LQ4 swap issues

[Red Alert]

Hi everyone, name is Craig and I am a new member here obviously, and have some issues with my latest project that I sure hope some of you can assist with :)

Details, my son and I are working on a 1979 Olds Cutlass with the factory Hurst option (gold/white car), bought it with no engine and transmission, after finding a donor 2005 Silverado HD with the LQ4/4L80 and all needed parts to complete this swap.

I have a 1971 C10 that I did a previous LQ4 swap into with great success about 4 years ago still running strong so I have done this before.

All harness mods were done by me referring to LT1swap.com, great site BTW.

Anyhoo, we got everything bolted in, very little custom work to make it drop right in, except the exhaust which I struggled with but after denting up a used set of Chevelle Edelbrock LS1 swap headers fit right in. The engine runs good, fires right up, idles high but smooth. BUT, here is the issue, we cannot get the drive by wire throttle to work. Well, it did work for a short period of time, then very intermittent, now nothing. We get key on trigger to it (hear the motor closing the blade when the key is turned on) but very quickly after the engine fires we have no throttle.

SO far this is what I have done, replaced the pedal sensor, we modified the pedal and did some welding to the arm so I just bought a new sensor thinking that might be it but no change in anything, so back to square one.

I have read the codes, and here they are:
P0120
P0220
P0758
P1516
P2761
P2101
P2135

Lots of codes, any direction that I can start with? I have not replaced the throttle body OR the TAC module which match the harness and computer (came out the donor truck)

[joecar]

Great project :cheers:

So engine, trans, PCM, throttle pedal, TAC all came from same donor vehicle...?

Hi idle indicates an air leak.

[Red Alert]

Thanks joecar, we just kind of stumbled on this car on CL when we were looking for a recipient for the engine/trans/

Yes, all of the systems came from the same truck, nothing has been changed. High idle, I guess I should have explained better, the idle when I first fire it up is normal, then when the throttle decides it does not want to work (which is all the time now) it will go from normal to higher like around 1200 rpm.

[Red Alert]

One of my sons friends are bringing by a data reader today so I can dip further into this. I just read a P1125 now, this thing is a mess :) What info do I need to pull from the PCM?

[Jetmech442]

Aside from rpm and ect, I'd say grab the 5 throttle pids :SAE .App_A and b, as well as sae. Tp(absolute, B, and relative).

Sorry I just have a second to post, so search absolute and "B", iirc they should be exact opposite of each other or else the tcm thinks it's a pedal issue and freaks out.

I haven't looked up those codes to see what they mean, maybe someone else has and it will point to showing me definitive.

Sent from my Nexus 6P using Tapatalk

[Red Alert]

I put a multi meter on the A and B circuits off of the pedal key on, A has about .80V at rest and evenly rises to over 3V. Circuit B has the exact same, not the opposite, this would be my issue? It's a brand new pedal sensor, why would this be different than designed?

[Jetmech442]

No, I must be remembering wrong. I thought they were opposite. I'm under the car right now, or I'd check.

You can log these channels if you feel it is connected. Obviously getting a capture of the right pids when it shuts itself off would be ideal. Sorry if there's any typos in having Google do the speach to text...

Sent from my Nexus 6P using Tapatalk

[joecar]

Is this your vehicle:
2005 Chevrolet Chevy C Silverado - 2WD (http://127.0.0.1:9001/servlets/SMSCTSrv?bookid=50&booktypeid=1) - 4.8L, 5.3L, and 6.0L (http://127.0.0.1:9001/servlets/SMSIT?bookid=50&booktypeid=1&SCT=Engine&svc_cat_no=4&sec_id=1&SC=Engine+Controls+-+4.8L%2C+5.3L%2C+and+6.0L&mspsdsubkey=4250)


The attached files may help.

[Red Alert]

Thanks for the links and info, sorry for the delayed reply I have been a busy employee this week...

I have a scan tool today (Bosch OBD1150) so if that has the ability to read what the throttle body is seeing I will post the results here tonight.

[Red Alert]

This code reader is not giving me the info that I need, but it does say that the TPS is at 99.6%? Dunno what that means

[Jetmech442]

99.6 during what condition? When I key on engine off (koeo), the ecm command shut. I would think that means close to zero, but I'll try and grab a quick scan tomorrow to verify.

