Engine Codes

Briann1177

Goblin Guru
I don't know how to bench test an O2 sensor. I don't really have anything necessarily saying it's a bad O2 sensor other than it's not showing up correctly in Torque and it sort of makes sense how it might be causing a super rich fuel mixture.

I also don't have any codes related to the primary O2 sensor. However, my I've read that no codes doesn't really mean there aren't issues.

*Edit* Thanks, Slider. I was typing this right after you posted.
 

Briann1177

Goblin Guru
I unplugged my MAF sensor and went for a test drive. I drove probably twice my normal amount and by the time I got home I still had boost. In all of my previous 20 drives or so, I was never able to make it home without the boost dying off. Every time I mashed the throttle, the turbo kicked in right on cue and built up to 20 PSI no problem. With the MAF plugged in, the boost was very inconsistent. I could mash the throttle and it might go up to 10 PSI one time. The next time might be 15, but most of the time it was right around 5 PSI. Then when I got home, I'd see the P0101 code and maybe a P2178 (Too rich) code.

I didn't see a P2178 code when I got home this time which is promising. The LTFT's still hover around -10 still which is a little concerning so I need to keep an eye out on them. They're definitely way below the -25% I was seeing before I disconnected the MAF.

I'm going to monitor this over the next few drives. If things remain the same, I'm going to do some testing with hooking the MAF tube directly up to the turbo. I know you're supposed to have a certain length of of pipe between the MAF and turbo inlet, but I'm kind of curious to see how that changes things.
 

ctuinstra

Goblin Guru
I unplugged my MAF sensor and went for a test drive. I drove probably twice my normal amount and by the time I got home I still had boost. In all of my previous 20 drives or so, I was never able to make it home without the boost dying off. Every time I mashed the throttle, the turbo kicked in right on cue and built up to 20 PSI no problem. With the MAF plugged in, the boost was very inconsistent. I could mash the throttle and it might go up to 10 PSI one time. The next time might be 15, but most of the time it was right around 5 PSI. Then when I got home, I'd see the P0101 code and maybe a P2178 (Too rich) code.

I didn't see a P2178 code when I got home this time which is promising. The LTFT's still hover around -10 still which is a little concerning so I need to keep an eye out on them. They're definitely way below the -25% I was seeing before I disconnected the MAF.

I'm going to monitor this over the next few drives. If things remain the same, I'm going to do some testing with hooking the MAF tube directly up to the turbo. I know you're supposed to have a certain length of of pipe between the MAF and turbo inlet, but I'm kind of curious to see how that changes things.

Good to hear you are making progress. I'll bet dollars to donuts that this needs to be corrected.

I'm no expert, but from what I've read, when you change the intake track, the MAF really needs to be calibrated to the new airflow. How one does this for sure, I'm not sure without investing in a lot of expensive equipment. Otherwise it's trial and error tuning using inputs.

I would love to read yours to see where it's at compared to stock LNJ. I know they can be read without having to buy credits, just can't be changed without credits.


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SliderR1

Well-Known Member
There are some pretty good how-to's on MAF tuning on the HPtuners forum and youtube. Probably won't help much since you don't have HPtuners though... I'm guessing there are plenty of tuner places for you to take the car to in OKC... Give Big Chief a call at Midwest Street Cars Automotive :p
 

RichRich

Well-Known Member
So I think we found the problem, part of it, all of it, only time will tell but wanted to post it here considering there are other turbo builds in progress that could encounter the same thing . This was all through about 20 personal messages and a dozen questions and things to check I started looking into areas for abnormal turbulent flow across the MAF sensor and found a problem when I really started dissecting pictures. Noticed the MAF tube seemed a little short, then after comparing to mine I noticed it was quite a bit shorter. Few questions later we found that in order for him to fit the intake parts in the small mounted location, the air filter was slid on too far causing significant surface area of the filter to be unused and also a change of air direction near the end of the filter before entering the MAF tube. (MAF tube was mounted to the frame, compared to mine pulled closer to the motor and mounted to the front alternator bolt)

