4v issues

[cobra3338]

my 4.6 4v is running bad the motor idles great and revs good until 5000rpm from there until 6800rpm redline there a serious drop off in power and it will misfire on cylinder 8? theres also a ticking noise from around 1500 to 3000rpm. someone said it could be a cracked valve? compresion test was
1 205
2 195
3 190
4 195
5 180
6 185
7 180
8 185
spark plugs were clean and good shape to

 

[trinity_gt]

Long shot but: You might want to pull the valve cover on the driver's side and have a look at the rocker arms/finger followers for #8. I've heard of 4Vs tossing followers. This results in a valve not opening which can be pretty restricting at higher RPM/power demands.

 

[cobra3338]

you mean the follower is broken off?

 

[trinity_gt]

you mean the follower is broken off?

Not broken, just out of place. Basically, the follower is kept in place only by the valve spring pressure and the pivot on the lash adjuster. It's not unheard of to see the follower, under certain circumstances, literally fall out and end up just lying on the cylinder head, leaving that valve inoperative. Usually you can just pop it back in.

Like I said, it's a long shot. You may also want to check the fuel pressure to make power drop-off isn't caused by fuel starvation.

 

[wmburns]

Might be handy to know the model year. If the IMRC's weren't opening, that would certainly cause a drop in power.

 

[cobra3338]

03 mach 1

 

[cobra3338]

Long shot but: You might want to pull the valve cover on the driver's side and have a look at the rocker arms/finger followers for #8. I've heard of 4Vs tossing followers. This results in a valve not opening which can be pretty restricting at higher RPM/power demands.

nope, everything looks great in the valvetrain tops of pistons are good to. tomorow im gonna check fuel pressure running out of ideas.

 

[cobra3338]

fuel pressures good to..i cant figure it out?

 

[trinity_gt]

nope, everything looks great in the valvetrain tops of pistons are good to. tomorow im gonna check fuel pressure running out of ideas.

1) Which valve cover did you pull?

2) How did you look at the tops of the pistons?

 

[cobra3338]

mainly looked at driver side but pulled both sides just to check everything and a fiber optic camera put it down the sparkplug holes