LS Engine Help Please
Discussion
Guys
I'm hoping someone out there may know of a fix? Engine is a stock crate unit from PW Performance. Original Pedal, ECU & Loom are from American Speed.
OUTLINE OF PROBLEM
The car drives fine at normal & medium speeds with up to approx ¾ throttle applications. If you apply FULL throttle the car pulls good & strong and keeps pulling until you lift, even slightly (feather) then it cuts down to about 4-cylinders and will not react to any throttle movements. It does this both on the road and sat in the workshop with just the ignition on. (you can watch the throttle butterfly move with pedal movements.) If you turn the ignition off and then on it clears and drives normally. The problem occurs on about 90 – 95% of full throttle requests. The Throttle Butterfly does not appear to be binding or snagging.
Because of the performance potential, all tests on the road have been done at low revs and low road speed in 4th & 5th gear (1.75k – 2.25k revs when full throttle is applied)
OBD2 codes from ECU are (taken on 5 different occasions) ECU has been cleared after each reading.
P1516 or P2101 every time. Normally both codes appear
P0122 and P0223 have appeared twice
P0833 has appeared once! (Clutch Switch)
P0101 MAF has occurred twice.
P0650 MIL Light – not connected.
Actions taken so far are to change the Throttle Pedal. (We had a Corvette one fitted and have now fitted a GM one believed to be from a Cadillac from PW Performance.) This made no difference. Problem still existed. We have now changed the Throttle Body to another LS7 one and the problem still exists!
(Thanks to Kyle for donating a spare TB to try & fix the problem)
I'm hoping someone out there may know of a fix? Engine is a stock crate unit from PW Performance. Original Pedal, ECU & Loom are from American Speed.
OUTLINE OF PROBLEM
The car drives fine at normal & medium speeds with up to approx ¾ throttle applications. If you apply FULL throttle the car pulls good & strong and keeps pulling until you lift, even slightly (feather) then it cuts down to about 4-cylinders and will not react to any throttle movements. It does this both on the road and sat in the workshop with just the ignition on. (you can watch the throttle butterfly move with pedal movements.) If you turn the ignition off and then on it clears and drives normally. The problem occurs on about 90 – 95% of full throttle requests. The Throttle Butterfly does not appear to be binding or snagging.
Because of the performance potential, all tests on the road have been done at low revs and low road speed in 4th & 5th gear (1.75k – 2.25k revs when full throttle is applied)
OBD2 codes from ECU are (taken on 5 different occasions) ECU has been cleared after each reading.
P1516 or P2101 every time. Normally both codes appear
P0122 and P0223 have appeared twice
P0833 has appeared once! (Clutch Switch)
P0101 MAF has occurred twice.
P0650 MIL Light – not connected.
Actions taken so far are to change the Throttle Pedal. (We had a Corvette one fitted and have now fitted a GM one believed to be from a Cadillac from PW Performance.) This made no difference. Problem still existed. We have now changed the Throttle Body to another LS7 one and the problem still exists!
(Thanks to Kyle for donating a spare TB to try & fix the problem)
Sounds like it's cutting into some sort of safety map. Once into this 4 banger mode does the throttle blade still seem to get fully open if you want it ?
Can you get into the software and see the throttle % opening ?? Perhaps the 100% area needs calibrating ??
Not dealt with the GM stuff..... Post a request on the LS1 Tech forum bud..
Can you get into the software and see the throttle % opening ?? Perhaps the 100% area needs calibrating ??
Not dealt with the GM stuff..... Post a request on the LS1 Tech forum bud..
GTRCLIVE said:
Sounds like it's cutting into some sort of safety map. Once into this 4 banger mode does the throttle blade still seem to get fully open if you want it ?
Can you get into the software and see the throttle % opening ?? Perhaps the 100% area needs calibrating ??
Not dealt with the GM stuff..... Post a request on the LS1 Tech forum bud..
