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  #1  
Old 12-06-2007, 06:09 PM
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97 f150 4.6 intermittent rough idle when warm

Searched the threads and tried many of the items found there, can't find the problem. 121k miles. Happens only when engine is warmed up, shakes and feels like it will die at some stop lights, runs fine driving no power loss, etc. No shake if it is in park.

Used to have check engine light for egr flow, no light since bypassing broken vacuum canister (see below)

Mechanic replaced: EGR valve
EGR solenoid
Metal tube from exhaust to egr
Found cracked vacuum cannister in passenger side wheel well, bypassed it
I replaced: spark plugs with bosch 4's (is it a big deal that they aren't motorcraft?)
wires with oem
checked for vacuum leaks as best I could, no smoke machine, didn't find any vacuum leaks
cleaned throttle body
cleaned MAF
cleaned what I think is the idle control valve (on top and to the back of intake)
don't know if it is related but AC compressor makes a loud metallic click when engaging/disengaging

Is this likely to be an o2 sensor? Is there a way to test the idle control valve? If it was the Idle control valve, would it shake when engine is still cold? Thanks a lot for any help, I am stuck at this point.

Last edited by saaber; 12-06-2007 at 06:11 PM.
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  #2  
Old 12-06-2007, 06:14 PM
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Holy Hell !! Get those plugs out of there!!

That's the problem.
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  #3  
Old 12-06-2007, 08:45 PM
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Quote:
Originally Posted by jbrew
Holy Hell !! Get those plugs out of there!!

That's the problem.

give it to him strait doctor!
He can take it

lol
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  #4  
Old 12-07-2007, 07:10 PM
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Quote:
Originally Posted by jbrew
Holy Hell !! Get those plugs out of there!!

That's the problem.
Will change them out tomorrow. On the way to parts dept now. $8 per plug? Daaaayuuuuum! Looked into autolite equivalent but they are around $6.50 and not immed. available.
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  #5  
Old 12-07-2007, 07:18 PM
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Quote:
Originally Posted by saaber
Will change them out tomorrow. On the way to parts dept now. $8 per plug? Daaaayuuuuum! Looked into autolite equivalent but they are around $6.50 and not immed. available.

Autolite Equivalent?? Geezz - there is no such thing, you'll have the same problems with those . You drive a Ford - get the Ford plugs - They read MOTORCRAFT..

I tried both Bosch and Autolites way back when I didn't know any better - Mannnn , did they goof things up..When you said it idles erratically when warm, that is a strange problem in itself which tells me it's a plug problem. When I tried the Autolites , the plugs got so hot they turned different colors..When I tried the Bosch , the truck fired once and wouldn't start after that..

Last edited by jbrew; 12-08-2007 at 08:34 AM.
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  #6  
Old 12-08-2007, 06:38 AM
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I hope you are changing the wires while you are in there.
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  #7  
Old 12-09-2007, 01:00 PM
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Quote:
Originally Posted by saaber
Found cracked vacuum cannister in passenger side wheel well, bypassed it.
the canister stors vacuum as a reserve. It is also in the egr circuit.
could this be the problem?
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  #8  
Old 12-09-2007, 01:06 PM
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you change that fuel filter often?
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  #9  
Old 12-09-2007, 01:14 PM
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Quote:
Originally Posted by Tumba
the canister stors vacuum as a reserve. It is also in the egr circuit.
could this be the problem?

It holds pressure for a long time. I remember unplugging after being down for 3 days - A blast of air shot out of there - caught me by surprise

But , yea, it's a direct feed to the EVR (solenoid) (White Line) which routs to the EGR. I imagine when the PCM commands the EVR to open the poppet valve in the EGR , it uses that air pressure to do so.

You can see the white line in this shot - released air uses the green line to open the valve under PCM command.

Click the image to open in full size.

Bypassing ? I'm not exactly sure what would happen ? Non command EGR flow code should be set I would think? BUT! If it's not openning , that should not effect idle. Like I said -not sure , but I would get to a junkyard and grab one..It's there for a reason.

Last edited by jbrew; 12-09-2007 at 01:20 PM.
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  #10  
Old 12-09-2007, 11:02 PM
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Quote:
Originally Posted by jbrew
It holds pressure for a long time. I remember unplugging after being down for 3 days - A blast of air shot out of there - caught me by surprise

But , yea, it's a direct feed to the EVR (solenoid) (White Line) which routs to the EGR. I imagine when the PCM commands the EVR to open the poppet valve in the EGR , it uses that air pressure to do so.

