Too hard throttle response at low rpm - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums
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post #1 of 19 (permalink) Old 04-08-2019, 01:41 PM Thread Starter
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Too hard throttle response at low rpm

Hi :-)

My first post here, but have been lurking around for some time now.

I just bought my first camaro.

1997 with LT1
Edelbrock Performer heads
BBK nickel plated shorty headers
MSD opti spark
MSD wires
K&N CAI
The engine has new pistons, rods, and bearings all over about 25.000km ago. (Due to lack of engine fluid)

It runs really great and pulls strong. But I have noticed a strange problem with low rpm. People always seem to complain about lack of throttle respons. My problem is kind of reverse. It has too much throttle respons from idle / low rpm.
It idles fine and stable. A little high around 1000 rpm.

If I very slowly press the gas pedal from idle, it jumps straight up to about 1600-1700 rpm. When I release the pedal it drops down to idle speed as normal. Its impossible to make an easy throttle from idle, and hit a rpm between 1000 and 1700(ish) rpm. It jumps from idle to 1700.
Same goes when cruising at slow speed with low rpm.
An example: If I try cruising with cruisecontrol below 1700 rpm, it kind a accelerate > engine brake > accelerate > engine brake.

I meassured the voltage on TPS. Idle shows 0,55v and WOT shows 4,95v - No jumps when slowly goes WOT
I tried reset the IAC valve - no luck

Does anyone have any good ideas ?
Thanks in advance.
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post #2 of 19 (permalink) Old 04-08-2019, 01:46 PM
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Automatic? What stall speed is the converter?

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post #3 of 19 (permalink) Old 04-08-2019, 01:47 PM Thread Starter
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Oh sorry.. 6 speed manual
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post #4 of 19 (permalink) Old 04-08-2019, 01:48 PM
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No problem.

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post #5 of 19 (permalink) Old 04-08-2019, 03:27 PM
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A vacuum leak will cause high idle on a fuel injected engine.

I would disconnect vacuum lines and plug the ports temporarily one at a time to see if an accessory is leaking vacuum (brake booster, PCV valve, cruise control, purge, etc...

The diaphragm in the brake booster can leak intermittently as it flexes.

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post #6 of 19 (permalink) Old 04-08-2019, 05:06 PM
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Yeah and added air intake might make the rpm" s wonky.

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post #7 of 19 (permalink) Old 04-09-2019, 07:21 AM
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You might have a computer tune problem. However, it would take an obd 2 computer tuning program to read the bin file that is in the 97 computer.

With the contents of your computer read, a pcm tuner could look over the bin file data and make suggestions on correcting the possible over fueling problem you have.

Another possibility would be a throttle position sensor that is not reading correctly. IE, it jumps from 0 to a much higher value with very little movement of gas pedal. You can check tps data with an obd 2 scanner that does real time sensor data. Check tps data, starting with throttle closed, open throttle slowly from closed to fully open. Make sure the data increases smoothly with no big jumps in data increase.

Check the gas pedal cable to throttle body for smoothness in it's operation. Also check throttle lever for smooth operation. My throttle lever on my 95 would stick closed from time to time. It took a hard push on the gas pedal to get throttle to open. The effect was too quick of throttle response.
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post #8 of 19 (permalink) Old 04-09-2019, 02:35 PM Thread Starter
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Thanks for advices

dkimbocz >> I changed all vacuum lines and rubberhoses everywhere today. Every hose is brand new. The problem is still there

cocobolo95 >> I tried what you suggest with the TPS. I have no OBD scanner but did it with a voltmeter. The TPS works smoothly. No sudden jumps in voltage.
I also tried twisting the TPS a little so instead of showing 0,55v on idle, it shows 0,85v. Just to try eliminate the possible jump there might be down there. Of cause I am using the throttlebody and not the pedal, and it still jumps from idle straight up to 1700 rpm - So still no luck.

Funny you mention the computer tune problem. I talked to the previous owner who said he had it tuned 12 years ago by some dude he dont have contact to no more.
Since then, the engine had an overhaul and other things installed (new heads with bigger valves and so on). So now suspect the PCM tune doesnt fit this engines setup.

Here in Denmark there is absolutely no one with JET Dynamic Spectrum Tuner. As far as I know, thats the only program to tune this PCM (?) ...or do I miss something?

Thanks for the replys so far..
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post #9 of 19 (permalink) Old 04-09-2019, 02:40 PM
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Tuner pro but I'm not sure it works on obd 2

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post #10 of 19 (permalink) Old 04-09-2019, 02:47 PM Thread Starter
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Quote:
Originally Posted by Stormyweather View Post
Tuner pro but I'm not sure it works on obd 2

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It doesnt work on Camaro 96/97 :-/
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post #11 of 19 (permalink) Old 04-10-2019, 07:35 AM
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Since there are no pcm tuners, in Denmark, that familiar with the lt1 platform, you will either have to bite the bullet and buy the jet 0bd2 tuner and learn to make the pcm data changes yourself. Or send pcm to US to a pcm tuner like LT1 PCM Tuning - Welcome!

Solamon can make the changes and send the tuned pcm back to you. Downside would be the long wait as pcm goes through customs in both countries, etc.

If you choose the buy Jet and learn how to tune, same site above has some goood learning info. And you can go to the gearheadefi forums. They have many stock & modified tuning bin files available. Might get lucky & one of those will meet your fueling needs.

.Or if they don't have a proper bin file, the members can guide you in the right direction for changes you need to make. It sounds like your basic tune is mostly correct. Just the off idle fueling needs to be tweeked. Which mean only a few changes will need to be made to tune bin file aready being used.


Final though; If you learn to live wiyh the too much response of oof idle throttle, you'll save yourself time, money, & much aggravation.

Last edited by cocobolo95; 04-10-2019 at 07:40 AM.
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post #12 of 19 (permalink) Old 04-10-2019, 12:08 PM Thread Starter
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I spoke with the guy who "tuned" it today. He just used a Hypertech Power Programmer III for a camaro 94 :-/
That was done while the engine was still stock. And I guess it would need a whole different tuningmodule for the 96-97 PCM (?)

I have never tuned a car, but have experience with motorcycles with Dynojet program, tuning by O2/Air/fuel values. So tuning with another program might not be the biggest problem for me. I also have access to a dyno for cars, making it a whole lot easier.

So I guess I'll just get the Jet DST program and start learning :-)
Will do some other mods while I am at it anyway.

Last edited by CamaroZ28_DK; 04-10-2019 at 12:14 PM. Reason: Missing information
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post #13 of 19 (permalink) Old 04-10-2019, 12:27 PM
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Hyper tech is easy more like a question answer deal.

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post #14 of 19 (permalink) Old 04-10-2019, 12:59 PM
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The trouble with the hypertech is it is a one tune fits all tuner. It's very expensive to buy for what it does. And once it tunes a pcm, the hypertech is locked out of tuning any other cars. So the hypertech tuner that tuned your car, is out there somewhere, and it is useless until it returns your car to stock.
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post #15 of 19 (permalink) Old 04-11-2019, 10:18 AM Thread Starter
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OK - I just ordered Jet DST and some other stuff I might find usefull in the future :-)
I have read alot about jet dst. Should be an OK program with a lot options for modifications.
I will thou need a datalogging software since Jet do not have it.

Any suggestions on a program I can be using on a laptop side by side with Jet DST ?
Freeware is of cause preffered ;-)
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