Truck: 2002 F-150 XL Regular Cab
Engine: 4.2 liter V-6
Transmission: 4R100 Automatic
Mileage: 174,000+

This truck just made a 3000-mile trip from NY to California pulling a 3700 lb travel trailer. Mileage while not towing is 18+ mpg; while towing it is 10.3 mpg.

Yesterday, I changed spark plugs (Autolite AP5144) and noticed a pronounced cut-out/ stumble on hard acceleration from a stop. One thing to note: when I removed the two rear driver-side plugs, they were loose in their holes. I get normal acceleration if I step on the pedal gradually, though. Parked idle was normal. When parked & I make a sudden jab to the accelerator, a small "pahh" sound was heard for a split second before the engine revs normally.

Today, I noticed a rough idle that seemed to be intermitent, and it gradually got worse. After reviewing this forum, I removed the IAC and throttle body; I thoroughly cleaned both IAC and entire throttle body & plate with choke cleaner, as well as the PCV valve since I had it out of it's bore. I put everything back together.

Upon starting, I now have a pronounced "surging" idle. When operating in reverse, allowing idle to move truck, there is a pronounced surge. When I run the engine up to maximum rpm, there is a high speed surge -- but that may be just the PCM limiting rpm -- so I am not sure that is actually a symptom.

Since I do not have access to a code scanner of any type (located in California -- you can't borrow one or have a parts store run a code scan -- stupid state law), I have performed some rudimentary diagnostic steps listed below:

1. While idling, un-plugging & re-plugging the IAC improves the idle for a few minutes, then surging resumes & gradually gets worse.
2. While idling, un-plugging the TPS results in an approximately 800 rpm smooth high idle; re-plugging the TPS results in a good 600 rpm idle for up to 10 minutes -- then surging resumes.
3. Anecdotal Symptoms: When surging becomes really pronounced, a "chugging" sound can be heard from the MAF/ IAT/ air cleaner housing. When light surging begins, the heat shield on the passenger side catalytic begins to rattle; this rattle ceases when smooth idle is restored.

This truck ran like a raped ape from NY to California, and has run fine here until I changed plugs -- and made sure all plugs were tight. The loose plugs (with the intermittent ground that implies) make me wonder if the coil pack is now going out -- but idle is the only running condition that I am having a problem with. A coil pack would manifest itself during loaded operation before it would effect idle -- wouldn't it?

I am leaning toward a bad TPS as a cause -- with maybe a secondary cause being the IAC. But to be honest, I am a Navistar diesel mechanic -- so I am sort of out of my element when working on newer gas engines.

Can anyone either confirm my diagnostics, or maybe point me in a more likely direction? I would appreciate any help -- I am at a loss here!

Thanks in advance!

 

wow a diesel mechanic... well first thing you need to do is to throw out the autolite plugs and get a set of motorcraft plugs... no B.S. as for getting codes read, AAmco transmissions will diag for free... stupid state is givin away all the money we normally get for diag. second as for a surge one is the plugs, second is to check the pvc system for a vacume leak or a possable stuck open egr valve. you didnt say if you are running a cold air system on the intake... like a k&n filter, possable something on the hotwire side of the maf sensor use some maf cleaner made by "CRC" a good parts will carry it, oh and dont forget to get rid of the autolites... i converted to diesel when the gasser side went to being overpopulated with wanna bes. so now i spend my days fixing FORD err i mean IHC powerstrokes, it's like haveing a licence to make money.
P.S. i too drive a f-150 with a 4.2 M/T, and did i mention get rid of the autolites!!!
Good luck

 

Thanks, Dr. Rik...

I forgot to mention one thing, though... when I changed plugs, the guy at Kragen suckered me into buying the Motorcraft SP504 "Finewire" plugs. After I put them in, gapped at .054 per spec, was when the cut-out/ hesitation began. So, after finding out that these were not the right plugs -- and completely wrong tip design -- I pulled them & put the old Autolite plugs back in their original holes.

That makes me think, though... when I pulled the Autolite plugs, they were gapped at .045. When I put them back in, I re-gapped them to .054 which is the spec listed on the sticker under the hood. I wonder what will happen if I pull them & set them back to .045?

I think I will do that in the morning & see if it works. If it does, then I may have a weak coilpack if it turns out I don't have enough juice for the spark to jump the extra .009 -- which could have been caused by those two loose plugs.

