I have a '97 5.4 with 85k on it. I just replaced the plugs with Bosch +4, cleaned the IAC, and replaced the PCV. I have also ran some good fuel inject cleaner through it and cleaned the throttle body with some throttle body cleaner.......

And i still have a rough idle while in neutral and in drive. It is not too rough, just a slight shake every once in awhile. In addition, while in neutral...if i rev my motor slowly from 800-1,500rpms, the mis in the engine is very very prominent but fades after 2000rpm!!! When I drive down the highway everything sounds fine and the mis is not noticable...it seems. If there is a slight mis, i can't notice it very well while actually driving. What could be the cause of this mis at idle and especially when i rev it in park? I have no pinging in the engine under load.

Please advise...

By the way, thanks for the advice about the f150 clunk that is present from a stop. I greased the slip yoke on the drivehaft and it is totally silent..thanks again.

 

a slightly rough idle is perfectly normal for the triton engines, you should probably be hanging around 700 rpm's or so while idling. if the truck is really shaking bad, then that is a problem. does it do it more often when the truck is hot?

you should clean the MAF sensor for sure.

if the engine idles worse when warm, it will most likely be the EGR valve, DPFE sensor, or the O2 sensors...

test the EGR valve by putting a piece of tubing on it and crank the truck. while its idling, suck on the end of the house, the truck should start idling bad and act like its going to die out. that means the EGR is fine, you'll have to check your DPFE sensor, and also check voltage on the TPS sensor.

the O2 sensor will cause a rough and erratic idle when it is faulty, however, the O2 sensor only kick in once the truck reaches operating temperatures. once the exhaust hits 600 degrees, the O2 sensor give feed back to the PCM. a bad sensor will cause the PCM to send too much or too little gas to the injectors...

hopes this help, maybe you could tell me where you're rpm's are at, and if the truck does it only when its hot.

i'm also assumming you do not have a thrown code?

 

Along with the suggestions above I would also look into a minor vac. leak.

 

Thanks, i apprieciate the advice. The check engine light is not blinking. I am not sure exactly what the rpm's are. I will have to look at that tommorow to check. By the way, how do you clean the MAF sensor?

I will do those tests that you talked about in the meantime. Thanks for you help.

 

The symptom is when the engine is warm and at normal operating temperatures. It does not do it when it is cold. I checked the EGR valve like you said....it is functioning normally. Do you suppose it is the oxygen sensors? I have the o2 sensors that are located behind the catylic converters. Do you suggest I go ahead and change both of them?

 

Not trying to sound petty here at all. It is probably the Bosch plugs. They seem to run way leaner and produce those problems in most 5.4's not all.

I suggest trying either Autolite or Motorcraft Double Plats. I couldn't get mine to run right with Bosch plugs either.
I currently run Autolite douple plats and am happy as can be. I know lots swear by the Motorcraft plugs as well. Gotta be something to so many problems when running Bosch though.

I hear often the rough idle is part of these engines. I have yet to have mine idle any thing other than smooth as any other engine I ever owned did or the reason was found for it not idling correctly.


Couple of times just reseating the COP coils again stablized my idle. I think sometimes we may be gettting the spring on the coil off to the side and not around the plug.

Good luck


tom

 

I replavced the O2 sensors on my 2002 Screw and it cleared the idle right up.


Rick

 

Replace the upstream O2's first if you do them(before the cats) also replace the dpfe ...if it goes bad it will cause a rich mix and rough running plus your mileage will drop like a rock...and yeah toss the Boshe..stay with the motorcrafts..oh yeah...and check the return ports behind the throttle body coming from the EGR...willing to bet thier clogged up

 

hey this sounds almost like the problem my 4.6 is having, except for misfire, but it idles real low (490 -510) drive and when at opperating temp. i had 2 o2 sensors replaced year and a half ago along with plugs and wires and had the iac a couple months ago. can someone tell me where the EGR valve is and where the DPFE or what was said. should i try to replace the other 2 O2 sensors? thanks