Please help!! I have a missfire or surge at highway speeds. When I am cruising at 100 km/hr and hit a hill or slight incline i get a surge or miss, buck(do not know for sure but a power loss) as i depress throttle slowly. If i push the throttle to the floor she takes off like a raped ape. Well as good as 4.2ltr can imate a raped ape.

I have twice now in the past had CEL come on. Both times showing code P0174 (system lean bank 2). I have checked all my vacuum lines and found nothing wrong. I have cleared those codes and they have not come back. But the above noted problem still exsists.

Then last week in a snow storm I had a real bad missfire as i accelerated from a stop. This has never happened before and the CEL came on immediately. These codes where P0301 and P1120. I though it may have just been due to storm so I cleared the codes and they have not returned. But the miss is still there at highway cruise.

I did check the coil pack and all seems fine. Could i have an intermittant coil pack but only at a certain throttle setting for highway cruise? Any ideas would be appreciated.

Oh one more thing. When cold it seems to crank longer when cold out -10C or colder but does start then stumble and quit almost lik its flooding itself. Try again and it may start or repeat the stumble and quit again. Third time is always a charm it starts seems to clear itself and runs great.

 

How old are those spark plugs? What brand are they?

 

Maybe a year and they are ngk. But to be honest this problem has been around since before changing the plugs. it has only been the last few months that i got a CEL. Before the light came on I was just living with the problem hoping that something would give a definite sign to a problem. I have changed plugs fuel filter and cleaned MAF sensor.

 

Plug wires?

 

I have been thinking of changing the plug wires. But if they were breaking down would they not continue to break down when engine load gets greater. As i stated earlier miss fire or stumbling is only felt when you slightly increase throttle from cruise position. If pedal is pushed to flow truck shifts and takes off with no problems noticed.

 

That sounds like the same type of low grade misfire that plagues the V-8's that have cops instead of a coil pack and wires - when the plugs and/or cops get a bit weak.

If this were my truck, I'd replace the plugs, wires, and coil pack with MOTORCRAFT parts - in that order. In other words, get those NGK's out of there.

 

I will start with the plugs then. Please keep in touch and thanks very much.