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#1
07-06-2011, 04:54 PM
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System too lean
hello everyone!
Having some problems w/ my 1997 gmc truck. 4.3 vortec. Getting codes for system too lean for bank 1 and 2. Idles rough, runs terrible. If I let it idle for maybe a min, and then take off then it will do alright. It idles and runs kinda like the timing is way off but you don't adjust that on this engine. New fuel pump, lines and regulator. New gaskets for upper intake assembly. Fuel pressure: turn key on shoots up to 55-56 psi, then after 2 secs, drops and holds at 50 psi. Idles anywhere between 45-50 psi. Anyone have any experience w/ this please? Thnks! 
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#2
07-06-2011, 05:35 PM
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Re: System too lean
Try to get a Smoke test done for unmeterd air leaks, and focus on the PCV, EGR, and Air Intake systems.
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#3
07-07-2011, 04:02 PM
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Re: System too lean
Hi,
Thanks for your answer. I checked the pcv valve today and the valve is good, it's not sticking, the pipe is unobstructed, and the pipe and boots look good. How do I examine the egr valve on this? is this something a dealer or mech. would have to diagnose? Is there some way I could perform a smoke test on my own vs. taking it to the shop? I was looking for vac leaks also, and I can't find any, and it would seem to me that any leak to cause this bad a performance would be significant, and not too hard to find...am I off on this though? I do notice that when I have the air bonnet (?) off I hear a loud hiss coming from w/in the throttle body. Is this a normal thing? Anyway, thanks again, and any experience you can pass on is appreciated!
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#4
07-07-2011, 04:03 PM
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Re: System too lean
"I was looking for vac leaks also, and I can't find any, and it would seem to me that any leak to cause this bad a performance would be significant, and not too hard to find...am I off on this though?"
...thought!!!:
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#5
07-07-2011, 06:20 PM
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Re: System too lean
Just finished cleaning my iat and map sensors, took it for a drive with my scan tool hooked up and suddnely, I got a link error and now can't link up with the comp? Are we having fun yet?
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#6
07-07-2011, 06:57 PM
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Re: System too lean
See Smoke test for vacuum leaks, see http://www.youtube.com/watch?v=FfiQ7qWiG-M
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#8
07-12-2011, 06:03 PM
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Re: System too lean
Hi there!
Did a smoke test a while ago and all i saw was a little intermittent smoke coming from the manifold side of the brake booster hose. maybe there is a small split. I'll examine the hose closer and replace if needed. Perhaps replacing the old clamps is all thats needed. Other than that I saw no eveidence of other leaks. There was plenty of pressure in the intake, yet no other signs of a leak. Can the egr be taken off and inspected and cleaned? Pcv is good. Anything else I should check? Is it possible the maf is sending inaccurate info that would cause the engine to run lean? Thanks for your help!
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#9
07-13-2011, 10:07 AM
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Re: System too lean
The breake booster rubber hose garment, looks like one problem.
If smoke test passed after replacing rubber garment: Yes - Usually a cold hard start, or slow to reponse is a symptom of a bad/dirty MAF/IAT sensors. 1) Clean both the MAF + IAT sensors with CRC Massive Air Flow cleaner. 2) Also clean the electrical connections, and use dielectric grease for protection. 3) Clean Throttle body with WD40 and a micro cloth. 4) New upstream H02 sensors only.
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#10
08-05-2011, 06:15 AM
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Re: System too lean
put a new fp regulator in the other day and that solved the problem. Feels good to be able to drive the thing w/o it falling flat on it's face! Now on to the body work, fixing the front driveshaft etc......
Thanks for your help, hopefully this was THE prob!!
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