking EACV- Disconnect EACV connector. Idle speed should decrease. With the connector disconnected block the hole in the intake port or pinch the hose from the air cleaner to the EACV. If the idle speed decreases the valve is leaking. This condition will not set a code. The ECM can only detect an open or short circuit. It also may clog it’s screen if it has one.

Leaking IAC- (Idle air control valve) Disconnect IAC connector. Idle speed should decrease. With the connector disconnected, block the hole or pinch the hose to the IAC valve. If the idle speed decreases the valve is leaking. May not set a code and may not be a codeable circuit on all models.

TW or ECT sensor- (engine coolant temperature sensor) voltage should be about 3.0 volts @ 60 deg F and between .55 & .7 volts @ normal operating temp. If the voltage is above .8 volts at normal operating temp, will cause rich mixture and high idle speed. May not set a code because it is not far enough out of its operating parameters. **Also this sensor will not read temperature correctly if coolant is low. (beware)

Vacuum leaks- a loose vacuum hose or leaking intake manifold gasket can cause high idle speed and/or fluctuation. Also check for bad PCV valve.

Fast Idle Valve- (if equipped) a fast idle valve that is sticking can cause high idle speed and fluctuation. Check it by removing the steel cap on the top and putting your finger over the hole in the middle of the seat under the cap or block the port just inside of the throttle body opening, when the Idle is fluctuating or staying high. When the engine is warm this valve should be closed. You can tighten the seat but it will also change the idle speed warm up values (closing).

Throttle valve- throttle position sensor voltage should be .5 volts with the throttle closed. Make sure the throttle valve is fully closed and voltage is within spec.

ECU-If all else is good, if you reset the ECU and the problem goes away temporarily, the ECU may be defective.

 

thanks, im off to work now, ill do some of these there and see if it fixes

thank you.

 

Check coolant level before you begin any test. Air trapped in the small coolant lines that go to the IACV and the Fast Idle will cause both sensors to think the engine is still cold. Have you recently had the coolant system apart or do you have a small leak that requires you to add coolant ? Also, a bad ECT sensor is not the problem. If it was bad the engine would not be surging. After checking the coolant and burping the air, then check the other things on Duane's list.

 

The ECT sensor could be bad, think about the ECU operation strategy. The ECT sensor has high authority during warm up and still has some authority during closed loop operation. If the computer thinks that the engine is cold but the exhaust system is hot enough to make the O2 Sensor work then the computer know something is up so it goes into control mode.

The ECU sees a closed loop operation, a cold engine still at high idle (posibaly due to a bad ECT) and the speedometer states zero miles per hour (VSS). The ECU sees the idle go up too high to @1500 RPM, it shuts off the fuel injectors and the idle dies down to @700 RPM and the ECM turns the injectors back on and there you go, engine surge.

All of the problems on my list could cause a surging idle, putting your finger over one of the holes in front of the throttle plate will troubleshoot both of those posibilities, you just have to understand how the ECU works with this problem.

 

I do very well understand the injector cutoff function in closed loop. It's not the VSS that is limiting, it's the TPS. If it sees an idle ~1500~ and the throttle plate is closed it shuts off the injectors. It does it when you let off the gas in gear as well.
He had already stated, however, that he had a warmup ~2000~ and then it went into surging. If it was malfunctioning, I don't think you'd see a transition. Those sensors usually just go bad. Had he not said that, I would agree. Good to see you back around.

 

ok, ive done some checks on it. my coolant level is fine. pvc is ok. i dont know if tthis may be the problem, but i do have a "chip" installed on the wiring to my IAT sensor. could that be causing my car to go over the cliff? if so ill take it out, never did make much of a difference. ill cover a few others tonight at work. see ya

 

Ding, I'd say that garbage eBay 20hp chip is the culprit.

 

hahaha i think so, those chips, all they are is a resistor correct? if so i can get industrial quality ones at work and just swap it out

 

I had this problem on my 96 ex. There is a module on the bottom of the throttle body, im pretty sure its the fast idle thermo valve or something. Either way, its got coolant lines going to it. There is a metal plate on one end of it. Take this off, and you will see a white screw with a hollow center and a metal stud inside of it. There are grooves on the outside of this white screw, and with a small screwdriver, screw this all the way back down until it stops.

The white screw backs itself out during normal operation. I did this fix 2 years ago and havent had a problem since.

Be careful not to damage the gasket between the throttle body and the intake manifold.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by peiceofshitaccord &raquo;</TD></TR><TR><TD CLASS="quote">hahaha i think so, those chips, all they are is a resistor correct? if so i can get industrial quality ones at work and just swap it out</TD></TR></TABLE>You should mention bonehead mods such as this in the beginning of the post. That thing doesn't make your car faster, but it will cost you alot of gas mileage. Take it out and plug the sensor back up. Clear your ECU codes and be done with it.

 

yes, i should have. it didnt hit me till later and slapped my forehead, doh!!...
its too late for me to test it now but i will take it off int he morning if its fixed then imma be happy if not, there will be a new dent in my car and head. btw..... i will be starting a thread with the progress and pictures of my car. it was stolen from me 3 weeks ago, got it back last week, second time grrrrr anyway, i will start working on it. look out for the thread and please leave me comments and/ suggestions on different body mods and paint schemes and colors. i will be doing all the work myself so it will be a while in action. look out for that coming soon. will post if problem is fixed tomorrow. thx for the help so far.

 

ok, i took off the ebay junk, and it still did it when i first started up. i drove it for 12 miles, it seems to have corrected it. either it fixed it and the ecu needed to clear its self, or it just said f**k it and gave up

 

i was working on my car today, and while i was digging under the hood, one of the mechanics i work with came over, i explained the problem... he told me that it was a loose vaccuum hose and to spray brake clean to find it. well my dumbass did and now its fluctuating from 1000 to 2000 and its pissing me off. tomorrow im going to check for air in coolant, and tighten valve on throttle body. if it doesnt work, does anyone want a blown up f22a1 engine?

 

i find when i do a tune up and expletive stuff up that if you put things back to how they were before i touched it then it usually solves the problem..

I am sure the problem can be traced to something you did..