Re:03 Suburban 2500 Quad Steer - LSX 376 Swapped with Blower - Intermittent Stall

Here we go!

In July of 2020 I bought an 03 Suburban 2500 Quadrasteer with a swapped in GM LSX 376 B8 (58X reluctor) and a 2.9 Whipple supercharger. There is a lingenfelter module to adapt the reluctor signal to the 24X the ECM is looking for. We drove it from Reno, NV to Duluth, MN with no problems. It's been a fun rig for my wife to haul our 3 kids in. We were rear ended in December of 2020 in a Blizzard. Burb held up great (Car that hit us was totalled) and we decided to fix it. Got the frame straightened out and reinforcements welded in. Drove it for a few weeks with no issues. I replaced the damage reverse camera one Saturday and shortly after that started experiencing stalling while driving. I did not unplug the battery but its connects to the fused radio. I did try to activate the camera without ground connected but I'm not sure if that would do anything. connected ground and good to go. Sometimes it starts right back up after coasting off the road, Sometimes It will crank but not start. It will usually re-start if jumped or if you wait a while. Worst part - NO CODES or CEL.

Brought it to a shop and it never died for them, figures. $50 down the drain.

Suspected the charging system so I threw in a new alternator, no improvement. Had the battery (new in October 2020) tested at Advance auto and tested good. checked the wiring with ohmeter and alternator to battery and battery to ground beeped. looked for broken grounds and nothing seemed loose and I had continuity. Changed the crank position sensor because I had one handy.

Then, in desperation, I found ScannerDanner on Youtube, Started backprobing the alternator and I wasn't sure my readings were making sense. I'll add them here later. Feeling a little overwhelmed by all the "possible" issues I'm finding wwith no clear direction.

I do have VCM suit from HP tuners and the only thing that seemed off at idle were negative fuel trims. I did also see a tone of engine codes were disabled. I may try to re-enable the codes to give me some more direction.

Cleaned the MAP sensor near the airbox, and am going to clean the throttle body next. After that I'm gong to pull my plugs and check gaps.

I have a scanner on the way and picked up Pauls book.

I did find that the SBA supplemental Brake Assist) fuse was blown. Not sure if this is related to my issue or if braking while coasting off the road caused this. I changed the fuse and no improvement. Fuse has not re-blown.

Have not checked fuel pressure yet, but I have no reason to suspect it. Power was good, also fuel level is good per guage. I'd also filled it up recently enough to trust the guage.

Seems like if you keep the RPM's high it will stumble and come back instead of stalling. Drove it home in 2nd gear too keep them up after it died on my 3 times in a mile or so.

Burb is parked in the driveway right now and tried to start it yeasterday with good crank no start at all. Could be that battery voltage is below some threshold? Seems weird to me that it will usually start if jumped but it cranks fine when not jumped. I did not jump it yesterday. Hoping the tool gets here and I can see the issue.

I'm going to be the wiser for fixing this thing, but getting my tail whipped right now. Looking forward to no longer being a parts changer.

-Brady

Some pictures below

I would like to know what fuel pressure is doing when this happens certainly worth renting a gauge from your local parts store if you don't own one, another thing is when its being jump started where are the jumper cables being connected? (Positive and negative of battery or elsewhere) does the amount of amperage load seem to make a difference? eg headlights on wipers on defrost on turn signals brake lights Yada yada. what ignition system does this engine have? Alot of the codes turned off in the tune are probably not any help the reason to turn them off is there values would not be what the computer expects anyways.

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I would like to know what fuel pressure is doing when this happens certainly worth renting a gauge from your local parts store if you don't own one, another thing is when its being jump started where are the jumper cables being connected? (Positive and negative of battery or elsewhere) does the amount of amperage load seem to make a difference? eg headlights on wipers on defrost on turn signals brake lights Yada yada. what ignition system does this engine have? Alot of the codes turned off in the tune are probably not any help the reason to turn them off is there values would not be what the computer expects anyways.

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I do hear the fuel pump kick on wen the key is on. I'll get a fuel pressure reading next time I'm working on the vehicle. It has an aftermarket fuel pump ( walbrofuelpumps.com/450lph-walbro-e85-ra...-f90000267.html.html )

Jumping is of the GM post in the red box and the alternator body, but I've also done it on the TINY gm side posts.

haven't noticed a change in cranking speed when I jump it, just that when jumping it it starts and when not jumping it sometimes starts. I will try turning everything on/off and see what it does.

It has the facory EFI ignition system but it's plugged into this: ( www.lingenfelter.com/product/L460065397.html#.YJRGGB-SmUk ) before the crank and cam sensors. This is so it can use Gen 4 engine sensors with my Gen 3 system. I am slightly suspicious of the wiring for this and the crank sensor because it's routed close to the aftermarket JBA headers in some kind of heat jacket. It's got aftermarket injectors, plug wires etc.

