I recently got a new old 98 Ford F150 XL and have some problems with it.

Problem: Truck turns and starts normally, but rough idle. If I press on the gas there is a second hesitation before it revs up. The engine vibrates excessively before the lag time until it smooths out. I rev the engine to about 4000 rpm and it stays relatively stable. Once I let it go then it goes into this sputtering noise and it almost seems to back fire. A couple of times it has backfired but not as much. Sometimes it won't idle when in gear, and a loss of power, it won't shift upwards to the fourth gear, and it reaches about 40 mph.

Tried: Replaced spark plugs, replaced fuel filter, replaced spark plug wires, checked for grounding of wires, checked for broken vacuum hoses. Checked for codes and it came up with P0174 lean on bank 2.

Possible: O2 sensor senses something wrong with bank 2 or broken wires, stuck EGR value. I have made a suggestion that maybe the timing chain might have jumped a notch but i'm not sure if it would cause such sputtering. I know I would have to remove the front end of the engine in order to see this, but would that be something probable or even fuel injectors.

Anyone know of another good starting place?

[I've had this issue before and I don't remember how I fixed it. It's been a long time since I had a vehicle to tinker with.]

 

A local mechanics shop suggested I use a can of Seafoam, and used a 1/3 of the can.

Drove the truck but still hesitation and sputtering, however power has increased. Noticeable change in power.

Tried checking EGR but seems to be functioning well, and no code was generated, meaning check engine light did not illuminate.

Next attempt: Inspect fuel injectors, check fuel pump pressure, and check compression.

 

Seafoam doesn't clean the injectors well, put some Techron in the gas. Remove the throttle body and thoroughly clean it.

You say you just got it - could there be some old bad gas in the tank?

 

Yes, recently got the truck, but when we first started working on the truck it had no gas. So we filled it with 5 gallons and started from there.

I will clean the throttle body, thanks for the advice.

 

So I checked the fuel pressure and found it to be about 32 psi at idle. Checked out the compression of each cylinder and found 5 of the 6 read at 130 psi, however the 5th cylinder is reading at 95 psi.

Reading "http://easyautodiagnostics.com/ford/4.2L/how-to-do-a-compression-test-1" states the compression for all the cylinders should have a margin of 15% well the 95 psi in the 5th cylinder is way off.

So an internal mechanical issue might be the cause for the misfire and sputtering.

Still haven't cleaned the intake or bought new injectors but that will be my last attempt before I take the entire engine and start from anew.

Keep you guys updated.

 

Even 130 is kinda low - I think it's time for an engine rebuild or replace.

 

For sure pull the upper and lower intake. Clean the injectors, clean as much as you can and put it back together.

If I had a mechanic tell me to sun Seafoam, I'd run away.