Originally Posted By: beast3300
Originally Posted By: OVERK1LL
Originally Posted By: beast3300
It looks like it was running rich to me. Maybe vacuum leak. Is the EGR tube still intact on that 2.0 split port?
It's MAF, not MAP. A vacuum leak would cause a LEAN condition, not rich.
How does the PCM compensate for a lean condition? Oh that's right it runs rich.
This isn't an '88 K-Car or an '87 Mustang. The latter which I've had a vacuum leak on and got a rich condition due to reduced vacuum at the MAP and subsequent over-fueling by the ECM; fueling beyond the "trim" factor from the feed-back O2 system.
The Focus we got for my wife had a MASSIVE vacuum leak when we got it; the PCV hose was disconnected. Guess what? It ran LEAN. It ran LEAN because the MAF was telling the ECM it was getting "X" amount of air, and it was getting MUCH more than that. And the amount of air exceeded the enrichen factor based on O2 feedback. It made the car very doggy and it was running VERY lean.
I have a fair deal of Ford experience. I have witnessed BOTH conditions on more than one occasion. On a MAP-equipped car, they will often run rich if the leak is large enough to affect the amount of vacuum seen by the MAP sensor. If not, they can run lean.
On a MAF equipped car, if there is unmetered air entering the system, they will run lean. Of course in closed-loop feedback from the O2 sensors will attempt to bring the A/F back into the acceptable range, but if the amount of correction exceeds the range specified in the ECM, you simply end up with an uncorrectable lean condition. And there is of course a code for this, as we experienced on my wife's Focus. I have NEVER witnessed a MAF Ford vehicle with properly functioning O2's run rich due to a vacuum leak.
The ECM doesn't just magically know there is a vacuum leak and start dumping fuel at it to compensate. It uses O2 feedback, which as StevieC touched on, would at most lead to the car running a "normal" A/F, and if it runs out of correction, lean, as I stated above.
