Problem with conversion using 2005 LQ4, will not run off idle
Thread Starter
Launching!
Joined: Sep 2009
Posts: 250
Likes: 3
Problem with conversion using 2005 LQ4, will not run off idle This issue is it idles like a champ. But any throttle and it bogs down.
Here is the setup:
Things I've done/tested so far:
Would a plugged fuel filter cause this? Even though it is still giving the right pressure reading.
Here is the setup:
- 2004 LQ4 from Silverado 2500HD swapped into an old Toyota Land Cruiser
- NV4500 swapped in place of the stock 4l80e it came with
- e8248 fuel pump
- Corvette regulator and filter combo(AC Delco P# GF822)
- exhaust leak on passenger side
- no cats
- VATS programmed out as well as rear o2 sensor (JET DTS programmer)
- STOCK harness with un-needed junk pulled(autotranny wires, rear o2 wires, and purge valve)... only the VSS wires were removed from the PCM plug and put back on.
- headers
- new hard and flex lines throughout (3/8" and 6an but also about 12" of 5/16" at tank)
- VSS installed
- Drive by wire system installed
- everything else stock
- I've got engine block grounded directly to the battery... all other stock grounds for the harness are at stock locations.
Things I've done/tested so far:
- fuel pressure is at 60psi
- soaked injectors in sea foam (no change)
- run engine with a can of sea foam and about 7 gal of 87 oct gas (no change)
- no engine codes aside from no MIL (P0650)
- checked the TB butterfly to ensure it opens both with and without the engine running
- replaced a E2000 fuel pump with e8248
- confirmed MAF functionality by pulling MAF away from TB as well as unplugging. Both cause the engine to idle like crap.
Would a plugged fuel filter cause this? Even though it is still giving the right pressure reading.
Thread Starter
Launching!
Joined: Sep 2009
Posts: 250
Likes: 3
As mentioned in my initial post, the TB is definitely moving with the throttle pedal.
Would the lack of transmission input cause an issue like this but not throw up any codes?
I've run the engine for about 10 minutes idling and never received any codes aside from the missing MIL.
On The Tree
Joined: Jun 2008
Posts: 102
Likes: 0
From: Covington La
you should check your fuel pressure at the rail mine did this same thing that was the problem. if you have 60 psi at the rail you said you maf is good and your tps is working idk other than that, but the fuel pressure was my issue.
edit: I would also ground the block to the chassis
edit: I would also ground the block to the chassis
Last edited by brandon1566; Sep 30, 2009 at 01:16 AM.
Thread Starter
Launching!
Joined: Sep 2009
Posts: 250
Likes: 3
you should check your fuel pressure at the rail mine did this same thing that was the problem. if you have 60 psi at the rail you said you maf is good and your tps is working idk other than that, but the fuel pressure was my issue.
edit: I would also ground the block to the chassis
edit: I would also ground the block to the chassis
Would a clogged fuel filter still give the right pressure but not flow enough fuel?
I will also double check that I grounded the block to the frame. I know the battery is grounded to the block.
I think that the pcm will put the DBW into a limp mode as described here.
Reduced Engine Power Mode
When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
Acceleration limiting- The control module will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
Limited throttle mode- The control module will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
Throttle default mode- The control module will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
Forced idle mode- The control module will perform the following actions:
Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
Ignore accelerator pedal input.
Engine shutdown mode- The control module will disable fuel and de-energize the throttle actuator.
If there's no VSS, you may get this type of problem.
A few $$ spent on a yrs sub to www.alldatadiy.com, is well spent. [Like <$40.00]
Do you have access to EFILIVE, etc?
Reduced Engine Power Mode
When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
Acceleration limiting- The control module will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
Limited throttle mode- The control module will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
Throttle default mode- The control module will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
Forced idle mode- The control module will perform the following actions:
Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
Ignore accelerator pedal input.
Engine shutdown mode- The control module will disable fuel and de-energize the throttle actuator.
If there's no VSS, you may get this type of problem.
A few $$ spent on a yrs sub to www.alldatadiy.com, is well spent. [Like <$40.00]
Do you have access to EFILIVE, etc?
Trending Topics
Thread Starter
Launching!
Joined: Sep 2009
Posts: 250
Likes: 3
Old Geezer thanks for that.
On the TAC module, I've got a few questions:
FWIW, I do have the FSM for this engine. All 5 thick books worth.
AFAIK, every thing attached to the engine came from the donor rig(ie MAF, TB, TAC, o2s, all sensors) The only thing that didn't come from the donor rig was the VSS and it was a new one from an autoparts store in a custom housing.
Jet DTS confirmed the PCM is what I was told the engine is from.
On the TAC module, I've got a few questions:
- Is there a way to verify it is the correct one for my PCM/engine(p# or something)?
- Will leaving all the cruise control wiring unconnected effect its function?
- If the throttle pedal causes the throttle body to move, does this say the TAC module is good?
