LT1-LT4 Modifications 1993-97 Gen II Small Block V8

i think i figured it out...

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Old 12-10-2007, 08:25 PM
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Default i think i figured it out...

well my car runnin like **** after i got my gears installed... it started like an hour after i got it back and while it was runnin the speedo was WAY off like 30mph over how fast i think i was goin, so i was talkin to my buddys dad that used to be a machnic and he was sayin that it was floodin becasue the computer is giving more gas then it needed reading off the speedo...so he said change my plugs and get my computer flashed and it should work...what dose ever one think?
I went from 2.73's to 3.73's it that make a diffrence
Old 12-10-2007, 08:53 PM
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That doesnt sound right to me at all. Im just a kid with little experience, but in my opinion, the speedometer is just a sensor and has absolutely nothing to do with your air/fuel mixture.
Old 12-10-2007, 09:00 PM
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My knowledge comes mostly from GM OBD2 vehicles, but I think I can help you, unless OBD1 is THAT much different.

The speed sensor has nothing to do with how the PCM controls the air/fuel mixture, as stated above. The PCM uses the speed sensor to control the speedometer, and also to control shifts. (when an automatic transmission is in use)

If you haven't had the car flashed to match the gear ratio you are now using, you should definitely get that done. You probably have symptoms with your A4, if you haven't. Typical symptoms would be erratic shifts; problems getting into OD as well.

If you can give us some symptoms of what you're seeing, as far as your car "running like ****", then we can help you find that problem.

Sorry to say, but your buddy's Dad, has no idea what he's talking about. You would be wise to not trust anything he tells you about your car.
Old 12-10-2007, 09:07 PM
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Guy that had my car before me ran for a month without a tune for the 3.73's. It ran fine except the speedo was horribly off. I think he said it would hit the speed limiter quick too.
Old 12-10-2007, 09:25 PM
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Must just be coincedence then that the problems started shortly after you put the gears in.

What is the car doing?
Old 12-10-2007, 10:17 PM
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Hey man... I know I can shed some help here.....I installed a six speed car rear-end into my Formula Auto.. Mine had 2.73's and I went to 3.42's. When I did, the only difference was that at WOT the car would bounce off of the rev limiter about 4-5 times and then shift. Also the cars Speedometer was way the hell off. As well as the fact that my odometer was changing way too quickly. I drove say 4 miles and it would say I drove like 6-7miles. While driving the car though (untuned) it showed what the car would have been showing as if I still had the 2.73's in it. It would say I was at 80mph and I'd really only be at say 40-50 MPH. At 80 MPH with 2.73's I was at 2,000 RPM; But with the 3.42's and the car tuned....I'm at 81 MPH at 2700 RPM. I had a buddy tune mine and it drives flawlessly. Although my mileage dropped a bit. As far as the car running like ****...I don't know about that.... May be a coincidence....Try to tell us more about how it is acting and maybe we could help ya out a little bit.... Good Luck. James
Old 12-11-2007, 03:35 PM
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well my car started to stutter real bad like it didnt want to drive when i was on the gas a lil and when i let off it would be fine..and also i would get on the gas and it would have almost no power what so ever, fell flat on its face and it felt like it was only runnin on 4cyl. and my car start smokin and it sounded like i had a cam in it.....i changed opti and it started and sounded like i had a cam it and wouldnt want to run unless i tapped the gas then it ended up dieing....and now i can just crank my car over for ever and it dosnet even sound like it is attempting to start
Old 12-11-2007, 09:39 PM
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Those symptoms sound like the car needs new wires/plugs. All except the last statement, that it doesn't sound like its firing at all. Check your fuel pressure.

