After installing a air/fuel gauge it reads rich at 15psi and 20psi at WOT. Is it time for a new o2 sensor?

It's normal for these cars (or any car) to read rich under acceleration. A good O2 sensor should also bounce at cruise and at idle.

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Francois Villeneuve
Le Talon
Working on it...

It sure dose bounce at idle and while cruise. But should it read rich at 20psi with a stock fuel system? Am I missing something here?

It had better read rich, or you're screwed.

You likely have a stock turbo, which can be run at higher altitudes in hotter weather at 20 psi or so without hitting fuel cut. I've done it. You are not likely to get any more power at 20 psi than at 15 psi, however; it seems the stock turbo heats the air up too much.

The stock fuel system is actually pretty good. Upgrades are usually only necessary when a turbo upgrade in planned. Some people rewire the pump just because it's better to be safe than sorry, or because they plan to upgrade the turbo later.

Try that 15 psi with a 16G and you might run into fuel problems, assuming that you could drive without hitting fuel cut all the time. This is where people need a method of defeating the fuel cut, and (usually) some way of getting more fuel into the engine. Often a fuel computer is used, since some can do both jobs at once, along with bigger fuel pumps and injectors.

It sounds like your O2 sensor is working just fine.



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S.
1000 AAQ: 1000q.dsm.org
ECU Primer: members.home.net/costall/ECUprimer/index.html

As long as it stay rich you are fine. BUT make sure it stays rich and doesn't fall off as the rpms increase. At higher rpms is where the fuel system will fail if it's insufficient.

To add my .02 about the stock system.... I had the rewire done and my a/f started dropping at higher rpms at any boost over 17 psi on my stock turbo.

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Mike J
-Quadcylla-
92 Laser RS-T, FWD
'Pimpin ain't easy'

Thanks for the info guys . I was setting the boost controller when I hit 20psi . 15psi is good for now. While on the subject I plan to install a FMIC, do I need a upgraded fuel pump or will a rewire do the job? The car is a 91 AWD with 2.25 catback exhaust, K&N air filter, custom boost controller and yes a stock turbo.

You will have to try it to know for sure. The incoming air will be colder, but denser.

When in doubt, it is best to do the rewire. It is relatively easy and very cheap.



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S.
1000 AAQ: 1000q.dsm.org
ECU Primer: members.home.net/costall/ECUprimer/index.html