I was hesitant to post this as it technically is a repost. But the former post was very mixed up. I was thinking about posting this in the advanced section, but decided I'd just post it in here rather than waste the moderator's time by moving it out of there.

First question... What parameter's throw off the p0171 code? Okay? Have the answer in mind? Will you now please read the following and offer any suggestions?

This has just started happening recently. When I'm at a stop light or place my car in park, it randomly lopes to 300 and then up to 700. Afterwards, it’s either one of two outcomes – the car runs fine or it dies. I do have an SES light in (p0171), but the car runs just as strong on the road as it ever did.

I’ve checked: The alternator
TPS
The battery
02 Sensors
MAF Sensor / Eng Sensors Fuse
Vacuum Leaks
Cracked/Broken Porcelain of the Spark Plugs.

I don't have time to get things checked out so I'm trying to draw up some hypothesis before I start to get into it. I took the car to autozone. They told me the alternator and the battery are good. Then, I started to think it was the TPS. The throttle used to feel like it was sticking, so I decided to try and replace the TPS. Afterwards, it seemed to idle a little better, but the root of the problem was still there. The car still refused to idle while in park; however, the problem was not solved with the new TPS. Car actually died at idle shortly afterwards. Next, I thought it was MAF fuse. The last time my car threw codes it was because of that fuse. I'm lost. Cleaned the MAF, and now I think it's idling a little better. Let's recap my last wonderful day out and about (this was Saturday, 18March06) Waited at a GM Dealer to get car diagnosed because of the car repeatedly throwing a p0171 Bank 1 lean code (for 4 hours!) only to be told they can't even touch my car because of how modded it is. He even went so far as to ask where my MAF was and write on my estimate that he recommends I put the car back to the original factory setup before they start to work on my car. All I wanted was for them to test my injectors to make sure each of them was operating properly because I’m unaware of know how to do that. Sorry, nope. They can’t do it. So, I left.

Another post I read with the same problem suggested that I get my fuel injection system clean. I took it to the same shop I always go to and they cleaned it and I left. Everything seemed to be fine. I pulled in, put the car in park and the son of a bitch died. So far, I've inspected for leaks, removed my secondary AIR system/blocked off pipes, cleaned the MAF sensor, cleaned the FI system. It's still actin' up and now I'm at a loss for a place to take it to. :-/ I'm running short on ideas and help. Checked for burnt/broken vacuum hoses and did not find any. Pulled my spark plugs and looked for a crack hose/wire/plug or anything out of the ordinary. Nothing too exciting there. I, also, checked the O2 sensors because I thought it was the problem because when I put it on the other side that side showed up lean too. So I'm like okay, I'll change the o2 sensor, and then I'm in the clear. Nope, Motherf*ck** light in again. Is there anything that I haven't checked? Every thread I’ve ever read about this has either been solved by one of the many fixes above or just abandoned. I’m posting this in the advanced section because thus far the normal section hasn’t been able to submit a solution that fixes my problem. What should I do?

I could use some help from some pretty experienced people. I feel that I’ve gone through all of the simple solutions and now I’m trying to think more critically. Any suggestions? I've searched here and camaroz28 to no avail. What are some other LS1 forums? T.I.A.

Justin

PS. Sorry if this is a fairly jumbled. I pieced many of my previous posts together to make one, hopefully, more coherent story.

 

T T T T

 

usually po171 is a plugged fuel filter, weak fuel pump, and then possibly at dirty MAF. could also be a large vacuum leak.

 

PO171,lean bank 1 correct? Sorry at home not at work so working from memory, and no 174 lean bank 2? In the post above some good info on the normal maintainence that needs to be up to date,but also check that there are no leaks in the exhaust from the header to the 02 sensor first. After that we will run down all the test that need to be performed. Hope I can help in PM's etc.

 

Usually I see this code along with a p0174, since you are only throwing p0171 I would be inclined to look towards a fauly o2 sensor. It's possible but highly unlikely that a vacume leak or fuel starvation problem would only throw lean codes on a single bank.

