No power in 4&5

[macdaddy55]

I need help fast. My son is out of town with the MSP and he said the car is running very rough in 4th and 5th after he get up tp 50 mph. It runs and idles fine. and ever rev the engine it does fine. We have replaced the intake manifold and it has a cold air intake. No ck eng lite. please help , he is about 5 hours away

 

[CHIQLES]

What rpm is he in while being in thoughs gears?

HE COULD BE GOING TO SLOW.

 

[macdaddy55]

It's the normal shifting range. It seems to be a speed issue. in 4th and 5th. He said exceleration is normal 1st -3rd and into 4th until @50 mph then it starts to run rough and loose power

 

[HighSpeed]

Has it had a recent tune up ?. Is it throwing a CEL? If you had that info it would help in figuring out what is wrong

 

[macdaddy55]

Did plugs when I did the new intake.

 

[Wagonbacker9]

I'm just gonna throw out the usual suspects and see if you can get anything out of it:

wires
coils
vac leak
bad gas

Has it got a boost gauge on it?

 

[macdaddy55]

Yes but I haven't talked to my son this am .The puzzleing thing is that it idles and revs fine. It is just under load that it seems to have the problem. I did have a car once that the ALT was going bad and it did some of the same things.

 

[Wagonbacker9]

my experience is that problems under load are a spark issue, but that was universal for me, not just upper gears... so I'm not sure if you're having a similar issue or not. Mine also ran well when cold, and started to sputter under load as it warmed up.

 

[macdaddy55]

Just talked with my son, it sounds like a coil problem. The plugs have less than 1000mi. on them. The booast gauge is working but has stopped osolating at idle. He did say that the problem was universial during load. Hope this fixes it. thanks for everyone advice

 

[Wagonbacker9]

definitely sounds like ignition with that update, and with coils being only like $26 each... worth doing anyway.

I'd also check the gap on the plugs.

 

[Laser Blue]

+1... that was my first thought too. NGK's for example come gapped at .43 or .44, when our cars want the plugs gapped at .30 to .32. Lots of folks install plugs assuming that the pre-gap is sufficient or don't check the gap at all. That is the kind of problem that would likely show up only under load.

 

[macdaddy55]

coils, wires and plugs and she is running like new. Thanks for everyones inputs