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spyysee
04-18-04, 11:32 AM
Hope everyone took advantage off the top off/down days we've just had.
OK. Here's my problem. Intermittent code 44, which is a lean condition. The transmission(auto) was replaced at the end of the winter, and this was the first time I saw the check engine light. Could be a coincidence.
I replaced the o2 sensor, replaced the fuel pump, cleaned and oiled the
K&N, opened the cover.
The car seems to run well and has plenty of pull. Mileage is down, however.
Let the experts chime in.

jmccloud
04-18-04, 04:32 PM
Did you do the fuel filter? Some early models had a service bulletin recommeded added return line filter to reduce pump noise. You may have 2 filters.
PS TOP IS OFF TODAY, YES IT'S SHOUTING

MBDiagMan
04-18-04, 06:05 PM
If the lean condition problem started at the same time as the transmission replacement, then you need to check your vacuum modulator line. If it did not get reconnected or split when trying, the vacuum leak would be leaning it out.

Good luck,

vettenick
04-18-04, 06:53 PM
Sounds like you have a vacuum leak somewhere. Your mileage is down because the computer is dumping fuel to compensate for the leak and it can't keep up, that's why you have a code 44. One other thing to keep in mind ...is the exhaust system tight, because if there is a leak before the oxygen sensor, it will draw extra air into the exhaust stream and fool the oxygen sensor into thinking you're running lean. I'm assuming the exhaust was dropped when the trans was done.

spyysee
04-18-04, 06:53 PM
If the lean condition problem started at the same time as the transmission replacement, then you need to check your vacuum modulator line. If it did not get reconnected or split when trying, the vacuum leak would be leaning it out.

Good luck,
I'm starting to suspect that.
I cleared the codes, which I failed to do after installing the o2 sensor and fuel pump.
I drove for about 30 minutes and got on it a few times. I let the ECM "relearn"
and so far the code has not re-set.
What are your thoughts on that?

vettenick
04-18-04, 06:56 PM
Also, make sure that your air pump control valve is working properly. If its still pumping air into the exhaust manifolds after it goes into closed loop, then that's another source of air in the exahust.

spyysee
04-18-04, 06:56 PM
I read something like that in my helms... I really don't detect any telltale sign of leakage.
My tranny man DID replace some exhaust bolts however.

spyysee
04-18-04, 06:57 PM
Also, make sure that your air pump control valve is working properly. If its still pumping air into the exhaust manifolds after it goes into closed loop, then that's another source of air in the exahust.
How do I check that?

spyysee
04-19-04, 10:05 AM
well, I checked for the vacuum modulator line and was told by my tranny guy that
there isn't one!
Checking MAF and will borrow the scan tool next.

mattyg92
04-19-04, 10:35 AM
44 is oxygen sensor lean

things to check

exhaust leakage or air pump tube loose

maf sensor out of range or dirty

fuel pressure not set right

SSTibet
04-20-04, 02:34 AM
I found the following from http://autorepair.about.com/library/faqs/bl178g.htm

It says:
"Code 44 means a lean condition. Could be it ran out of fuel temporarily. Fuel pressuretoo low? Clogged fuel filter? It could also be an exhaust leak near the O2 sensor. There are lots of possibilities!"

Hope this helps...

vettenick
04-20-04, 07:07 AM
To check your air pump valve, just disconnect the electrical connector. By default the pump should pump air to the air cleaner. If this doesn't happen, the valve is stuck. If that tests OK, then get a scan tool to look at the oxygen sensor voltage values. Once the car goes into closed loop, voltage should vary between .900 volts and .100 volts...and should be constantly changing back and forth. If the voltage is constantly low, check the wiring to see if it's rubbing against something. If it's doing that, it will keep the voltage low.

MBDiagMan
04-20-04, 09:59 AM
Even though I passed the ASE automatic transmission test, I don't consider myself an a/t person. It makes sense that the Vette has no vacuum modulator due to it being an early computer controlled car.

If you suspect a vacuum leak, and that sounds like a legitimate suspicion, you should connect a vacuum gauge and see where you stand.

Good luck,

spyysee
04-20-04, 11:42 AM
I'll have the scan tool this weekend and will hopefully narrow it down with the help of the Helms and this forum.
Thanx for the input.