miss during acceleration

My LS V6 has started to to miss during low rpm acceleration. Usually when it's in 5th gear. Let me start from the beginning, at first about 6 months ago I noticed it started to have an engine miss whenever it rained really hard or I took it through the car wash. It showed to have a code for cyl. 3 misfire and a p0420 code for catalyst eff. I changed the plugs and replaced the #3 COP(pass side near firewall) that took care of that problem. Well now , it is showing codes p0108 & p0403 and is kinda doing the same thing as when the miss code showed up the first time. The car runs fine whenever it has sit over night or enough to cool off, but after about 15 or 20 min of driving it starts to have that stutter . I have a Matco scan tool, that I can check data with. Any help would be greatly appriciated , as I am diesel tech and don't get to stay to current with late model gas engines. TIA

Welcome to the forum!

According to the Factory Service Manual for the 2002 model year (you don't specify year), P0108 - BARO/MAP Sensor High Voltage Detected. Likely causes for this code can be:

VREF shorted to VWPR
BARO/MAP signal shorted to VPWR
Damaged BARO/MAP sensor
Damaged PCMP0420 - Catalyst System Efficiency Below Threshold (Bank 1)
Likely causes for this code are:

Use of leaded fuel
Damaged HO2S
Malfunctioning ECT
High fuel pressure
Damaged exhaust manifold
Damaged catalytic converter
Oil contamination
Cylinder misfiring
Downstream HO2S wires improperly connected
Damaged exhaust system pipe
Damaged muffler/tailpipe assembly
Retarded spark timingI'd suggest you start by making sure the MAP sensor is correctly connected and that the air intake tubing is connected securely and correctly. Using your Matco scan tool, see if you can determine how many engine starts since either of the codes were set. Also, check for freeze frame data, specifically what the MAP voltage was when the code was set. Enable the datastream mode and record a run when the car is acting up. Monitor the MAP, misfire counts, and oxygen sensor voltages to see if something stands out as abnormal.

-Rod

The problem ended up being a wire for the egr harness rubbing inside of the harness wire loom. I guess I helped it along further whenever I removed the intake to replace the coil. However , now that the miss problem is gone, the p0420 code came back. I had checked the list of possible causes that you gave and narrowed it down to being a defective converter.I know the warranty on converters is 8 years or 80k miles, and mine is an 04 with 45k.I had to take the car to the dealer this morning for a pcv hose recall. I had the dealer to do a diagnostic check on it for which they wanted to charge $89 if it was something wrong other than the converter. I had told them about the checks that I had already made, and of course they wanted to do their own... naturally. They came back and said that it was probably the converter , but since the codes had been erased recently , they had to document the CEL and clear it themselves. Then call them when and if it came back on. I will post the results of this outcome as they happen incase anyone else is having the same problem. Thanks for your help.

Thanks for the follow-up with what you've found so far. Hopefully the P0420 stays away.