One other thing is it has a Viper anti theft/autostart system. This has exhibited no strange behavior so I don't expect that this has anything to do with vehicle ATS.

I,ve had some issues with broken/ missing body and frame ground straps on chevys causing no start and when jump starting them you would get enough current to flow through whatever fasteners was still making the connection.( the fuel pump could run but would'nt be able to make enough pressure to start the vehicle) it may be worth doing voltage drop test on the body and frame while it is doing its crank no start. if you dont have a DVOM you could also do a quick and dirty test by connecting a jumper cable from batter ground to the frame and again to brake master cylinder and see if it starts

also I just seen the pictures and your voltage is 11.76??? I cant make out what wire is being tested if that is battery voltage that very well could go to low during cranking for the pcm to operate.

I'll post up the wiring diagram this evening with respective tested voltage. Battery tested 12.6 across the posts if I recall.

Ben wrote: I,ve had some issues with broken/ missing body and frame ground straps on chevys causing no start and when jump starting them you would get enough current to flow through whatever fasteners was still making the connection.( the fuel pump could run but would'nt be able to make enough pressure to start the vehicle) it may be worth doing voltage drop test on the body and frame while it is doing its crank no start. if you dont have a DVOM you could also do a quick and dirty test by connecting a jumper cable from batter ground to the frame and again to brake master cylinder and see if it starts

I was thinking the same, particularly the ground for the fuel pump on the frame in the rear of the truck.
I second a fuel pressure reading when the truck is acting up.

Didn't get to the wiring diagrams last night, but I will take a good look at the ground for the fuel pump. I appreciate the direction.

Bkorwin wrote: Here we go!

In July of 2020 I bought an 03 Suburban 2500 Quadrasteer with a swapped in GM LSX 376 B8 (58X reluctor) and a 2.9 Whipple supercharger. There is a lingenfelter module to adapt the reluctor signal to the 24X the ECM is looking for. We drove it from Reno, NV to Duluth, MN with no problems. It's been a fun rig for my wife to haul our 3 kids in. We were rear ended in December of 2020 in a Blizzard. Burb held up great (Car that hit us was totalled) and we decided to fix it. Got the frame straightened out and reinforcements welded in. Drove it for a few weeks with no issues. I replaced the damage reverse camera one Saturday and shortly after that started experiencing stalling while driving. I did not unplug the battery but its connects to the fused radio. I did try to activate the camera without ground connected but I'm not sure if that would do anything. connected ground and good to go. Sometimes it starts right back up after coasting off the road, Sometimes It will crank but not start. It will usually re-start if jumped or if you wait a while. Worst part - NO CODES or CEL.

Brought it to a shop and it never died for them, figures. $50 down the drain.

Suspected the charging system so I threw in a new alternator, no improvement. Had the battery (new in October 2020) tested at Advance auto and tested good. checked the wiring with ohmeter and alternator to battery and battery to ground beeped. looked for broken grounds and nothing seemed loose and I had continuity. Changed the crank position sensor because I had one handy.

Then, in desperation, I found ScannerDanner on Youtube, Started backprobing the alternator and I wasn't sure my readings were making sense. I'll add them here later. Feeling a little overwhelmed by all the "possible" issues I'm finding wwith no clear direction.

I do have VCM suit from HP tuners and the only thing that seemed off at idle were negative fuel trims. I did also see a tone of engine codes were disabled. I may try to re-enable the codes to give me some more direction.

Cleaned the MAP sensor near the airbox, and am going to clean the throttle body next. After that I'm gong to pull my plugs and check gaps.

I have a scanner on the way and picked up Pauls book.

I did find that the SBA supplemental Brake Assist) fuse was blown. Not sure if this is related to my issue or if braking while coasting off the road caused this. I changed the fuse and no improvement. Fuse has not re-blown.

Have not checked fuel pressure yet, but I have no reason to suspect it. Power was good, also fuel level is good per guage. I'd also filled it up recently enough to trust the guage.

Seems like if you keep the RPM's high it will stumble and come back instead of stalling. Drove it home in 2nd gear too keep them up after it died on my 3 times in a mile or so.

Burb is parked in the driveway right now and tried to start it yeasterday with good crank no start at all. Could be that battery voltage is below some threshold? Seems weird to me that it will usually start if jumped but it cranks fine when not jumped. I did not jump it yesterday. Hoping the tool gets here and I can see the issue.

I'm going to be the wiser for fixing this thing, but getting my tail whipped right now. Looking forward to no longer being a parts changer.

