4v issues

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cobra3338

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Mar 21, 2011

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Mar 26, 2011

#1

• Mar 26, 2011

• #1

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

10 Year Member

Jan 31, 2003

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Mar 26, 2011

#2

• Mar 26, 2011

• #2

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.

 

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cobra3338

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Mar 21, 2011

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Mar 27, 2011

#3

• Mar 27, 2011

• #3

you mean the follower is broken off?

 

trinity_gt

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Mar 27, 2011

#4

• Mar 27, 2011

• #4

cobra3338 said:

you mean the follower is broken off?

Click to expand...

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

SN Certified Technician

Aug 14, 2009

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Mar 27, 2011

#5

• Mar 27, 2011

• #5

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

 

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cobra3338

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Mar 21, 2011

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Mar 27, 2011

#6

• Mar 27, 2011

• #6

03 mach 1

 

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cobra3338

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Mar 21, 2011

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Mar 28, 2011

#7

• Mar 28, 2011

• #7

trinity_gt said:

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.

Click to expand...

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

 

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cobra3338

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Mar 21, 2011

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Mar 29, 2011

#8

• Mar 29, 2011

• #8

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

 

trinity_gt

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Mar 29, 2011

#9

• Mar 29, 2011

• #9

cobra3338 said:

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

Click to expand...

1) Which valve cover did you pull?

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

 

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cobra3338

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Mar 30, 2011

#10

• Mar 30, 2011

• #10

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