Slight persistent stutter in idle

[rc1626]

Hey folks,
I have a 99 Explorer 5.0 AWD with 152k on it. Last March it started with an idle stumble. Noticed it while sitting at a light. Previous to this the only thing that was done was new Champion plugs a Seafoam treatment through the PCV line and a new PCV valve. After the stumble I threw a couple of bucks at it with new coils and wires. I've cleaned my MAF, tried a new IAC and TPS with no luck. I've gotten maybe 2-3 misfire codes since this all started in March. The truck runs well otherwise. Runs strong with no known change in fuel economy. I do feel some pulses when cruising at low speeds ie.up to about 30mph. I also pulled the cam sensor cap and did not see any damage, dirt, etc.

The other night I pulled all the plugs and did notice a tiny amount of hard crusty carbon deposits on the electrodes which I cleaned and reinstalled with no change in performance. As for vacuum leaks I don't hear or see anything.

I plan on testing the compression numbers as well as vacuum numbers. I'd also like to replace the plugs again as I feel the Seafoam treatment may have been the cause for the plugs looking the way they were. I'm also thinking I might pull the plenum to get a look at all the vacuum lines and check for any issues. I have a scan tool but have limited knowledge as to what the numbers mean for o2 banks and fuel trims etc. I don't particularly want to be throwing money at the vehicle and thought I'd post here looking for some direction.

Any help would be appreciated.
Thanks.

 

[koda2000]

change your spark plugs to Motorcraft double platinums gapped to .054. these seem to be about the only plugs these engines like. also install some good quality plug wires if you have more than 70k on your old ones.

 

[rc1626]

Thanks.....I will try them. Wires were done back in March/April with stock Motorcraft wires along with new coils.

 

[rc1626]

Any other thoughts/comments would be appreciated.
Thanks.

 

[koda2000]

Any other thoughts/comments would be appreciated.
Thanks.

if you had vacuum leaks, you should have a CEL with P0171/P0174 codes. are you sure your CEL is working?

as long as you have the plugs out, it's always a good idea to do a compression test. the cylinders s/b w/in 10% of each other and don't forget to have the throttle body open during the test. if you find a low cylinder, squirt some oil in the spark plug hole. if the pressure goes up = bad rings, if it doesn't you have a valve problem.

other than the carbon deposits you saw on the Champion plugs, did they all appear to look the same?

throw some Chevron Tectron injector cleaner in the gas tank. it might help if it's fuel injector related.

 

[rc1626]

Koda, thanks so much for your input. Well I changed out my plugs today and low and behold my months long issue seems to be gone. It turns out the plugs in there were Motorcraft double platinums. Why I thought they were Champions is beyond me. Anyways I put a new set of the Motorcrafts in and so far it is purring like a kitten. My guess is either a bad plug out of the box or it one or more fouled out after the Seafoam treatment. Either way I'm a happy camper. I hope I'm not adding to this thread in the near future that the problem is back. Fingers crossed!!
Thanks again.

 

[koda2000]

Koda, thanks so much for your input. Well I changed out my plugs today and low and behold my months long issue seems to be gone. It turns out the plugs in there were Motorcraft double platinums. Why I thought they were Champions is beyond me. Anyways I put a new set of the Motorcrafts in and so far it is purring like a kitten. My guess is either a bad plug out of the box or it one or more fouled out after the Seafoam treatment. Either way I'm a happy camper. I hope I'm not adding to this thread in the near future that the problem is back. Fingers crossed!!
Thanks again.

cool beans. my fingers are crossed for you too. BTW, i'm not a believer in the Seafoam treatment. it doesn't make any sense to me, but i know there are some here that swear it does something, besides smoking up the neighborhood.

 

[swshawaii]

Ditto that koda2000. I was a believer in it for the longest time. After all, so many users claim it's benefits. My fear with Seafoam was always fouling plugs and contaminating oil in an engine that idles and runs perfectly fine. I just never saw the miracle of additives on a properly maintained vehicle with the exception of Techron F/I cleaner before changing oil.

 

[koda2000]

Ditto that koda2000. I was a believer in it for the longest time. After all, so many users claim it's benefits. My fear with Seafoam was always fouling plugs and contaminating oil in an engine that idles and runs perfectly fine. I just never saw the miracle of additives on a properly maintained vehicle with the exception of Techron F/I cleaner before changing oil.

snake oil imo, but it's been scientifically proven that Tectron works.