Mad Customs

[0xDEADBEEF]

This is a Summit brand exhaust for a NBS reg long bed truck. I think all we need to do is take that extra length out of the mid pipe and it should work. There's a long straight section that should be easy to cut. It bolts up to the factory NBS y-pipe that I am using. Now we can do some tuning without pissing off the neighborhood. It's a "turbo" style muffler so it should be quiet-ish, also it looks like it necks down 1/4" inside. He doesn't the need the power it kills anyway.

It would have been cheaper to take it to an exhaust shop I'm sure, but it's all mandrel bends and I don't have to fuss with my trailer.

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[0xDEADBEEF]

Sounds great. A lot mellower. Deeper and quieter too. When you get in the mid-range rpm it sounds mean.

I drove down the street and back. The trans shifts. It drives like crap though. It literally won't get out of its own way until probably 3500 rpms and then it takes off like the proverbial bat outta hell. I definitely need to fix that because a new driver would end up rear ending someone within a few traffic lights. I think it needs a lot more timing down low, or something. It does not want to run there.

HP Tuners is fighting me. It won't let me license the tune file in the PCM so that I can try to fix any of that stuff.

 

[0xDEADBEEF]

I got hpt to work starting with someone else's stock LM7 tune. I bumped up the idle RPM and fixed the tach. I had to set the tach resolution to 3, which I guess makes sense ... 24/3 = 8. I guess the OBS dash is different and doesn't want the 4 cylinder tach like the later trucks.

It idles great until you give it gas and then it really doesn't want to run until it gets to 2000 rpms. Very similar to my drive earlier.

 

[stutaeng]

Man that is just Awesome! You are making strides!

I'm installing a shower door... Your day sounds more exciting than mine! LOL

 

[0xDEADBEEF]

Man that is just Awesome! You are making strides!

I'm installing a shower door... Your day sounds more exciting than mine! LOL

My wife decided she wants a new couch so we spent 4 hours looking at couches this morning. It wasn't very exciting. LOL. I was ready to buy anything just to get out of there, but she couldn't make up her mind.

I took a look at the logs and one bank has the LTFT pegged at 25. I think that's part of the problem.

 

[stutaeng]

Is the LTFT 25% at idle? Does it change with increase in RPM? If the % lowers when you increase RPM (value gets closer to zero) then high likely a vacuum leak.

Otherwise:
The upstream O2 sensor on that same bank look okay? Waveform oscillates ok? Does it respond when you either a.) flip the throttle b.) spray some carb cleaner in the intake c.) unhook a vacuum hose? Also, look at the LTFT concurrently and see what they do.

 

[0xDEADBEEF]

Is the LTFT 25% at idle? Does it change with increase in RPM? If the % lowers when you increase RPM (value gets closer to zero) then high likely a vacuum leak.

Otherwise:
The upstream O2 sensor on that same bank look okay? Waveform oscillates ok? Does it respond when you either a.) flip the throttle b.) spray some carb cleaner in the intake c.) unhook a vacuum hose? Also, look at the LTFT concurrently and see what they do.

The vacuum leak theory makes sense because once the rpms get up above 2k or so it acts right and it pulls hard, and I've already fixed a couple so there could be more. I think I could disable the MAF in the tune and if it behaves better it's validation of the theory.

I've had O2 problems in other vehicles and they didn't even drive bad, but I'm going to check all the bolts and what not. My son did that work and he doesn't have that manly upper body strength yet. We did torque the manifold bolts to spec, but they could have backed off. I'll also check the switching. I don't have the log in front of me.

And to answer your question about the throttle, no it does not respond quickly at all. You have to ease into it or it just goes blehhhhhhh until the rpms come up. LOL. It reminds me of a bad accelerator pump, but I thought it could also be the tune.

 

[0xDEADBEEF]

First thing I did today was go over all the exhaust before the cats. Nothing was majorly loose, but I was able to get some extra oomph on the collector bolts. It started off this morning running good. I was able to give it throttle and it was responding. The O2s were bouncing around like you would expect. About 10 minutes into it bank 2 O2 is constantly low.

Went all over the intake with starting fluid, no changes noted. I decided to pull the brake booster hose and did exactly as expected, idled up and made hissing noise.

Uploaded the MAF disable tune and no change. At this point I don't think it's an exhaust or intake leak.

Exhaust is too hot to touch right now, but I think I'll swap the bank 1 and 2 O2 sensors next time I can and see if the problem moves or not. I think it has to be a problem with an O2 or an injector. The O2s are new. The injectors I got off craigslist with some other stuff.

 

[stutaeng]

It seems like O2s are working fine then, but swapping them is a good idea.

Without testing the injectors individually with that pulsing device, I would swap them between bank 1 and bank 2, then see if the lean bank also changes...if you can't find vacuum leaks.

BTW, I was able to get the injectors unstuck per your suggestion on my 99 project truck. I soaked them in some carb cleaner/seafoam mix, then powered them with a 9V battery. I did buy the OTC pulser to do an injector balance test, but haven't done it yet.

 

[0xDEADBEEF]

It seems like O2s are working fine then, but swapping them is a good idea.

Without testing the injectors individually with that pulsing device, I would swap them between bank 1 and bank 2, then see if the lean bank also changes...if you can't find vacuum leaks.

BTW, I was able to get the injectors unstuck per your suggestion on my 99 project truck. I soaked them in some carb cleaner/seafoam mix, then powered them with a 9V battery. I did buy the OTC pulser to do an injector balance test, but haven't done it yet.

That's great. Glad it worked. I should have tested mine before I installed them. Won't make that mistake again.