Hey guys,
i have an 03 navigator with the 5.4 dohc. I posted a thread last month about a misfire when at idle, and since then i had a friend hook up an ids to the truck, and he came back with cylinder 6 being 10 percent lower on compression than the others. Cylinder number 6 is definitely still contributing because when i unplug the coil it runs noticibly worse. The truck has never given me a check engine light for a misfire, but i can feel it shaking slightly at idle. I know that the truck probably needs new motor mounts, but thatll be my next project. It also has the timing chain clatter when first started up after sitting for a few hours, but it goes away after about 5 seconds. I am going to change the guides and tensioners this week.

i know its a stupid question, but can tensioners that are going bad cause surging under acceleration due to the timing changing when its not supossed to? When i have had to replace timing tensioners in the past they were either totally bad to where they wouldnt pump up at all, or they would leak and bleed off pressure, but leaky ones never presented an issue while the truck was running, itdd just make noise at startup.

The surging was really noticible today when i had to merge onto the freeway and no one would let me over. It literally felt like i was pulling a 5k lb trailer, then all of a sudden it got unhooked, and it did that a few times until i was at speed.

I am planning a complete rebuild in the next few months, but my wife is due to have our first baby any day now, so i dont have time at the moment.

I have had the truck a few months and since then, i have replaced all the plugs, cleaned the maf, replaced 4 of the coils, and fixed a few vacuum leaks. The truck has 200k on it.
when i plug in the scanner, i get no codes, pending codes, and it has even completed all the readyness monitors.

what yall think?

Thanks,
Andy