Another Idle issue

SO, my beloved VX had started giving me issues about a month ago; I went out one saturday morning and started the car up, but it would not run. Starts just fine, but won't idle. When I got back to the house from picking up my kid (with the GF's car), I called AAA to tow it to my mechanic.

The AAA guy says it's likely the "cam sensor", and that the engine needs to be held at approx 2500 RPM for a bit, and the computer will figure out that the engine is running and all will be good. Lo, and behold, he was right. I take it to the mechanic anyway. It starts up fine for him, and he says to bring it back when the problem is there again, so that he won't just be shooting in the dark trying to figure it out.

It happens a few more times (always when the shop was closed, so I couldn't have him try to diagnose it over the phone, like he suggested) over the next couple of weeks. I find that if I can get into gear, it works fine.

I do some reading here, see that the FPR/fuel filter is a common culprit, as are the intake manifold gasket, IAC, and EGR (still don't know that acronym). Then it dies on me while idling forward at a stop light. I pull over, and it starts right back up. I take it to the shop and have them look it over, telling them that the FPR is a likely problem (he looks at me like I have a penis growing out of my forehead and says he thinks it might be the ingnition switch, but checks it out, and after consulting an Isuzu forum, he replaces the FPR). Good to go, until yesterday.

Same song, different day. I found a thread here about the same thing, and post #7 says it was the idle solenoid. Since this is one of the things that won't throw a check engine code, I figured I would give it a go. Take it to advance auto parts, buy a t-20 screwdriver and some carb cleaner, take out the idle solenoid, and it looks nasty. I give it a cleaning, (at one point the plunger launched, that was unpleasant), and put it back together just like before, with no extra parts.

Now, every time I take my foot off the gas, it dies. Getting home was interesting, to say the least, even though I only live about 4 or 5 blocks away.

I never get a check engine code; AAA will be taking the car back to the mechanic tomorrow. Where should I have them look?

EGR= Exhaust Gas Re-circulation valve.

Sounds like you are trying to cover all the bases, so clean the MAF sensor, and clean or replace the PCV valve, both cheap and easy to do yourself.

Intake manifold gasket is one thing thats common, but you did not say you checked for leaks (spray ether aka. "starting fluid" around the base of the intake manifold while the engine is running, if the engine ups its speed while spraying the fluid, you have likely located a leak in the manifold gasket).

My idle probs were solved by bypassing a steering fluid pressure sensor of all things. I was mostly getting high idles, tho a couple times I would get a very low idle or no-idle. Kind of sporadic as I assume the ECU was adjusting to the invalid sensor output.

I'm sure the sensor could have been replaced, but the mechanic who found the prob did not consider it worthy of replacement.

I dug into the VX shop manual and discovered that the "idle solenoid" I cleaned is actually the IAC. After taking it off, having the spring launch the plunger out, reassembling it, and putting it back on, the problem got worse. Would it stand to reason that this could be the problem? Will a bad IAC throw a code?

Mine was doing exactly what you describe.
Fortunately I am used to left foot braking from some old racing experience, so driving around with my right foot on the throttle to stop it from stalling while I used the left foot for braking worked for me.
Eventually changed out the EGR valve and it fixed the problem. Old valve was stuck half open, so when the engine tried to idle, it was not getting the right mixture. EGR valve should be closed at idle.
Have a listen around the EGR valve - if you can hear a soft whistle, or hissing noise, but feel no air flow, that is your problem.

PK

Quote:

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Originally Posted by housertl

I dug into the VX shop manual and discovered that the "idle solenoid" I cleaned is actually the IAC. After taking it off, having the spring launch the plunger out, reassembling it, and putting it back on, the problem got worse. Would it stand to reason that this could be the problem? Will a bad IAC throw a code?

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The IAC caused high idle for me.

Change the fuel filter and clean the MAF.

The MAF could be bad or just dirty. Also check the EGR valve.

Jon

I would try to troubleshoot this one on your own. This problem is finicky at best and almost always inconclusive when you try to have a shop "decode" it. You tinkering away and getting your elbows dirty, one thing at a time, will yield better results. Like others have said already, start basic.

Clean MAF/check for induction breaches
PCV replacement
IAC cleanup
Fuel filter replacement
EGR cleanup (replacement?)

The ones that take a bit more elbow grease ....
FPR cleanup/replacement
Cam or Crank sensor replacement (VERY rare but I did have a crank sensor go bad and alter idle)
Manifold gasket

Chances are, 1 of these is the culprit. Hopefully it's one of the ones listed in the first list. ;)

So I took it in, and the IAC was apparently not functioning at all, so it was replaced. More expensive than it could have been if I had done it, but faster than I could have gotten it done with my work schedule; it's my daily driver, and I would have hated to have to cancel my dinner date with my kid tomorrow night. The VX purrs now, fingers crossed that it lasts.

Thanks for all the advice, if I continue to have problems, I will start with the MAF and such.

Quote:

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Originally Posted by WormGod

I would try to troubleshoot this one on your own. This problem is finicky at best and almost always inconclusive when you try to have a shop "decode" it. You tinkering away and getting your elbows dirty, one thing at a time, will yield better results. Like others have said already, start basic.

Clean MAF/check for induction breaches
PCV replacement
IAC cleanup
Fuel filter replacement
EGR cleanup (replacement?)

The ones that take a bit more elbow grease ....
FPR cleanup/replacement
Cam or Crank sensor replacement (VERY rare but I did have a crank sensor go bad and alter idle)
Manifold gasket

Chances are, 1 of these is the culprit. Hopefully it's one of the ones listed in the first list. ;)

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I have just put all of these parts in my watch list on ebay JIC. At 78,000 miles should I have all of these valves (EGR, IAC, PCV) just cleaned or should I start replacing?