Beware of Shoddy Aftermarket Add Ons
This past week a shop called me to check out this old Camry that would not pass emissions. It had lean codes but otherwise ran fine. The scan data was quite strange. The LT fuel trim was up to 50%. I have never seen a car run so good with fuel trims that high. When the hood was opened, I saw something that caught my eye right away. A large Aluminum pipe with an aftermarket air filter installed. What concerned me was the MAF bolted into the pipe. There was a boss welded onto the pipe. So the assumption is that the intake pipe was manufactured specifically for this model car. At idle the MAF grams were very low at 2.5 gpm. I would have expected close to 3 gpm. No wonder the trim was high. My diagnosis was to remove the aftermarket pipe and replace with original air box. Fortunately, the customer was able to find an original air box and intake tube from a wrecking yard. After installation, the trims dropped to 2 to 3%.
There are aftermarket manufactures that take the time to flow test their intakes. They make sure the form and function meet or exceed the OEM. In this case, the manufacturer did not do their due diligence and this part is causing headaches for technicians.
Even some mainstream well known manufacturers skip some of this testing. Dinan, a very well known BMW tuner has this exact problem with their exceedingly expensive carbon fiber intake for F chassis cars
Was the maf sensor mounted within 6 inches of a bend in the pipe?
J, is 6" the minimum or maximum spec to cause/not-cause issues?
I don’t have a rule. It’s been my experience that under 6 inches definitely causes issues.
Hi Geoff, Fyi, GM has an installation guide for their performance applications that describe the best practices around MAF placement which aligns with Justin's findings. I posted some of that info on DN previously in this thread:
Thanks Scott. That picture leaves much to be desired. Looks like the MAF just needs to be CENTERED in a six inch section (so 3" form a bend).
Justin, It was more than 6" from bend. I don't think the element was into the airstream at the same spot. The MAF was a bolt in without a housing.
I had a similar experience on a Ford F-150 with a goofy aftermarket intake tube. The truck was towed in and barely ran. Come to find out the MAF was installed backwards. The aftermarket pipe had no indexing for the sensor.
I have seen aftermarket K&N filters affect the airflow in stock airboxes enough to throw MAF readings way off. Ford, Benz, Duramax, Toyota, it doesn’t matter the brand. If I see aftermarket anything on the intake, bring it back to OE is usually the first recommendation I make.
"I have seen aftermarket K&N filters affect the airflow in stock airboxes enough to throw MAF readings way off" - Hi Rich, you're probably too busy to watch all the "other guys" training videos, but both Paul D and a few others, had some great examples on crazy MAF readings with a missing air filter, crushed air filter, and even a bad latch on the box (the lid was playing jack-in-the-box…
Yup. See that crap all the time out here. Usually the current owner has no idea it is there, as these POS cars are sold-off from one man-child-moron to the next. I paraphrase some of my diag classes when I tell them, "look, ALL the training I have, says that STEP ONE is to remove ALL aftermarket equipment and re-evaluate". Since there is no "CEL laws", and they think it "looks cool" most will…
It's kind of like a bunch of chrome parts on a Harley. “Chrome don't get you home, but you look good standing on the side of the road”. LOL Keep it in the wind.
My experience in the Diesel industry is there are a lot of great fabricators out there but seemingly very few engineers.