Howdy! Newbie to the forums...


Vehicle:
'96 Aerostar Cargo
3.0L w/219K mile
Electronic auto tranny


So, after starting the van up today for the first time in 5 weeks, I let it idle till warm and noticed the idle never kicked down. Its done this before and I knew it would go away after a mile ot two. Anyways, I get a few miles down the road and notice its still idling high. I turn off the motor and tried to restart - no go. After a 10 min cool-down period, the motor still wouldnt start giving nothing but more starter wear and tear. After 30mins, while I waited for a buddy, I tried again to no avail.

Back in the driveway, I set out to check the usual suspects:

- Cranks good and strong
- Have spark (good and strong through spark gap)
- Have fuel pressure in the rails (~40psi)
- No loose wires/connectors
- Cannot hear the injectors open/close (normal?)
- Cannot hear rocker arms through valve covers

I pulled the crank sensor and lost spark, so assume that that system is good. I also purged the fuel rail of ~ a gallon to purge any air/water. Starter fluid/fuel sprayed in throttle body gave no hint of engine trying to catch.

Only thing I can figure is a broken timing chain, but not sure if this could keep injectors from firing..? I havent done a compression check yet.

I searched the forums, but other starting probs seem to be either fuel or ignition related, I have both good.

Anybody wanna help a (primarily) Mopar man out here?

Jim

 

you can check if chain jumped by putting timing mark on top dead center. rotor in distributor should be at number one or 180 out otherwise the chain jumped. hope this helps

 

Most problems like this are due to either the Idle Air Control (IAC) valve or the Mass Airflow (MAF) sensor. The former gets gummed up and sticks open/closed while accumulated fine dust particles on the latter gives faulty data to the engine control module. You can try to clean the IAC with a few shots of carb cleaner but most people wind up replacing the IAC which is by far the most common source of problems with these engines. Replacement is a very simple procedure. The MAF can be cleaned with a spray of aerosolized electronics cleaner found at all parts stores. (CRC Electronics Cleaner). You can do a search on this forum for additional details.

 

aerocolorado,

I could see the IAC being the problem for the idle, but wouldnt having even a dead MAF still allow the motor to at least start? Not sure about Ford 3.0's, but I assume the ECM starting mode would be the same as any other, ie: bypasses the MAF , retards timing, set timing and fuel maps, etc ?

Thanks for the replies guys..

Jim

 

It seemed the discussion went immediately to the more obscure problems. I was trying to start at the more basic end of the trouble shooting chart. The high idle clue was a common thread to the IAC and by custom/past experiences, onto the MAF. On my 4.0L engine with the MAF disconnected, on a cold start up the engine briefly fires up but dies quickly thereafter. Not sure if this is the same with a 3.0L. Sounds as if you may have a more serious problem than these two items but a broken timing chain would not have been my first impression. There have been several reports on this forum of broken timing chains in the past, but if memory serves, they were always while in transit rather than start up situations. Let's hope its nothing serious.

 

My 3.0 ,94, had similar starting problem. Cranked well, spark ok, no go. Turned out to be the MAF sensor (before joining this forum, took it to Ford dealer, waited 4 days for diagnosis, took it home and fixed it ). Got one from a wreck and it started right up. Oh yeah, if you replace it, the numbers on the sensor are VERY important. Make sure the replacement has the same number. Different ones won't work

 

Believe it or not my 96 Aero 3.0 engine starts right up without the MAF I even revved it and it didn't stall I guess the 4.0 isn't the same.

I didn't do it on purpose I just put the top air cleaner assembly on and forgot to reconnect the MAF. Luckily I realized it before I took it for a test drive I was replacing my alt that day the idiot light came on because it wasn't charging properly.

 

Well, today it fired right up and ran until I shut it off, then no go. Let it cool for ~3 hours and started right up, then wouldnt again. The first time I let it run till warm, the second was only about 4 mins.

The reason for the timing chain idea was that I have had it before (not this vehicle) and becuase I couldnt actually hear the rocker arms while cranking. Found today that I wont hear them , and obviously the chain is good.

Guess it could be an intermitten MAF failure, will hit the bone yards and let you know.

Thanks guys

Jim

 

I think the 96 uses a different type of Electronic Engine Control than the 94. That could explain starting with MAF disconnected. All I know for sure is that mine will not even fire without it connected. Midniteoyl, try spraying your MAF with the spray electronics cleaner before replacing it. The actual sensing wires that the air flows by are very touchy to handling with tools or touch. Just spray them and air dry. Don't try wiping them off directly. A new one at the parts store runs around $110.00. Have you pulled the codes yet? That may help locate the problem.

 

I drove my 1994 Aerostar for 3 months without a MAF because i didnt want to spend 200$ on a vehicle that i was gonna get rid of, the only difference I ever noticed was that the van seemed to idle pretty rough, the 1996 has a different computer system I believe, OBD II, which the 94 does not, so that might be the difference.