The issue:
Idles 1700 when cold.
Idles 750 when warm.
When I approach traffic light, put in neutral, let it coast to stop, idle drops too low, maybe 400 rpm.
Sometimes, it drops too low, engine dies at the stop light. It starts right up before green light.
It gets annoying. Sometimes scared it won't start back up.

I cleaned the IACV, FITV, throttle body, air passage for IACV and FITV in the TB. No change.

Any ideas?

Thanks.

 

first off, manual or auto...

second, does it do this when only cold? only warm? or mix of both?

 

Its a 5-speed manual.
It does it when car is still warming up.
30 minutes later, it's fine.

 

ok, well since its a 5 spd. that shoots down my theory...

there could be a possibility that the plunger shaft on the IACV is gummed up... u said u cleaned it, however, things can be missed. I say this cause the gumminess would soften when warm, allowing the IACV to move normal.

 

Is your idle speed screw set properly?

After that most likely it's your fast idle thermo valve or idle control air valve.

Next it could be your it could be your throttle body sensor, MAP sensor, air leak (bad gasket) or vacuum leak (hose off).

A SEARCH would give you lots of info.

 

maybe you should possibly let your car warm up before taking off.it is double sided argument when it comes to letting your car warm up from a cold start....but maybe that would help.

 

I really appreciate the ideas.

gulfview, Idle set screw set at 750 idle rpm.
Vacuum leak will cause high idle so no vacuum leak.

Sorry Tech-Nics, but warming up an engine for 30 minutes to me is just wasting valuable resource.

It seems like fuel is getting cut-off when throttle is let go when coasting to stop.

I will try to replace the IACV since I cleaned it so many times with same problem.

I have started pulling out a spare fuel rail and injectors and see if it helps.

Any more ideas.

 

have you noticed any drop in fuel milage..? i say this cuz it may be the fuel pressure regulator... idle is high vacuum.... if the diaphragm is ripped, the fuel pressure would jump, flooding the engine at idle and fouling the plugs

easy way to check is to pull the vac. hose off the regulator and if theres gas in it, then u know its bad.

 

bad egr valve or egr solenoid valve could do it to; is it every time you slow down or sporadic?

(a stuck open egr valve/solenoid would dump exhaust gas into the intake at idle)

1700 rpm? I'd screw in the plastic thing in the thermal idle control valve to bring that down closer to 1300..that is also a common vacuum leak point

 

1700 rpm's isnt far off for a cold start, my 99 will hit 2000 on cold start and drop to 17-1600 with in 5 seconds of being on

 

To set the record straight, a defective vacuum hose CAN cause an unstable idle. For a recent example, take a look at the reply of "vtec26."

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hammer99EX &raquo;</TD></TR><TR><TD CLASS="quote">have you noticed any drop in fuel milage..? i say this cuz it may be the fuel pressure regulator... idle is high vacuum.... if the diaphragm is ripped, the fuel pressure would jump, flooding the engine at idle and fouling the plugs

easy way to check is to pull the vac. hose off the regulator and if theres gas in it, then u know its bad. </TD></TR></TABLE>

Yes, the gas mileage is down to 23 mpg. Used to be 27 mpg. I will check the FPR vacuum line.
Thanks for the suggestion.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hecubus &raquo;</TD></TR><TR><TD CLASS="quote">bad egr valve or egr solenoid valve could do it to; is it every time you slow down or sporadic?

(a stuck open egr valve/solenoid would dump exhaust gas into the intake at idle)

1700 rpm? I'd screw in the plastic thing in the thermal idle control valve to bring that down closer to 1300..that is also a common vacuum leak point .</TD></TR></TABLE>

I already cleaned the EGR ports by drilling out the plugs.
Yes, I think 1700 a little high. I could still drop it to 1300 thru the FITV.
I will check the EGR valve for possible stuck in open position.
Thanks.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gulfview &raquo;</TD></TR><TR><TD CLASS="quote">To set the record straight, a defective vacuum hose CAN cause an unstable idle. For a recent example, take a look at the reply of "vtec26." .</TD></TR></TABLE>

When I unplug one of the vacuum hoses, the idle rpm goes up, so it's not a vacuum leak.
Thanks.

 

Found the problem.

The paper air filter is clogged. Bought a new air filter. Problem solved.
I left out the air filter when I replaced the plugs, wires and ignition coil. Doh!