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i have a 999 chev pu 4/4 have trouble codes p0171 and p0307 ...
Sent to Chevy Experts February 22 05:07 PM

i have a 999 chev pu 4/4 have trouble codes p0171 and p0307 have replaced ass airflow sen, and fuel filter could the problem be the coil pack also replaced wires and plugs checked for vac leaks also

Customer (name blocked for privacy)
Status:  Closed   Value: $15
Answer
February 22 5:20 PM (12 minutes and 19 seconds later)
         
ACCEPTEDCheck Mark

Hello.

Code P0171 is a code telling you that bank 1 of the engine is running lean.

Code P0307 is telling you that cylinder 7 has or is missfiring.

I am assuming that the engine is an 8 cylinder and that a miss can be felt in the engine.

 

You have one of a few possible problems. Lets think about this for a minute.

Cylinder 7 if missfiring and bank one is running lean. Cylinder 7 is located on bank 1. Therefore, you can assume that the lean condition is due to the cylinder missfiring. Since the exhaust gases show lean, you can eliminate the ignition system as the problem as that would cause a rich condition.

Now... What can cause a lean condition. Well, a lack of fuel is a start. Lets find out if the injector for the 7 cylinder is commanded to open. Do this with a noid light.

If it is, check the compression of number 7 cylinder. This will tell you if there is carbon on the valves which may also cause a lean and misfore condition.

If the compression is good, an injector balance test must be performed to make sure the injector is not spraying fuel. The injector may have clogged, failed mechanically or electrically. The computer driver for that injector may have failed which would result in no injector noid light pulse.

My suspicions are that the injector for the #7 cylinder has failed or clogged. An injector and a good injector cleaning service (professional not bottle in tank stuff) is a good start in this situation.

Please, if any part of your question went unanswered, let me know.

 

 

rmldaytona -- ASE technician -- 100% Positive Feedback on 130 Chevy Accepts
ASE Certified. Aerospace engineering studies. Drivebility.
Reply
February 22 6:04 PM (44 minutes and 32 seconds later)
         
Relist: I still need help.
since i posted this question codes 307/102/332/131/ have now posted truck will not run unless mass air flow is un pluged, then only 35 miles per hour, could it be fuel filter, have mad x

Edited by Customer (name blocked for privacy) on February 22 2007 at 6:07 PM
Customer (name blocked for privacy)
Info Request
February 22 6:17 PM (12 minutes and 19 seconds later)
         

Ok.

We might have to do more testing.

Could you please do me a favor. Lets clear the codes and see which come back.

Are there any other symptoms the truck is showing? What's the engine size? Is this a 1500 pickup. 4x4 or 2x4? Auto or manual transmission?

Let me know and we'll get to work.

 

 

rmldaytona -- ASE technician -- 100% Positive Feedback on 130 Chevy Accepts
ASE Certified. Aerospace engineering studies. Drivebility.
Reply
February 22 6:26 PM (9 minutes and 46 seconds later)
         
1500 4/4 cleard codes drove truck 4 blocks code p0307 is what came up truck feals like lack of fuel , auto trans ,307 code came up twice ,,wife was on way to store ,truck just felt like it died but would idle , had her unplug mass air flow, till truck got home ,let it set 5 min ,sprayed b-12 on m,a f let dry plug back in then drove 4 blocks
Customer (name blocked for privacy)
Info Request
February 22 6:28 PM (2 minutes and 1 second later)
         
Does it run now? The only code that comes back is the P0307? What engine size?
rmldaytona -- ASE technician -- 100% Positive Feedback on 130 Chevy Accepts
ASE Certified. Aerospace engineering studies. Drivebility.
Reply
February 22 7:19 PM (50 minutes and 45 seconds later)
         
it does run now , has lack of power, slugish,idles ruff, drove it 4 miles to get a new fuel filter but walmart out ,it now has 2 p0307 codes 350 auto
Customer (name blocked for privacy)
Answer
February 22 7:32 PM (13 minutes and 14 seconds later)
         
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rmldaytona -- ASE technician -- 100% Positive Feedback on 130 Chevy Accepts
ASE Certified. Aerospace engineering studies. Drivebility.
Reply
February 22 8:06 PM (33 minutes and 7 seconds later)
         
would 1 cly miss fireing, make the truck die ,or feal like you ran out of fuel going down the road at 70 miles hour, run rough in gear to the point it almost dies put it in gear it woud not move , then un plug mass air flow then can drive it 35 mph ,let trck set 10 mins then it run ok with big lack of power, 1st time it happened i replaced maf sensor,and tps to be safe,,, just gotthis truck paid 2500. for it might have wire proublems with key off push brack pedle and key chime sounds, push brake and dash lights dim
Customer (name blocked for privacy)
Answer
February 22 8:45 PM (39 minutes and 23 seconds later)
         
ACCEPTEDCheck Mark

NO.

One injector is not going to do all that. It will make the truck run rough and have low power.

However,

The only piece of diagnostic data you have at this time is that cylinder 7 is misfiring, there was (still might be) a problem with the MAF (P0102), The o2 sensor circuit (P131), and knock sensor (P0332). The only thing is that if you chase something that is not there, you will not find it. You replaced the MAF?

We do know that # 7 is missfiring at this time. Now, why would it do that? Cylinder compression, no spark, no fuel. A MAF will cause all cylinders to miss. An o2 and knock sensor problems could be caused by something else. We do know that the number 7 cylinder is missing. So, it will have to be fixed. Also, it may lead you to other problems. Check the injector pulse. Check for spark. Check the compression. You have to start somewhere.

I can tell you to change the fuel pump, the regulator, the coil, the cap. rotor, plugs, clean the injectors, and replace the pcm. And then, your problem is still not fixed because the wiring problem is still present. You WILL be mad at me.

I have had much better experiences with diagnosing a problem before you repair it. I don't mean to be sarcastic, but it is true.

But...

If you want to test the MAF. With the ignition on engine off. Verify that the MAF sensor has good power (pink wire). Check the yellow wire for 5.0 V. If not 5.0 V .2 V +/-, unplug the MAF and test again. If voltage goes to specs, replace the MAF. Also, the frequency needs to be checked with scan tool data or a scope. Engine running at idle Must be 10 mHRz. +/- 700.

Test the o2 by graphing them on scan tool data. If bank one looks diffrent when running, replace it.

And you can't really test the knock sensor as no ohm specifications are provided by the manufacturer.

 

But, now you know that cylinder 7 is missfiring. None of the other codes are a problem right now. Yes, you may have more than one problem. But the name of the game is that you got to find it to repair it.

Now, if you test the compression, see if the cylinder has good compression, and see if you have injector pulse I can help you with further diagnostics on this problem. I can't guess at the problem as there could be MANY unhappy customers of mine. I can only provide you with the information and guide you in a direction.

But... You have to start somewhere.

 

 

 

 

rmldaytona -- ASE technician -- 100% Positive Feedback on 130 Chevy Accepts
ASE Certified. Aerospace engineering studies. Drivebility.
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