Sometimes no power on WOT and other times lots of power on WOT???
10-17-2013, 11:56 AM
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Sometimes no power on WOT and other times lots of power on WOT??? Hopping someone has had a similar experience or might know what the solution to my problem might be.
Car in question: 99 Camaro Z28 with a Auto 4L60E level II tranny with stock torque converter (clutches, shift kit, cervos and the whole shebang)
Ok heres my issue that just has me confuse.
After i purchased my car a few years back i ended up swapping out my stock auto tranny for a level II tranny and i put a stock vmaxx torque converter back in as i was short in funds for a performance one.
Why is it that when i smash the throttle pedal to the floor that i sometimes have great hard downshift and the car moves like its on steroids and there are other occasions when i smash the throttle pedal to the floor and the car has a super soft down shift with a gradual pick up????
I really hate the moments when i try to do a WOT run and the tranny downshift softly and has a slow pickup thus not showing any performance and other times its just a beast.
I've notice that there are days that the car feels great and fast and other days it feels like i'm pulling a damn semi truck.
Anyone could shed some light.
Everything is working fine on the vehicle.
Car in question: 99 Camaro Z28 with a Auto 4L60E level II tranny with stock torque converter (clutches, shift kit, cervos and the whole shebang)
Ok heres my issue that just has me confuse.
After i purchased my car a few years back i ended up swapping out my stock auto tranny for a level II tranny and i put a stock vmaxx torque converter back in as i was short in funds for a performance one.
Why is it that when i smash the throttle pedal to the floor that i sometimes have great hard downshift and the car moves like its on steroids and there are other occasions when i smash the throttle pedal to the floor and the car has a super soft down shift with a gradual pick up????
I really hate the moments when i try to do a WOT run and the tranny downshift softly and has a slow pickup thus not showing any performance and other times its just a beast.
I've notice that there are days that the car feels great and fast and other days it feels like i'm pulling a damn semi truck.
Anyone could shed some light.
Everything is working fine on the vehicle.
10-17-2013, 05:39 PM
#2
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This sounds like an engine sensor problem to me, perhaps the TPS or MAF. When it shifts well, the PCM knows you are at WOT and might even be downshifting two gears and is setting the line pressure to max. When it shifts softly the PCM thinks you are at partial throttle and only downshifts one gear and is setting the line pressure at a lower value.
10-18-2013, 01:16 PM
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So the problem may rely on the TPS or MAF. So far i have not gotten any cells telling me these sensors might be going out.
So my car does exactly that,
When it shifts softly it feels like it downshifts one gear only. Also cruise speed performance always varies, certain days it feels sluggish and i need to press the trottle a bit more to feel a good pickup and other days its just running like it should.
How would i go in testing these sensors out to find which are no good.
So my car does exactly that,
When it shifts softly it feels like it downshifts one gear only. Also cruise speed performance always varies, certain days it feels sluggish and i need to press the trottle a bit more to feel a good pickup and other days its just running like it should.
How would i go in testing these sensors out to find which are no good.
10-18-2013, 02:48 PM
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Some people simply disconnect the MAF which forces the PCM torely on the VE tables (Speed Density mode). If the VE tables are good (e.g. in a stock tune with mostly stock engine, or non-stock engine properly tuned) the car should run just fine.
There is a slight danger that with an improper tune WOT might run too lean and damage the engine. (Thats kinda like a legal disclaimer.)
It is hard to diagnose an intermittent problem. Might start by ensuring the connections to these sensors are clean.
There is a slight danger that with an improper tune WOT might run too lean and damage the engine. (Thats kinda like a legal disclaimer.)
It is hard to diagnose an intermittent problem. Might start by ensuring the connections to these sensors are clean.
10-18-2013, 03:03 PM
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i could try disconnecting the MAF and see if the transmission downshifts properly when WOT.
Also if it helps, i have a locked diablosport tuner laying around in which i could read live data in case you know what parameters i should be reading.
So you think that the problem may lay on the MAF, i have the Saxon Honeycomb on the maf just fyi.
Also if it helps, i have a locked diablosport tuner laying around in which i could read live data in case you know what parameters i should be reading.