- Does the TAC module require a special ground? Or is through the bolt to the mount sufficient?
- If the TAC is bad or faulty, wouldn't it throw a code? (as mentioned, I get no codes besides the missing MIL)
FWIW, I do have the FSM for this engine. All 5 thick books worth.
AFAIK, every thing attached to the engine came from the donor rig(ie MAF, TB, TAC, o2s, all sensors) The only thing that didn't come from the donor rig was the VSS and it was a new one from an autoparts store in a custom housing.
Jet DTS confirmed the PCM is what I was told the engine is from.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
TECH Fanatic
Joined: Jul 2005
Posts: 1,685
Likes: 7
From: Beebe, Arkansas
John,
I did you flash the PCM with a manual tune. I still think that might be your the problem if its still has the 4l80 tune.
The TAC should be OK, but read this! Info on DBW and TAC
Also let it idle and watch the TB and have someone get the gas and see if it moves and the engine dies or if it doesn't move and dies.
I did you flash the PCM with a manual tune. I still think that might be your the problem if its still has the 4l80 tune.
The TAC should be OK, but read this! Info on DBW and TAC
Also let it idle and watch the TB and have someone get the gas and see if it moves and the engine dies or if it doesn't move and dies.
Thread Starter
Launching!
Joined: Sep 2009
Posts: 250
Likes: 3
John,
I did you flash the PCM with a manual tune. I still think that might be your the problem if its still has the 4l80 tune.
The TAC should be OK, but read this! Info on DBW and TAC
Also let it idle and watch the TB and have someone get the gas and see if it moves and the engine dies or if it doesn't move and dies.
I did you flash the PCM with a manual tune. I still think that might be your the problem if its still has the 4l80 tune.
The TAC should be OK, but read this! Info on DBW and TAC
Also let it idle and watch the TB and have someone get the gas and see if it moves and the engine dies or if it doesn't move and dies.
On the TB, I tested it without the engine running and it followed the pedal. Would this change while running?
TECH Fanatic
Joined: Jul 2005
Posts: 1,685
Likes: 7
From: Beebe, Arkansas
Not 100% sure it is the correct direction. But mine has the word Flow and an arrow. I assumed the arrow points toward the throttle body.
I have not flashed the PCM for a manual tranny.
On the TB, I tested it without the engine running and it followed the pedal. Would this change while running?
I have not flashed the PCM for a manual tranny.
On the TB, I tested it without the engine running and it followed the pedal. Would this change while running?
Thread Starter
Launching!
Joined: Sep 2009
Posts: 250
Likes: 3
Yes, I've got the Jet DTS programmer.
I've also got a scanner with real time data logging. Diagnose by B. Roadman.
I'm currently looking at trying to convert my PCM for manual trans functionality. But Jet DTS documentation is a bit sparse so I'm being careful with what I change.
I did get a 4.8L manual tune and I'm currently checking differences.
I've also got a scanner with real time data logging. Diagnose by B. Roadman.
I'm currently looking at trying to convert my PCM for manual trans functionality. But Jet DTS documentation is a bit sparse so I'm being careful with what I change.
I did get a 4.8L manual tune and I'm currently checking differences.
Teching In
Joined: Feb 2009
Posts: 7
Likes: 0
From: SPRING,TX.
same problem Hey guys figure I'd share some input. I am having the same problem. I have 04- cts-v ls6. I currently have a fast 90/ls2 90 mm throttle body with piggyback harness. I bought a 90mm TPIC throttle body so I could go back to my original LS6 IAC and tps because I like the drive by wire response on the ls1/ls6 style better. Anyway, my car is going into limp mode also, I double checked everything and it was all good but still in limp mode and no cel. So.... I put my ls2 back on and no more problem what gives? The LS6 TB will open fully and close fully when the key is in ON mode, but when its at idle (which it barely does) it will not move. The check oil level kept popping up on the nav screen too. But when I went back to ls2 all was good.
You said you used a JET DTS programmer right. I am thinking your going to have to have the PCM flashed to a manual tune. The LQ4 had the NV4500 as a option for a number of years. I bet that will fix the problem. The PCM mostly thinks there is a problem with the trans (4l80) since it doesn't see one. It in limp mode.
Thread Starter
Launching!
Joined: Sep 2009
Posts: 250
Likes: 3
If I am understanding this correctly, if an automatic trans tuned PCM sees no transmission input, the PCM will go into limp mode. Is this correct?
If so, it sounds like a simple one parameter change using DTS
If so, it sounds like a simple one parameter change using DTS
TECH Fanatic
Joined: Jul 2005
Posts: 1,685
Likes: 7
From: Beebe, Arkansas
I don't think the DTS will do it. I would contact them and tell them your problem.
Thread Starter
Launching!
Joined: Sep 2009
Posts: 250
Likes: 3
I believe I set that on my intial tune but won't swear 100% to that. The problem is I am not sure if there are any related parameters that need to be set(if any) when the transmission type gets changed.
