OBD II woes

[SondraS2k]

My S, which has a CT s/c w/ aftercooler, kicked on the CEL on Saturday when I was almost to Houston. I had no choice but to drive it home, which I did with no apparent issues (no knocking, sputtering, increased idle, etc... everything seemed normal). CEL was still on yesterday, so my bf and I took his car to the autocross instead (:cry:... I really wanted to drive mine). I took mine down to his place so that he could hook up his OBD reader to it, and.... the light wasn't on when we started it this morning. We hooked up the reader anyway, and it kicked back a code of P0171, which Google tells me is a lean condition.

Unfortunately, I don't have gauges on the car yet to know if that's right or not, or if it's even still a valid condition, since the light isn't lit anymore. Notably, this isn't the first time my car has done this. Any ideas? Is it really running lean, or should I go back to blissful ignorance and enjoyment of my car?

TIA!

[repiv]

This may be a temporary condition that could lead to a more permanent situation. The service manual states as follows to diagnose this, however, since you car has a supercharger, I will add a couple more points to look into at the end.

It is possible that, in time, other codes will pop up in conjunction with P0171 (lean condition). Troubleshoot these, then re-check for P0171.
1. Codes for MAP sensor. Might want to try the old "MAP Whack" trick or even to clean the sensor air passageway underneath the sensor. It ends up in the inner edge of the throttle body. Remove the intake tube and you'll see it. Spray with WD-40, then with compressed air. Collect the spray with a rag.
2. Code for Primary O2 sensor. This is the one in the header. I doubt this one will show up but if you run too lean for too long, that sensor could get fried.
3. Code for Secondary O2 sensor. This is the one in the cat. I also doubt this one will show up unless your cat is in real bad shape, but this usually only happens if you've been running really rich for a long time.
4. Code for VTEC system. If, for some reason, your VTEC is not actuating, then this can affect the burn situation in the engine. You should be able to tell if VTEC cuts in at around 6000 rpm. If not, then you need to check oil level, oil pressure and possibly consider checking the wiring harnesses going to the VTEC solenoid. Lastly, you might have to check the VTEC oil screen, just behind the solenoid, to make sure it's not clogged.

A. Check fuel pressure. A lean condition can be the result of low fuel pressure. This can be caused by a clogged fuel sock, failing fuel pump, clogged injectors, failing fuel pressure regulator. In your case, you need much higher fuel pressure than stock due to the S/C.
B. To check the O2 sensors, you'll need to check voltages and stuff, so this is best done at a shop. You need to bring the engine up to operating temp (after fan comes on) and then take measurements with a scan tool.
C. The EVAP purge valve may need replacing. To determine this, you need to apply a vacuum on the intake manifold side of the canister to see if it holds. Again, this is best done at a shop.
D. If all else checks out, then you need to check valve clearance and possibly replace fuel injectors.

Now, since you've got a supercharger, you should probably check fuel pressure and spark plug gap and condition first and consider a fuel injector cleaning. Depending on which plug you're using and what gap you have, the plugs may not be operating properly anymore. The best plug to use in your case would be the OEM platinum plugs at a gap of 0.032".

[My_yella_s2k]

p0171 sounds like a primary o2 sensor...

didnt u have a problem w. the CEL before as well Sondra?

[Bipod]

Just a liitle FYI... I also had this problem on my AP2 with the CT s/c (no aftercooler)... I went thru new injectors, a new fuel pump and new plugs and each would quell the situation for a little while, but it always came back... unfortunately I ran out of $$$$ to keep fixing the problem so I sold it... :sad:

[Chris S]

Just a liitle FYI... I also had this problem on my AP2 with the CT s/c (no aftercooler)... I went thru new injectors, a new fuel pump and new plugs and each would quell the situation for a little while, but it always came back... unfortunately I ran out of $$$$ to keep fixing the problem so I sold it... :sad:

Which leads to my big problem w/ aftermarket FI - after doing it, there have been so many "cooks in the kitchen" than nobody is accountable for your problems, leaving the customer holding the bad for diagnosis and repairs.

[Randy W]

If it is the primary, I do have a spare. It isn't new, but it is good. You can pick it up at anytime.

[SondraS2k]

head -> wall, repeat. I'm sure this is all normal stuff with FI, but MAN am I ever tired of it...

Will update when I know more, assuming my brain doesn't explode in the meantime.

[repiv]

Oh, one last thing that I overlooked. The Comptech kit has always been plagued by poor wiring connections of the ESM. That's the little MAP clamp they use to hide boost from the ECU. I've consulted on about 1/2 dozen Comptech kits back in the early days and in virtually all cases, anywhere from about 1 month to a year after installation, it turned out that it was the wiring connections playing havoc with the system (humidity, corrosion, vibration caused the connections to degrade). After the owner had gone back and ensured that all connections were checked and soldered or re-checked and re-soldered, there was never a problem again. If the ECU even sees a hint of manifold positive pressure (as in a poor signal clamp from the MAP sensor) all sorts of weird symptoms and codes can arise, mimicing various ECU faults. One dealer had gone through all sorts of parts replacements and still got no joy. Since they installed the kit, they felt obliged to continue the diagnosis. It was only after I insisted that they go back into the wiring and painstakingly soldered all connections thoroughly, that the car ran perfectly. That owner is still running the same trouble free Comptech car today and it's been 5 years now.

[hecash]

Your fuel pressure regulator is an adjustable, rising-rate type in the CTSC, Sondra. Have someone check it, and if necessary, adjust it for you (pull the manifold vacuum line to test). You should get 43-47 psi at idle and 65+ at full boost as I recollect.

[griffon]

My bet would be a loose connection