Do fuel injected engines have an automatic choke?

[joshhemming]

My '93 3.0L Aerostar has always started and idled great, even in the coldest of weather. A month ago, the cold idle got crappy. It still starts fine, but instead of the normal fast, smooth idle, it's a rough idle and unless I manually increase the RPMs for about 5 seconds, the engine dies. After 5 seconds, it idles and runs fine for the rest of the day, with no starting and idling problems until the next cold start.

If this were a carburated engine I'd suspect the auto choke and/or fast idle cam isn't engaging. But this is fuel injected, and my FIRST fuel injected vehicle, so I don't have a clue as to what is causing this problem. All I know about servicing fuel injectors is to change the air filter and add a bottle of Techron to the tank annually.

Can you think of any measures I can take to get the cold idle back to where it was?

 

[colintrax]

It's not really a choke but the computer does make the engine run richer when cold. Try cleaning the MAF and maybe throw a bottle of injector cleaner in the tank.

 

[BrooklynBay]

In addition to cleaning the mass air flow sensor as previously suggested, check for vacuum leaks, and clean the idle speed control solenoid. There's a special spray cleaner which is designed for mass air flow sensors. It doesn't contain any chemicals which leave oily residue, and it's fuel injection safe. Never use carburetor cleaner on a fuel injected engine system.

 

[rv4fun]

I'm not familiar with the older Aerostars anymore but a good place to start looking is under the air cleaner box (you'll have to remove the whole box) to see how the hoses to the vapor recovery canister look. They could be shot and allowing a lot of air to be sucked into the system.

 

[BrooklynBay]

My 1995 van had a broken emissions elbow under the air cleaner box, and one vacuum cap was missing on the vacuum tree. The van was running rough, and was hard starting when it was raining & cold outside. Follow the vacuum diagram under the hood.

 

[Fordsgalore4]

my 96 ranger would run ruff at start up and it was the IAC valve that mounted to the throttle body try cleaning that with some throttle body cleaner or replace it it made my ranger run and start great and its the same for the 3.0 and 4.0

 

[joshhemming]

Thanks guys. I now have some likely things to check.

Just in case the problem turns out to be the MAF....I see a WIDE range of prices for replacement MAFs. Do the aftermarket versions have a decent reputation for quality, or should I go with a genuine Ford part? And should I buy the whole assembly, or just the small module?

 

[BrooklynBay]

Clean the mass air flow sensor before you decide to replace it.

 

[joshhemming]

I'm not familiar with the older Aerostars anymore but a good place to start looking is under the air cleaner box (you'll have to remove the whole box) to see how the hoses to the vapor recovery canister look. They could be shot and allowing a lot of air to be sucked into the system.

I guess I owe both you and BrooklynBay a beer or other adult beverage of your choice!

I took loose the two nuts in the bottom of the air cleaner box, removed the box and staring back at me was one connected vacuum hose and one empty connection where an AWOL hose should be. The culprit was the hose with the elbow. It had a split in the elbow and had worked itself completely off the connector. This hose appears to run over to the throttlebody. I taped it back together as a temporary fix, finished spraying the MAF sensor probe with the overpriced CRC stuff and now the van starts and fast-idles perfectly in the mornings.

Does Autozone sell the replacement rubber elbows for the vacuum lines?

 

[BrooklynBay]

Any auto parts store with the Dorman/Motormite/Help section should have what you're looking for.

 

[rv4fun]

I had trouble finding an exact replacement. The one I bought at O'Reilly Auto Parts was almost $10 - it was the right size on the large end but too big on the small end (about 3/8" instead of the 1/4" it needs to be). I used a clamp to squeeze it down to size and hold it on tight.

 

[Aerostar96]

I've had similar problems with the elbow in the emissions tubing, with a rough idle and setting off the CEL occasionally. After much searching I found the ford replacement part on eBay. The tubing for the whole section comes together, a little pricey at $38, but at least it is the exact part I have needed for a year or more. The part number is F69Z9G271BA if anyone is trying to find it.

 

[BrooklynBay]

Thanks for posting the part number. I found the listing on EBay. It had a Ford diagram: