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Tpi 350 missing and no power

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Old 07-04-2016, 08:36 AM
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Tpi 350 missing and no power

Hello appreciate any help. Got a issue had a small miss at idle figuring it was Plugs or wires I ignored it. I put on edelbrock runners couldn't get them to seal. So I went back to stock and now the cars is crap. I then tore it apart and replace Plugs wires cap button coil injectors and fuel regulator and Icm. Still it runs horrible. It starts hard and runs idles rough and u smash the loud pedal and it breaks up won't even turn the tires. Again any help would be great thank.
Old 07-04-2016, 01:04 PM
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Car: 1991 Trans Am GTA
Engine: 350 tpi
Transmission: 700R4
Axle/Gears: 3.42
Re: Tpi 350 missing and no power

I had the same problem when I tried to switch to accel runners couldn't get them to seal so put my stock runners back on but the car ran like crap after that. I went thru everything again check for vacuum leaks maybe a broken line somewhere. I recently put edelbrock runners on. And while I was taking the stock ones off I noticed a few bolts where not tight causing a vacuum leak. And some lines where broken by my egr too.
Old 07-04-2016, 01:06 PM
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Car: 1989 Pontiac Formula 350
Engine: L98
Transmission: 700R4
Axle/Gears: BorgWarner 3.27 Posi
Re: Tpi 350 missing and no power

-Getting any codes?

-Is timing correct?

-Coolant Temp Sensor working properly?

-Still run like crap when you unplug the MAF (if you have one?)

and as aforementioned, check all vacuum!
Old 07-04-2016, 03:28 PM
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Car: 87 GTA, 88 GTA, 92 TA, 72 RS SS
Engine: 350, 350, 305, 396
Transmission: T56, 700r4, 700r4, T56
Axle/Gears: 3.42, 3.23, 3.23, 3.73
Re: Tpi 350 missing and no power

Year of car? Original injectors?
Old 07-04-2016, 04:16 PM
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Re: Tpi 350 missing and no power

The timing is good. New injectors from Southbay. No vacuum leaks spray it don't when it's running with cleaner and the idle don't change. It's an 88 350 tpi
Old 07-04-2016, 04:17 PM
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Re: Tpi 350 missing and no power

No codes either
Old 07-04-2016, 04:34 PM
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Car: 1991 Trans Am GTA
Engine: 350 tpi
Transmission: 700R4
Axle/Gears: 3.42
Re: Tpi 350 missing and no power

Mine would not come out either with the spray. Turned out to be the one bolt all the way in the back towards the firewall...check that all ur sensors are connected tpi iac etc....just really have to go over everything u got near while changing the runners. Also one of my spark plug wires was off and was causing it to act up.
Old 07-04-2016, 04:45 PM
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Re: Tpi 350 missing and no power

I've been over it 100 times. Everything's connected good. And bolts are tight. Plugs and wires are good. Just to many different things that it could. I'll keep digging
Old 07-04-2016, 05:38 PM
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Car: 1991 Trans Am GTA
Engine: 350 tpi
Transmission: 700R4
Axle/Gears: 3.42
Re: Tpi 350 missing and no power

Did u confirm u got the firing order correct when swapping the spark plug wires?
Old 07-04-2016, 06:17 PM
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Engine: 350-TPI
Transmission: 700-R4
Axle/Gears: 3.27 Posi
Re: Tpi 350 missing and no power

Originally Posted by I_R_O_C_Z_2_8
Mine would not come out either with the spray. Turned out to be the one bolt all the way in the back towards the firewall...check that all ur sensors are connected tpi iac etc....just really have to go over everything u got near while changing the runners. Also one of my spark plug wires was off and was causing it to act up.
x2

I couldn't find any runner leaks until I did a smoke test. The leak was on the bottom part of the RH runner by the plenum.
Old 07-07-2016, 05:53 PM
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Re: Tpi 350 missing and no power

Backtothe80s I had the same problem when I went to start my new tpi for the first time. The runners were leaking in the same spot bottom right side in the back. Smoke test was the only way we found it.

If you don't have a smoke machine it might be worth it to get a shop to do a quick test for you. It shouldn't cost that much and you will know for sure you don't have a vacuum leak. I'm running the Edlebrock intake and runners they were a little harder to get everything sealed up right.
Old 07-07-2016, 06:24 PM
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Engine: 350-TPI
Transmission: 700-R4
Axle/Gears: 3.27 Posi
Re: Tpi 350 missing and no power

Originally Posted by johng1
Backtothe80s I had the same problem when I went to start my new tpi for the first time. The runners were leaking in the same spot bottom right side in the back. Smoke test was the only way we found it.

If you don't have a smoke machine it might be worth it to get a shop to do a quick test for you. It shouldn't cost that much and you will know for sure you don't have a vacuum leak. I'm running the Edlebrock intake and runners they were a little harder to get everything sealed up right.
I'm an automotive student so I had access to the machine, however, it's not needed to find vacuum leaks. While we were waiting for the machine to warm up, one of my classmates whipped out his vape and blew from the booster line into the intake. It was almost as accurate as the professional machine. We used the pro machine to confirm. True story!
Old 07-07-2016, 10:52 PM
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Car: '87 IROC
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Transmission: TH700R4
Re: Tpi 350 missing and no power

You'll never get manifold/runner/plenum leaks if you line up and assemble everything loose first.

Then starting at manifold, snug up the runner bolts and then the plenum. Go back to the bottom and tighten the runner-to-manifold bolts to spec. Then tighten the runner-to-plenum bolts.
Old 07-08-2016, 12:08 AM
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Engine: 350-TPI
Transmission: 700-R4
Axle/Gears: 3.27 Posi
Re: Tpi 350 missing and no power

Originally Posted by paulo57509
You'll never get manifold/runner/plenum leaks if you line up and assemble everything loose first.

Then starting at manifold, snug up the runner bolts and then the plenum. Go back to the bottom and tighten the runner-to-manifold bolts to spec. Then tighten the runner-to-plenum bolts.
Thanks for the advice. I haven't addressed the vacuum leak there yet and will definitely keep your advice in mind. I suspect the previous owner may have caused it by replacing some of the torx bolts with Phillips head bolts. He likely also did not torque them in the same sequence that you suggested.

I would also suggest the original poster check fuel pressure, replace the fuel filter, and do the smoke test. Find a friend who smokes and have him/her blow into the vacuum line on the passenger side. That's how we found the majority of the leaks. I also wanted to add that when I did the smoke test, the throttle body had leaks at the shaft from years of use. I will have to send that out for repairs.
Old 07-12-2016, 09:56 PM
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Engine: 350-TPI
Transmission: 700-R4
Axle/Gears: 3.27 Posi
Re: Tpi 350 missing and no power

Originally Posted by backtothe80s
I suspect the previous owner may have caused it by replacing some of the torx bolts with Phillips head bolts. He likely also did not torque them in the same sequence that you suggested. .
Nope. The incorrect bolts weren't the reason. I think this was.

Sorry to hijack the thread, but I had to share it.
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