94 Areostar 3.0 VERY ROUGH IDLE!!

[jsnyder49090]

I am beating my head against the wall here.New plugs,wires,cap,rotor,fuel filter,air temp sensor,coolant sensor.Still wont idle when i unplug the MAF it idles fairly smooth or 95% better but a new MAF did not cure the problem.When you first start it it idles smooth and after about 10-15 secs will idle rough.It seems to have most of its power off idle but i know it has to be costing me some mileage.The van has no codes i am at a loss with it.

 

[demarpaint]

How is the IAC? Is it plugged up with junk?

 

[punisher]

Originally Posted By: demarpaint
How is the IAC? Is it plugged up with junk?


Ditto. Check for vac leaks, breaks between MAF and throttle body.

 

[jsnyder49090]

IAC looks beautiful took it off twice and cleaned it.It did have a crack in air intake hose i repaired but it was just a small crack.Why does it idle good with MAF unplugged??

 

[SwampSurvivor]

The IAC can look good but go bad. It's nearly 20 years old.

 

[demarpaint]

Originally Posted By: Miller88
The IAC can look good but go bad. It's nearly 20 years old.


+1 Vacuum leaks can also be causing the problem and be a PITA to find.

 

[ksp7498]

When there's a crack in the intake you have unmetered air entering the engine. Meaning, the amount of air the MAF sensor tells the ECU is entering the engine is wrong because "extra" air is leaking in. So the air/fuel mixture is wrong and the car runs like [censored]. When you unplug the MAF it resorts to a pre-determined air/fuel table which is not perfect but bypasses the MAF's faulty readings.

Either your MAF sensor is bad or you still have an air leak somewhere.

 

[jsnyder49090]

Yeah they are routed crazy and the engine compartment is a joke!I will have to check it again but it idles smooth for the first few seconds and if i unplug the MAF it idles good but just dies every now and again.

 

[46Harry]

Do a compression check, my cousin had an Aeroster years ago that developed a burnt valve causing the engine to idle rough. I also agree that an air leak somewhere in the induction system can casue a rough idle too.

 

[Chris142]

The first thing I'd look at would be the fuel pressure regulator. If it's bad it will dump gas into the vacuum hose and that dumps it directly into the intake manifold.

 

[TallPaul]

I have a 92 Aerostar 3.0 and that was a problem all it's life, we changed all kinds of components but it still has that problem as well as a pinging under hard acceleration that cannot be cured. Never changed the fuel pressure regulator though. IAC was changed once and seemed to help but not for long.

 

[jsnyder49090]

The thing is i had the parts store send down a MAF and it did not change anything.If it had bad valves it wouldnt idle good with the MAF unplugged either.And it idles at 95% with it unplugged it just dies everynow and again.It starts and idles good for a min and then goes to [censored].I dont believe its the fuel pressure regulator.But i appreciate any input!

 

[TallPaul]

Hmmmm, what if there is a vacuum leak? Of course, unless you have a newer transmission design than my vacuum modulated transmission, a vacuum leak will firm up the shifts (a good thing), but obviously too big of a leak would make it idle rough.