how do you know when you have to change your leading or traling coils? My car is starting to choke out but it only does it from time to time and its start to backfire a little more so I think its either the leading or traling coils but I don't want to purchase them for nothing.

I already had the tps sensor changed and had it adjusted, map sensor, o2 sensor, air sensor, spark plugs and wires (ngk), fuel filter, oil and oil filter, air filter, and just for other work i also had all 4 belts changed, brakemaster cylinder, and i also changed the brakes so I think its the coils but how would I know the check engine light doesn't turn on at all. And I've also reseted the computer. So can anyone help?

 

A worn out AFM is also a possible cause.

A longshot might be fuel pressure problems.
Check the voltage at the fuel pump. A weak connection or worn out pump are possible.

Or maybe clogged secondary injectors.

 

They don't go bad very often. If you are troubleshooting an intermittant problem, the best be is to probably buy a used set (they're cheap) and swap them on if there is any doubt. It will be hard to bench test for an intermittant issue.

Sounds like you've covered all the other bases.

Another thing to check is the engine coolant temp sensor on the water pump housing. If it is reading low, the car will run richer then it shoud. Exhaust leaks can also cause backfiring.

 

How about this guess - a cracked inlet duct?

 

The guy at the muffler shop said the car is backfiring due to an engine problem not my exhaust.

 

what's that?

 

The plastic pipe from the AFM to the TB.
It can be cracked but as long as the engine sits still the crack can be pinched shut.
Then under load the engine moves over just enough to open the crack.
Bingo - an intermittant vac leak.
It's more common on turbos, but it can happen to NA's.

 

Does anyone have any coils for sale???