A few diagnostic questions.
 

I'm the proud new owner of a 97 ext cab XLT. 5 speed, 3.0. 136K

It starts and idles fine, although warm starts sometimes take a second crank.

Under load it is dog slowand develops a substantial vibration across the rpm spectrum.

i suspect i'm running on 5 cylinders.

haven't torn into anything yet. first thing i plan to do is pull the plugs and see what they look like.

from what i've read here so far, plugs/wires/coils packs seem to be a common problem.

talking to the previous owner, i don't recall him mentioning anything about ignition parts ever being replaced. the plug wires are not original (carquest). hard to say how old they are. plan on replacing them with motorcraft/autolite. will probably do the same w/plugs.

if i do have a spark issue, what is the best way to diagnose it? is it OK to lift a wire off the coil pack with it running, for a short time to check for rpm changes? or should i shut off the engine, pull the plug, ground it, then start it?

i suppose an inductive timing light would be handy. too bad i tossed mine years ago thinking they were obsolete. :(

as for injectors, i know that running cleaner may/may not help. can they be removed and cleaned? is it worth it? can i run it with an injector pulled to see how it fires or is that a good way to get blowed up?

would it be money well spent to just take it to my local mechanic, who i trust and have him run diagnostics on it? will he, with all his computerized gizmos be able to diagnose things I can't?

Re: A few diagnostic questions.
 

pulled the plugs. they all look pretty normal, color wise. a few of them did have some sort of crud built up between the electrode gap.

cleaned them, reinstalled. not really noticing any difference other than the amount of roughness in the engine seems to vary a bit, but, that could be my imagination.

i did refill the tank. 9.2 gallons over 201 miles which works out to a smidge under 22 mpg. this was mixed highway/back road driving. Probably 75% highway.

Seems to me that the mileage would be worse if it was really running on 5 cylinders.

Re: A few diagnostic questions.
 

having flex fuel issues can anyone help.what other yrs have this prob

Re: A few diagnostic questions.
 

seems to be running a bit better after topping the tank off today.

i called the previous owner to ask about when plugs/wires were done. he said a few years ago. he also mentioned that it really hadn't been run much over the last year, so i am beginning to think that i just might have a tank of stale gas.

will run this tank down close to empty before refilling. also, picked up a bottle of lucas fuel treatment. supposed to clean injectors as well as the valves. i have heard good things about lucas products. the guy at NAPA said it was good stuff. guess we'll see.

Re: A few diagnostic questions.
 

You need the Seafoam...Especially if the plugs had build up on them. Run it threw the brake booster vacuum line for about 1/2 the can and dump the rest in the gas tank....then get on the highway for a few miles and let er run.