My 98 4.6L auto 2wd idles rough. There was some vibration shortly after I got it in 10/97, but it's gotten worse since. Two dealers have told me that engine vibration is normal, that their diagnostics tell them everything is OK, and that I have to live with it. It's as if the idle rpm is a tad low. Anyone else with this problem?

 

I too have a rough idle problem that has been getting worse and has driven me crazy since I got my truck (11/98). I've had it into the dealer 3 times but they always say their diagnostics came out normal. "Just drive it" they said. Lately I've been hearing what sounds exactly like the piston slap after my truck's been sitting for any more than 4 hours. I'm going to take it in to the dealer this week to check that but I'm afraid I'll get the standard "No problem found at this time" again. There's something definitely wrong with this engine, if they can't do something with it soon it'll be time to trade it in. Of course, I haven't tried changing the plugs or checking the wires, but wouldn't the dealer have checked these things? If anyone has had these problems PLEASE let us know if you have solved them. (The piston slap concerns me particularly because I have the Romeo 4.6 which isn't supposed to have this problem.

 

FYI - The 2nd dealer did some test where they look at the power produced by each cylinder, and claimed they were all close enough to say it's "within spec". This supposedly takes into account the plugs and the wires (if there was a bad plug or wire, they would know it, they would know it from this test).

I'd like to know exactly how they can determine the power produced by each cylinder. To tell the truth, I think their diagnostic system printouts are designed to snow the customer. I wish they would cut the BS, as I've learned more from this BB than I ever did from the dealer (nothing!)
I also wish could speak to an actual mechanic instead of some service "manager" who believes only what his computer tells him and refuses to even take a ride in my truck.

 

Look at tis thread it seams to effect the 4.6 also https://www.f150online.com/f150board...ML/000676.html
hope it works for you, it worked for my friends 98 4.6

 

My '99 5.4 Triton shakes my side view mirror, causes noticable vibration throughout the cab and elicits responses like "sounds like your motor is missing" from passengers. I too have taken it to the dealer (not one but two different). Same responses as the others, all is well, no noticable problems. I also got the same reply as kog, "live with it". I spoke with the master mechanic at the dealer where I purchased the F150. He said that the vibration is attributed to the computer margining the engine to achieve the most efficient fuel consumption. Sounds like horse hooey to me. I still have to check where the engine was manufactured to determine if this might be the beginnings of Piston Slap. I wonder if an aftermarket chip would correct the problem??

 

Check the thread that Don C referenced. It has a really simple fix for some of the rough idling problems. It worked for me as well as a few others.

 

I have a 4.6 with an automatic. I have taken it to the dealer 3 times for rough idle. They have checked it out and told me everything is fine. It is getting worse and now it misses at low rpm when the transmission is in 4th. Now it is out of warranty. I have changed the plugs and it didn't help. I have talked to the mechanic and all they know how to do is plug it into the computer. If the computer does not show any codes they say it is OK. Anyone else having a problem?

 

Try moving the wiring harness around the a/c accumulator tank like some others have done.

The following things, the dealer should cover it even if it's past warranty since they should have fixed the problem to begin with while under warranty.

Some trucks with a/c had a problem with condensate water dripping on the O2 sensor on the passenger side exhaust. As I recall, this caused the engine to miss, yet it didn't code. There's a TSB on it.

I think there's also a TSB on the transmission. While driving, many people have had a shudder, which some have described as a missing engine, and this has been traced to the automatic tranny and the fix is a complete drain and flush of tranny fluid.

 

So far my 4.6 has given me no problems yet and hope it stays that way hope you all get yours fixed soon.

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2000 F150 XLT Reg. cab
4.6 Triton Engine
4x2 3.55 rear end gear
sliding rear window
automatic keyless entry
white styleside short box

 

My 4.6 has a slight vibration at idle, and I've already moved all the wires away from the A/C Accumalator. I'd be curious to know if the super chip will cure this? I've not had it in to the dealer to be checked because every time I bring it in they keep it for a week! Maybe when I get back to GA if it keeps up!

