How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Master Auto Tech. Your Own Question
Master Auto Tech.
Master Auto Tech., master tech.
Category: Car
Satisfied Customers: 612
Experience:  A.S.E. Master technician. Over 20 years working on import & domestic. Owner/operator of an auto shop
Type Your Car Question Here...
Master Auto Tech. is online now
A new question is answered every 9 seconds

Engine idle is slow after warming up. No codes. Checked

This answer was rated:

Engine idle is slow after warming up. No codes. Checked signal on idle control with scope and it is getting the PWM signal. When the idle is warm, revving the engine and letting it drop back to idle will stall. PWM increases trying to recover, but still stalls. Applying signal to idle control causes the engine to cycle up and down in RPM.
I'm sorry you are having problems with your vehicle. I will try to help.I'm a full time mechanic and have been a mechanic for over 20 yrs and I work part-time here on JustAnswer to help you and others repair their own vehicles, and I get credited by your ratings.. So before leaving the site make sure and leave me a rating. You can still reply to me as many times as neeed, even after the rating.. I will need for you to be my hands and eyes since I'm not there.First of all may I ask what is the year, make, model and engine size of the Honda? and have you tried cleaning the throttle body? And have you cleaned IAC and MAF?I strive to provide 5 star service. If I have satisfactorily answered your question please rate it as such and hit submit. Doing so is the only way I get compensated for my time. Also it doesn't close the discussion so we will still be able to communicate if there are further questions.
Customer: replied 11 months ago.
1997 Honda Prelude. 2.2L VTEC. Cleaned the air induction system and replaced the injectors. Have not tried cleaning any sensors.
Customer: replied 11 months ago.
The throttle body was not cleaned, but didn't look very bad.
Customer: replied 11 months ago.
I take that back, it was cleaned.
Give me a min to look up a few things on your car.
Check this:
1. Disconnect the idle speed control valve. If the engine stalls, check the base idle. With the idle speed control valve disconnected, the idle should be 550 RPMs. If it is low, adjust the idle air bypass screw. If the idle is normal, check for carbon build-up and then check to see if anyone has touched the screw and maybe turned it in.2. Check that the EGR valve is not sticking. Remove the valve and block the port to see how it runs.In some cases the fast idle air regulator can stick open and people will then lower the idle with the bypass screw. The fast idle valve will then close and then the idle speed will end up too low.
Customer: replied 11 months ago.
Ok I'll need to check again. I tried increasing the base idle before and you can get the car to idle, unless you rev it up and allow it to go back to idle. It doesn't always recover. As far as the EGR, I tried connecting a hose to the vacuum input and stalling the engine when activating. How do you block the port? It looks like the EGR is on top of the intake manifold. We checked the fast idle valve and it seems to be stuck closed. We put it in ice water and it was still closed.
Customer: replied 11 months ago.
If I am going to pay to call you, I would rather call when my son is with me so I don't miss anything. It's his car (he's 35) and I got involved after he tried everything we could think of.
Sorry the system Automatically asks if u want a phone call. I can't call now anyways.
To block the egr you have to remove it and bolt a piece of metal over it.
Also if the valve is stuck then it needs to be replaced.
Also do you have any codes?
Have you checked your coolant level?
Finally the iac controls the idle when warm and if it's slow or stuck you will get the conditions you describe. But they aren't cheap so I'd suggest cleaning it first.Just FYI, I work nights so I'll be signing off. But I will be back on from midnight - 3pm eastern.
Do you still need help with this?
Please let me know.Did my advice help? If so would you leaving a positive rating for me?
But if you still need help please let me know and I'll continue to help.Thanks
Customer: replied 10 months ago.
I will probably still need your help. The car is currently parked outside and we are dipping below freezing delaying the diagnostics. I can pay you anyway as long as we can contact you later when we can get back to the car.
Of course. The question remains open and you can post later no problem.
Customer: replied 10 months ago.
I can pay you and still get back to you?

Yes. but if you want to wait to pay, that is fine as well. :-)

i just may send a reminder every couple of days to see if you have had a chance to check it yet. But it is up to you either way. no pressure.

were you able to fix the issue? was I of help?

Master Auto Tech. and 4 other Car Specialists are ready to help you