I did the plugs and coil pack boots today in a friends 2005 F150 with the 4.6L V8. The truck had 128k miles on it. As he had installed a aftermarket remote start, I decided to disconnect the battery before I serviced it.
These are the plugs I removed:
5 of them were about .075 gap and the other three were around .090. They are all wet with oil because I had backed them off about half a turn, squirted half a teaspoon of ATF in each hole, and waited about 2 hours before actually removing them. Except for the dry one. That one was already about a turn loose and came out clean on its own. The coil boot on that cylinder was cooked black from the hot combustion gasses escaping around it. My guess is, he would have popped that plug eventually.
After I got all the plugs and boots replaced, I hooked everything back up and started it up.
It ran terrible. It couldn't hold an idle and would oscillate from about 300-500rpm.
I thought, oh, Ill just give it 15 minutes and it'll learn. I went inside and left it idle for 30 minutes. It was no better. I decided I would drive back to his house, and get my OBDLink MX out of my car.
I actually ended up going back there 3 times because I kept forgetting the keys to my car. While I was driving I discovered that it would stall at every stop. And it also stalled often when making turns; not a fun one to loose power steering halfway though a turn. Around this time it started stalling out as soon as I let off the key. So I would have to hold the throttle a bit to keep it running, at least initially.
I ended up calling on my forklift experiance and two-footing it through turns and down to stops, keeping the throttle held a little as my left foot did the braking. I can brake with my left foot as smooth and precise as with my right. So I was able to drive it with only a few incidents of stalling from there on.
After getting my OBDLink out of my car, I discovered it couldn't really tell me anything about what was going on that I didnt already guess.
I had pretty much come to the conclusion that the DBW throttle body was so far out of wack it couldn't learn how to idle with it except in the long-term learning that occurs over 10s of thousands of miles as the throttle body wears out and the PCM adjusts along with it. Since I had disconnected the battery, the PCM had lost all its learning and my fear was the only was to fix it in a reasonable amount of time would be to replace the TB.
In a last ditch effort with a probable dead TB, I pulled it off, and cleaned it out with brake cleaner and a rag. Cleaning all the black gunk off the back and around the sides of the throttle plate.
I also cleaned the MAF, in an effort to eliminate that as a possible problem as well.
I started it up, my foot far away from the gas; it was all on its own as it fired up quick and went straight to 600rpm idle and purred.
I let it idle for a few minutes as I got my laptop setup to datalog and kicked on the A/C. It had no trouble compensating and raising the idle to 650rpm while the compressor was engaged.
I proceeded to drive it around through all kinds of turns and stops and even a intentional panic stop from 55 on a back road. It handled it, no problem; a review of my logs shows that it just went down to 550 rpm and held, with no underrun of its desired idle. In addition, the throttle response was much improved.
So, Since I did both a MAF clean and a TB clean, I have no idea which did the most good. I should have done them separate, but to be honest, I didnt think anything less than replacing a part would fix it, so it was sort of last ditch. It was running so bad. Do you guys think it was necessary for me to clean it, or do you think the MAF did all the fixing?
These are the plugs I removed:
5 of them were about .075 gap and the other three were around .090. They are all wet with oil because I had backed them off about half a turn, squirted half a teaspoon of ATF in each hole, and waited about 2 hours before actually removing them. Except for the dry one. That one was already about a turn loose and came out clean on its own. The coil boot on that cylinder was cooked black from the hot combustion gasses escaping around it. My guess is, he would have popped that plug eventually.
After I got all the plugs and boots replaced, I hooked everything back up and started it up.
It ran terrible. It couldn't hold an idle and would oscillate from about 300-500rpm.
I thought, oh, Ill just give it 15 minutes and it'll learn. I went inside and left it idle for 30 minutes. It was no better. I decided I would drive back to his house, and get my OBDLink MX out of my car.
I actually ended up going back there 3 times because I kept forgetting the keys to my car. While I was driving I discovered that it would stall at every stop. And it also stalled often when making turns; not a fun one to loose power steering halfway though a turn. Around this time it started stalling out as soon as I let off the key. So I would have to hold the throttle a bit to keep it running, at least initially.
I ended up calling on my forklift experiance and two-footing it through turns and down to stops, keeping the throttle held a little as my left foot did the braking. I can brake with my left foot as smooth and precise as with my right. So I was able to drive it with only a few incidents of stalling from there on.
After getting my OBDLink out of my car, I discovered it couldn't really tell me anything about what was going on that I didnt already guess.
I had pretty much come to the conclusion that the DBW throttle body was so far out of wack it couldn't learn how to idle with it except in the long-term learning that occurs over 10s of thousands of miles as the throttle body wears out and the PCM adjusts along with it. Since I had disconnected the battery, the PCM had lost all its learning and my fear was the only was to fix it in a reasonable amount of time would be to replace the TB.
In a last ditch effort with a probable dead TB, I pulled it off, and cleaned it out with brake cleaner and a rag. Cleaning all the black gunk off the back and around the sides of the throttle plate.
I also cleaned the MAF, in an effort to eliminate that as a possible problem as well.
I started it up, my foot far away from the gas; it was all on its own as it fired up quick and went straight to 600rpm idle and purred.
I let it idle for a few minutes as I got my laptop setup to datalog and kicked on the A/C. It had no trouble compensating and raising the idle to 650rpm while the compressor was engaged.
I proceeded to drive it around through all kinds of turns and stops and even a intentional panic stop from 55 on a back road. It handled it, no problem; a review of my logs shows that it just went down to 550 rpm and held, with no underrun of its desired idle. In addition, the throttle response was much improved.
So, Since I did both a MAF clean and a TB clean, I have no idea which did the most good. I should have done them separate, but to be honest, I didnt think anything less than replacing a part would fix it, so it was sort of last ditch. It was running so bad. Do you guys think it was necessary for me to clean it, or do you think the MAF did all the fixing?
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