Hey, just did a cam swap (Sum-8701 Stage 2 Truck Cam) on my 2001 Chevy Tahoe and replaced the lifters, pushrods, trunnions,springs, and even put a TBSS intake that has 36# injectors and a 92mm TB opening. I did a blackbear mail order tune as well which might be part of my problem I suspect.

Ever since we put it back together I've had a P0121 and P0122 code with and unstable idle. It also drives by itself up to about 30mph depending on where the set screw is on the TB. While it's doing this you can hear the air getting sucked through my K&N cai.

Here is everything I've done so far.

Cleaned the MAF per Blackbear's instructions.

Replaced TPS and the connector.

Tested the TPS signal voltage. It was far below .45V at idle.
- ended up drilling out the holes on the sensor to adjust it and I was able to get it maxed at .54V at Idle but couldn't get it over 4.24V

I noticed that the braided ground wire that is in the same harness as the engine bay light was no longer connected. I fixed that. I also just bypassed the grounds on the back of the head in case those connection points were corroded, I put those on the firewall with the other braided ground.

Cleaned the new TB with CRC brand cleaner.

I've followed the steps for an IAC relearn for a DBC TB.
-set the screw until my scanner read 2% throttle, unplugged things, turned the key on and off etc.

That didn't give me the idle I wanted or get rid of the TPS codes.

I tried the IAC relearn again at 1.5% throttle and it got worse and dies after running idle after 30 seconds.

Ended up going to 4% throttle on the relearn. Idle got more a stable but still dies after 30 seconds.

Currently the signal voltage is .47V act idle, still have P0121 and P0122. I also have lean codes for bank 1 and bank 2.

I'm lost. Is this a tune problem or a calibration problem?

 

Took the intake off completely. Replaced the gaskets cause it was pinched in some spots. Verified no leaks on any part of the intake or vacuum lines.

STILL have p0121. But I seem to have got rid of the lean codes

I could use input..

I'm going to test continuity between tps and pcm today. I dont know what that is going to solve since I've already verified the TPS works and is within voltage spec.

 

Bueller? I mean damn, I got nothing left to do but rip on Blackbear Performance's support. It's nonexistent. Whatever you do don't do a mail order tune. I hear his in person tunes are great. But he is either over loaded with work, or else doesn't care enough about tech support to be bothered to respond to emails in a timely manner.

Every correspondence has been him saying it's something wrong on my end. There's nothing left to do troubleshoot.

Does anybody have any suggestions?

 

You just turn that code off in the tune. From memory, its just a sanity check for the PCM. It basically looks at your TPS and see it's closed, but then sees the MAP signal is too "high" (not enough vacuum) and assumes the TPS is faulty, when in actual fact the PCM just doesn't know it has a big cam in there causing the low idle vacuum.

Once you slot a cam in, most people turn off p0300 but forget about that one.

Edit: sorry just re read your post, the driving on and not idling bit I missed. Regardless of TPS % or voltage, if you can get it to idle at all, what is your IAC count?

Edit 2: more specifically, in HPtuners, you can adjust the parameters of the sanity check rather than just turning the code off.

 

This is what I've been wondering and trying to get the guy at Blackbear to figure out. Something about min MAP and Max MAP settings or something?

I don't have anyway to edit these myself.

I would think it drives by itself cause I have my set screw open to far?

I only have torque pro and I actually don't even see anything about IAC counts.

 

That's correct, from memory you can set min and max map values at closed throttle, then anything outside of this is assumed to be a TPS error.

I would guess that you have the throttle screw too far open also but it's hard to say exactly where to set it without a good data feedback for things like IAC steps.

 

This.

It will take care of your P0121 code at least...

[ECM] 4020 - P0121 Error Max MAP: The VCM will calculate an expected TPS position in two MAP ranges. If the MAP is less than MinMAP then it will use one table to calculated expected TPS, if MAP is greater than MaxMAP it will use a different TPS calculation table. To disable this test set MinMAP to 0 and MaxMAP to 100.

Most idle issues have to do with the idle adjustment screw... Get the counts down in a reasonable range 20-80 or so, depending, and go from there. Lower the better really, but not zero.

 

So. I looked into torque pro and found out how to see IAC counts... it is currently reading 0. At cold start, in drive, whatever it is, it reads 0.

That would mean we have a vacuum leak. I have no idea where. My brother and I just redid the intake manifold gaskets in case and made sure no hoses were broken when we put it back together. I just don't see how there could be a leak.

