99 toyota corolla hesitates while excellerating

mine did the same thing and it was oxygen sensor
since engine light came on there should be an error code
on computer.Get a diagnostic checker or take to a garage and have them hook uo to the diag connector. I bought a diagnostic checker few years ago and it has come in very handy
sure hope this helps!!

does it seem to sputter or hesitate when you excellerate through a turn?

P0171 is a lean code. Most common cause for this is a vacuum leak. The cat would throw a P0420 code. Don't mess with the cat. The P0300 code is a random misfire code. Look for a vacuum leak first.

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

i would check your fuel filter and air filter first if they are dirty then i would change them. and if it still does it then it might be one of the sensors on your throtttle body. like your tps sensor or the iac valve or it could be your mas sensor you can also clean these with some throttle body cleaner and mass air flow cleaner that you can pick up at any auto parts store

The jerking and shuddering at 45-50 mph seems like it could be a transmission/torque converter problem. Check your transmission fluid. Make sure it is at the right level, and that it is not dark or burnt. It should be a bright red or pink.

Frank
Frank's Friendly Cars Maui Car Rental
www.MauiCarRental.biz

have you made sure its not an engine cylinder.Dodgy H/T lead,spark plug,vacuum leak,It seems to happen when engine is under load.Are your ht leads showing any signs of tracking?

it could could be the coolant temp sensor.

check sparkplugs and airfilter

it could be TPS or MAP. corolla dont call it a map but its on the firewall near the brake booster check your vacume lines see if any have come off or cracked or dry rotted. vacume leak could be the problem. there are a lot of them to check.