Combined this was choking out the engine making it run rich because the engine was waiting for boost to roll but the MAF sensor wouldn't let it. This would explain most or all of the issues. When the MAF was unplugged it would just run rich but still build boost because it wasn't trying to throttle back the fuel curve from the readings of the MAF sensor. First drive went well with the MAF plugged in and sure hope it continues. I would be a little skeptical as well if I was banging my head against the wall for a week but best of luck, hope this solves all the problems and you can move on to the fun part....driving and enjoying the car!!

Keep us updated
 

Briann1177

Goblin Guru
I drove two times today about 20 miles or so total, an I had zero issues with inconsistent boost pressures, boost dying off, and the dreaded P0101 code. Things were solid and felt good.

Still having issues though with some pretty high negative fuel trims. They're -10 right now but will probably climb the more I drive it. They're somewhat slow. They might change by -.5% over 10 miles or so.

I don't have anything to compare to so I don't know if this has anything to do with the redesigned intake, tune, or if I have something else going on.

I appreciate everyone's help on this. Before I started troubleshooting this, I couldn't even begin to tell you what the he'll a fuel trim even was. Lol. You guys are awesome.
 

Briann1177

Goblin Guru
Rich definitely fixed my issue with the P0101 code. I've been working on the fuel trims now. I bought an HP Tuner and messed with it a bit today.

Here is what I found out. This is probably obvious to evryone but me, but it didn't really sink in until I saw what was going on. The air flow between a stock Cobalt TC and the Goblin are definitely different. The Goblin intake has slightly lower flow numbers. This could be related to the size, length, bends, or a combination of all those. The stock numbers are very precise from the factory and it's **** near impossible to duplicate those numbers in a different configuration. However, DF did design it well enough that I and probably most builders wouldnt have noticed this unless they had another issue and started looking deeper.

I found that if I reduced all my air flow rates by a percentage that corresponds to my long term fuel trims, -15% for me, the trims are significantly better over the short term. They seemed to have leveled off around -5%. This is all very preliminary though without driving.

Once the weather clears up, I should be able to dial things in quite a bit more. I thought I could get by without forking out the cash for an HPT, but I'm glad all the talk here about them convinced me otherwise. It's very handy and powerful.
 

Brian74

Goblin Guru
Rich definitely fixed my issue with the P0101 code. I've been working on the fuel trims now. I bought an HP Tuner and messed with it a bit today.

Here is what I found out. This is probably obvious to evryone but me, but it didn't really sink in until I saw what was going on. The air flow between a stock Cobalt TC and the Goblin are definitely different. The Goblin intake has slightly lower flow numbers. This could be related to the size, length, bends, or a combination of all those. The stock numbers are very precise from the factory and it's **** near impossible to duplicate those numbers in a different configuration. However, DF did design it well enough that I and probably most builders wouldnt have noticed this unless they had another issue and started looking deeper.

I found that if I reduced all my air flow rates by a percentage that corresponds to my long term fuel trims, -15% for me, the trims are significantly better over the short term. They seemed to have leveled off around -5%. This is all very preliminary though without driving.

Once the weather clears up, I should be able to dial things in quite a bit more. I thought I could get by without forking out the cash for an HPT, but I'm glad all the talk here about them convinced me otherwise. It's very handy and powerful.

Glad to see you finally got it worked out. It may be worthwhile bringing it in to a knowledgeable dyno tuner and have him recalbrate & resolve MAF baselines and curves to settle air/fuel flow issues at various throttle ranges under a dyno load. I know the Bosch E69 ECM’s fuel maps are very complex in that respect. If you figure anything else out, please let us know.
 

SliderR1

Well-Known Member
There are some pretty good videos on YouTube from username cssob on using hpt to tune LSJs and LNFs. I thought they helped a lot when I was first starting.
 
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