Bad Idle on '96 3.8L

martymoose32 · #1 12-23-2004, 04:14 AM

Merry Christmas all!!

Ok, my problem: Bad idle and occasional stall when engine warms up. Stalls when turning into a parking space, or the driveway at home. Once you get up above 1300 rpm, engine smooths out and accelerates perfectly. Yes, the CEL light is on. It flashes when slowing down to a stop. Once you get going, the light goes steady on. This started about 2 weeks before Thanksgiving. I had the motor checked out by the engine mechanic. Said engine vacuum perfect. Also said one of the coil packs was cracked. Changed it out and problem solved...right?? Right after Thanksgiving, bad idle came back. I changed the IAC at that time. Problem solved, again...right?? Bad idle came back a few days ago.

I had the engine replaced a year ago, so I don't think it is the dreaded "isolator bolt" problem.

Ok...now what??

As long as I drive above 1300 rpm, the van runs like a bat out of you know what!! But I know I will have to eventually slow down to a stop.
Would like to change the fuel filter, but I don't know where it is.

Any help would be greatly appreciated.

pryornfld · #2 12-23-2004, 06:29 AM

I kind of have the same problem from time to time. Notice it more in the cold weather.I let the van idle in the driveway , when it warms up, ocassionally it will stall. I wonder if the problem could be a battery? If I find out anything,I'll let you know.Do you find that the RPM sometimes bounces just before the stall?

Dngrsone · #3 12-23-2004, 11:37 AM

Fuel filter is under the van on the driver's side.

Get the codes, that will help immensely in troubleshooting the problem. You can get tehm read off for free at many auto parts stores like Autozone.

martymoose32 · #4 12-23-2004, 01:10 PM

I noticed something else today. I was adding trans fluid with the engine running and I unplugged the vacuum line going into what I think is the EGR valve. I read in a post that if you unplug the line, the engine should bog down. It didn't change at all. I did it as a check.

Did I do it right??

Was it the EGR I was checking??

martymoose32 · #5 12-23-2004, 01:12 PM

Oh, btw is the EGR under the IAC?? Diaphragm looking thing with a vacuum line out the top??

wiswind · #6 12-23-2004, 07:16 PM

Marty,
On the 1996 3.8L engine (Is also what I have...so I know this) the PCV valve is on the BACK valve cover.....
There is a elbow on the top of the upper intake manifold, right next to the trottle body. There is a hose going from this back toward the firewall. Then there is another elbow that turns down.....to the PCV valve. You will find that there is a "T" with the vacuum going to power a couple of other things....one of which is the EGR vacuum regulator (that takes a electrical signal from the computer....and converts it to a vacuum that goes to the EGR valve) Check the PCV vacuum line for leaks. A small leak will have a bigger effect at lower RPM's.....so look first for a vacuum leak.

The item on the FRONT valve cover...is the Crankcase Breather.....this has a hose going into the big, flexible hose that goes from the air filter to the throttle body. Air travels into the engine through the Crankcase Breather.....and is pulled out through the PCV valve. The air that enters the crankcase breather is measured (along with the air going into the upper intake manifold through the throttle body) by the MAF sensor (Mass Air Flow sensor).

Dngrsone · #7 12-24-2004, 01:48 AM

Marty,

You had the EGR alright, but what you need to do is plug taht vacuum line, then use a hand pump to apply vacuum to the EGR... it should open with around 10-15 inches of vacuum, and the engine idle will drop about 100 rpm.

Winny_the_Pooh · #8 01-04-2005, 06:35 PM

I think the flashing CEL indicates a severe misfire/behavior while the steady CEL indicates just a bad misfire/behavior.

NYranger · #9 01-04-2005, 09:32 PM

Mine doesn't do exactly as yours but when i park,the rpm drops and few times the engine went off.I thought this might be an air sensor,because at higher spped driving on the street or highway,i had no problems at all.
Soon i am going to check this at Autozone as Dngrsone has mentioned.I just wonder why Autozone does a freee check up . lol

sohcfreak97 · #10 01-04-2005, 10:46 PM

Well A Rapidly Flashin Cel Is Called Mis-fire A, While A Steadily Flashin Cel Is A Mis-fire B, A Is Most Serve And Cause Most Damage To The Cat.conv. If It Only Flashes On Decel I Think Their Maybe A Problem With Your Ckp Because Misfire Data Is Learned On A Decel Only, But I Think It Could Also Be A Headgasket, I Had A Few Of These With The Same Concern. -ford Tech-

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