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Old 05-23-2011, 06:36 AM   #1
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LT1 runing rough

Definetly need a good opinion on my car !!! New to the forum and Lt1's in general. I just recently got a 94 z28 with 90k miles on it. Havent had a problem since i got the car. Three days ago i took it to the office to finish up some paperwork when I noticed the fuel was low. i killed the car went inside and finished paperwork, came back out to crank it and it took forever to crank. Since i have owned the car it starts pretty fast usually after a second or two. i left and the car began runnning bad, stumbling, jerking, so i figured the fuel was low and i went to fill it up. did not kill the car, left the gas station and it still ran rough. i hit WOT and it was stumbling even worse and missing. limped the car home and figured i sucked up some trash off the botom. replaced fuel filter, mass air was extremely clean, car still took a while to crank, had to cycle the key about 4 times to get it to fire, fianlly cranked after patting the gas. still has problems at low rpms and even at WOT, car sat for two days, went outside pulled a plug and they were clean. put plug back in and car cranked a lot faster but still took a lil bit. took it out on highay and it runs a lil better , still a stumble but not as bad, and improved a lil at WOT. im kinda lost at this point , any helpful hints will be greatky appreciated, im about to pull my hair out!!! thanks
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Old 05-23-2011, 12:23 PM   #2
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Re: LT1 runing rough

Welcome to the lt1 forum!!
I too have this exact problem, it stumbles, jitters, vibrates . I just did a tune up and the only thing i did not do is the optispark. So might be the optispark or ur catalitic converter is clogged. Dont mean to jack the thread but .Would the optispark make the car perform sluggish? If so im definitely replacing it!
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Old 05-23-2011, 01:00 PM   #3
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Re: LT1 runing rough

check fuel pressure at the rail if low Id suspect a bad regulator or fuel pump. Also try to clean up the injectors by running a bottle through the rail. Get one of those injector cleaners that hook up to the rail pull the fuel pump fuse and let the car run off the bottle till it dies. If you sucked any dirt up from the tank it could be clogging your injectors.
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Old 05-23-2011, 01:02 PM   #4
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Re: LT1 runing rough

Quote:
Originally Posted by cobrakiller650 View Post
.Would the optispark make the car perform sluggish? If so im definitely replacing it!
Yes the optispark will make it run like crap and in some cases the car won't run at all.

Have you scanned it for codes OP?
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Old 05-23-2011, 01:14 PM   #5
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Re: LT1 runing rough

its all good man, maybe we can fix both of ours lol, my car isnt throwing a code at all, plus when my car is hot or cold at normal operating temp it idles up when u first crank it , kinda seeming like an egr (but no code), ill have to check fuel pressure, guy i got it from said the opti spark was new before i got it.
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Old 05-23-2011, 01:33 PM   #6
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Re: LT1 runing rough

Quote:
Originally Posted by easttexasZ28 View Post
its all good man, maybe we can fix both of ours lol, my car isnt throwing a code at all, plus when my car is hot or cold at normal operating temp it idles up when u first crank it , kinda seeming like an egr (but no code), ill have to check fuel pressure, guy i got it from said the opti spark was new before i got it.
Did you actually scan it for codes, or are you assuming there are not codes because the SES light is not on? The codes for the optical cam position sensor in the Optispark distributor do not turn on the SES light, but will make it run rough, or maybe not run at all.

My guess would be you ran it dry on fuel (1/4 tank on the gauge is virtually "empty" on most of the 93-97 4th Gens), and that's all it takes to screw up the fuel pump. As suggested above, check the fuel pressure.
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Old 05-23-2011, 01:55 PM   #7
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Re: LT1 runing rough

k not a problem will check that , didnt know running it at 1/4 tank was really that low, will definetly be getting it scanned though, thanks for the help
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Old 05-24-2011, 01:49 AM   #8
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Re: LT1 runing rough

Yeah right. Hopefully its somewhat an inspirational fix on both of the cars. I might just buy the optispark. Because i think the owner before me never ever did a tuneup on it. Sparkplugs where really black and messed up. It didnt start stutterin til one of my close friends ran it hard early morning with out warming the engine
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Old 06-04-2011, 12:37 PM   #9
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Re: LT1 runing rough

problem solved, took it to shop, fuel pump was only pushing 18 lbs of fuel pressure, new pump and problem solved!!!!
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Old 06-05-2011, 08:42 PM   #10
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Re: LT1 runing rough

Saw someone mentioned the injectors could have picked up junk from the bottom of the fuel tank. I assumed the fuel filter would get all that stuff first. I have always go with the filter first and then the pump. The cheapest thing first of course.
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Old 06-05-2011, 10:36 PM   #11
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Re: LT1 runing rough

Appears he has already solved the problem with a new fuel pump.
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Old 06-05-2011, 10:36 PM
 
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