Mechanics

LOW POWER AFTER INTAKE R&R

2007 Chevrolet Impala • 159,000 miles

First off I'm sorry for asking a bunch of questions on this car I just want it fixed so I can get rid of it.

Before the intake it was running funny, hesitating on take off and hesitating on accel, I tore it down after it started leaking coolant from the crossover.

After I replaced the intake and plugs/wires the car started funny and was noisy on startup, the valve train started making more noise then before and my power loss/ hesitation became worse

Basically my question is.
Could this be an out of place Pushrod?
Could I even drive 5k if I did misplaced a Pushrod?
Lifter issue?
Or a clogged cat?

I ask this bc all I have tested so far came out good except manifold vacuum
Compression 200 -/+ 5 all 6
Fuel pressure 58 to about 60 on accel
Spark strong
Fuel Injectors all working
Air filter new
Maf/map good
Coolant/iat good
Throttle clean
Plugs(ac delco.040)

Only thing standing out is vacuum fluctuates 2-4 at idle but OS pretty steady at 19

Any ones knowledge on this homogulation of the 3.4 please help me out, I'm stuck between a rock and a hard place I would tare into it again but I want to be 110% sure of what I need to fix

Thanks again
Avatar
Pos07impala
March 7, 2012.



Lifters stick after this repair and I always recommend replacing them with this repair. It most likely is part of your issue.

As far as the push rods, no, you are good. If you messed them up, you would have bent a valve and had many other issues and no compression.

The vacuum fluctuation concerns me. You may have a valve not seating or burned.

I would start with the lifters.

Roy

Couldnt that fluctuation be from the lifters sticking? And I take it if a valve got burned it was most likely due to the lifters sticking?

And can you explain a good prep for installing the lifters?

Tiny
Pos07impala
Mar 7, 2012.
Yes, the lifters could cause it.

Soak them in oil before installing.

Roy

And I know this is a bit of a joke but will any sort of additive help? A tech from justanswer recommend try marvel mystery oil on a oil change

Tiny
Pos07impala
Mar 7, 2012.
I dont believe in oil additives. Todays oils have all the additives we need.

Roy

Ok and should I rotate the engine with the plugs out a couple times before I start it? Just to make sure the lifters are all pumped up a little? I've never touched lifters so I have no clue, and is it a sure bet on a high mileage cam?

Tiny
Pos07impala
Mar 7, 2012.
Oh and if I burnt a valve wouldn't it miss/backfire? The exhaust note is irregular but to an untrained ear it isn't a very pronounced difference, I would expect a burned valve or one that isn't seating to be far more noticable. Am I correct on this?

Tiny
Pos07impala
Mar 7, 2012.
Forget the burned valve. It would have come up on the compression test.
When you install them, just be double sure the push rods are in the correct position. No need to do anything else. It will start up, clack for a second and the noise will go away.

Roy

Alright do I just let it idle or rev it up on start up? The rev up I think is just for new cams right?

Tiny
Pos07impala
Mar 7, 2012.
Just let it run till it stabilizes.
Yes, 1800 rpm is for new cams for break in, not your case here.

Roy

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