5.7 Vortec Loss of Power Up Hill Final Straw

My Chevy Tahoe with a 5.7 Vortec looses power when going up hill and I get the usual Engine Miss Fire Code. Dealer completed a $100 diagnostic and recommends a $2000 valve job. I replaced plugs, fuel filter, plug wires, dist cap, and air filter. No change in performance and the check engine light still comes on going up hill. I took the advice of a poster who suggested cleaning off the mass air flow detecter with carb cleaner since I have a K & N filter. This improved performance, thanx for this info, but did not fix the problem. From all the posts regarding this problem, Tahoes, Burbs, Silverados,... etc, it seems to me that GM made a bad design. Everyone is being told that the valve guides need to be bored out. Not a simple job. Not a cheap job. Every dealer wants to charge upwards of $1500, and some people are getting GM to pay half. This is unacceptable. GM is responsible for selling a bad desing that needs fixing after normal use. I suggest contacting consumer reports and the Better Business Bureau to force GM to change the design to prevent this, and to fix the bad product they have already sold. Had I known about this design flaw, I would not have invested in this engine.

I believe brand new vortec heads are $500 each at the dealer, wouldn't hurt to check. I'd compare that to a valve job, I believe the new heads are complete with valves/guides/springs/keepers/locks/etc. and ready to go.

Most of that $2k is labor, it's definitely an all day job to swap heads and I've done it a few times.

to find if your valves are bad have compresion check performed if compresion is low have oil squirted into cylinder ifcompresion goes up its rings if it doesnt its valves if the compresion isntlow then you can rule out cylinder problems

sounds more like your poppets are sticking. Check fuel pressure should be 53-65 psi. Is it random misfire or specific cylinders. Had the same prob with mine. dealer gave me the same line and I converted mine to multiport for around 500.00$ and gained mpg and power.

My Chevy Tahoe with a 5.7 Vortec looses power when going up hill and I get the usual Engine Miss Fire Code. Dealer completed a $100 diagnostic and recommends a $2000 valve job. I replaced plugs, fuel filter, plug wires, dist cap, and air filter. No change in performance and the check engine light still comes on going up hill. I took the advice of a poster who suggested cleaning off the mass air flow detecter with carb cleaner since I have a K & N filter. This improved performance, thanx for this info, but did not fix the problem. From all the posts regarding this problem, Tahoes, Burbs, Silverados,... etc, it seems to me that GM made a bad design. Everyone is being told that the valve guides need to be bored out. Not a simple job. Not a cheap job. Every dealer wants to charge upwards of $1500, and some people are getting GM to pay half. This is unacceptable. GM is responsible for selling a bad desing that needs fixing after normal use. I suggest contacting consumer reports and the Better Business Bureau to force GM to change the design to prevent this, and to fix the bad product they have already sold. Had I known about this design flaw, I would not have invested in this engine.
Please don't tell us what model year the truck is, whether the engine has been replaced or had prior work done, or what the mileage on the truck is. It's so much more fun for us to take wild guesses.



Everything wears out eventually. I know of some problems with the Vortec heads, but wiping the guides prematurely isn't one of them. Sure, it can happen. Not a common problem though.

to find if your valves are bad have compresion check performed if compresion is low have oil squirted into cylinder ifcompresion goes up its rings if it doesnt its valves if the compresion isntlow then you can rule out cylinder problems
A leakdown test--properly performed--would be MUCH better than a plain ol' compression test. Doing both would be best.
sounds more like your poppets are sticking. Check fuel pressure should be 53-65 psi. Is it random misfire or specific cylinders. Had the same prob with mine. dealer gave me the same line and I converted mine to multiport for around 500.00$ and gained mpg and power.
The fuel injection system is much more trouble-prone than the valve guides. Injection issues seem more likely to me.



What's clear here is that a PROPER diagnosis has yet to be done--or--the original poster hasn't shared the complete results of that diagnosis.

I'm quite sure DUTCH has this problem corrected.

this post is 8 years old ///// LOL....

The issue is some times not the valves. If you are having the problems i would check in to the spider injectors and the upper and lower intake