-Rod

The problem ended up being a wire for the egr harness rubbing inside of the harness wire loom. I guess I helped it along further whenever I removed the intake to replace the coil. However , now that the miss problem is gone, the p0420 code came back. I had checked the list of possible causes that you gave and narrowed it down to being a defective converter.I know the warranty on converters is 8 years or 80k miles, and mine is an 04 with 45k.I had to take the car to the dealer this morning for a pcv hose recall. I had the dealer to do a diagnostic check on it for which they wanted to charge $89 if it was something wrong other than the converter. I had told them about the checks that I had already made, and of course they wanted to do their own... naturally. They came back and said that it was probably the converter , but since the codes had been erased recently , they had to document the CEL and clear it themselves. Then call them when and if it came back on. I will post the results of this outcome as they happen incase anyone else is having the same problem. Thanks for your help. You don't have to take off the air intake manifold to replace any coils or plugs on passenger side. I've done it, ain't easy but can be done but I have thin hands so to speak, lets say just wanted to take out C coil and plug ( which is closest to firewall on passenger side) you have to remove the bolt and 2 nuts holding wire harness (that runs along the side). remove the hose that snaps in between coil A & B , remove coil A, then B, I could reach hold down screw for coil C then pull out coil (which is kinda tight) pull up and push top of coil towards firewall or what ever direction to get it out the side where the wire harness that had been lowered earlier, slip coil out the side and undo wire clip one handed. Spark Plug just use a swivel head attached to the medium extention and full ratchet head. When replacing each coil take each one apart pull off long rubber boot, twist and pull off long spring, (if replacing used coil make sure long spring is clean no water stains (lime deposits on spring) Lightly lube around the rings on rubber boot (with light oil) where it fits snuggly back in spark plug hole making sure it seats, (You HAVE to use a little oil or you probably won't be able to push coil back in , in such a tight space. Then drop spring in and push down and make it catch on inside lip of rubber boot then on C coil one handed clip on electical clip slip through side and down hole also a little oil on end of coil, push into rubber boot. So how long did it take to do it your way, and how much would a dealer charge to take off intake and do the coils? any idea on cost? Show Rod? you know?.

Hi LS DUDE I had mine done (2 rear pass side coil) by my local mech and was charged 2 hours labor plus 2 coils ($160) for somewhere south of $400. Prior to that had in dealer for cat converter(covered) 3 coils (drivers side) DCCV, and Control Head. That trip was a $3K lesson. What a piss poor short sighted design by Ford. At least they did the right thing and extended coverage to 100K. Im averaging aprox 8 months between failures of various coils. Changed plugs and hoping this extends coil life. This car is nice but High Maintenance. Good Luck With Yours A.C. ED

Forgot to add that the car was in 3 times to dealer for coils while under warnt. Rear coil(C?) has been changed 3 times in 55k miles. Ford must have some Q.C. problems with their C.O.P. vendor cause they sure are crap. I have spent about $700 on repairs for these coils. Think Ill buy another Ford again? I dont think so

There are a lot of comments about the chance for water to run off the base of the windshield and onto the rear coils, maybe the dealer isn't reading their TSB documents are following common sense. Where the wires enter the coil covers, they are sealed with RTV. If they are not reapplying RTV when doing the coil replacement, it's only a matter of time until water will get in there.

-Rod

There's a vent hole on top of each rubber boot, hope they put in coil with the hole on higher end.

Hi LS DUDE I had mine done (2 rear pass side coil) by my local mech and was charged 2 hours labor plus 2 coils ($160) for somewhere south of $400. Prior to that had in dealer for cat converter(covered) 3 coils (drivers side) DCCV, and Control Head. That trip was a $3K lesson. What a piss poor short sighted design by Ford. At least they did the right thing and extended coverage to 100K. Im averaging aprox 8 months between failures of various coils. Changed plugs and hoping this extends coil life. This car is nice but High Maintenance. Good Luck With Yours A.C. EDExtended coverage to 100K ? Does that apply to my car also? 05 LS V6 is what I have with 56K miles...

The dealer checked the codes again after the CEL came back on, and agreed that it was the converter that was the cause of the cat code. Thankfully it was under warranty. ( 8years or 80K miles for cats). As for not taking the intake off to change the coils... more power to ya, if thats how you want to go about it. It only took me an hour from start to finish , for removal of the intake , and changing the parts. Dealer book time is 1.4 hrs. for doing them all on a v6. As for water getting to the back coil, you can see this happen if you leave your hood up and pour water down your winsheild. You can attempt to combat this problem by using an ample amount of dialectic grease around the sealing flange of your new coil whenever you reinstall it. That way no moisture can get down between the boot and head.

Extended coverage to 100K ? Does that apply to my car also? 05 LS V6 is what I have with 56K miles...
It might apply to you! I, too, have an 05 LS (V8). The extension is a one time fix up to 100,000 miles. I found the dealer leter and customer letter. It says the extension is for autos from the Wixom Assembly Plant (I think). I'll have tofind it again.