 

not true I'm ASE certified in engine performance and have seen 100's of cases like this where the only code was a po171 and a fuel filter or vacuum line was at fault and the ones that where not that where often a MAF being dirty. I would not try an o2 sensor on this one unless the above doesn't work for 2 reasons 1. experience shows that those i've mentioned to be the most common and 2 what I've mentioned doesn't cost much to try. a fuel filter is like $15, you said you already cleaned the MAF, and to check for a vacuum leak all you need is a $3 can of carb cleaner, a good ear, and take a little time. $18 and you can safetly eliminate those things and if you still have a problem then put in a $100 O2 sensor.

 

Thank you all for your helpful ideas. I'm going to try all of this and then get back to you guys. The one thing that seems to be a topic of concern is the 02 sensor, and I've all ready eliminated that as a possible faulty component because I all ready changed it out. :-/ I know. I wasn't like 70$.

I'll try and replace the filter (it's only about 4 months old) and see if that has anything to do with it. Would the filter not working properly not throw a code on both sides? T.I.A.

Justin

 

not always. keep in mind the way a lean or rich code is thrown is based on fuel trims which if you look at them on a scan tool are always a little different from 1 bank to the next one side might be 13 and the other 11, if it can't be above 12 for more than 5 seconds and its 13 on one side and 11 on the other then yes both banks are lean just ones is a little more so than the other.

 

Funny thing, I'm ASE certified too...

Now that you have added some more info we can try and narrow it down a little. You said that you swapped the o2's and it followed to the other bank yet after replacement it did not correct the condition? If this is so Cody has a good point in that both banks are lean, but the o2 on bank one was reading a little leaner than bank two o2.

To answer you question p0171 and p0174 are set when the average long term fuel trim cell value is above 23 percent and some other basic conditions are met for 6 seconds.

Some freeze frame data would really help out with this one. So we would know when it is actually seeing the conditions to throw the code. Without it we're just throwing darts at a trouble chart. Does the car drive fine other than when you put it in park? No stumble or hesitation under a load? Are there any other codes p0300 maybe?

You also said it felt like the throttle was sticking and that you replaced the TPS, but did you clean the throttle body or IAC? It's possible that if the IAC has carbon build up it would not adjust air flow properly once the load on the engine has been removed by putting the vehicle in park.

 

To answer a few of your questions: The car does drive really good, I raced a cobra in between throwing codes (ie. code came in, I cleared it and thought everything was fine, and then the code came in again a few days later.) and beat it pretty bad. I don't notice any actual loss of performance with the code in. Very rarely. ( I count about half a dozen times during this whole ordeal) The car, when sitting at idle, at a stop light will dip down to three hundred and then bounce back up to 700 and then steady back out around 500 or 600.
I haven't received any other codes with the car. I haven't cleaned the throttle body. I did assume that when the fuel injection system got clean the stuff they ran through the systme flushed everything out. Should I take off the throttle body and give it a good clean? And how do I clean the IAC? Isn't it just a small plastic sensor like the TPS? (I'm on a steep learning curve )
I bought a fuel filter yesterday. Because of my charge piping I can't jack the car up to put it on because I can't get the little tire jack underneath. I'm going to have to wait until sometime this weekened to change it out and work on all these possible causes. As always, I'd like to thank you all for you help, and I hope that once I get this problem solved someone in the future can read through this and cover these basis on their own car. T.I.A

Justin

 

To clean the throttle body just pop your boost tube off the throttle body, and open the blade. Clean all around the blade and inside the holes in the upper left hand corner. You can take the IAC off the throttle body it you want to, but you shouldn't have to unless it is just caked with carbon.

You might try searching in the Forced Induction forum and see if you can find a similar problem. If the things that have been suggested in this thread don't help you might have to find somebody who is willing to work on your car, cause all we can really do is guess. You might be able to take it to your tunner and find out when it's running lean.

 

My tuner is in North Carolina. I'd love to take it to him, but I have a fear of my car being hurt by driving three hours. I do thank you for your help and I'll keep you informed of any progress/solutions to the problem. Everything that has been suggested is pretty helpful and atleast has some bearing to the situation.

Justin

 

I took the car into the shop because I gave up looking. It took them about 5 hours of searching before checking the MAF sensor. It was slightly out of range but was the only lead they had to go with. Replaced it w/ a re-man'd MAF and now the car's running as good as ever.

 

you guys rock, i have same lean codes and changed front o2s , cleaned maf, but never thought fuel filter might be clogged. thanks