TPI Tuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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Old 03-14-2018, 10:25 AM
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Car: 1986 IROC Z
Engine: 305 TPI
Transmission: Auto
Bucking..

I finally got the car finished enough to drive and drove her down to the glass place yesterday to have a new windshield installed. I noticed while driving at about 35mph with my foot barely on the gas the car would buck some. I dropped it down out of overdrive and it went away. Like it wanted a little more RPM's. Is this normal for low speed overdrive and if not what should I check out?
Old 03-14-2018, 10:51 AM
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Car: 1984 Trans Am L69
Engine: Sniper EFI Powered 355
Transmission: WC T5 w/ Steel Support Plate
Axle/Gears: 3.42 10 Bolt Posi
Re: Bucking..

The car should drive smooth and not buck and if your sig is correct and you have TPI then it should be nice and smooth. It could be a variety of things but just a couple questions first.

What car?
What engine?
What trans?
Is it stock?
When was the last tune up?
Have you adjusted the TV cable?
Have you checked the Trans Fluid?
What overall condition is the drivetrain?
Old 03-14-2018, 10:57 AM
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Car: 1986 IROC Z
Engine: 305 TPI
Transmission: Auto
Re: Bucking..

86 IROC, 305 TPI, What ever the stock trans would have been. Engine has been rebuilt and bored .030 over I believe. Took me three months just to get it running a couple years ago. Haven't driven it in over a year due to the restore and paint I did. Have not checked the fluid in the trans. What is the TV cable? Now that she is road ready I'd like to get her tip top mechanically.
Old 03-14-2018, 11:03 AM
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Car: 1984 Trans Am L69
Engine: Sniper EFI Powered 355
Transmission: WC T5 w/ Steel Support Plate
Axle/Gears: 3.42 10 Bolt Posi
Re: Bucking..

TV cable
https://www.thirdgen.org/forums/tran...djustment.html

If the car has been sitting that long it would be wise to change all the fluids. Check the trans level make sure nothing leaked out or it is not low. You should probably do the rear and as well. Personally I would bleed the brakes as well and get some nice new fluid in the reservoir.

As the problem goes away with the trans in a different gear I would look at that direction.
Old 03-14-2018, 11:04 AM
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Car: 1984 Trans Am L69
Engine: Sniper EFI Powered 355
Transmission: WC T5 w/ Steel Support Plate
Axle/Gears: 3.42 10 Bolt Posi
Re: Bucking..

Did you check your timing after the engine rebuild?
Old 03-14-2018, 11:07 AM
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Car: 1986 IROC Z
Engine: 305 TPI
Transmission: Auto
Re: Bucking..

Okay, thanks. Before I started the restore I drove it daily for a few months once I got it running. I was planning on taking it to a transmission place for a fluid and filter service. It shifts really strong. Seems almost too strong and kind of feels like it slams into second gear. I will check that cable. Thanks.
Old 03-14-2018, 11:14 AM
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Car: 1986 IROC Z
Engine: 305 TPI
Transmission: Auto
Re: Bucking..

When I got the car running I adjusted the timing per the service manual. What would you suggest it be set at?
Old 03-14-2018, 11:19 AM
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Car: 1986 IROC Z
Engine: 305 TPI
Transmission: Auto
Re: Bucking..

A little history... I bought the car from a guy who could not get it running. It would start but not idle and would barely stay running. He had removed the TPI and put a 4bbl carb on it. He still had all the TPI components and gave me those with the car. I bought a factory service manual and put all the TPI stuff back on. It still ran the same. After checking all of the sensors and senders it still ran like crap. Long story short I found out from him when he rebuilt the engine he only did the bottom end and slapped the old heads back on with no work done to them. Well, they were bad, like really bad. Only one cylinder had compression over 100. So I had the heads done with new valves and springs. She fired right up and ran great after that. Still has a few idle issues that I can get to later but overall it runs really good.
Old 03-14-2018, 11:20 AM
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Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Bucking..

6 dbtdc with the est disconnected.
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