You can see the white line in this shot - released air uses the green line to open the valve under PCM command.

Click the image to open in full size.

Bypassing ? I'm not exactly sure what would happen ? Non command EGR flow code should be set I would think? BUT! If it's not openning , that should not effect idle. Like I said -not sure , but I would get to a junkyard and grab one..It's there for a reason.
Thanks for all the ideas!

Replaced plugs with motorcraft, no change.

Re Fuel filter: wouldn't something be noticable while driving, or idle cold in drive, or idle when hot in nuetral/park. It runs excellent at those times so I don't think this is the problem but let me know what you think

Re wires: replaced with oem

Re Vacuum cannister: This could well still be the problem. No check engine light anymore but may not be right for proper idle when warm. The truck only has a miss after sitting about 2 min. at a stoplight after coming off freeway etc. so it is not all the time and I guess it is more of an anoyance. Let me explain how he bypassed it:

The cannister is a one-piece, 2 chamber plastic piece that sits behind the plastic fender liner on the pass. side directly above the tire (it is not the 2 seperate plastic cannisters sitting directly behind the battery). The rear chamber is fine and has 2 lines running to it. The front chamber is broken off and the two lines that run to that were coupled together. There doesn't appear to be any leaks there at all but obviously it doesn't have the "pressure reserve" or whatever you want to call it anymore for those two lines.

After spending this last money trying to fix this anoying problem I think I will just sell this truck. I am out of energy trying to fix this problem. Maybe I will change my mind in the morning... We need a smily on here for "extremely frustrated" ha ha Anyway thanks for your ideas. I appreciate it.

Last edited by saaber; 12-09-2007 at 11:20 PM.
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  #11  
Old 12-10-2007, 01:11 AM
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You have Motorcrafts in there - now we can fix her . You should of said that you bypassed the Charcoal canister in the first place - That's WAY different..

Good luck on your next ride , you'll need it..
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  #12  
Old 12-10-2007, 07:27 AM
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if what i read is right, you've got a bypass on the charc can. im surprised your not getting a code.

have you considered o2 sensors? injectors? usually cleaning the IAC helps, but it may not resolve the issue completely. i'd suggest grabbing a charcoal can and fixing that issue.
btw, you did read somewhere along the line that these motors appreciate dielectic compound right? motorcrafts are a must, although i think denso or ngk is suitable quality since the L boys run them.

im curious to see if your bypass is your problem, if it is maybe i'll look at mine when its in for my swap.
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  #13  
Old 12-10-2007, 08:30 AM
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Quote:
Originally Posted by jbrew
You have Motorcrafts in there - now we can fix her . You should of said that you bypassed the Charcoal canister in the first place - That's WAY different..

Good luck on your next ride , you'll need it..
I'm not sure what you are referring to here. It is definately not the charcoal cannister. I double checked 3 auto parts sites to confirm and it doesn't look anything like that.
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  #14  
Old 12-10-2007, 08:35 AM
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Quote:
Originally Posted by Klitch
if what i read is right, you've got a bypass on the charc can. im surprised your not getting a code.

have you considered o2 sensors? injectors? usually cleaning the IAC helps, but it may not resolve the issue completely. i'd suggest grabbing a charcoal can and fixing that issue.
btw, you did read somewhere along the line that these motors appreciate dielectic compound right? motorcrafts are a must, although i think denso or ngk is suitable quality since the L boys run them.

im curious to see if your bypass is your problem, if it is maybe i'll look at mine when its in for my swap.
I was thinking O2 sensors also due to no issue until really warmed up. Haven't got an O2 sensor code but that doen't mean they are contributing to the problem.

Haven't looked into fuel injectors yet but that is certainly possible. See previous post regarding charcoal cannister. Did use dieletric grease on wires.

Is there any way to test the IAC?
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  #15  
Old 12-10-2007, 01:41 PM
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He's right !! Why did I think that was a charcoal canister ?? My bad . The two behind the battery are called the auxiliary vacuum reservoir and the A/C vacuum reservoir.

The one in the fender itself is called - engine vacuum reservoir ..I don't know how this effects the system bypassing but, I 'm curious to find out.

Suck test the EGR , make sure it's operating correctly . If you haven't cleaned the MAF - do that as well and test the pcv valve. Other than that I would say it 's a low grade misfire that the monitor isn't picking up. If the O2's were that bad it would provide a code IMO.

I thought you were selling?

Last edited by jbrew; 12-10-2007 at 01:54 PM.
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Old 12-10-2007, 01:41 PM


 
 
 
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