1997 tahoe, shuddering at highways speeds - Page 3 - Off-Road Forums & Discussion Groups
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post #21 of (permalink) Old 02-02-2004, 12:22 PM Thread Starter
 
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Re: 1997 tahoe, shuddering at highways speeds

I will do that at lunch, I added some injector cleaner ( berryman stuff) and some fuel dry, and 15 ghallons of good gas to see if it makes any difference.

thanks, ill keep you updated!
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post #22 of (permalink) Old 02-02-2004, 02:50 PM
 
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Re: 1997 tahoe, shuddering at highways speeds

ahhh, i forgot aboutt eh berrymans. good stuff there. has a ring compound as a base to it kinda like benzene. outstanding organic solvent. if you search for a post titles "so you want cleaner injectors, eh? or something like that, you'll get some info on cleanign the intake and injectors for the SBC engines.

yeah, i just found it for ya
http://bbs.off-road.com/ubbthreads/s...ue#Post1080159
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post #23 of (permalink) Old 02-02-2004, 05:46 PM Thread Starter
 
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Re: 1997 tahoe, shuddering at highways speeds

ok, went back and rescanned.

codes 0122, and 0300

so 122 is low voltage for the TPS right? I tested it yesterday its maximum reading was the same as the reference voltage reading but only 4.53 volts.

does this mean my wiring is bad or the ECM is bad?

I put a new TPS on anyway thinking that COULD be the problem, to no avail.

the old one moved pretty smoothly thru tehrange also ( 0.5-4.5 V)

so now IM lost again.

ive now put several miles on it, with the injector cleaner, and fuel dryer in the tank with 15 gallons of good 93 octane gas, and its getting worse and worse.

How do I check the spider or poppets inside the manifold?
how big of a job is it to remove the upper manifold and check, are the gaskets expensive?

argggggggggggg
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post #24 of (permalink) Old 02-02-2004, 06:42 PM
 
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Re: 1997 tahoe, shuddering at highways speeds

if its worse on better fuel,could it perhaps be the knock sensor? if its i nthe operating range of set parametes it wouldnt show up on a scan, but may effect timing enough to give you probs? just something else to consider
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post #25 of (permalink) Old 02-03-2004, 05:56 AM
 
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Re: 1997 tahoe, shuddering at highways speeds

Ok man.. Do yourself a favor and get a fuel pressure tester and tell me what your trucks fuel pressure is running at idle. Also, check it cold first thing in the morning. All of GM's modular fuel pump assemblies (of which you should have since you have the first year they used a modular assembly in these trucks) have a problem getting enough pressure to the poppet valves if your charging system is not supplying enough voltage to the pump. This is especially prominent in trucks in cold weather, as your battery doesnt put out enough voltage (in some cases) to start the truck. This would also apply to you if your pump is defective and just not supplying enough pressure to force open all 8 poppets. Poppets need 52+ pounds of constant operating pressure to STAY open. If it drops ANYWHERE below that, they will close and you will have a rough idle condition.

On another note. Lets assume you have enough fuel pressure at the schrader valve on the line there... This could be the pressure regulator is not keeping enough of the fuel pressure at the meter head. Unfortunately due to the placement of the regulator, testing the fuel pressure at the schrader valve will only give you pump pressure, not line pressure. Your pressure regulator regulates fuel on the return side of the line, not pressure (amazingly). So the fuel meter body and or injectors could still be the cause of issue for you. Two sticking poppets could very well make your truck not run correct as you are stating.

Finally... if you want GOOD parts to put back in your truck, call me at Brown and Sons Automotive in Flint MI. My number there is 1-800-852-6933. Ask for Mike. I will even give you the GM employee discount on anything you need to fix this truck of yours. I keep the pump, fuel meter assembly, pressure regulator, poppet injectors and anything else that you can imagine needing for the job right in my store.

I want to see you get your truck working to its fullest again. I hate to see someone with a problem they cant figure out, fix it by not buying Chevy again. So let me know if I can help you anymore, ok? Later!
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post #26 of (permalink) Old 02-03-2004, 02:36 PM Thread Starter
 
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Re: 1997 tahoe, shuddering at highways speeds

Thanks Krayzi!

I dropped it a local dealorship today, $73.99 diagnostic fee, Ill see what they say, I looked around and I couldnt find a pressure tester, I guess I would have to make one from hardware store parts.

Hopefully the techs looking at it right now arent boneheads, and can pinpoint the problem. I may or may not fix it myself, depending on the weather ( its cold and wet here!) or how much time/$$$.

I apreciate your help, and offer of more help, I very well may take you up on it!

Ill post the outcome either way.

Thanks guys!
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post #27 of (permalink) Old 02-03-2004, 03:18 PM Thread Starter
 
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Re: 1997 tahoe, shuddering at highways speeds

well, the tech just called my wife, she has relayed to me these problems.

1 vacum leak under the upper intake manifold ( wife wasnt sure if that was it exactly hehe)

and collant leak that supposedly somehow contributed to teh vac leak ( again as explained by the wifey)

and the EVO is bad, thats the variable steering oriface isnt it? the asme one thats been bad since the truck was new that GM wont recall? hehe

so now Im out to find out how much the manifold gasket costs and fix that collant leak, and give it a try.

IM sure it wont be fun, but I cant pay $550 for them to change a gasket.

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post #28 of (permalink) Old 02-03-2004, 03:40 PM
 
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Re: 1997 tahoe, shuddering at highways speeds

Wow. I would not have imagined that one! I hope they are not just jerking you around... It just seems too odd that this happened RIGHT after you had your pump swapped! Oh well, hopefully thats all it is and you will be all set. Good luck to you man! If you need any advice, give me a call here at work 8AM-5:30PM EST and I will hopefully be able to help ya! Later.
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post #29 of (permalink) Old 02-03-2004, 04:29 PM
 
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Re: 1997 tahoe, shuddering at highways speeds

You can check for a leaking intake manifold gasket by spraying carb cleaner around the gasket area with the engine running. If the rpm changes, the cleaner is getting sucked into the engine through a leak.
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