-Brady

Stop running down the rabbit hole. Disconnect the radio, radio harness and see if that helps. If it has a security bypass module check that and make sure it's not melted, or any other issues with it as I've seen them go bad in the past. I wouldn't be turn on the parts cannon at it, chasing other things until I'm sure that the electrical revolving around the radio and/or camera is isolated and working properly and without issues going down the road. If someone else did the reinforcing such as welding check harness as well as even some slag from welding can cause big issues if left undetected.

Let us know what you find.
If you need any readings, troubleshooting how to's, etc private message me as I've saved alot of troubleshooting stuff.

The rabbit hole is a deep, dark, and desperate place. The fuel pump wiring is relatively close to where the welding, seems I need to go take a look there. I pulled the radio out with no change but I didn't disconnect my camera wire. I'll do that and report back.

Got out with the scan tool last night and made the following notes:

1. There is no fuel pressure port on my Whipple fuel rails. There is a bung for one, so I need to get something that fits in there.

2. Battery voltage was 11.5, threw on a jump pack and I was up to 13. Threw on the battery charger and this morning I had sulfuric acid on my work bench. looks like that was an issue though I'm not confident it is THE issue. we'll see once I can get to costo to warranty this one out.

3. No RPMs on crank, I suspect the wiring to the crank position sensor. or the TRG-002 module. Cranked great with the 13volts off the jump pack.

4. Disconnecting the radio did nothing for me.

5. Looked for the fuel pump ground strap and couldn't find it. Need to look when it's not cold and dark.

6. Cleaned the throttle body just because I wanted to feel like I was accomplishing something. checked the wiring and connections and no issues visible.

7. There's a module that goes bad in the windshield wiper system. I have anew one to swap in, may as well do that while I'm doing this.

Need to check the Viper security bypass module and see if it seems ok.

Got into the vehicle yesterday,

Found that my wiring loom going to the crank and cam sensor were both melted. Pulled the harnesses out and will be testing wire continuity to see if I found my issue. hoping after I get this back in I get my RPM signal back.

Also have the fitting I need to check fuel pressure. More updates to come.

Good to hear !

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Got the wires relocated away from the headers and tried it last night. the Lingenfelter module was displaying a "no crank in" error.

Also dud out my autostart system and no blown fuses and it generally checks out. At this point I feel pretty good about ruling out the possibility that my issue is related to my reverse camera install.

Thoughts,

1. Need to test my system under load to see why my voltages are at my sensor. I have continuity but I'm suspecting there is something gong on inside my wires. Just have a multimeter but Paul to the rescue:
()

2. Could be a crank sensor but it's brand new higher quality unit (Autozone Duralast Gold). So I'm not thinking so. It's also grey which is the right one for a 58X reluctor wheel. Might put the one that was in it before I swapped it out just to remove that variable.

3. Something wrong in my connectors.

4. Bad Lingenfeltor module, fortunately I do have a spare I could throw on if is comes to that.

4. Something else on the reference circuit that's throwing the crank signal out of whack. (shorted sensor or ECM)

To be continued...

Got down to testing voltages, my saving grace was that the issue was no longer intermittent. This made my path a LOT more linear.

on the 5V side of my module everything checked out. On the 12V side I had 12V at the OEM harness, and only 100MV on the wire in the other side. This to me meant either the Lingenfelter module, the wiring, or the connecter were bad.

I wiggled the connector and wiring and suddenly got 10.5 V. From under the vehicle I yelled HA! and went to crank it and it fired right up. Guess the Camera install was a unrelated. 

I should have back probed the harness to know if it was the wire or the connector but I got so excited I forgot to check. I also should have wigged it some more with the engine running to see if it killed it but I had bare wires near the headers so I didn't let it run long.

I'm re-doing and re-locating the wiring anyway because it was melted from the exhaust piping. 

Thanks to all who offered direction. This has been quite the learning experience. I'm very familiar with mechanical repairs but this was the first electrical head scratcher I've dealt with, and the fact that so much of my engine bay and PCM is not factory really threw me for a loop.

If I could do it again I'd follow this path instead of checking what felt like every ground for continuity, checking for vac leaks, fuel pressure, worrying about my PCM and how I'm going to re-tune it, wondering if my autostart is broken, taking it to a shop so it could not exhibit issues for them, running down the rabbit hole etc.:

Notice problem with vehicle and put on advanced scan tool > Know that my PCM cannot throw "x" codes and not worry about it* > start recording and Note no RPM's on crank/RPM loss before it dies > Check for 5V Ref, ground, and 5v output at sensor plug > Check for 5V Ref, ground, and 5v output at input side of Lingenfelter Module > Check for 12VRef, ground, and 12v output at output side of Lingenfelter module. Note low voltage on input side >  check OEM output > Find short in connector or wiring >FIX!!!

*I didn't know that a bunch of DTC codes were disabled due to the motor swap when I started.

I'll post up some pictures once it's all back together.