Starts Right Up, Then Calmly Dies

[pdr51]

IAC cleaning

My vote goes for cleaning the IAC. Did this on my '87 B2 and it solved the problem. Cost me nothing but my time.

 

[broncogirl]

Got it to stay running - thanks!

Since it was cold, raining and dark when I got home, I took the advice of whoever it was the PMed me and said to try staying on the gas pedal and keeping it running until it warmed up. (I had been afraid to do this, as I was taught that running with a check engine light risks catastrophic damage.) He said if this "cured" it - which it did - that means it's the IAC - which I plan to thouroughly clean ASAP.

At first, I didn't think it worked. I held it between and 2 and 4K RPMs with few revs to 5K for about four minutes - until the heater was blowing warm.

The check engine light stayed on this whole time. When I took my foot off the pedal after about four minutes, it idled normally (at about 1.2K, I think) for only a few seconds, but then started to dip down like it was dying. To keep it going, I stepped on the pedal again - pretty hard this time. This rev made the check engine light finally turn off.

Reved it a few more times and held it a few more minutes and then it idled perfectly on it's own. Drove it back and forth a few feet, let it idle for about ten more minutes. Turned it off and started it up again with no gas pedal and it idled nicely with no check engine light.

Didn't drive it for work today, as I couldn't risk it acting up. Will try starting it again when I get home late tonight. Will definitely get the IAC off and cleaned this weekend, if not sooner.

Anyone still wanting to give advice on cleaning the IAC?
Read some other posts and am still not completely clear on some things - though they probably aren't important things:

Is Carb cleaner or Electrical cleaner is better?

Especially because it gets so damp, should I use a bit of oil or grease on any moving parts?

Dielectric grease on plug and..?

Some people called it the IAC "Motor" - is it a motor?

Is it likely to wear out? They run for $40 on Ebay and if it's like a 50/50 chance that mine is starting to fail, I'd buy a new one. Are there cruddy brands to watch out for or preferred brands known to be better?

Anything to look for as signs of impending failure when cleaning it?

How about cleaning the holes that it attaches to? Think I saw somewhere that they should not be cleaned, as they have a special coating in there, but most said, if they are grimy, to go ahead and clean them. Should I be extra carefull - maybe just gently wipe the worst of the gunk off? Or, liberally spray carb or electric cleaner in there and shove a paper towel in to get all the gunk I can reach?

If I do find that my IAC is really dirty, does that maybe mean I should do something different with my air filter? I have an old K&N and clean and oil it probably less often than I should - though it never looks really dirty.

 

[retep88]

Use carb cleaner to clean the IAC. The carb cleaner will eat through the gunk the clogs up the plunger. Yes, it is an electric motor that turns a plunger.

as far as the rest of the stuff, I am not sure.

 

[detty_motorsports]

Dielectric grease is never a bad thing:icon_thumby::icon_thumby::icon_thumby:

 

[adsm08]

Carb cleaner is better to clean it, Brake parts cleaner is a close second. Electrical cleaner won't do much. Putting di-electric grease in the connector won't hurt.

Its not a motor, its a valve. There is a variable position solenoid that pushes a plunger based on how much current it is given based on a duty cycle determined by the engine computer. Most of the time when they get stuck they are just gummed up from the EGR gasses flowing through. about 20-35% of the time though its a solenoid failure. I would guess that yours is gumming as it starts to work when it's warm, and the parts have expanded and the gum and carbon have melted.

Bosh is a good brand and can be had for $40-50 at the local auto parts store. Napa Echlin parts are also very high quality. I like to stay away from Duralast parts.

You can clean the crap out of the holes if its built up in there. The intake is not coated with anything special except crap from 21 years of running. Some newer engines have a special teflon coating on the throttle plate that is meant to keep the carbon from building up on it, which the cleaners remove. The 2.9 was discontinued before that practice was ever started.
Clean them up good, put it back together and then fire it up. Those cleaners will mix in and burn with the fuel without hurting anything.

It WILL look really dirty. I don't generally support the use of K&N filters, despite my hypocritical use of one in my own truck. In the 2.9 they shouldn't hurt much. I wouldn't put it on anything with a MAF.

 

[broncogirl]

Dug into it last night. First tried starting just to check and it died as before. Pulled IAC off (mine looked a bit different that the pic-does not have the black cap with the felt filter thingy). Did not look very dirty inside the module to me. Seemed like a very, very light coating of black stuff - no clumps of gunk visible through the little ports. Realized it was two parts and took the two screws out to take the solenoid/plug half off.

Then I could see in a bit better and push the plunger. Found the plunger to have some resistance - not difficult to depress with my thumb, though and did not feel like it was sticking.

First used electric cleaner, as I'd seen that recomended for the IAC in another thread and hadn't seen the recent advice here. That seemed to do nothing, so I then used brake cleaner. Was a bit worried using brake cleaner, since the plunger felt like it might have a rubber diaphram or rubber parts hidden from my view, but I did it anyway. I was carefull not to get it on the solenoid half, as that clearly had a hard rubber or plastic insert/sleeve inside - used just a bit of electric cleaner on that half. Cleaned the half with the ports and plunger very thouroughly, actuated the plunger repeatedly while full of brake cleaner. Let it dry well, put it back together and back on (the holes it attaches to seemed gunk-free, so I didn't mess with them.)The gasket looked fine and the electric plug connections looked very good. I did notice a red marker stripe on the unit, so I am assuming it came from a junkyard.

Then, when I went to start it, it did the same dying thing. Argh! I started again and, as it was about to die, held the gas pedal down and let it warm up. Let it run for about a half hour while I pulled the bezel off my 4x4 shifter to investigate my other problem (slips into neutral from 4-high - has no neutral lug in the plate to prevent this). Then turned it off and started again and that time it started and stayed idling.

So, I figured the cleaning had not cured the problem and wasn't sure about next steps, as I really would like to use it this Sunday for a snowboarding event.

Figured I'd warm it up and try driving it to work today and maybe take it by my mechanic at lunch. Surprise! For the first time since last Thursday, it started right up and idled perfectly with no gas pedal.

***Editing again, 21 days later, to say I have yet to get around to replacing, but have had no more trouble. THANKS AGAIN!***