I just picked up a '97 Aerostar from auction for just under $500. Besides some minor issues like replacing some lights and tightening the belt, the engine rpm bounces when low and cold. It does not bounce nearly as much as when the engine is warm though. My thought is that it could be solved my slightly increasing the idle speed. How would I do that or what is a better alternative?

 

You have to tell us which engine you have!!

 

If I understand it right, from my readings, its the 4 liter, 6cyl.



While testing lights out, I found something a little odd. The headlights work, but only the low beams. The high beams only work on the momentary switch but not on the continuous. This confuses me.

 

First off you can't tighten the belt. How did you manage that? The term bounce isn't usually used to describe an idle.. Does the idle change or surge. whats the frequency?
Any check engine lights..We need more info..

As far as the lights the multifunction sw is most likely at fault if your low beams are working..Could be wiring also..

 

I'll put it this way, the engine will will start to die and then try to revive itself. It begins a continuous pattern of almost dead to alive and repeat.

There are no check engine lights. When the engine is cold, it does this "bounce" more often and when warm, every now and then.

 

IAC valve could be going bad or dirty.. controls the idle.

 

Your engine has a PCU,the heart of which is the EECV computer with OBD2 diagnostics. Idle speed cannot be changed without the use of an engine tuner.

Your idle problem could be several things but Idle air controller (IAC) could well be the culprit. You also need to rule out fuel pressure, fuel filter, Mass air flow (MAF), Engine coolant temp (ECT), Air charge temp (ACT) & Throttle position sensor (TPS). When was the last tune up? (Air,fuel filters plugs etc)

The engine will still operate with most of these disconnected, one at a time, so it is possible to pull the electric plug & observe if the engine runs better or worse or no change. The IAC is an air control which bypasses the throttle plate which is shut at idle, so if the IAC is malfunctioning the engine may get almost no air & will die. Since this control works on a "duty cycle" it can work at some of it's range and not at the lowest settings. What if you give the engine a "tiny bit" of throttle does it then immediatly pick up speed? I dont think you can really clean the IAC but you could clean the MAF sensor, but be careful it is very delicate!
When the v 6 ford engine starts up from cold it will "roar" for about 20-30 secs at about 1500rpms & then slowly drop back to around 600, then slightly increase rpms up to a steady idle of around 800. The pcm is able to test out the IAC with this sequence so when it gets bad enough you should get a code!

Aeroman.

 

The issue seems to have progressed since I started driving it. Along with the rpm bounce (which it goes right out of as soon as the accelerator is depressed), a chugging seems to be happening.

When driving around town 35mph, it shifts up to 4th or 5th gear so its at low RPM around town. When it comes to accelerating, the engine chugs and it seems like the transmission cant make up its mind on what gear it wants so the vehicle shakes. The only way to stop it is too let up on the accelerator or floor it (not really but give it some fuel) It then decides on the lower gear and takes off. Normal shifting on it is smooth and the acceleration is strong. One thing I have started to notice is that when idling though town, the engine does its bounce thing it seems and the transmission follows. What I mean by that is you feel as if the transmission went into neutral and you are coasting and then engages with a slight pull (accelerating) This is more common when going down a hill.

The indecisive transmission shifting and shaking seems to be getting steadily worse over these couple of days.

One thing I found a little odd, if the vehicle is parked and you rev the engine, its smooth but when driving and you accelerate, there is a slight squeal in the belt.

Pulling up in the driveway tonight, I smelled a rich fuel mix and my GF confirmed this, when I first got it, the engine was clean and fluids good for the most part. It only has 135K on the engine and the trans and oil were rather clean. The power steering was a white and grey paste almost and I emptied what I could and replaced with fresh fluid.

On a small note, there almost seems like one of the cylinders could be misfiring but it could be a mistake on my part.

I hope all the issues could be something simple. I would like to keep this vehicle but I can't afford to put much into it. One thing I noticed while checking fuses, on most fords I've had, on the fuel panel, there was always a metal round one (fuse, relay) in the corner. This one has a spot for one but does not have one. The vans radio or 12 volt plug does not work either but it could be something completely unrelated.


This IAC, is it something that could be easily or inexpensively replaced?

Thanks for your time and advise,

Steven.

 

Taking off the first part of the air intake today and listening to it run, I believe I hear a bit of sucking but I'm not sure where exactly. I'm going to get some cleaner and see if I can clean out the IAC and see if that helps out.

 

In the back of the engine drivers side there are a bunch of vac lines sometimes they fall off..pull the cup holder one screw in bottom pull up.Take off small electrical box above 2 8mm nuts then remove engine cover.

 

Will have to try it tomorrow after work.

 

Never ever ever touch the idle adjustment. The correct thing to do is to clean or replace the idle air controller assuming that it is the problem. If you mess with the idle adjustment, you can make it worse, you cannot make it better, and you and increase the fuel consumption.

 

Its not really an idle adjustment its just there to keep the butterfly from getting stuck in the bore.. I agree don't touch the stop..

 

Orpackrat,
Would your description of "bouncing idle" be more like a surging? If so, you likely have a vacuum line loose/broken somewhere. Since this would be a cheap and relatively easy fix, I would suggest you check this possibilty first before replacing any parts.

 

An air leak is another possibility and it would cause the injectors to add fuel creating the rich smelling exhaust. Have you checked the vac line to the Fuel pressure regulator? This will create problems if it's fallen off or leaking badly.