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Running lean on bank 1

N

nathnn99

New member
So I have tried to find a cure for this and right now I feel like I am just throwing parts at the car. I am getting a P0171 Fuel Trim System Lean Bank 1 code on and off again.

So far I have replaced the stock injectors with rebuilt flowmatched ones from ZZP. I have changed the fuel filter. I have changed the fuel regulator. I have changed the two fuel pump relays. I have bent the one pin on the outer relay out to make the pump stay in "high" mode. I have changed the MAF. I have changed the MAP. I have replaced all of the vacuum line with new rubber line. I have tested the fuel pressure. It is 41-42 normal and with the vacuum line from the fuel pressure regulator pulled it goes up to a steady 50.

The code is intermittent and usually only comes on when the car is coasting, at idle or bearly above idle. When I'm pressing on the gas more than a little bit, then it doesn't come on. Yeah, I know. Just keep it to the floor, but seriously I need help fixing this. I have a new AC Delco pump coming to me and a high flow fuel filter on the way also, just in case.

Any knowledge, thoughts, or enlightenments would be greatly appreciated.

For the sake of getting help, I have a 99 GTP 3.8 Supercharged stock.
Thanks again in advance.
 


At this point I would be doing a smoke test.

Could be a crack in the EGR tube, could be a leak between the TB and supercharger. Hard to say when we are just guessing and you are tossing parts at it.

I would be watching fuel trims on a scanner and either spraying carb cleaner or brake cleaner around anywhere that can suck in extra air past the MAF sensor. Watching for a change in the numbers, only nice data logging scanners will pick up the minor changes as they have fast refresh rates.
 
But hey if you wanna toss more parts im putting money on O2s, or you could do it the right way and start checking like ^^ said.
 
Fivefingerdeathpunch said:
At this point I would be doing a smoke test.

Could be a crack in the EGR tube, could be a leak between the TB and supercharger. Hard to say when we are just guessing and you are tossing parts at it.

I would be watching fuel trims on a scanner and either spraying carb cleaner or brake cleaner around anywhere that can suck in extra air past the MAF sensor. Watching for a change in the numbers, only nice data logging scanners will pick up the minor changes as they have fast refresh rates.
Click to expand...

If things go over my head, then I apologize for my ignorance as I am not a mechanic, but I am trying to pour my love of my car into fixing it. I am not sure what a smoke test is. I assume it has to do with trying to find a vacuum leak? While replacing the vacuum lines I did a recommended check of spraying WD40 and seeing if the car changes how it runs. This is the check that lead me to find a bunch of cracked lines. I replaced them and now the test doesn't reveal any more leaks. How does this smoke test work?

I replaced the paper gasket between the throttle body and the super charger with the rubber one from ZZP performance. I retightened it after you said it. It is very tight still.

As for scanners, what type of scanner are you talking about and where can I get one. Right now I just have a code scanner that tells me the code and resets the CES light. I am more than happy to get good tools to trouble shoot. I just need to know exactly what is needed so I get the right one.

Thanks again for the quick replies.
 


The egr tube goes into lower intake just below the throttle body. Its a metal flex tube that's known to crack. Check out torque pro app for Android if you want something cheap to scan with. You need a Bluetooth obd II adapter. There is a ton of info around about it and which BT adapter to buy. This will allow you to monitor fuel trims and can help find a vac leak. Helped me find one on my sienna and netted me 4mpg after I fixed the leak :)

If your code is coming on shortly after you reset it, I'd say you have a decent sized vac leak. It took me about 4 cans of carb cleaner before I found my leak. I had to spray it in just the right spot/angle to make it register. Could be something you overlooked like o-ring on dipstick or oil filler neck.
 
BillBoost37 said:
For a lot of great info...without me having to repost it. Please search on P0171 and my username.
Click to expand...
Bill, I did what you said, but it only returned 19 results with most stating you were a great help when they read what you posted, but I couldn't see the older posts for some reason. I did see that I should clean off the battery terminals and check the EGR tube. Is the EGR tube easy to replace or even get?
 
Bummer

I've posted quite a bit as I fought this code a lot.
Can be MAF
TB gasket
EGR tube, you have to pull it to check it. Do not trust spraying carb cleaner at it. I have seen a bad tube test good with this method.
Battery cables like you mentioned
Even a bad ground at the transmission stud.
 
One overlooked item people miss is the BBV or boost bypass valve. If you spray carb cleaner up into where the rod actuates you might find the diaphragm could be the cause, you would see you fuel trim readings change when you spray at the base of it.
 


Thanks, brother, I will check those. Are those tubes an item that can be picked up at a parts store, or do I have to junk yard hunt?
 
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