Yes, the ECU is going into some kind of LIMP MODE. No the throttle will not respond once it has gone into this mode. All you can do is cost to the side of the road. Switch off & start again. No access to the software. We only have OBD2.Can you get into the software and see the throttle % opening ?? Perhaps the 100% area needs calibrating ??
Not dealt with the GM stuff..... Post a request on the LS1 Tech forum bud..
IS this a stock factory/crate engine ?
Had very similar on a cammed version with GM controller... had to turn off one of the throttle trim features.. engine would start surging then the throttle blade became unresponsive and cut out.
Mechanically..... air leaks (in one case I read a crate motor had a missing intake port seal as supplied)
Had very similar on a cammed version with GM controller... had to turn off one of the throttle trim features.. engine would start surging then the throttle blade became unresponsive and cut out.
Mechanically..... air leaks (in one case I read a crate motor had a missing intake port seal as supplied)
It's an LS7, stock with the LS7 throttle body.
Our most recent investigations show a few thing to add in the mix.
With the throttle body laying on top of the engine, (engine not running) ignition on, you can watch the throttle opening and closing. You can do this as much as you like without problems as long as you keep moving. At full throttle you can also hold it there as long as you like. As soon as you feather the throttle the butterfly slams shut and will no longer respond to the pedal. Switch of and back on again and all is well.
Whilst playing these games we found that the throttle body had gone to fully open before the pedal was fully down, about 25mm remaining travel. This would likely be why the OBD codes talk about a mismatch between the throttle position and the predicted throttle position.
We could likely cure this by adjusting the throttle stop behind the pedal but that feels like a cheat and does not address the actual problem.
Finally a question for other LS7 owners. Is your throttle butterfly plate bare brass or silver plated?
Seems there may have been a change and the later (Brass) ones have a different gearing in the throttle body.
We don't understand why nobody has had these problems before us.
Steve
Our most recent investigations show a few thing to add in the mix.
With the throttle body laying on top of the engine, (engine not running) ignition on, you can watch the throttle opening and closing. You can do this as much as you like without problems as long as you keep moving. At full throttle you can also hold it there as long as you like. As soon as you feather the throttle the butterfly slams shut and will no longer respond to the pedal. Switch of and back on again and all is well.
Whilst playing these games we found that the throttle body had gone to fully open before the pedal was fully down, about 25mm remaining travel. This would likely be why the OBD codes talk about a mismatch between the throttle position and the predicted throttle position.
We could likely cure this by adjusting the throttle stop behind the pedal but that feels like a cheat and does not address the actual problem.
Finally a question for other LS7 owners. Is your throttle butterfly plate bare brass or silver plated?
Seems there may have been a change and the later (Brass) ones have a different gearing in the throttle body.
We don't understand why nobody has had these problems before us.
Steve
Gulf LS3 said:
yes it is...... you spoke to Rich yet Paul
Yes mate. I have also emailed Gail. Following on from my conversation with Rich I am asking the question re the early/later TB's with differently geared drivers. Having so much travel left after the butterfly has reached fully open is a concern. Especially when all the issues lie within this area of pedal travel. I'm hoping it is a simple case of the ECU needing a tweek to deal with the faster operating driver unit.We had concidered simply moving the pedal stop forward but felt this would simply mask the problem rather than solve it!
Magic919 said:
Have you checked the voltage being fed to it?
It would seem a difficult job to do! The ECU sends no feed to the TB/TPS unless it is plugged in (they appear to do some kind of hand shake when you turn the ignition on) and getting a probe in behind on the multiplug is not possible. The check voltage pin is reading within 0.02v of the 5v it should be.Can anyone suggest an easier way to check these measurements?
Where is the ECU fitted....are you using an extended pedal loom or patch lead, if so have you tested a stock unmodded pedal loom..has it ever worked properly at all ??
Had a loom issue on the dyno not too long back....not so easy to find and those micro pin connectors soon become dislodged if not fully seated .
Had a loom issue on the dyno not too long back....not so easy to find and those micro pin connectors soon become dislodged if not fully seated .