I did get an email back from blackbear and he said everything is good on his end.

I'm lost

 

Is the "desired IAC position" also zero? You can check for a vacuum leak with propane or another flammable gas and spray it around the intake manifold area seal by seal and see if the engine responds. You don't need much. Butane/MAP gas works too.

Is there a hole in you TB blade? Also what is it set to? If you have it too far open, the counts will indeed read zero because the PCM is trying to choke the air off but it can't, and can only then control the idle with spark. Might also be worth a shot to check the IAC harness and make sure there's continuity between the plug and the PCM.

 

I will definitely try these things tomorrow, but the kicker of this is, I had been driving with this TBSS intake and 92mm TB for a few weeks with absolutely no codes before we did the cam project.

Which leads me to question the timing.. if the timing was off, would that cause air flow problems like this?

The last time I played with the set screw I had it at 2%. There is no hole drilled in this one.

 

Throttle % isn't too relevant as you can just reset it anyway. Get the car running and warm, in gear and wind the throttle screw out (closing the throttle) until the IAC count comes up to 40. That should get you pretty close to start. Do a tps relearn, and see how it all goes. Report back.

 

Well I gave up and brought it to a shop 4 weeks ago. They can't figure out the minimum throttle setting either. It's back to looking like it the tuners fault. Speaking of the tuner. Did I mention that blackbear performance has been the absolute worst part of this project?

Even the stuck lifters... where we had to take off the oil pan to punch them through the other side... was not as difficult as dealing with blackbear.

I ended up paying extra for the scan cable tune and the dude still doesn't do tech support even though I've given him all the money I can for his services. It's been weeks since I've heard from him.

Whatever you do. Don't do a mail order tune from blackbear performance. He doesn't have the ability or even the common courtesy to offer support on his own mistakes.

 

Here is where we are at. The shop thought they fixed the TPS code by repairing a ground. The TPS p0121 came back they said.

They currently don't know how to set the TB screw because they dont know what the computer wants for idle speed or minimum airflow.

All voltage is in spec and confirmed by the shop.

We get 0 IAC counts wherever the idle screw is set.

Also the MAF is reading something massive like 15 grams a second

 

Did you ever get this sorted out?

 

Turns out Blackbear performance guy didn't correctly tune the MAP sensor with my TBSS intake. With the tbss map I was getting a constant 4.1v instead of it fluctuating with the pressure. Had to rig the MAP sensor from my original air intake, didn't quite fit.

 

Im currently in the bowels of waiting for a tune from them (for months so far) starting to get nervous. They recently did a tune on my buddys lq9 swap with an ls3 topend and he said its not quite right, i also got a 6.0 but want to do hci and im not hearing as good things lately as much as older forum posts over the past decade... not sure what other options id have...not sure how dynos compare and i dont know if i wanna plop down $600+... i dont know nothing about computers but almost wondering if i should learn hptuners.... hope your setup is running better now this is good to know

 

That is quite sad to hear. Honestly something's funky with the idle and I'm getting way less mpg than I used to 🤷and when I came to him with research and questions he insisted it was right. Of course this was after waiting 4 weeks from a ****** response from the guy.

I really wish I would have gone local and even gone for a Dyno tune.

 

yeah so i spoke with my friend he says the tune is ok but it idles pretty poorly. he went with the autocal v3 so he could switch between tunes and they...never sent him the other tune. he says he totally wish he went with a dyno tune in hind sight. idk wtf is going on over there but im not too thrilled anymore, hearing this from a lot of sources lately.

i am unsure about local guys because i guess you dont have much of a reputation to work off of, bbut then again the reputable guys seem like theyre getting a bad reputation!

 

Yeah I've shopped around the twin cities and found a couple tuner guys. It just sucks cause I already paid for a scan cable tune with lifetime free updates. I was expecting more considering all the praise they got. Whenever I get my hands on new heads, I'm going to just bite the cost and have someone else tune it. I've put 30,000 miles on this thing since I built it. It isn't a mechanical problem that's causing my issues, it's the tune.

 

Another thing that pissed me off now that I think about it. I had some questions about the tune he was sending me for my long tubes. But he never answered. Just sent the tune without addressing my questions. And said pay him for shipping. Well I was unsatisfied and I didn't pay for shipping. ******* haven't emailed me back since.