 

Doesn't Autolite supply Motorcraft plugs or is that just a rumor?

 

Different "quality levels" -- but yes, Autolite is the actual manufacturer of Motorcraft plugs.

 

Update...

Problem fixed.

I managed to get the codes from the PCM:
P0102 = Mass or Volume Air Flow Circuit Low Input
P0443 = Evaporative Emission Control System Purge Control Valve Circuit
P1131 = Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P1151 = Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2
P1504 = Intake Air Control circuit malfunction

The P0102 code caused the other 3 codes -- simple deduction. Mass air flow sensor broken/ dirty causes a lean condition in both banks (P1131 & P1151), and the resulting lack of combustion volume causes a lower vacuum reading -- which causes the P0443 code by keeping the evap circuit from operating at spec. On the way back from the shop, I stopped at Kragen & picked up a can of CRC Mass Air Flow Sensor Cleaner -- gave the MAF sensor a good bath when I got it apart. Problem with stumble & hesitation cured -- above idle, it runs like a raped ape now.

The P1504 code is, of course, a bad IAC -- so that is getting replaced tomorrow.

Thanks for all the input & good advice!

 

But did u get rid of the autolites?

 

Nope... still got them! I happen to have good luck with Autolites.

Most people don't understand... you cannot get OEM quality parts from an auto parts store, or even a dealer. Parts made for OEM installation at the factory are made to the highest level of quality -- after all, if one fails the manufacturer has to pay for it, as well as pay a dealer the labor to fix it. These parts are not available to the general public -- if you have a buddy who happens to work at the plant & can sneak you out one, that is the only way you are gonna get one.

As far as Autolite, they market two quality levels -- the higher one is marketed under the Motorcraft name, while the lower one is marketed under the Autolite name. But there isn't that big a spread in the levels -- and I have found there to be virtually none in their plugs. But the Autolite plugs are $2.00 cheaper each than the Motorcraft -- and the actual AGSF-34EE plugs that the 2002 4.2 V6 requires are getting harder to come by. In fact, the only place I have been able to find them is on Ebay -- for $10 each.

So, since they cross over to the Autolite AP5144 plugs -- which are cheap, give me the same level of performance and longevity -- I guess I will stick with them.

 

No reason to get rid of the Autolites as they are good plugs. Provided they are the right plug for the application. As good as the EXACT same motorcraft counter parts . Made in the very same plant as the motorcaft ones . Does any one really think that they would waste all that engineering and design to compete against themselves . The plugs are the same up until they print the name and part # on them.

 

No way you have a 4.2 V6 and the 4r100 in the same truck. no way.

 

Yea, I would have to say you have the 4R70W trans in there...check your door jamb, and it will prob say "U" under Trans code
Rich

 

Right... my mistake. It is a 4r70W (uses Mercon V, according to the manual).

In any case, had an interesting failure today... that MAF sensor that I so painstakingly cleaned went out. Before I returned the old one for core, I took it apart -- both heater wires were broken.

And, to top it all off, when I started it up with the new MAF I promptly got a P1400 code! I guess the trip from NY to CA was too much for the old girl, after all! I'll get a new DPFE next Wednesday, and I should be ok for a while... hopefully, a LONNNNNNNNNNNNNNNNNNNNNNNNNNNNGGGGGG while!!

 

i really dont believe the autolite are same quality as the motorcraft... for us that have had the "misss" with the autolites, you will have a hard time convincing us to put in ANYTHING but Motorcraft. I cant say they are the same as the OEM factory plugs, but i have NEVER heard of an aftermarket motorcraft plug going bad.. so i vote them to be the best plug for the 5.4

 

I would be willing to bet that all those people that have had trouble with ( any other ) than motorcraft plugs then switched to motorcraft have also changed boots or plug wires during the second go round. This second go around, not wanting to have to do this again, add the parts they should have done the first time. The changing of these boots and or plug wires and use of dielectric grease most likely solved the problem not the motorcraft plug .

These modular motors don't know what brand of plugs are going in them . They are just a combustion chamber . Chrysler uses a very very similar chamber and plug location . Their engines don't know to use motorcraft plugs and they run just fine .

I don't use motorcraft plugs in any thing and have NEVER had a plug problem with any thing I have worked on