Help! Bad Dyno, Lean Condition

[Chris Corolla S]

I hope someone can offer some insight into a problem with my 2001 Corolla.

Over a year ago my local car club got a group rate to do dyno runs. I decided to take my Corolla (only mod CAI) over for a baseline run. Stock 2000-2002 5-speed Corollas generally put down about 110 hp and 110 lb-feet of Tq to the wheels. Mine dynoed at 88 HP and 98 lb-feet of Tq. The techs were afraid to do a third run because my A/F ratio was “dangerously lean” up to almost 17 around 6,000 RPMs. The obvious reason for the low power was the lack of fuel. I had no check engine light at the time.

A few months later I got a check engine light, but it was “rich condition cylinder #1” which was solved by ditching my CAI, which had a muddy, clogged filter.
Later on during this year, my clutch started slipping badly, and I am now having it replaced. I haven’t driven the car yet with the new clutch, but I noticed a lack of power at high RPMs before the clutch was slipping.
If I put 87 octane in the car, which it is supposed to run on, it knocks a little. It seams to run better on 89 octane, but still lacks high-end power.
I asked the guys that are doing my clutch to put the car on their engine analyzer, but they said they can only reference trouble codes and there is nothing to check if it isn’t throwing a code.

Questions:

How can my A/F be so bad without throwing a check engine light?

Is it possible that the Wide band O2 sensor could have been thrown off by a slipping clutch (to my understanding it is independent and does not reference the dyno output, plus I do hear knock with regular fuel)

What could be causing the lean condition if one exists? (I checked the O2 sensor voltage and it was working right if I checked it right, I cleaned my MAF as well.)

My last idea is to pull the fuel pump and see if the inlet screen is clogged up.

Answers/guesses/thoughts appreciated.

-Chris

[Toysrme]

You must keep the exact same diameter pipe for the MAF. Otherwise the mixture will swing wildy rich, or wildy lean (larger/smaller). You also must keep a MAF away from bends in piping. Which will also throw them off.
The wideband would not care about the clutch. It cares about the exhaust stream.

I would start by checking the fuel trims. Resetting the ECU to clear the fuel trims & checking the fuel pressure.
Vacuum leaks 2 win.

[Chris Corolla S]

Thank you for your reply

Originally Posted by Toysrme

You must keep the exact same diameter pipe for the MAF. Otherwise the mixture will swing wildy rich, or wildy lean (larger/smaller). You also must keep a MAF away from bends in piping. Which will also throw them off.

Hhmmm yes I have certainly heard of this.
The celica GTS guys do a mod where they hack the maff holder section of piping from their stock airbox and insert it into their CAI to smooth out the power band.
I still wonder why it wouldn't throw a code if that was hapening. I think the EL Prototypes CAI I was using DID have smaller diameter piping than the stock MAF location.
That would be great though because the CAI is gone now, so the problem would be solved.

Originally Posted by Toysrme

The wideband would not care about the clutch. It cares about the exhaust stream.

I figured

Originally Posted by Toysrme

I would start by checking the fuel trims. Resetting the ECU to clear the fuel trims & checking the fuel pressure.
Vacuum leaks 2 win.

I have unhooked my battery several times. Infact recently I did for hours while I hooked up the new stereo. I'm not sure if that would re-set the fuel trims but I believe it would.
I'm not sure how to check fuel trim/pressure. Maybe with a volt meter at the injectors? I can check my hayne's manual for that stuff and for how to check for vacum leaks. I don't currently have access to a wide-band.

Thanks again.

[Toysrme]

np
Fuel pressure gauge.

[Eye8Pussies]

^ yup yup....go through one thing at a time....

and worst come to worst, get a new fuel pump and FPR and then get an safc to tune it out as well

[Chris Corolla S]

I'm not sure but maybe the problem is OK now.
I took off my intake right before I drove accross the country. I got 40mpg on the trip, which is great. I was getting bad gas mileage as one symptom of my problem. Now that I have a new clutch the car does seem to pull more normally. Once I break it in I will do some full throttle runs and see what my but-dyno says about the lack of top-end power.