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3.8 lean O2s blues..

I've a 90 Tbird with a 3.8, which began running like it was missing a couple plug wires only when cold, and giving me a check engine light after ~20min of driving.. Any time I turn the car off the light stays out for about the same period after restarting, even if it starts back up immediately.. So I borrow a code scanner, and retrieve codes for the O2 sensors being lean on both sides (41 & 91).. So I buy both O2 sensors, new plugs,wires,dist cap, rotor button, and coil. I installed everything except 1 O2 sensor which I couldn't remove for the life of me.. just couldn't break it loose in that small of a space (was hard pressed to even get the ratchet to click). So I stuck with the parts that were in, reset the ECM by disconnecting power 60secs, fired it back up, and tested again.. SAME CODES =( Well that pretty much tells me it wasn't the sensors.. return the other one and put the 40 bucks into something else.. But the car runs like a champ now, no more miss, but I still get the check engine light and same codes.. So I replace all the vacuum lines that don't disappear into the firewall on me.. no change.. egr was mounted a little loose(had to do head gaskets last november), tightened it up.. nada.. no change.. I waited until the light came on and tested without turning the car off.. same codes.. but the check engine light did go out after the test.. So what could be causing the lean O2 codes without really hurting performance much?

Reply to
Dark1
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Possibly a dirty injector or two - it only needs ONE cyl to be lean to throw a code. My 2.5 Mysique was doing the same until I ran a motorvac session on it -(cleans all injectors and FPR)

Reply to
nospam.clare.nce

But it's throwing a code for each side.. so I would think it would be something common to them..

Reply to
Dark1

Does it have an air pump?

Reply to
aarcuda69062

no

Reply to
Dark1

Okay...

Of all the parts you've mentioned, there isn't a fuel filter listed. A restricted fuel filter would cause a lean condition common to both banks of the engine.

What is the fuel pressure and delivery volume?

Have you checked for vacuum leaks?

Reply to
aarcuda69062

good question, and if I was still equipped to answer them, I would.. I figured a fuel pressure problem would result in it falling on it's face when it was hammered down, or atleast some loss of power @ high RPM, the opposite being true, the higher rev, the better acceleration is.. either way a fuel filter isn't costly enough to skip over, I'll be sure to pick one up tommorow. As for the vacuum, I've had my head around the EGR for a while swearing I hear a hiss, but could never pinpoint it with that mechanical fan clutch the guys at advance auto parts talked me into making it windy as hell under there..that's why I replaced all the lines short of the firewall. I don't own a vacuum guage but if this is really the direction I'm going in I could get ahold of one and plug those that do go into the firewall for a test,reconnect them and test again to narrow it down those just run the heater controls and shouldn't affect anything if disconnected and plugged right?

Reply to
Dark1

Did you clean the MAF?

It COULD be the Filter, but the one common thing that would act as you described would be a dirty MAF, though you dont describe 'pinging' or spark knock on acceleration.

Go to tccoa.com for general directions - EXCEPT:

It's NOt as fragile as described,

  1. a medium bristled brush - like a cheap paintbrush- will help lots, just dont 'bump' the element

  1. do NOT use windex, unless you clean its residue with alcohol.

- but why not just use rubbing alcohol in the first place

"Dark1" wrote in news:q8zee.439$ snipped-for-privacy@tornado.ohiordc.rr.com:

Reply to
Backyard Mechanic

I wish mine was quite as well placed as that site has it.. lol.. I'll give it a shot though.. thanks..

Reply to
Dark1

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