Have you cleaned the MAF?
Old 12-11-2007, 09:48 PM
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make sure you have the basics- fuel, spark, and compression (air is a given). unless you have a bag over your air filter

it could be: ignition module, coil, fuel pump, clogged fuel filter, fouled plugs, burned wires, bad opti (even though you just replaced it, it can still be a lemon), and possibly other things but you need to check the basics first to make sure its not anything stupid.
Old 12-11-2007, 09:51 PM
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Please, let's not just start tossing parts at it, playing guessing games. I see far too many people do that on here. You can save yourself a lot of time and aggravation by working your problem, isolating it down to the problem child. PLUS, it's a great excuse to buy tools!!
Old 12-12-2007, 04:54 PM
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Sounds like my car when the fuel pump went out. Just take a fuel pressure gauge and check to see if you have enough fuel pressure to make it run. Also check if it does start; what the pressure goes up to at idle and at part throttle.(by giving it gas) And what it's at with the vacuum hose off of the Fuel pressure regulator. Then if that checks out to be ok...Check the spark, to be sure your getting sufficient spark. Also you may want to pull the plugs and check them to see if they are fouled out. Good Luck man.
James
Old 12-12-2007, 09:14 PM
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well tonight i replaced the spark plugs like my buddys dad told me to (even tho i just changes plugs and wires about 5 months ago) and wouldnt u no it my car started up for the first time ....so i put everythign back on, plumbed everything and took it for a drive..... it ran ok ...still not shifting right after gear install which is expected....and all of a sudden about 10 mins later it startin stuttering and had no power and wouldnt accelerate at all....so i thought i was runnin out of gas, so i was right by a gas station, filled it up and still the same problem i am so stumped... it feels like it has a really bad miss
Old 12-12-2007, 09:31 PM
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If new plugs temporarily fixed it, you're probably running really rich, fouling out the plugs.

Again, tossing parts at it just creates frustration on your part. It's time to diagnose the problem by following good advice you've been given above. I would clean the MAF, and check your fuel pressure as stated above.
Old 12-12-2007, 09:50 PM
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check your fuel pressure and see if it is bleeding off or staying steady. it also should be around ~42psi i think.
Old 12-13-2007, 11:09 AM
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i cleaned my maf not to long ago and im not sure how to check fuel pressure and not sure what tool i use so i will try to check that and im also goin to get my computer retuned (any mail order suggestions?) because every time i got in to it and it missed the shift it would start actin like it is......and when my check engine light isnt on my car runs somewhat normal, but when the check engine light comes on thats when it really starts to miss and carry on ...any idea why this is?
Old 12-13-2007, 11:21 AM
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I'm not going to say that I know what is wrong with your car, but I had what sounds like a similar problem with my LS1... The only difference is that once I got the car up and running for a little, that the loss of power when trying to accelerate would sometimes go away. What was the matter with mine was the cam sensor. This could also mess up your speedo if you've had it reprogrammed after the gear swap. It is rare that it would mess the speedo up, but in my case it did. If it isn't the cam sensor, then it could also be the crank sensor. Best thing to do is if you have a buddy with an extra cam sensor lying around, just borrow it and swap em out and give it a try. That or borrow someones... Good luck with it, and let us know how it turns out.
Old 12-13-2007, 11:37 AM
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If it is running rich DO NOT count out a dieing fuel pump. You would be amazed what happens when the fuel pump starts to die.
Old 12-13-2007, 04:07 PM
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I would still check the fuel pressure. Also just because you cleaned your MAF doesnt mean that its good, un plug it and start it up and take it for a spin. If it stops running like **** then you need a new one, ran into this problem with both my zr2 and the camaro.
Old 12-13-2007, 04:11 PM
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slvrbrd was ur loss of power when accelerating when your check engine light comes one because that is when my car starts do that and when i dont have a light it runs some what normal but i can feel a slight hesitation and how would i no if my fuel pump is goin out would checkin my fuel pressure tell me this? thanks for all the help guys
Old 12-13-2007, 04:19 PM
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Try replacing the 02s. Sounds like that might be wat is causing the car to run rich. Especially, since it only doing it after it comes up to operating temp.


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