Edited by 738 driver on Friday 29th July 19:56
Paul, having exchanged pedals and T/B's, the loom/connectors have to be next or very finally a fragmented ECU/map.
Am unfamiliar with the A/S kit/loom but assume its either stock GM or one they have made up.
An improperly crimped connector was the fault traced on a dyno motor recently, not at all visible when assembled.. many hours and two previous visits to the dyno trying to sort this 'crap engine youve built Capt'... lots of strange running faults displayed.... one poor injector connection had the ecu trying to compensate in all sorts of ways...
.... it soon transformed into a monster engine..
Electrics are fantastic when they are working.
Good luck.
Am unfamiliar with the A/S kit/loom but assume its either stock GM or one they have made up.
An improperly crimped connector was the fault traced on a dyno motor recently, not at all visible when assembled.. many hours and two previous visits to the dyno trying to sort this 'crap engine youve built Capt'... lots of strange running faults displayed.... one poor injector connection had the ecu trying to compensate in all sorts of ways...
.... it soon transformed into a monster engine..
Electrics are fantastic when they are working.
Good luck.
738 driver said:
Paul, having exchanged pedals and T/B's, the loom/connectors have to be next or very finally a fragmented ECU/map.
Am unfamiliar with the A/S kit/loom but assume its either stock GM or one they have made up.
An improperly crimped connector was the fault traced on a dyno motor recently, not at all visible when assembled.. many hours and two previous visits to the dyno trying to sort this 'crap engine youve built Capt'... lots of strange running faults displayed.... one poor injector connection had the ecu trying to compensate in all sorts of ways...
.... it soon transformed into a monster engine..
Electrics are fantastic when they are working.
Good luck.
If this were a wiring fault/bad connection you would expect it to.....Am unfamiliar with the A/S kit/loom but assume its either stock GM or one they have made up.
An improperly crimped connector was the fault traced on a dyno motor recently, not at all visible when assembled.. many hours and two previous visits to the dyno trying to sort this 'crap engine youve built Capt'... lots of strange running faults displayed.... one poor injector connection had the ecu trying to compensate in all sorts of ways...
.... it soon transformed into a monster engine..
Electrics are fantastic when they are working.
Good luck.
Be there all the time and throughout the throttle range.
Be intermittent.
Be there only when engine is vibrating.
When hot or cold.
However it is none of these and is very specific…Only happens at wide open throttle and only happens if you have held full throttle for a few seconds then released it. If you go WOT and back off straight away it does not do it.
Steve
Steve_D said:
If this were a wiring fault/bad connection you would expect it to.....
Be there all the time and throughout the throttle range.
Be intermittent.
Be there only when engine is vibrating.
When hot or cold.
However it is none of these and is very specific…Only happens at wide open throttle and only happens if you have held full throttle for a few seconds then released it. If you go WOT and back off straight away it does not do it.
Steve
I have a mate who is building a car locally hear, he works for the biggest auto maker. even had access to the engineering development and diagnostics computers. and even this could not prevent the electronics from not picking up that one of the earth leads in the loom was not connecting properly.Be there all the time and throughout the throttle range.
Be intermittent.
Be there only when engine is vibrating.
When hot or cold.
However it is none of these and is very specific…Only happens at wide open throttle and only happens if you have held full throttle for a few seconds then released it. If you go WOT and back off straight away it does not do it.
Steve
Car would run up through the rev range and drive ok, even if somewhat down on power. Went for the emmissions test and it was a pig, overly ritch to the point where it was preventing the cat from getting up to temperature and lighing off. No codes come up what sowever as the computer was reading values that it thought were correct from the O2 sensor. Problem was there was a whole lot of extra resistance in the loom as the earth wasnt making properly.
Im not sure how smart the GM stuff is. I know that the ford drive by wire pedal for the falcon has 2 sensors in it to measure position, a double pole potentiometer if you will.
Ill think about it some more, dont have any answers at the moment.
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