So you think that the problem may lay on the MAF, i have the Saxon Honeycomb on the maf just fyi.
10-18-2013, 03:53 PM
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These are all possibilities but it seems to me you
lack the tools to disposition them as true / false.
This could all be as simple as the difference between
a one-gear and two-gear downshift, it could be that
what you think is WOT and what the PCM thinks is
WOT are two different things (how's your gas pedal
slack? What does TPS read, matted and what angle
does the blade draw to, by a ruler across the throat?).
On stock tunes the part-throttle shift tables are not
right for performance driving, maybe you just have a
marginal setup that falls short of WOT voltage on the
TPS sometimes, and sometimes doesn't. Or maybe
you went over the top with that throttle porting (bump
stop) and are hitting TPS high fault causing short shifting
fault strategy.
lack the tools to disposition them as true / false.
This could all be as simple as the difference between
a one-gear and two-gear downshift, it could be that
what you think is WOT and what the PCM thinks is
WOT are two different things (how's your gas pedal
slack? What does TPS read, matted and what angle
does the blade draw to, by a ruler across the throat?).
On stock tunes the part-throttle shift tables are not
right for performance driving, maybe you just have a
marginal setup that falls short of WOT voltage on the
TPS sometimes, and sometimes doesn't. Or maybe
you went over the top with that throttle porting (bump
stop) and are hitting TPS high fault causing short shifting
fault strategy.
10-18-2013, 04:27 PM
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This issue still occurred with a stock throttle body (un polished)
A buddy of mine was selling his PP TB after his vehicle got totaled by another person.
When i installed the PP TB on my car the RPM's were a bit high and i didn't bother to check the voltage on the TPS to see if it was measuring the same as my original TB. So what i did is block the small breather hole in the blade with a rivet and that brought the RPM's down to regular operating. Also i think the TPS sensor on the TB was new i need to double check with my buddy if he recalls.
I got rid of my original TPS but by chance do you know what the TPS voltage should be reading close and open? I could check with a volt meter tonight.
what would be the possible approriate tools to determine the fault of this issue?
A buddy of mine was selling his PP TB after his vehicle got totaled by another person.
When i installed the PP TB on my car the RPM's were a bit high and i didn't bother to check the voltage on the TPS to see if it was measuring the same as my original TB. So what i did is block the small breather hole in the blade with a rivet and that brought the RPM's down to regular operating. Also i think the TPS sensor on the TB was new i need to double check with my buddy if he recalls.
I got rid of my original TPS but by chance do you know what the TPS voltage should be reading close and open? I could check with a volt meter tonight.
what would be the possible approriate tools to determine the fault of this issue?
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10-19-2013, 06:58 PM
#8
You would be getting a constant tps error code if the voltage was wrong, I tried someone's homemade throttle body stop job once and it sucked dick...also enlarging the hole in the throttle body or "riveting" it closed is not the correct way to do things, spend the money and diagnose the problem or get a tune if it's idling too high
10-20-2013, 09:44 PM
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No, you will get a TPS voltage high code only if
you stay in it longer than the timeout for that code.
Ten seconds, I think is the number.
Hard to do on the street or a short track. But in the
moment an out-of-range TPS reading will invoke a
few "I don't know what to believe, so play safe"
strategies instantly.
you stay in it longer than the timeout for that code.
Ten seconds, I think is the number.
Hard to do on the street or a short track. But in the
moment an out-of-range TPS reading will invoke a
few "I don't know what to believe, so play safe"
strategies instantly.
10-21-2013, 05:55 PM
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right, never gotten a TPS code well while the blade is riveted. Without blocking the breather hole on the TB blade i will get a code ( i forgot which one exactly i was getting) but the code was indicating that the engine was revving high.
So i been driving the car with the MAF disconnected and i did a few test (pedal to the floor). Results are that the car doesn't feel sluggish while cruising anymore, exhaust rumble sound definitely increased. I tried to do some WOT pulls on the highway around 70mph 75mph and i was still downshifting one gear. When i tried doing a WOT pull on the street results were 50-50, transmission would downshift 2 gears and other times 1 gear.