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Paul... :-)
99 F-150 XLT SC Sport, 4.6L, Auto, Captain Chairs, Class III Towing Package, 3.55 LS, Sliding Rear Window, White, 4X2, CD, Soft Factory Tonneau Cover, K&N Filter, WMS Velocity Tube, Line-X Spray on Bed Liner, Gibson Side Swept Cat Back System, F150online Decal...
More to come

 

HELP. I am having the rough idle. I have read the threads. I have looked under my hood. I am feeling stupid and blind. Mechanics is not foriegn to me and still for some reason am not picturing the wires their location and stuff. would someone who has fixed this problem email me a "word picture?" I know this is the remedial way but PLEASE?

wesanders@earthlink.net


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rev.
99 reg. cab, flareside,
true dual exhaust. I call
it candy apple red w/ metal
flake. (medium turodour?)

 

I suffered from a wee bit of rough idle in my 4.6 auto, but it wasn't enough to cause me any grief. I really just ignored the problem, till I calibrated the TPS (throttle position sensor) to .999 volts(at idle). That's when I noticed the idle settled down much smoother. It seemed to "hunt" a little up, then a little down. There was a thread for TPS tuning quite a while back that enabled me to plug my voltmeter right into the correct coloured wires and adjust the sensor.

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'97 S/C XLS black/silver 157" WB, 4.6/auto, 3:08, home made custom tube grille, terminator muffler, phantom sweep wiper switch(factory installed), a few billet aluminum goodies (the list grows), airbox mods, TPS tuned
email: bazils@hotmail.com

 

My 4.6 does this sometimes too, but only rarely and I have noticed it is usually when in gear with my foot on the brake. It will idle rough for only about a second and then be back to normal. Hasn't been too much of a problem for me so far.


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Chris Thomas
1998 F-150XLT Flareside STX Sport Package, 4.6L Auto 3.55 Oxford White/Gray interior, Factory Anti-theft system
Picture: http://216.147.104.171/Y2K/members/ChrisT/christ1a.jpg
Homepage: Chris & Brandi's Universe
Mods: A.R.E. Decklid/Oxford White with gray fabric liner, K&N filter with Airbox Mod (removed silencer), Tinted Windows, GTS sloted taillight covers (painted Oxford white to match), Removed STX stickers
Audio: Kenwood Truck speakers with 10" woofers, Rockford Fosgate and Alpine Amps, Ford 10 disk CD changer
Future Mods: 3/4 Lowering Kit (Maybe 4/6 if I don't have to change tires at the same time), 20" rims and tires, True duals with Supertrap tunable mufflers, Superchip, Supercharger, Jacobs Ignition, NOS, and whatever else I can think of!!!

 

Brazil1,

Can you posts those instructions here?

Thanks!!!!

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Paul...
99 F-150 XLT SC Sport, 4.6L, Auto, Captain Chairs, Class III Towing Package, 3.55 LS, Sliding Rear Window, White, 4X2, CD, Soft Factory Tonneau Cover, K&N Filter, WMS Velocity Tube, Line-X Spray on Bed Liner, Gibson Side Swept Cat Back System, F150online Decal...
More to come!

ptarnuzzer@megsinet.net

 

PaulT,
Noticed you didn't get a reply yet.
I think he was refering to the following:

First remove the plastic cover over the throttle body. ( 3 10mm bolts) Remove the two hoses that go to the throttle body. As you face the front of the motor, the TPS sensor is located on the right hand side of the throttle body and is attached by two phillips head screws. Now with the ignition in the on position, but motor no running, use a digital multi-meter to check the voltage going to the sensor. I use a Craftsman #82029. its about $20. Set it register VDC. The negative of the multi-meter connects to any good ground, and the positive probes the middle wire on the TPS. Read the meter and adjust your voltage. Your target range should be in the .995-.999 area. DO NOT go above .999 or you may encounter idle problems. You adjust the voltage by loosening the screws on the sensor just enough to get some play and while watching the screen on your multi-meter. If you cant get it to go above say .956 like mine, you might have to remove the TPS sensor and enlarge the mounting holes slightly to get a little more play. Don't enlarge to much it only takes a little to get some more adjustment. Once you get the setting you want, tighten it down, and while watching the screen on your multi-meter, move the throttle to wide open once or twice to make sure your setting is correct. Re-assemble everything, and star the engine. I know that on the older mustangs, 95 and down it would pick the cars up about a tenth in the quater mile, all for free. It seems like alot of work I know, but every little bit counts.



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'99 Black F-150 Sport
Extended Cab
4.6 Romeo Triton
3.55 Rear-end, Black low- profile bug deflector.

Wife's wheels: '91 Green Ranger XLT 3.0L
http://hometown.aol.com\riadan1