I will condense this as much as possible

98 F150 4.6L Triton Auto 4x4 cyl 4 not firing - checked spark and it is good - swapped injectors - still no fire - had tuned up 6 months ago - ran good then - when we just pulled plug on cyl 4, was not even hand tight and wire end was melted some what - tried new wire with no luck - took plug out and there was "no end on plug"(bent piece where spark comes from), burned or broken off. Did compression check (very hard to get to and could not get guage to screw in so used the rubber push in guage - only 50lbs of preasure. Truck not back firing, just not firing so I am thinking the plug end broke off and got pushed up into the Ex. valve opening and is causing it not to close?? Was thinking of putting oil in plug hole and retesting to see if compression will build. Wondering if possibly washed walls down when plug was bad and injector was dumping gas in cyl.?

Is there a possibility that it will build preasure and go good again if rings are just washed and not bad? If I unplug the injector so not putting gas in cyl can I drive on 7 cyls? What damage will this cause if any? Could driving it on 7 cyl possibly free that plug end and get cyl to come back?

This was a used truck, and we have dumped well over $1500 into it trying to get the dash light to go off (for inspectioin)with out luck. Every time we fix one code, we get another??? Can't afford a new truck but also can't afford to rebuild this one????????? I need major help.

Thanks for ANY IDEAS

 

Did you try replacing the bad plug?

 

Yes, that's when we found it was not even hand tight in there after they had done the tune up.

Checked spark on new plug and was good but still not firing.

 

Anyone have any thoughts on this problem? Is there anything other than what I mentioned above that could cause the low preasure in the cyl?

 

So you are saying the plug/wire now fire, but cylinder 4 is misfiring ? I'd rent a screw in compression gauge, and check that cylinder, dry first, then with a squirt or two of oil. If the reading is still double digit, and there is no sign of a blown head gasket, either where you can see/hear it, check the cooling system for excess pressure. If it is OK, the next fairly cheap thing I would do is pull that valve cover and see if you have any broken worn out parts ( or less likely, a bum cam lobe).

Dave

 

Thanks Dave

Yes, the new plug and wire are firing fine but still get misfire on cyl. 4 error.

Can the truck be driven with the fuel injector unplugged without damaging the engine further. Need to get to town to rent the compression tester but had a death in the family yesterday and my wife is out of town for the next two days with our other truck. Kind of stuck here if mine can't be driven. ????

 

Rael

Honestly, I can't remember ever unplugging an injector, and actually driving it that way. Never have done it longer than it takes to test them. However, thinking the problem through, in reverse, how many vehicles on on the road right now with non-working injectors ?

I'd be more concerned about mechanical damage from additional road use, than I would be about unplugging the injector.

Dave

 

Yeah, that's true

Was just thinking that if the injector was continually putting gas in the cyl that was not being burned it would wash the walls and possibly burn a set of rings. With the injector unplugged, no gas would be going in the cyl and it would pick up oil from the pan as usual so seemed like a possible short term solution. I live about 12 miles from the nearest town and with
my wife having her truck out of town currently I am stuck being able to not even get things to test it with.

I called Auto Zone and they have the compression guage with the long screw in hose. The back cyl on this F150 is VERY hard to get the guage in to because of the resessed plug and the heater line directly above it. Need one that can bend out of the way and then hook up.

 

Rael

If it's going to be a long wait, I suppose you could just unplug the injector. That will trigger a couple more DTC's, which can be cleared later. Just keep an ear on the engine for mechanical issue's.

When you use the gauge, use one hand to align and steady the rubber line/end fitting, and the other to spin the gauge end. If #4 plug was loose originally, the threads may be suspect a bit.

Dave

 

Thanks, I'll do that

When we did the compression check before the threaded end of the tester I borrowed was to short to thread in and then get the guage on it. The one at Autozone is a much longer and flexable one so should be alot easier.

Thanks again