Car shakes under light acceleration.
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Teching In
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From: Ohio
Car shakes under light acceleration. Looking for some help here. Recently after my 93 Trans Am has sat for 7 months it has started to shake under light acceleration. I have checked tires, maf sensor(new), plugs(good), plug wires(good), put on new fuel filter today and had dyno done. They said car is running lean and experienced the shaking too. They think maybe the torque converter. It has a Hughes TCC with 2200 stall. The shudder seems to be felt around 50 mph and goes away around 70 mph. No codes are popping up either. I drove car to almost empty and put 93 octane in it. We recently put a Walbro 255 LPH pump in tank also. Getting ready to turn into a 383 or get rid of LT1 and Ls1 383 it. Either way putting a D1SC Procharger with a twin high flow intercooler on it, but need to surpass this problem first. Usually I think misfire....third plug back on passenger side underneath headers, but all good. My AFR is 14.5 so not an issue. My pressure is 40ish. When I turn the key I can hear fuel pump. My guess is Torque converter shot or fuel pump went bad and not giving volume needed??? Any help would be great. Also hear what sounds like an exhaust tick....could this be converter also? Tightened all bolts on exhaust. Thanks.
Last edited by DoYouLikeMyGun2; Apr 19, 2012 at 11:00 PM.
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From: New Hampshire
I have checked tires, maf sensor(new), plugs(good), plug wires(good), put on new fuel filter today and had dyno done. They said car is running lean and experienced the shaking too. Fuel pressure gauge is 12 to 14.5 so pressure not an issue. When I turn the key I can hear fuel pump. fuel pump went bad and not giving volume needed???
You contradict your self twice in one post lol
Running lean can be from lack of fuel, 12- 14 psi is WAY low, 40+ is what your looking for at the fuel rail. idle and WOT
And if you think the pump failed, why would you say the pressure is not an issue? They go hand in hand, a failed pump WONT push enough gas causing the pressure to be low can cause can a lean situation.
Also not sure why the shop who dynoed your car said it was fine being lean....Do you have any AFRs from the dyno?
shot in the dark but do you still have A/C? When my compressor pulley started to self-destruct, it ticked like an exhaust leak and the motor would vibrate at idle and light throttle every time it cycled on...
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From: Ohio
(VinR1) funny you ask.....I'll have to try it. Never used the A/C. LOL Thanks though. Like the ride. Is that a 93 also? I have the exact same color....grey-purplepearl metallic. Will post a pic.
(Army)- will check the O2s tomorrow....wouldn't throw a code though???
(Sandman and Z), my bad I meant Air Fuel Ratio from dyno. Pressure was good but still question pump???
(Army)- will check the O2s tomorrow....wouldn't throw a code though???
(Sandman and Z), my bad I meant Air Fuel Ratio from dyno. Pressure was good but still question pump???
Last edited by DoYouLikeMyGun2; Apr 19, 2012 at 11:26 PM.
Lazy O2's will not throw a code. At this point, check everything. Fuel pressure, O2, Datalogs of all sensors to make sure they are reading within spec.
I'm fighting a similar issue once my car gets into closed loop. Slight stumble at idle and partial throttle at idle. If you hold the throttle at 1500-2000 rpm at a stop, you can feel it. Funny thing is when I am in 5th, 6th gear..... nothing. It just comes and goes. Going to add cooling paste to the back of my ICM and space it from the head while the weather is bad today so I can test it out tomorrow. New OS's New Delphi Opti, New Wires, New Plugs, New Cat, New Injectors, Cleaned MAF, no leaks I can find. Most of these parts I replaced when I did a refresh of the car, I just noticed the stumble last week when taking off from a light.
I'm fighting a similar issue once my car gets into closed loop. Slight stumble at idle and partial throttle at idle. If you hold the throttle at 1500-2000 rpm at a stop, you can feel it. Funny thing is when I am in 5th, 6th gear..... nothing. It just comes and goes. Going to add cooling paste to the back of my ICM and space it from the head while the weather is bad today so I can test it out tomorrow. New OS's New Delphi Opti, New Wires, New Plugs, New Cat, New Injectors, Cleaned MAF, no leaks I can find. Most of these parts I replaced when I did a refresh of the car, I just noticed the stumble last week when taking off from a light.
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Thread Starter
Teching In
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From: Ohio
Sandman, that's pretty much what mine does too other than it idles perfect. It seems like under acceleration/stress it shudders. It really feels like a misfire, but nothing showed up on dyno. They said its definitely a fuel issue and probably TCC locking up when it shouldn't. You may want to change fuel filter also....could just be something small. I questioned optispark in mine, but the dyno people said its not that, plus its a pretty new MSD one from Summit. Thanks.
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Verdad Gallardo Fuel pump and filter have less than 200 miles on them, changed them out this winter as well. Nobody else notices it, so I guess it is just me. Weather is nice tomorrow, so going to hook up my scanner to it and watch what it does driving around.
Think I have it fixed. MAF extension was missing the weatherpack rubber, so the connector was moving around loose. I shook it and the SEL turned on, put one on it, cleared the code and no more hiccup so far.
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From: Ohio
Well, in the process of putting in a dual fuel pump (2x 255 LPH pumps) tandem setup and a tune on the dyno again. Will see if that fixes lean problem. Plus it will get motor ready for overhaul. Now thinking of going with iron block 6.0 L LS with a yank Torque Converter. Probably take block to over 400 cu in. and forge the hell outta it. New ECM and wiring harness, LSX intake with 80-90mm port and a nice set of trick flow heads. Probably a nice set of headers too. Dyno says probably get 600 to rear wheels. Depending on tune, then I will look at forced induction. ATI Procharger with twin high flow intercoolers. Dyno states probably get just above 900 to rear wheels. Wish me luck. Thanks for all the input.
