Hey guys here's my problem. Tranny went out on my bronco (4.9L I6), it sat for 3 weeks. When I got it moving again, the engine started acting funny. On occasion when I start it the idle drops dramatically almost killing it (I can watch the volt guage move from 10-14 volts) but it will clear up once I give it a rev. And at a cruising speed of about 40 it will jerk off and on, pretty sure it has to do with the rpm range but I don't know what is making it run so rough. Also when it is cold it will often die if I try to turn the wheel as I back out of somewhere or something. I was going to replace my oxygen sensor, if it isn't solved by that I was going to do the fuel filter, and then have to injectors cleaned. What is giving me so much trouble?!?!
Thanks,
Sam

 

Sounds as if the IAC (Idle Air Control) valve is dirty or faulty. You can do a search on how to test it and clean it, or just replace it.

 

Ditto to what justshootme said. If it hasn't been run in a while or tuned in a while, might try a complete tune up if the problem persists.

 

I'll third that. Sounds like an IAC. Although it is a idle air control valve, it still affects overall driveability if it is bad. It sounds like it needs a tune-up as well.

 

I had a similar problem. Rough Idle, jerking or stalling when Turning Steering wheel (under 10mph), also stumbling when shifting, running rich. I also saw that Voltage fluctuation.

It turned out to be the Fuel Pressure regulator. All those problems disappeared after replacing it.

 

Yes BTB, it could be that too. Remember that many, many things could cause your symptoms. Just because three people said IAC does not mean that that it is the problem. Do yourself a favor and try to narrow it down first, before throwing money at the problem.

When a vehicle is having driveability problems, the first thing that needs to be done is to verify the vehicle's state of tune, and to tune it up if necessary. If it has not had a tune-up for a while, do a major tune up including the cap, rotor, wires, air filter, fuel filter, and PCV replaced as well as just the regular tune-up parts (which are basically just the plugs on our vehicles). Also make sure that your timing is correct, it could be something as simple as the timing being off to cause your symptoms.

Of course you should try to pull any codes. Even though I am an old-school, shady tree mechanic and don't usually do that, pulling codes can help you a lot, especially if it is one of the sensors that is bad.

 

sorry j bronco, as a retired ford driveability tech i would pull the codes first,likely there is a code for the iac, if not, repair and clear any codes you found and see how it does then.If problem is still there clean or replace iac. spending good money on parts without at least a hint that it will fix your concern is a waste of money.there is a better way

 

No problem, I told him that he should pull codes. But any vehicle that is not running properly still needs to be in a proper state of tune before other problems are suspected.

I don't bother with codes because I have been working on cars (not professionally as my career, but I have repaired other's cars for money at my house or theirs) for so long that I have good intuition about what the problems are. And to be totally honest with you, any time that I had someone pull codes, dealer or otherwise, the results were confusing and the mechanics still ended up having to guess a little and they did not get it right the first time. I think that some of you guys are overconfident about those computer codes. Maybe they are more reliable today, but on my truck they always seemed to point to the 02 sensor when there was nothing wrong with the 02 sensor, and it was replaced three times because of that code until the mechanic finally found something else that was causing the computer to throw 02 sensor codes.

So I hesitate to tell people to pull codes if they don't know what they are doing. There is no doubt in my mind that a vehicle that is not running properly needs to be in a proper state of tune to really know what is going on. Case in point, I once had a guy bring me a Ford that was not runing properly. It had symptoms somewhat like the ones here. Poor driveability, stalling, hesitating, etc. The car had about 50,000 miles on it. It was a an LTD, or a Taurus, something like that. Some boring car, I don't recall exactly. The car was clean and he was telling me that he bought it new and took great care of it, and it was in tune and it didn't need a tune-up and it was something else causing the problem, blah blah blah. The first thing I did was to pop the distributor cap off since it was right there and I just popped the clip. All of the contacts were completely covered with corrosion, and the rotor was worn so badly that it must have barely been causing any type of spark, especially with the corrosion. So I popped the breather cover and the air filter was totally blocked with black dirt and whatever. You can imagine the spark plugs... I'm surprised that the car even ran at all.

When I told him this, he was like "no way! I bought that car brand new and took great care of it!" It turns out that "great care" meant that he washed and waxed and vacuumed it. But he had never even checked the oil, much less changed it, or had it tuned up. I doubt that he ever even popped the hood on the poor car. He was saying "it's a brand new car!" and he thought that he didn't need to do anything to it! So we got it tuned up and changed the oil and everything and it ran like a top.

An extreme case perhaps, but pulling codes on the car wouldn't have told me anything. I prefer to use the codes as a secondary tool, if I can't decide what is wrong first. Today's cars, cars of 2005 and so forth, they are different. You can't even see the motor on some of these cars, and they have 100,000 mile tune up intervals and so forth. I would not even think of working on one of those myself, and the computer codes are probably very reliable. But for my Bronco, I' trust myself first and only use codes to help me diagnose if I am having trouble (which was only once, and that led to the three 02 sensors).

 

Yeah, I'll look into all of those. I actually just did the cap, rotor, plugs, wires, and air filter not just to fix it but just as routine maintence.