LT1 Computer Codes
Own a 1997 T/A stock LT1. Engine service soon light came on after last autocross. codes showed oxygen sensor - replaced oxygen sensor and now codes show PO171, PO174 and PO300. 171 and 174 state "banks running lean. 300 code states "misfire detected. Just for information - I have modiified induction elbow to gain clearance for electric water pump housing. Removed noise silencer tube and filled opening in induction elbow with homemade cover and sealed with silicone RTV. Checking for any air leaks in induction elbow appears to show no leaks. Am now replacing induction elbow with a 1995 version with no noise suppression connection. Any ideas on how to eliminate lean running condition, or other checks I can make to look for air leaks. All vacuum hoses seem to be good. car runs very well at the higher rpms - but is rougher at idle (no fat cam installed). Also what to look for as a checklist to eliminate misfire would be appreciated.
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Have you checked your fuel pressure and regulator? Not enough fuel volume can cause an overly lean condition as well as too much air. When you say it runs well at higher rpms, is that at WOT or part throttle?
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LT1 computer codes
Joe - car runs well at both part throttle and WOT. If car is driven sfor short distances in current condtion - what are my chances of burning a valve?Comment
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Another thought is that you may be experiencing a false lean....... any header or exhaust manifold leak prior to the 02 sensor will introduce additional air into the system and the computer would read that as a lean condition. Reading the 02 values and injector pulse widths could shed some light here, especially if there were a variance between banks. Since you say the car is stock, I am assuming the exhaust is untouched? Also be advised that silicone is bad for 02 sensors. If any little silicone pieces make their way into the combustion chamber, the residue coats the 02 sensors and renders them ineffective.
As far as burning a valve, it would usually take more heat and fuel that cruising would produce to burn a valve. That is usually a WOT casualty.Comment
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LT1 COMPUTER CODES
Joe, thanks for the information. I do know about the silicone problem and was careful not to let it get into the elbow. All other areas I use "sensor safe" RTV, but did not on the intake elbow. The fuel pump and regulator is an area I did not check but will. The exhaust system is a Flowmaster cat-back system. Cats are stock. Exhaust manifolds are stock. but maybe I caused a leak when I was removing the old system banging it about - I'll check.
Also engine is stock in regards to internals with exception to the addition of an electric water pump, throttle body airfoilComment
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