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SubarcticPig
New User
Mar 7, 2012, 6:31 PM
Post #1 of 6
(2973 views)
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I've got a 1988, single cab/short box, chevy K1500 scottsdale with a 5.7 and about 160k miles. when I bought the truck, (about a year ago) it had been previously sitting for about 5 years, in those years it was sitting it was only started a handfull of times. When I got it, there was a large lack of power, it was idling high, getting much worse gas mileage than it should have been getting and had a pretty stiff shake to it while it was in gear and sitting at a light, or stop sign. But just a slight shake while highway driving. All the fluids were replaced throroughly, new plugs, wires, cap and rotor. throttle body was cleaned in parts washer, new injectors and gaskets on the whole throttle body.(<---year ago | last week--->) Smog pump removed from serpentine system, long tube headers and dual exhaust w/mufflers installed. After all this, the passanger side exhaust was popping, ended up bad wire on #6 cylinder. replaced with used wire that doesn't arch, and no more popping. Now, driver side exhaust is burning white on start-up, but passenger side is burning black with no white what so ever. still a massive lack of power, throttle response is terrible, and mileage is still terrible(8-10mpg). the shake seemed to have gotten a bit better but has evened out more across the board. little worse on highway, a little better while in gear sitting. Also the truck has been running very rich since day one. I'm going to upgrade plugs, wires, cap and rotor to a performance grade on friday and see what happens. any more suggestions?
thank you
SubarcticPig
(This post was edited by SubarcticPig on Mar 7, 2012, 6:50 PM)
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nickwarner
Veteran
/ Moderator
Mar 7, 2012, 7:23 PM
Post #2 of 6
(2941 views)
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You have an H-pipe in this or true duals? This truck didn't have an O2 sensor for each bank as I recall. If it only gets input from one side it thinks the whole engine is doing what one side is doing. How close the the header collector did you mount it? You say this has never really made decent power. Have you done a compression test? Have you checked very closely for vacuum leaks? The intakes were prone to it and all of your vacuum lines are old enough to buy their own beer so I would right away swap those with new ones. The age in and of itself dictates replacement. Also get a fuel pressure reading and post it. While you're at it, pull any codes present and post those so we can see the bigger picture of what is happening with your engine.
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SubarcticPig
New User
Mar 7, 2012, 7:47 PM
Post #3 of 6
(2935 views)
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It was sent out for the exhaust, but my mechanic did the O2 sensor, as well as a compression check. He said compression was great. No H pipe, and sensor is about 6in away from collector on drivers side. Ill get on those boozed out vacuum lines asap, fuel pressure and codes as soon as I can. The guys I bought it from pulled a complete tank with pump from a junk yard and installed it because the pump was out, but I guess that really doesn't mean much since the junk yard tank probably isn't too much newer. Now that you reminded me, what are your views on H pipe v. true duals? I told my mechanic H pipe but apparently he didn't pass the word on to the exhaust fella.
thanks much
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nickwarner
Veteran
/ Moderator
Mar 7, 2012, 8:01 PM
Post #4 of 6
(2930 views)
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An h-pipe will allow a balancing of exhaust pulses and better scavenging. With your engine and chassis there is actually no need to run bigger pipe than 2 1/4". Cams and intake are neutered and you're not trying to pull 6500RPM. It also mellows the tone of the exhaust a bit. Keeps the cops off you and a bit friendlier to your neighbors. Louder doesn't mean more power, it just means louder. For lower RPM apps like trucks I run and H-pipe. For higher RPM power I go with an x-pipe. By higher I mean past 5500. No need for it at your rpm level.
We will be waiting for the additional info from testing your system so this can be solved.
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SubarcticPig
New User
Mar 7, 2012, 8:16 PM
Post #5 of 6
(2925 views)
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I had them put some mufflers on there for noise purposes, although it could be a little quieter for me. I will talk with them about the H pipe, I was just gonna forget about it but as I was thinking it might be beneficial. Thanks a lot for the help, you shall hear from me soon
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techforfree
User
Mar 8, 2012, 11:12 AM
Post #6 of 6
(2898 views)
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Alright..stop throwing money away here and find someone that has a fuel pressure tester (bypasses the fuel filter) .I know this sounds odd but those old throttle bodys (2 injectors) everything was based on the fuel pressure carrying between 9 to 15 lbs i'm betting on yours carrying about 7 or less.i used to run into this all the time with exactly what you're discribing and in about all cases it simply didn't have enough fuel and yes in this case low fuel pressure will cause poor fuel milage too...good luck
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