I doubled checked transmission oil and it was a bit low. Oil level was right in the middle of the low and full dots on the rod.
So i been driving the car with the MAF disconnected and i did a few test (pedal to the floor). Results are that the car doesn't feel sluggish while cruising anymore, exhaust rumble sound definitely increased. I tried to do some WOT pulls on the highway around 70mph 75mph and i was still downshifting one gear. When i tried doing a WOT pull on the street results were 50-50, transmission would downshift 2 gears and other times 1 gear.
I doubled checked transmission oil and it was a bit low. Oil level was right in the middle of the low and full dots on the rod.
10-29-2013, 02:04 PM
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Jimmy do you know by chance what the tps sensor needs to be set at closed?
Also would the Predator tunner give any useful data to determine whats going on.
It really hate the feeling of the car downshifting softly one gear and not getting the feel of great performance when needing to take off quickly.
Also would the Predator tunner give any useful data to determine whats going on.
It really hate the feeling of the car downshifting softly one gear and not getting the feel of great performance when needing to take off quickly.
10-29-2013, 07:49 PM
#12
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IIRC the TPS closed voltage needs to be between .25 and .75 volts.
After a TPS change, disconnect it and turn the ignition on/off three times to put the PCM into learn mode. Then reconnect the TPS and the PCM will learn what the new TPS-Closed voltage is.
(Note: all this is from memory, so someone please correct me if wrong.)
After a TPS change, disconnect it and turn the ignition on/off three times to put the PCM into learn mode. Then reconnect the TPS and the PCM will learn what the new TPS-Closed voltage is.
(Note: all this is from memory, so someone please correct me if wrong.)
10-31-2013, 10:38 AM
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hopefully i get a chance this week or the weekend to check what the TPS is set at. Also i would like to monitor the TPS or maf readings to see if either are faulty but not sure what are the acceptable parameters.
02-10-2014, 01:53 PM
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Jimmy,
Still wanting to get this issue sorted out.
I took some pictures a while back of the throttle body with blade fully open. As you can see the blade looks like its not opening all the way. I wasn't sure if the problem landed on the throttle cable pulley bump stop, so i bent the bump stop lip on the pulley a bit to allow more max travel on the throttle body blade. By doing so it allowed the blade to open up a bit more compared to the picture but it didn't solve my problem still.
Still wanting to get this issue sorted out.
I took some pictures a while back of the throttle body with blade fully open. As you can see the blade looks like its not opening all the way. I wasn't sure if the problem landed on the throttle cable pulley bump stop, so i bent the bump stop lip on the pulley a bit to allow more max travel on the throttle body blade. By doing so it allowed the blade to open up a bit more compared to the picture but it didn't solve my problem still.
02-27-2014, 05:19 PM
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I got a chance to go take my car to get some data logging to see what was going on. I decided to do this before i starting wasting money on sensors or chasing what could be the problem.
All sensors are functioning the way they should including MAF and TPS. ECU tables looked great and my shifting speeds were sooner than an OEM Camaro. What we did notice is that the fuel pump may not be working at its full capacity as its causing the knock sensor to kick in. Because of this, when the engine is getting a shortage in fuel, it is making sure it protects itself and changing some things around to compensate.
I'll be soon be swapping what ever fuel pump i have for a Racetronix fuel pump with with upgraded wiring harness and go from there to see if my problems get resolved.
Fuel pump does make sense as my power bands have always been variable. Days car feels great and other days it is just sluggish. Recently it has been staying on the sluggish side so can't wait to pick its chin back up.
All sensors are functioning the way they should including MAF and TPS. ECU tables looked great and my shifting speeds were sooner than an OEM Camaro. What we did notice is that the fuel pump may not be working at its full capacity as its causing the knock sensor to kick in. Because of this, when the engine is getting a shortage in fuel, it is making sure it protects itself and changing some things around to compensate.
I'll be soon be swapping what ever fuel pump i have for a Racetronix fuel pump with with upgraded wiring harness and go from there to see if my problems get resolved.
Fuel pump does make sense as my power bands have always been variable. Days car feels great and other days it is just sluggish. Recently it has been staying on the sluggish side so can't wait to pick its chin back up.
