98 I30 IACV overhaul

[berniken]

At 140000km I have quick stall on cold start unless holding accelerator slightly. Then, idle will hold, neutral or drive, at 200-300rpm. Dealer says IACV sticking.Can I remove, clean and replace without opening a hornet's nest?I am an engineer, with many years of hobby level auto repair, including valve jobs. Thanks.

[Q451990]

I don't know that much about your specific car, but I don't see why you would have a problem cleaning it. On the Q45, the valve is fed by a hose that connects back under the plenum. You might check to see what feeds the valve, and how much work you're going to have to do if the hose breaks while you're removing the valve.

Hopefully you can get it off without much trouble - a can of brake parts cleaner and a toothbrush should get the job done.

Welcome to the club!

Heath

[IvoryJ30t]

excuse the crappy camera phone pic, and kindergarden editing.

[berniken]

Thanks for your info. I'll post my findings.

[berniken]

Thanks Ivory. I saw the layout, but feared that removal might not be so simple, or might yield some hidden surprise. The notes on your photo are quite helpful. I'll proceed to pull it out and see if I can rehab it. I'll post my findings.

[IvoryJ30t]

no problem.

its not to hard. there was a gasket on mine, but it was in good shape, so i didnt replace it.

just clean the valve out with an old toothbrush and fuel injection throttle body cleaner [could use carb cleaner, but FI intake cleaner is a little less harsh, and i didnt want to take chances]

once its out, you will see a screw that lets you take the valve apart. i wasnt having a problem, just doing a tune up, so i didnt take the valve apart. its just a solenoid valve, so decarboning it shouldnt be too hard.

like i outlined, it would make the job much easier if you pull the intake tube, oil seperator, maf, and airbox top as one unit.

there are two screws [one is a bolt], the clamp on the throttle body, and two hoses [big one going to iacv, and a small vac hose] that need to be removed. after that, pull the whole assembly out. that gives you a lot of room.

after that, its just 3 12mm bolts, a few harness connections, and the valve pulls out.

you might as well clean the throttle body while you have everything out.

[berniken]

I did the deed last evening, and it is straightforward, as you say. I disected the thing totally. The two small cylindrical (pink and purple connectors) projections either side of centre are solenoid valves, to open on demand to allow a bit more idle air (port bore is less than 1/8") into the engine. My guess is air conditioner load and maybe window defogger switches these on. Central item is a stepping motor driven valve about 3/8" bore, the main idle air controller. This unit has a screw operator reversing motor. All easy to disassemble, with one spring that can fall out, but clear if you are observant. The coils for the solenoids (24 ohm) and the stepping motor (31 and 62 ohms both directions, no shorts) seemed OK, at least logical, on testing for resistance. All worked smoothly (but I did not power them), and valves were pretty clean. After assembly, the car started and idled perfectly, but on warming up, idle dropped to 300 or so again. It would not reset higher on hot restart. I tore it apart again (only 30 min to re & re this time) and found the larger valve screwed closed. I manually opened it before reassembly and it started and ran well until hot again.So, until more ideas come my way, I opened the idle-adjust screw more(originally 2.25 turns, now 3.25). Starts and runs fine, 1100 rpm park, cold, 700 drive cold, 800 park hot, 500 drive hot. I suspect the IACV is fine but is not getting correct temperature or RPM info or signal from the computer to adjust idle air as engine heats up.Engine has lots of pep at higher RPM and load. Any takers on this?I took more pics of the assembly, in case anyone can use them.

[IvoryJ30t]

the iacv is controlled by the ecu, compensating for loads [power steering, fans, ac]

the cold idle speed is also controlled by the fast idle cam. there is a unit to the lower left of the throttle body with two coolant hoses. when the engine is cold, its opens the throttle slightly.

the warm park idle should be 750 +/- 50, so your within spec. the warm drive idle looks a little low.

did you clean out the throttle body while you were at it? when was the last time it had a tune up?

[air filter, fuel filter, fluids, plugs, ect]

now that the base idle is set, drive a few days to settle the new iacv trim settings with the ecu.

[IvoryJ30t]

hows the car running?

[berniken]

Seems to start and idle very well now, but I have had one more instance on cold start when it reverted to stall. My wife drives it short hops daily and she is pleased, so I'm OK for now. I wonder if the stepper motor that adjusts the idle air is sticking a bit (maybe less after I cleaned it), but rotor shaft and bearings appeared very clean, lubricated and smooth when I had it apart. Time will tell.I priced an aftermarket replacement at Cdn $485 (tax in), and Infiniti quoted me about a hundred more, plus a hundrd installation. If I go, I am tempted to go with the dealer for the warranty.Thanks for your help.

[IvoryJ30t]

if it still acts up, you may want to find a wrecked maxima/I30 in the junkyard.

you could probably get another IACV for $50-100 USD