Can't remember, did you say you replaced the tps sensor already?

Sent from my Nexus 6P using Tapatalk

[Red Alert]

KOEO, yes. I have not replaced anything but the pedal sensor which did not change anything that I can see.

[joecar]

This code reader is not giving me the info that I need, but it does say that the TPS is at 99.6%? Dunno what that means

You could use the EFILive scantool to read sensors and DTC's.

[Red Alert]

You could use the EFILive scantool to read sensors and DTC's.

New to this, how do I go about using this tool?

[joecar]

Start V7 scantool, then do this:
- File->Connect, should see Connect button go dim and Disconnect button go red.
- Might have to go File->Select Controller and choose your PCM/ECM.
- Might have to go File->Enter VIN and enter your vehicle's VIN.
- Go Info->Validate Pids, wait for it to finish.
- Goto PIDs tab.
- Uncheck Supported.
- Set System to All.
- Select (double click on) some pids, include GM.ETCTP and GM.APP (you will have to select some others, i.e. play with it).
- Make sure your selected pids do not have a red X (if they do, on those pids go rightclick->More info to see why).
- Goto Dashboard tab, goto subtab B.
- If you don't see your pids on the dash B charts, goto a corner of one chart strip, do rightclick and choose the pid you want in that corner (e.g. ETCTP).
- Click the red record button at bottom of window.
- Goto Data tab to see logging data.
- Goto Dashboard tab, goto subtab B, you should see chart waveforms updating.

Then for OBD-II data, stop recording, and go Info->Diagnostic Trouble Codes.


( BTW: there is a V7 scantool user manual pdf that you should work your way thru )

[Red Alert]

Thank you joecar

Out of curiosity we drilled the rivets out of the factory TPS, pulled the switch off the throttle motor and we found water in there. The large gear is rusting, and looked like large droplets of water were sitting in the inside of the switch. I took an air hose and blew the switch out, smelled musty and water did come out of the switch cavity, by the way is sealed. Think this was the issue?

I ordered a new TPS, will be here tomorrow via AMazon (Dorman part)

[joecar]

Yes, I think your TPS is bad due to water damage.

$0.02

[Jetmech442]

Geez, that's a good find red alert. Not sure I would have had the guts to drill out rivets and check. Should go a lot smoother for you now hopefully.

Sent from my Nexus 6P using Tapatalk

[Red Alert]

Thanks, i olny did that due to your suggestions on this site :cheers: Plus I hve been working on cars for 30+ years, not much scares me anymore :)

I did replace the TPS and voila' we have throttle :notacrook: I took it for a short drive, engine runs good, throttle response is right where it should be.

Ahh, feels great to solve this one, I was just about to hit my head on something, I felt defeated for a while...

BUT, there i always one, I still have codes I need to solve before really driving this car because the trans is not shifting:
0758-shift solenoid B
0753-shift solenoid A
2761-Converter lockup

All sound complicated, but I am not afraid to dive into the trans again as I have already have had it all apart converting it to a 2WD from 4WD.
Any guidence here? I do have voltage at all pink wires in the harness at the connections down at the trans.

[joecar]

Thanks, i olny did that due to your suggestions on this site :cheers: Plus I hve been working on cars for 30+ years, not much scares me anymore :)

I did replace the TPS and voila' we have throttle :notacrook: I took it for a short drive, engine runs good, throttle response is right where it should be.

Ahh, feels great to solve this one, I was just about to hit my head on something, I felt defeated for a while...

+1 not scared of much anymore... it's just that anything takes a lot of time (remove A to get to B, remove B to get to C, remove C to get to D...).

Good job :cheers:



BUT, there i always one, I still have codes I need to solve before really driving this car because the trans is not shifting:
0758-shift solenoid B
0753-shift solenoid A
2761-Converter lockup

All sound complicated, but I am not afraid to dive into the trans again as I have already have had it all apart converting it to a 2WD from 4WD.
Any guidence here? I do have voltage at all pink wires in the harness at the connections down at the trans.Make sure wiring has continuity and good connections (zero voltage drop)(may have to test live with piercing probes; fill holes in with lacquer), check connector terminal pins for contact.