Quick and easy solution for curing the annoying hesitation, jittering, lag back feeling, stalling or whatever you wish to call it, which happens when you are accelerating your car.

(Note: While this article is dedicated to the Toyota Corolla late models, this will apply to most cars equipped with a MAF or flow meter sensor, either from Toyota or any other brand, like Nissan, Mitsubishi, etc.)

If you own a 2004, 2005, 2006 or 2007 Toyota Corolla and your car hesitates when you accelerate or it hesitates when driving, you should try the solution described here. Below is a list of the behavior your car may show that tells that you should try this procedure before going to a mechanic or repair shop.

• The accelerator is slightly pressed while the car is running and it slightly jitters or hesitates
• After completely stopping the car (a red light for example), it hesitates when you accelerate to continue driving
• Engine power is below the usual level
• Sometimes check engine light turns on

You should know that while those problems can be caused by several issues, including low quality or altered fuel or even a loosely tighten fuel cap, the most common cause is a dirty MAF flow meter sensor.

The MAF sensor (Mass Air Flow Meter Sensor) is in charge of detecting how much air (in mass, not volume) is coming in to the engine, so the ecm computer can calculate the amount of fuel to be injected.

Some times this sensor gets contaminated by lots of microscopic debris that scape the air filter and accumulate on its sensing parts over time. The resulting effect is that the MAF flow meter sensor gets less “sensible” and detects less air than it is currently entering the engine. The reaction of the ecm computer will be to inject less fuel to keep the air fuel balance, taking as reference the false reading of the MAF flow meter sensor. This will produce a too-lean mixture, which is responsible of the hesitation, the loss in power and the check engine light.

If your car engine, besides the hesitation, is also producing knocking or engine pinging at high loads, like when going up through a hill, it is attributed to this too-lean condition.

Before going to an auto parts store or to a mechanic to fix the problem, you should try fixing it your self. If the problem is a dirty MAF flow meter sensor, the solution is to clean it, plain and simple. That may save you some money that a mechanic will charge for cleaning it (you could do the same) or for replacing the part when most of the times it is not damaged, just dirty or contaminated.

Here are some guidelines to do it by your self. If you do, you will be glad that you saved money and learned how to do it for the next time it happens to you, your family or friends.

First of all, you will only need a #2 Phillips screwdriver (shown in the picture below) for removing just two screws and a spray can of electrical cleaner, specially designed for these jobs. Though I said “specially designed”, don’t worry as it is available on any Auto Zone or similar stores. The brand “CRC” is an excellent one and it is also shown in the picture below (I am not affiliated with CRC or Auto Zone in any way, just sharing my experience).

Now, you will need to locate the MAF flow meter sensor in your Corolla. It is very accessible and no mechanical experience is needed to do this. In the picture below, the location of the MAF flow meter sensor of the 2004, 2005, 2006 and 2007 Corolla (1ZZ-FE Engine) is shown. You will find it by opening the hood of your car’s engine compartment and looking at the air intake assembly behind the vehicle’s battery. It is attached in place by just two small Phillips screws. Take the screws out with a #2 Phillips screwdriver, carefully not to drop them off. If they drop, you may end up loosing them and while they can be easily replaced, this will turn from a quick fix to a time wasting ‘searching for a similar screws’ job that might involve a trip to the hardware store.

After removing the two screws and putting them in a safe place, now pull out the MAF flow meter sensor. Sometimes it could feel a little bit attached, but if both screws are removed, it will come out.

In the next picture, it is shown the MAF flow meter sensor already pulled out. Now you must disconnect the wiring harness that is attached to it, by pushing a plastic clip located in the plug, while pulling away the plug at the same time. It will easily come out.

With the MAF flow meter sensor already unmounted from your car’s engine, put it in a table over a paper towel or a cloth and with the CRC cleaner, spray directly to the connector harness to clean the contacts from debris and dust. Just spray it with full force for a couple of seconds. You should wear eye protection or be very careful so the spray back does not get in your eyes. Also, since this product is highly flammable, do this away from open flames, heat sources and in a ventilated area.

Now what will really fix the engine hesitation issue; spray with full force inside the MAF flow meter sensor openings for a couple of seconds on each opening. Avoid the straw of the spray can, to get inside the MAF sensor and touch anything inside. After that, repeat one more time and put the MAF sensor upside down, so the excess liquid drips out. Allow enough time for the MAF sensor to be completely dry before reinstalling it in your vehicle. The CRC chemical is designed to dry almost instantly and it does, but spraying for a few seconds over the MAF sensor’s surface, will considerably lower the temperature, causing condensation from the environment moisture. Just allow it to dry completely before putting it back in the engine. A good trick is, if the engine is warm by chance (you drove the car before doing this job), just put the MAF sensor on top of the plastic cover of the engine for at least 15 minutes and it will dry completely.

IMPORTANT! One final note. Please only use the chemical (spray) described here or one that is for similar purposes and (1) will not harm polymers (plastics), (2) will not harm electrical connections (not acidic) and (3) most important, will not leave any residue when it vaporizes. Cleaners that contain lubricants, like WD-40 for example, may not be used for this job. Any residue left inside the MAF sensor will damage the part. This job is about removing contaminants, not replacing them with some other substance.

That’s it! Enjoy your new-again Corolla!

Thanks for reading!