Dark1 2012-01-01 07:32:51
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
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
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
Mombu 2012-01-01 08:14:50
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)
Dark1 2012-01-01 08:14:57
But it’s throwing a code for each side.. so I would think it would be
something common to them..
Aarcuda69062 2012-01-01 08:15:03
Does it have an air pump?
Dark1 2012-01-01 08:15:05
Aarcuda69062 2012-01-01 08:15:09
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?
Dark1 2012-01-01 08:15:11
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
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 h*** 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
Backyard mecha 2012-01-01 08:16:04
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
2. do NOT use windex, unless you clean its residue with alcohol.
– but why not just use rubbing alcohol in the first place
Dark1 2012-01-01 08:16:08
I wish mine was quite as well placed as that site has it.. lol..
I’ll give it a shot though.. thanks..