bonefishr

I had this posted on the 4.2 6 cyl board but I'm getting no views. I'm hoping someone here could get me some help. There's gotta be a gearhead out there smarter than I that can figure this out.


1998 F150 4.2. No codes, no engine light,...the engine has no power.

I've been working with some very qualified gents on f150online trying to solve the problem. Everyone has been very helpful but we're out of options and I still have the problem.

Originally the truck would diesel and stall on first start up and then start ok on the second start. After all the new parts it starts good, sounds good….until you put it in gear. It has no power and hesitates, sputters, and sometimes stalls when you hit the gas. I can barely get out of my slightly uphill driveway and it definitely can’t pull a boat out of the water. When on the highway and you floor it there is no acceleration until it kicks into a lower gear.

I replaced the MAF, plugs, wires, coil, Manifold Runner Control Valves, PVC, EGR valve, fuel pump, fuel filter, Idle Air Control Motor, throttle position sensor, and air charged temperature sensor.

I can’t find any vacuum leaks. I made a visual inspection of the vacuum system and checked all the connections and replaced a few worn lines anyway. I plugged the intake and hear no whistling.

All plug wires are correctly connected to coil and plugs….firing order is good.

Fuel pressure is 34 psi. Increases to 42psi when disconnected from fuel pressure regulator. I did pull the vacuum line off the fuel pressure regulator. I didn't see, feel, or smell any gas. I also hooked up a piece of spare vacuum line and gave it a good suck......bone dry.

I did plug the brake booster vacuum. No improvement.

No leaks between throttle body and MAF.

Compression as follows...#1-195 psi, #2 - 200psi, #3 - 190 psi, #4 - 195 psi, #5 - 205 psi, #6 - 190 psi. No need for wet test, everything is good.


I’m on an island with no access to a high end scanner.

I did take it to a local a mechanic who cut open the catalytic converter and tore the guts out of it, he said something about a sensor and it appeared to be running hot, could be clogged. The converters where clean, no improvement. He removed and cleaned the injectors, said they were already clean. He cleaned the intake manifold. He’s stumped and says the timing chain may have jumped a link.

Any suggestions.....?

willy j

Has anyone suggested that the 02 sensors might be bad.thats the only thing you haven't mentioned

2thousand5.4

Hmmm this is very interesting. Sounds almost like a ECM/programing probablem. Is there any dealership that can reflash the computer? Other than that the only other thing I can think off is an extremely clogged exhaust or intake, but it sounds like you have gone through the intake and it's all good. And if you are getting those compression numbers I doubt the timing chain has jumped but I have been wrong before

bonefishr

I did buy an O2 sensor when all these problems started. I got sidetracked with all the other variables and never put it in. Turns out, it has four. With no codes I'm just throwing cr*p against a wall hoping something sticks. Jeez...what's next?....throttle body, brain,...is the tranny fried....something with the torque converter that's bogging the motor. I don't know.

willy j

I feel your pain bro. Process of elimination can be expensive

2thousand5.4

My money is on the brain sounds like there is something wrong in there.

kmpconley

I would have to agree with the previous 2 answers. My thought was exhaust. But u have a lot of factors here. How is the fuel? Did you get bad gas? Has anyone possibly tampered with you gas? I would drain the tank, fill with fresh, change the fuel filter and put a couple bottles of (heet) in. The Schrader valve where u check your fuel pressure I would trip it after putting a pressured load on the system and try and get whatever could be up top of the lines to squirt out. Check your catalytic converter/muffler and make sure it's not clogged, the O2 sensors on the 4.2 usually trip a light if they're not working properly, but it is still nothing more than a machine and could potentially fail. So I'd still check those. You also could try putting it in Neutral and see how the motor reacts. If the motor responds properly in Neutral, but not in Gear, it could be transmission related. I'm not in front of your truck so it's hard for me to diagnose, but I'm just rattling off random possibilities from the symptoms you gave. But if it's not any of those that I just mentioned, I'd venture to say it's ECM related. But with all that being said, just like anything else, try your "cheap" fixes first.

bonefishr

I had this truck shipped in. I'm on an out island in the Bahamas running a fishing lodge. I use it to pull boats and run the guests back and forth to/from the dock. Point is....I have limited resources. I have to figure it out myself. If I where in the states I'd have dropped it off at a dealer after the $1000 I blew trying to fix it.


The compression numbers were surprising to me. Those numbers were with all the plugs removed the throttle fully open. I did check one with all the plugs in except that particular cylinder and the motor running. PSI was 150 on that cylinder with the motor running. The odd thing was the motor sounded as good as if it were running on all six.


I don't think it's a timing chain issue either.


One would think it's a vacuum leak somewhere. If there is one I can't find it.

kmpconley

Where did you have this truck shipped in from? What state did it originate? It was more thank likely built in Lexington, KY or Kansas City, MO, but depending on where those trucks get shipped to in the states, they are tuned specifically for their destination before they leave the factory. You are in a different climate, more humidity, different pressure, all of the plays into effect. The newer trucks tend to have computers that self adjust for this, however your truck may not. After u saying that, I would think it could be an ECM issue due to the climate change the computer could be having trouble adjusting, not making proper air/fuel mixture or another emissions problem. A late model F-150 from Florida would not operate very well like say if it traveled to Alaska. It would possibly need tuning or a computer flash.

bonefishr

I do get a complementary quart of water with every 300 gallons of fuel I buy. It's always sitting at the bottom of the tank. I did put in a new fuel pump and filter. It didn't run any better.


What's an O2 sensor do? Will the computer know if I just unplugged the stupid things?


I'll try bleeding some of the fuel off at the Shrader valve.


A mechanic here on the island did cut and gut one of the four converters. He didn't do the rest because he said the first one was fine.


The motor runs good in neutral. In gear, stopping and starting it runs the worst. Maybe it's because the motor has no power, maybe because the tranny isn't slipping enough.


I'm out of cheap fixes. I'm thinking maybe I'll try replacing the brain next.