tpi surges and idle bouces at stop

1badelco

i just finished putting a SD tpi in my 87 elco and it fires right up everytime, drives well for now but when i come to a stop or brake hard the engine feels like it wants to die, when i am sitting at the stop sign the idle bounces from 300rpm to 900rpm like i have a big cam. do i have something hooked up wrong. please help
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87 TPI El Camino In the Process.
Man who stands on toilet is high on pot.

Harald K · Posted: Sat Apr 15, 2006 2:01 pm Post subject:

There are two things I would check. First make sure you have the VSS is properly connected. Your El Camino has a speed sensor connected to the back of the speedometer which needs to be integrated into your ECM if you used a harness that is integrated into your instrument harness then it should have been properly connected to the ECM. There is one thing that would need to be altered the El Camino VSS has a 2x square wave signal and the SD ecm is looking for a 4X wave if this was not altered in the modification of your harness you may not be receiving the correct indication telling the ECM what the vehicle speed is and causing the TPS to hunt for an Idle speed. If the VSS is correct and the signal is right, the other thing to check is the TPS to make sure it is correctly adjusted. Check www.chevythunder.com it is one of the best web sites for TPI installation instructions and also trouble shooting info. Harald K

Heatsoaked

1 badelco,

I finished installation of an Edelbrock Pro-Flo and have been driving it about a week now. It runs like a raped ape but I have the same problem as you describe. When coming to a quick stop it feels like the engine goes below my set idle and is going to die but it never has. The idle will stabilize after 3-5 seconds. Have you got any answers yet? I have complete control over all five of my idle parameters. It is dialed in pretty good so I don't know what the deal is.
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78 project car and 87 G-Machine.

Its better to have a bottle in front of me-
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elcam84 · Posted: Wed Jul 04, 2007 3:06 pm Post subject:

Recheck the minimum air settings and the TPS voltage. Also make sure the IAC and passage are not gummed up.

Often on high mileage TPIs the throttle bushings are worn which let the throttle plates close a little further so you have to open them up more.

The instructions are on thirdgen.org. I prefer to do it by watching the IAC counts. TBI engines run best with very low IAC counts. I have found that the TPI prefers low IAC counts as well.
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Robert Adams
http://gparts.freeyellow.com
84 Conquista

Bowtie · Posted: Wed Jul 04, 2007 4:12 pm Post subject:

Had the same issue with my 89 TPI. Two causes turned up.

First was an air leak in the intake. Anywhere from the filter down to the intake manifold may cause it. With Speed Density, anywhere from the throttle body on in. Found a few cases with leaks in the runner gaskets after they fooled with them. Easy to locate with a little spray starter fluid.

Second was as elcam84 cited - basically a worn throttle body. There is a guy on the internet who rebuilds, improves, and bores TB's.

http://stores.ebay.com/Xtremefi

Expect mine back in a few days. Had it rebuilt, powdercoated red, and bored with airfoil to 52 mm. Will let you know how it turns out.

Just contributing possibilities. If wired & grounded solidly and correctly, TPI's are extremely dependable.

Take care.
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84 Elky GTA
Most of the important things a human ought to know cannot be comprehended in youth.