'97 5.7 missing, no codes

Chris97K1500 · March 13, 2005

It's been doing this for a while. I changed the spark plugs, plug wires, cleaned the K&N (did not over-oil it), ran some SeaFoam through it, still misses. I changed the fuel filter last summer so I wouldn't think it was the problem, but I ran out of fuel back in October and I am wondering if that could have hurt anything with the fuel delivery. If I give it alot of gas taking off, it won't do it, but in traffic coasting along around 1500rpm, it'll sputter around. Hit the gas some, it'll go away. Any ideas? Thanks, Chris

Haulin' 8.1 · March 16, 2005

I'm mechanic and I see a lot of leaking fuel pressure regulators and injectors with those vintage Vortec engines. It will cause those symptoms. If you remove the upper intake then reconnect the fuel lines to the injector block and crank the engine while eyeballing the whole mess you'll see the leaks if there are any.

Ignition problems get worse under load so don't waste any time replacing cap/rotor/coil etc.

Vernon

Chris97K1500 · March 16, 2005

I think you've hit the nail on the head! I've also been getting less and less mpg as this problem has been getting worse and worse. I'm now down to about 11mpg, when it was closer to 15mpg back in September before this really started to be noticeable. What's your opinion? Thanks, Chris

Haulin' 8.1 · March 17, 2005

I think you've hit the nail on the head! I've also been getting less and less mpg as this problem has been getting worse and worse. I'm now down to about 11mpg, when it was closer to 15mpg back in September before this really started to be noticeable. What's your opinion? Thanks, Chris

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If it were me I'd buy an intake plenum gasket set, a pressure regulator, and a couple injectors then tear it open and fix it. Depending on what you find you could take some of the parts back.

Do like I said before and you'll find the leak(s).

It's not that hard just time consuming and tedious. You should have a good manual on hand to get the step by step info, specs, and tightening orders. You should buy a couple of cans of throttle/carb cleaner because you'll need them to clean everything up inside. Lots of lines, hoses, brakets, and wires to move then reinstall. Use bailing wire or similar to hold things out of the way and have an place to keep all the parts and bolts organized. You can leave the radiator hose on and sealed but it's easyer with it drained and moved aside. The one emmissions line with a plastic clip bracket on the end is removed by pushing the bracket into the hose end then lifting the hose off, not by removing the clip looking plastic. Open wire looms to move wire harnesses aside when needed. The intake plenum (the upper plastic section) is nothing. Just use one hand to hold the injector block down as you lift the plenum off. Then use some light grease to ensure the injector block slides back up into place on reassembly. Remove the inition coil power leads before performing the open intake leak test. Keep a fire extinguisher handy, just in case. Be extremely carefull not to drop one of the two aluminum nuts that hold the fuel lines onto the injector block into an intake port when reconnecting it with the plenum off. Use rags to plug the intake ports before holding any small parts above them (voice of experience talking here). The cleaned nozzles snap out the heads by pinching the ears. The injector block will slide over and come out once all the nozzles are loosed and their lines folded together so they clear the block bracket (you can leave the injector block bracket attached to the intake). The injectors can be shoved out of the block from the top with a screwdriver etc one at a time as needed. Use light grease on o-rings to aid assembly and prevent nicks/leaks. Line up the inector wire connectors with the others when replacing. Take your time, be careful, don't drink until you're done, put everything back like it was and you should be fine. The injector block is numbered like the cylinders. Make sure you install new spark plugs on the effected cylinders as they will be foulded.

I can't be there or accept responsibility for any occurrance resulting from use of these tips. Use common sence and if you get in over your head seek professional advice before guessing ahead. It's not a china cabinent but I have to say it.

Vernon