Fricking TPI!!!
Thread Starter
Burning Brakes
Joined: Nov 2007
Posts: 1,213
Likes: 2
From: Cincinnati oh
Fricking TPI!!!
Ok this damn thing is driving me nuts You tell me cause i am lost!
1985 corvette stock 160 deg thermo, performance chip,new fuel pump
Car was bogging down in corner under heavy accel
Put on a new TPS, and IAC valve. The TPS Moved and threw a cose 22, straightend it (with out a volt meter) cleared the codes and it seemed ok I noticed that at highway speeds when i let off the gas it seems to slow like it is not in OD
The Idle seems to be very low as well.
Ran a auto cross. would not accell worth a crap seemed like it was holding back when i mashed the gas. Driving home cruising at 75 mashed the gas same thing
Threw a code 43 (knock sensor)
The wire had came off the knock sensor.
put it back on cleared the codes seems to run OK
would the knock sensor cause it to hold back under load?
Please Please Please tell me what to do I am Lost if any one can recomend a good tune guy in the Cincincinnati Area would be awesome.
I also am considering getting rid of the Cat converters? would that mess up the ECM?
1985 corvette stock 160 deg thermo, performance chip,new fuel pump
Car was bogging down in corner under heavy accel
Put on a new TPS, and IAC valve. The TPS Moved and threw a cose 22, straightend it (with out a volt meter) cleared the codes and it seemed ok I noticed that at highway speeds when i let off the gas it seems to slow like it is not in OD
The Idle seems to be very low as well.
Ran a auto cross. would not accell worth a crap seemed like it was holding back when i mashed the gas. Driving home cruising at 75 mashed the gas same thing
Threw a code 43 (knock sensor)
The wire had came off the knock sensor.
put it back on cleared the codes seems to run OK
would the knock sensor cause it to hold back under load?
Please Please Please tell me what to do I am Lost if any one can recomend a good tune guy in the Cincincinnati Area would be awesome.
I also am considering getting rid of the Cat converters? would that mess up the ECM?
Thread Starter
Burning Brakes
Joined: Nov 2007
Posts: 1,213
Likes: 2
From: Cincinnati oh
Thread Starter
Burning Brakes
Joined: Nov 2007
Posts: 1,213
Likes: 2
From: Cincinnati oh
Burning Brakes
Joined: Aug 2005
Posts: 1,172
Likes: 9
From: '88 TPI L98/HotCam Powell, Ohio
It sounds like you fixed the lack of power problem when you found the Knock sensor wire. Also make sure your TPS is installed correctly so it is really at full throttle when you have the pedal to the floor.
Thread Starter
Burning Brakes
Joined: Nov 2007
Posts: 1,213
Likes: 2
From: Cincinnati oh
Ok so the knock sendor WOULD make it run like crap?
and how do i check the TPS? do i just adjust the Idle screw or do i need to do something to the IAC?
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Melting Slicks
Joined: Jun 2007
Posts: 3,389
Likes: 0
From: Poocakes loves teh sausage! N.E. Ohio
If you have'nt already go to the top of the page to Other > Tech Tips> C4 Check this stuff out.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
runs bad
When was the last time you had the dist. cap off?
wear and tear can fill up the cap and rotor with arcing dust, and create a path that will short out your distributor under heavy load.
If you didn't set the TPS with a volt meter, you need to set it right.
A knock sender will screw it up by retarding the timing 12 degrees, although un hooking it, I don't know...... mine's never come off.
I would ohm check your wires to the plugs, they wear out as well. If they have excessive resistance or short out, leak voltage, they can cause a multiple miss on acceleration.
Check the engine grounds on the back of the heads, and in the distributor, and on the coil in the cap.
check the volt meter in the car. It should at least be 13.5 volts.
Low volts or a bad battery can cause this as well.
Check your fuel pressure, and then pursue the fuel thing if that's suspect.
wear and tear can fill up the cap and rotor with arcing dust, and create a path that will short out your distributor under heavy load.
If you didn't set the TPS with a volt meter, you need to set it right.
A knock sender will screw it up by retarding the timing 12 degrees, although un hooking it, I don't know...... mine's never come off.
I would ohm check your wires to the plugs, they wear out as well. If they have excessive resistance or short out, leak voltage, they can cause a multiple miss on acceleration.
Check the engine grounds on the back of the heads, and in the distributor, and on the coil in the cap.
check the volt meter in the car. It should at least be 13.5 volts.
Low volts or a bad battery can cause this as well.
Check your fuel pressure, and then pursue the fuel thing if that's suspect.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
When you replaced the IAC you sould have cleaned the IAC pintel bore under the TB, installed the new IAC and then set base idle per the IAC setup procedure.
Then you should set the TPS low & high positions per procedure. For a little snappier throttle response I set the TPS low value to .65Vdc after assuring base idle is properly set to 450RPM.
Also, take some TB cleaner to the throttle blades and inside of the TB before setting base idle and TPS values.
Then check & set (if necessary base timing) with the EST connector in the Tan/Blk wire under the MC disconnected.
Then you should set the TPS low & high positions per procedure. For a little snappier throttle response I set the TPS low value to .65Vdc after assuring base idle is properly set to 450RPM.
Also, take some TB cleaner to the throttle blades and inside of the TB before setting base idle and TPS values.
Then check & set (if necessary base timing) with the EST connector in the Tan/Blk wire under the MC disconnected.
Drifting
Joined: Jan 2001
Posts: 1,408
Likes: 13
From: Dayton, Ohio
As far as the knock sensor affecting performance, ABSOLUTELY!
Most guys don't believe me until they see for themselves, but the knock sensor is VERY sensitive. If it starts picking up an unsatisfactory noise, or if it's not got a proper connection, it'll drive you nuts. Example, to see how a knock sensor works, put your hood up and let it idle. Take a medium sized, 9/16", open end wrench and start rapping on the plenum, the alt bracket or any metal that is directly bolted to the block or heads. As you start tapping, the knock sensor will pick up the sound and interpret this as an ignition knock. Then it'll send the info to the cars computer, and it'll start trying to adjust the timing to get rid of the knock. This sensor is so sensitive, if you have a loose bracket that rattles around while you drive, it'll act up and then correct itself when you get out to see what's wrong. This can happen on just about any car/truck with a knock sensor.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
The computer has to see the knock sensor input. No wire / no input.
If it does not see it then it probably defaults to a low / no spark advance setting to prevent damage to the engine.
When people disable the knock sensor with using noisy solid lifters or roller rockers , they have to put a resistor in so the ECM thinks the knock sensor is there and working.
If it does not see it then it probably defaults to a low / no spark advance setting to prevent damage to the engine.
When people disable the knock sensor with using noisy solid lifters or roller rockers , they have to put a resistor in so the ECM thinks the knock sensor is there and working.
Thread Starter
Burning Brakes
Joined: Nov 2007
Posts: 1,213
Likes: 2
From: Cincinnati oh
Gents good advice I will set my IAC and TPS and see how it does I got some directions off the web. ill keep you posted
The knock sensor plug shield was broken so i had to creative engineering session.
I need to Find a place to cut off the Cat converters for me...hmmmmm
The knock sensor plug shield was broken so i had to creative engineering session.
I need to Find a place to cut off the Cat converters for me...hmmmmm
Team Owner
Joined: Jul 2004
Posts: 28,430
Likes: 3,279
From: Hartford WI
In post #9 and other sources have said we need to set it for around 0.54V. If you set it for 0.65, the ECM will assume it is not in idle mode anymore and might run the RPM higher.
Team Owner
Joined: Jul 2004
Posts: 28,430
Likes: 3,279
From: Hartford WI
