hey guys got a little problem here. my truck idles really rough. like it going to stall u can hear it put put putting at the tail pipe. this is the part that i dont understand it only does it in park or nuetral. in reverse or drive it idles fine. i have checked the vacuum press. 19 inches at idle. this has been going on for a while now but got worse about 300 miles after insalling the egr restictor. 93 4x4 4.9l

 

hmmm no idea's yet huh. is there any vacuum lines that are only used when the tranny is in park or neutral?

 

i got the same problem. Did you ever figure out what it was. Let me know if you did at WisdomRacer@aol.com
Thank you

 

no i havnt . you have the same problem? it runs rough in park and neutral? do you have a egr restrictor plate?

 

sounds like it may be running too lean.

possibly a timing problem?

 

I thought the restrictor plate modification was for MANUAL transmission trucks only??

ftwfred

 

ftwfred, i have heard that, but i don't understand why.

The EGR seems to cause a lean condition, and also gunks up the intake pretty bad.

I don't quite see how an auto tranny would make a difference in this system, but it is weird that it seems to be a more common trend in the Manuals. It may just be due to the respective gear ratios and rotating wieghts and what not.

 

my tranny is an auto e40d. i had a terrible miss/stumble going down the road before i blocked the egr. the restrictor plate took care of that. now it is only at idle. ????? as far as the lean condition i have a KN air filter and my exhuast is 2.5inch staight pipe minus one cat. i think i read something in here saying that would cause it to run leaner if so what can i do to richen it up?

 

well there isn't much you can do to richen the set mixture as the computer will control all of that.

I would try resetting the computer, and changing the fuel filter. also try running some injector cleaner through her. That may fix your problem up right there, and it may not (as with all other repairs)

good luck

 

DDHJerk, you have a sensor going bad maybe? Your gonna need a book with the T's&A's for this one.
I had a similar problem in a Chebby 4.3 and it turned out to be Plugs.

 

thanks rhetor for the replies. i have already tried the injector cleaner and the fuel filter is new. to reset the computer just disconnect the negetive of the battery for how long? my truck has 175000 miles on it, maybe its time for new injectors? thudpucker any idea on what sensor? and what are T's&A's?

 

I don't quite see how an auto tranny would make a difference in this system, but it is weird that it seems to be a more common trend in the Manuals. ...............

There is no difference per engines. Being the manual is a solid link up, it makes the bucking stand out more than it would on the average automatic. The auto's tend to damp out the bucking a bit compared to the manual. Also, if you run an OD and run low revs at speed, this makes bucking stand out more. If the OD is a "lock up" type, as in the AOD, then that makes it worse, and much the same as a manual in OD. Bucking is actually normal per say. It's the slight missing of the engine at low revs that makes is stand out. Get the engine to idle ultra smooth, and usually you won't notice too much bucking. It's the same as coming to a stop in 3rd gear with a manual. Notice how it bucks a bit when the engine starts to lug? Same deal....The rougher the idle, the worse it will buck in either scenario. MK

 

does it sound like it has a miss at the tailpipe? mine does that

 

yes you can hear it at the tail pipe. i can feel just sittin in the truck too.

 

DDHJerk, I'm not sure what sensor it might be. You'll need a code and a book to look up the code. Most sensors are Heat or Vacuam switches. They tell the Computer to increase or decrease the fuel supply. Some of the sensors pull a Solenoid to increase the idle speed.
EGR might be a good guess, or the Modulator valve in the Transmission. The Vacuam line to the Modulator too.
T's and A's (Bless your dirty little mind) are "Test's and Adjustments" or the Repair manual. Try the library. They sometimes have the Mechanical manual and in the Reference section you can find the emissions manual.
I found them in the Anchorage, Albuquerque and DeRidder libraries.

Here's my guess.
When you put it in Neutral, there's no load on the engine. The Idle speed picks up, the computer sees this no-load condition, and cut's the amount of fuel going to the injectors.
In your case, it cuts down the Injector pulse length.
That's what should happen!
But on Your engine, in Neutral it Idle's up, one or more injector is feeding a low amount of fuel and the rest are still feeding a larger amount of fuel.
The energy difference is causing a Vacuam stumble, which really seems like a miss.
It could still be a plug, wire, dist cap too. Have you dont a compression check?