my car is hesitant and sluggish. its been like this for a month. so far i took to the mechanic and he gave these codes: po128-coolant thermostat, po300-misfire, and po502-vehicle speed sensor. So far, I put in new spark plugs, a new air filter, and fuel injector cleaner. my car idles fine but drives very inconsistent. if i press on the gas pedal too much, the CEL will be blinking. it also seem like the vehicle speed limit is around 70 mph before it hesitate. is it possible that the speed sensor and the wheel speed sensor not syncing caused all this problems? can anyone tell whats going on? thank you!!

I love this car. I'm making payments on this car even with the problems. buy here pay here. I would hate if something happened to this beautiful car

 

Your issue sounds like a plugged catylic converter. After drving a good distance (like 15-30 mins) look underneath the car, the cat will probably be glowing red.

 

PO300 Misfire! You need to go to a Mechanic who has a scanner that can pull detailed scans. He will be able to tell you what cylinders are misfiring. If your wires and plugs are good then the problem is 1 or more of your coils. These cars have 3 coils on the passenger side of the motor that send the spark through the wires to your plugs. They are numbered 1, 2 and 3 from front to back. They fire 2 cylinders at the same time.
They fire in the following order:
(1) 1 and 4
(2) 2 and 5
(3) 3 and 6
They fire both cylinders at the same time. That is Why your power loss is So great.
It is rare for a coil to go bad. But when one goes bad the result is a big loss in power because you are misfiring on 2 cylinders. I had these same symptoms I found my car was misfiring on cylinder 2 and 5, coil # 2 was bad. You should only have to replace the coil that is bad.
I replace all 3 when Mine was bad but that was my choice not a necessity. Replace the coil associated with the cylinders that are misfiring and you will be fine.
If you find that it is misfiring on only one cylinder, it could still be a coil but that is highly doubtful. That would be a wire or plug.
As David said, I would Also check out your CAT. If it is clogged it causes too much back pressure and could cause a misfire or backfire.
Between these two you should be able to find the problem and get your babe back in the peek of health.
Good luck and Safe Driving!

 

All my coils only quit firing on one side

 

What dose that mean? We need a little more detail in order to help!

 

I don't think its the catalytic converter. It might be the coil. The drives fine while engine cold other then the sluggishness then the hesitation shows up. So I'm going to drive the car w/o the tps (throttle position sensor) see if the sluggishness stop. If it does drive better w/o the tps, then it's most likely the tps.

 

P0300 is a random misfire, and that can usually be fuel related if it's not your ignition system. Which could explain why it is fine when it's cold, because the car just dumps as much fuel as possible until the o2 sensor warms up and begins to read.

 

you know what I take that back, it is the catalytic converter. Which means I'm going have to pay a pretty penny. It probably went bad a lil bit after I brought the car. The previous owner didn't changed the spark plugs because the rear facing spark plugs (2,4,6) look really bad and about time I changed them it became a bigger problem.

 

Glad I could help, glad top hear your getting your monte back up to tip top condition.

 

Sounds like prob I had is the cat. One thing u can try is drill a little hole in the cat and if it helps just a little there is your problem. If not u can just weld the hole back up! Hope this helps