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Discussion Starter · #1 · (Edited)
First off , does a 2002 Focus ZX3 manual trip a code if IAC is acting up ? Some cars do I was told but not sure about my car because it started weird again , after not doing this for almost a year.
It started really rough as if flooded , almost stalling , then finally smoothed out , BUT the idle stayed high like 1200-1500 RPM for many miles and it was surging while at light-throttle cruise. It was like this for like 8 miles , then I shut it off and when it restarted after a while , like 30 minutes , it ran normal ! What gives ??? NO CODES , EVER !
Last year I had bought a new Ford IAC but was talked out of installing it by a LONG TIME mechanic , who told me if it was the IAC , there would be a code. I am not buying this. I sent it back for full refund. Some more sophisticated later model cars probably do set IAC codes. Doubt mine does. FROM GOOGLE
one of the most common symptoms associated with a problematic idle air control valve (IAC) is, irregular idle speed. Because, the (IAC); is programmed to regulate and maintain the engine idle speed, at a constant rate. If the valve fails or has any issues, it can cause the idle speed to be thrown off. This may result in an unusually high or low idle speed; or in some cases, a surging idle speed, that repeatedly climbs and falls.
When this happened last year I ran PEA fuel cleaner for several tanks , it went away , of was just coincidence. ?
There is no 0505 code or any other code. 202k miles , uses very little oil in 5k miles.
Does it or the ports it connects to just need cleaning ? Here is a screenshot from a YouTube video.
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Discussion Starter · #17 ·
After reading other people with IAC issues I believe it is the case with mine. The fact it acts flooded when cold sometimes and tries to die points to the IAC not letting in air when cold-started.
Then , after that it acts like the throttle is hanging open , so if it is sticking open when warm it is essentially causing same symptoms as a vacuum leak (high idle speed). I have no idea why there is no IAC code , but some things require the same thing to happen a few times before it will set a code.
What is funny is I remember my dad keeping the choke plate from closing with a clothes pin on our 65 Impala wagon 4bbl Quadrajet carb when it was below freezing in Mammoth to get the car started back around 1974. 😂
 

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Discussion Starter · #23 ·
OP has the symptoms of a vacuum leak. Don't be surprised if IAC doesn't fix it. So many of you swap the IACs to get multiple problems when commonly they are not the problem. Vacuum leak is why no code shows until WAAAAY later, I've personally seen years to get one.

The rising and falling of rpm tells you the IAC is ranging properly, trying to fix the issue but the issue being not fixed will vary as most vacuum leaks do. The IAC goes low and so does the vacuum leak as engine rpm has decreased, and the same the other way too when the IAC then overcompensates too high for the engine speed slowing down the leak amount. What results in the infinitely variable 'rrr RRR rrr RRR' high/low rpm thing. Dunno why so many of you can't get that part.

So many change the IACs for no reason, the rpm suddenly going all over the place is enough for them but commonly it's NOT the IAC doing it.

To other, the IAC setting screw is to center the range of the pintle, that center will also vary the optimum amount of air perceived by the PCM. The center point is as important as the overall air amount setting, they both have to happen at the same time. Or as close as possible, it prevents unnecessary IAC ranging that wears the part out faster. And if too far off it will result in a IAC range limit code and pretty fast if it is a solid problem. The code will say something like IAC cannot control the rpm or similar.

OP's Dad should have known there is a quick setting to set the carb choke 'break or qualifying' setting on a Q-Jet. It can be adjusted correct for the weather conditions in seconds. And, if the linkage was correct and adjusted right to begin with simply pushing down gas pedal further opens that plate up more too. It is anti-flood prevention built right in.
He knew that it didn't help that's why I used a clothes pin He knew that it didn't help that's why I used a clothes pin.
 

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Discussion Starter · #26 ·
Many parts can impair AFR and driveability without setting codes. EVAP purge valve, PCV valve, EGR, etc. Without codes, make your best guess and see what happens.
I think it's APC V it's never been replaced all I replaced was at long back hose when it didn't pass smog the hose had collapsed but I never put APC V in it yet
 

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Discussion Starter · #28 ·
The PCV valve cannot leak, only clogs up and that lowers idle not raises it. The long back hose may be leaking again, if like a Dorman part, their rubber lasts maybe ten minutes. The worst rubber on earth for long life.

Bear in mind the TB base gasket has a thin seal at the IAC bypass that can blow out to leak and it shows at cold start to get much better when engine goes to closed loop and warm. When leaking the IAC settings go to h-ll. The seal can also seal back up again to quit leaking until it decides to do it again.
Yeah it's set for 2 days and when I started up it started up like AV8 with like a really lumpy idol where I put a scanner on it and it was going between like 750 and 400 RPMs seconds later went up to the 1200 like I'm supposed to smooth down never did it again
 

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Discussion Starter · #30 · (Edited)
That's exactly what my mechanic friend said last year , I guess I'm just in denial. It's not hard to replace those myself is it ? The price would have been lower last year. : ( what about that weird high idle the one time that took like 10 minutes to come down ? To me it acted like the IAC was stuck at 1200 rpm high idle for awhile. My pressure is right there (40) per scanner. Can I rent a gauge and put on Schrader port to test it. ?
Or just bite the bullet and buy 4 new ones. 😂
Also could the TB base gasket you described be the problem ? Lumpy idle ? Or just the stuck high idle for awhile.
 

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Discussion Starter · #32 ·
I have a mechanic friend with professional scanners and all he was a mechanic for many years at different dealers would he be able to do a pressure drop test using a scanner or do you have a gauge on the fuel rail ?
 

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Discussion Starter · #42 ·
UH, the butterfly does NOT fully close and never should. The IAC range is set up for a certain amount of air to go through the butterfly aircrack that is at idle. Why the setscrew to set that 'leak'.

I clean pretty much most of my butterfly without ever removing the TB, simply open the throttle and clean the edges of it. I have never cleaned the inside of an intake and no need.

Lumpy idle and high idle rpm are two sides of the same coin. Likely vacuum leak. You can have that leak and fuel pressure one from injector too, no law says otherwise. If you hold pedal down to stop flooding the other three injectors will be off too and engine may well not start at all.

And yes, I likely have the only two Focus cars in the US with schrader valves on the intakes.
What I was trying to imply as when you do a pedal to the floor flood clear then let the pedal up then try to start it it should clear the flood if it was flooded.
Otherwise it could be the IAC not opening at all to let air in on a cold start. Don't agree with the vacuum leak it's done this like once every 6 months where the idle goes up to 1200 and stays there that sounds just like the IAC and it is for a very short time. And it's right at the 1200 RPM of the IAC high idle point.
 
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