C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Throttle Question

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Old May 14, 2005 | 09:07 AM
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Just bought a 1987 Vette with 4+3 trans. The car is real quick and fun but I am having trouble with the throttle. When not started the trottle linkage operates smoothly with no apparent problems. When the car in running the trottle is tight and then jumps up and rev's high, almost all or nothing. (No smooth increase in RPM's) Also, it does not return to idle position all the time, probably only 1/4 of the time and only when I hit the gas and let off quickly. Again, the linkage seems fine with the car not running. Snaps back to idle position, no kinks or binding anywhere.


Maybe the spring on the throttle body is not tight enough??

It has been very hairy backing into my tight garage.

Please help.
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Old May 14, 2005 | 09:21 AM
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Does the DIC show any codes?
It could be a faulty Throttle Position Indicator Check the connections first to ensure they are tight and not corroded.
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Old May 14, 2005 | 09:32 AM
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Originally Posted by rws.1
Does the DIC show any codes?
It could be a faulty Throttle Position Indicator Check the connections first to ensure they are tight and not corroded.
Not sure what a DIC is but there is nothing showing on the dash. I looked at the TPI and it looked clean, not sure how to test it.
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Old May 14, 2005 | 09:42 AM
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DIC is Driver Information Center. The part of the dash that lights up when you turn the key to the on position just before the engine cranks.
Its the part that tells you whether you have problems with your ABS, or Airbags etc.

If your car has an electronic problem... it will "throw a code" this is what the technicians read .
You can buy a code reader or you can use a paper clip or Autozone gives away free code keys.

Follow this link below: read the thread about how to read a code ( Reading the first 5 posts will give you all you need to know)

the code will help diagnose the area in which the problem is occuring.

Once you have the code post it here and your fellow CFers will help you pinpoint the problem and advise how to fix it.
good Luck

http://forums.corvetteforum.com/show...es&forum_id=48
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Old May 14, 2005 | 01:00 PM
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Pull the air inlet tube and see how much crud has built up in the TB bore and on the edges of the butterflies. Also check for play in the throttle shaft. In time the bore gets elongated and the shaft is allowed to move back and forth causing the butterflies to come to a rest in different positions. Dave Koldos does TB rebuilds and machines a bearing into each end of TB. Cleaning the TB including the IAC passage may yield good results. Follow this with setting the min. idle and TPS.
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Old May 14, 2005 | 03:08 PM
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The throttle body is worn, where the throttle shaft passes through it. If you spray where the shaft goes into the casting at both ends, with a lube, you may get a temporary cure. The TB either has to be repaired with bushing or bearings, or the TB replaced.

RACE ON!!!
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Old May 14, 2005 | 09:31 PM
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Originally Posted by AGENT 86
Follow this with setting the min. idle and TPS.
TPS????
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Old May 14, 2005 | 09:47 PM
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Originally Posted by BRB
TPS????
Throttle position sensor
https://www.corvetteforum.com/techti...D=55&TopicID=2
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Old May 14, 2005 | 10:06 PM
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Duh!! I had TPS in my mind, I assume TPI is the same thing.

You guys are good. Sprayed some lube inside the throttle body right at the "butterfly axle" for lack of the correct term, and darned if it did'nt work. Probably a temp fix as stated but at least problem #1 of 200 is answered. A rebuilt or new throttle body is now on the "list".

At least I can back the car into the garage with out worrying about smashing the washer and drier into my daughters room.

Now for the tranny, hubs, UJ's, etc..........................
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Old May 14, 2005 | 10:10 PM
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Of course TPI "throttle position indicator"(in my mind) would conflit with TPI "Tuned Port Injection" I'll go with TPS.

My bad. Bear with me, I'm learning.
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