UPDATED: Stalling After Rplacing Idle Air Control Valve

[Annie Oakley]

I have an 88 Bronco II, 2.9L, standard transmission, 4-WD, fuel injection. Lately I've been having trouble with occasional stalling and a general loss of power (in addition to the intermittent engine hesitiation/stumble that many others complain about). I mentioned this to one of the Auto Zone staff and he suggested it was almost certainly what they list as the IAC (Idle Air Control valve - part number TV200 at the Auto Zone website http://www.autozone.com/autozone/parts/ ... ufj9Z9gsof . In the Haynes repair manual, they call it the air bypass valve (page 4-9, illustration 12.12). I followed the supplied instructions with the exception of testing the old part. It seemed to be a very easy job and took about 15 minutes.

The power seemed to improve and it runs smoother, but now after driving it about 1 or 2 miles, the engine stalls when I disengage the clutch. The RPM is lower and somewhat erratic at idle. Any quick suggestions? I'm going to have to take it into a shop due to time limitations, but I don't want to get ripped off like happens so often when a woman takes a car to a repair shop. If y'all could give me some advice, I'd have a better idea if the mechanic's recommendation is reasonable or if he's simply trying to make some extra beer money.

Many thanks in advance! You guys are always wonderful!

Updated on 21 August.....the shop cleaned the throttle body (bodies?) after finding some dirt in them. Then what I thought was the typical B2 hesitation/stumble occurred a day or 2 later and this time it backfired. Shortly after that, the B2 began suddenly accelerating without warning. Not a huge safety problem since it's a standard transmission and all I have to do is push in the clutch, but alarming. The only pattern is that going over certain bumps on a road I often travel tends to trigger this, and then sometimes it just happens on its own. If left in gear during this, it tends to lurch along. I've tried fuel treatments and switching to ethanol-free gas but it isn't helping. The repair shop thought they'd be able to figure it out on Friday when I dropped it off, but they are stumped at this point. They've been able to duplicate the problem but haven't been able to figure out what's causing it. I had to rent a car to make it to my military reserve training & now I'm gone on the remainder of 2 weeks of military training. I need the car repaired as cheaply as possible, so any advice I can forward to them would be appreciated by all concerned.

FWIW, the fuel system has been cleaned of water and had new filter in the last year or so, a new clutch about 8 months ago, routine oil changes, and the idle air control replaced within the last month.

Again, thanks in advance for any help.

[tekatlarge]

Well Annie, the first thing I would do would be go to auto zone again and ask them to scan the computer codes on your vehicle. They usually do it for free. That may give you some good information to work with. That may help you keep the shop in line.

A typical good shop will first scan the codes and run a basic fuel pressure test. and if necessary do some basic ignition troubleshooting.

Then, depending on results they will do system troubleshooting to identify the correct part.
One of the things I always do is I do a top to bottom visual inspection of the engine and related systems just to look for obvious problems and at the same time I note the condition of the components. I can see if the plugs are relatively new or old. I look for old hard cracked wires, loose connectors, broken items. I do this before I turn a wrench.

I hate to see a shop replace a bunch of things first before they actually find what the problem is. A good example was a person I know was on the road and his rig broke down. It cost him 1500.00 to get going again. The shop found the following parts bad. Bad distributor,bad fuel pressure regulator. Bad MAP sensor and Oxygen sensor and finally the computer. The computer was the actual bad part but they replaced all of the other stuff by what I call shotgunning. He had to pay for the parts or pay labor to have his old parts re-installed. It is a story still in progress with lawyers.

Finally make the shop mechanic explain in plain language what they did and why each part was replaced. a good shop will take a moment and explain why each part was replaced. if he says "Ahh it was bad man" and won't say what it was not working correctly, I would run.....

OK, I got to get back to work. Good luck on repair. I personally would think it may be 1 of 4 items. Fuel press regulator, Fuel filter, Egr valve or Oxygen sensor. Oh also don't always trust a replacement part just because it is new. I have had many times where a bad new part sent me in a circles.