immediately turn on the CEL after the codes were cleared? When I clear the CEL it stays off for about an hours worth of driving, I find that the engine runs better without it on. CEL codes are P0170 and P0171. Checked all the vacuum lines and they seem to be fine, there is a healthy suction at idle. When the car is warm the idle sometimes drops to 500, pretty low.

Any insight would be greatly appreciated,

Gunnar

 

The code P0171 is a system too lean issue. That will require an amount of driving for the CEL to come back on. Might seem to run better becuase the ECU is dumping more fuel into the combustion chambers?????? Have you ever replaced the primary O2 sensor?

If you have replaced the O2 it could be a fuel supply issue or something as simple as your valves may require adjusting.

 

[QUOTE=GhostAccord;45283396]The code P0171 is a system too lean issue. That will require an amount of driving for the CEL to come back on. Might seem to run better becuase the ECU is dumping more fuel into the combustion chambers?????? Have you ever replaced the primary O2 sensor?

If you have replaced the O2 it could be a fuel supply issue or something as simple as your valves may require adjusting.[/QUOTEi

Is there a valve adjustment write up?

 

[QUOTE=Gunnar24;45283840]There are write ups, a valve adjustment will not come close to solving this problem unless the engine is making an ungodly amount of noise, even then it would cause a rich condition, not lean.


First of all, what year and model and engine size are we talking about here.

You have too much air or not enough fuel, in most cases it is the former. The P0170 is for loss of fuel control, indicating you have a severe problem with the air/fuel mix. The engine will try to compensate until it determines it cannot maintain stability without exceeding emissions set by the EPA. So you will normally notice a change with the light on and off.

Check for an air leak on the engine itself, from the air flow sensor (if it has one, don't know what engine we are dealing with here) up to the cylinder head. 10/10 times its an air leak that will set that code.

If the idle is at 500rpm and the engine is not setting a code for loss of idle control, the PCM is telling it to idle at 500rpm.

 

[QUOTE=slowcivic2k;45284363]I have a 99 2.3CL. The CEL came on on a super humid day. The vacuum line has a healthy pull.

 

You could also check for any exhaust leaks between your cylinder head and the O2 sensor. The fuel pressure regulator would be another area to look at. I am going to assume that the air flow sensor being referred to would be the MAP sensor found on top of the throttle body. I also know nothing about the F23A1-5 engine. A dirty O2 sensor or bad gas will contribute to a code P0171 as well.

I still haven't found any Honda Diagnostic trouble code listing for a P0170. Where did you get these codes read?

If you call your local Honda/Acura dealer and ask about any Technical Service Bulletins (aka TSBs) pertaining to the 98-02 F23 and DTC P0171 they may have a better answer for you.

 

[QUOTE=Gunnar24;45284432]Clear the DTC, and see if it come back, if it does, its not a fluke.

An O2 sensor will trigger a DTC if it is bias in one direction for too long, or permanently, since you have no O2 codes, rules that out completely. DTC P0170 indicates loss of fuel control, so there is a large problem at work here.

Monitoring the O2 signal will only verify the problem, as it should be stuck lean. The engine will force flood the engine to make sure to O2 is not what is causing the lean condition. If it stayed lean during that test, it would set the mil.

"The" vacuum line? To which line are you referring? An engine will always have vacuum when it runs, because its a pump, the question is, how much.

Measure engine vacuum and compare it to the scan tool data for the MAP sensor. First ensure there is no loose lines, the next step tends to be a little more dangerous, but is deadly accurate.

 

i had a problem like that.. my h22 would only run perfect the first 20 min of driving then check engine light would come on and it would run a bit sluggish. I just got a tuned chipped ecu and now it runs rich and crisp w/ no check engine light. They disabled speed limiter, o2 sensor, ELD and vtec pressure switch, this fixed my problem.