I have a Mazda Miata,2000. It stumbles and occasionally misses on acceleration,just off idle. I have replaced timing belt,spark plugs,plug wires,coil packs,catalytic convertor,upstream and downstream O2 sensors. what can be causing the stumble and miss?

Did you replace air filter and clean throttle body and change fuel filter if have not done so in a while ?

new air filter,new fuel filter,sprayed throttle body. If anything,the stumble/miss is more pronounced. I had to disturb the throttle position sensor to clean the throttle body. maybe that is the problem??

Put in some fuel injection cleaner in gas tank.

I did that a few days ago. BG44

the stumble became more frequent and pronounced after i sprayed the throttle body. I removed TB,took throttle position sensor off to isolate it from the spray. whatever it is,it is getting worse

Clean throttle body again but this time use a old tooth brush to clean inside of throttle body while holding open choke and also use a micro fiber cloth and wipe the place were the choke sets when it is closed.

I cleaned TB again,per your advice. when i went to restart car,battery died. low voltage may be the culprit. i doubt I'll find a battery for a Miata on Sunday

Have you checked your idle control valve or idle air control located under the throttle body they tend to cause stalling, irratic idle, and idle droop on decel.

going away on vacation;will get back with you guys next week. thanks!

I removed the IAC,sprayed it with cleaner. I had done this with success on Ford 3.0 V6 engines. it made no difference. the problem is getting worse. I discovered a dead cell in the battery,installed a new one. sometimes low voltage affects electronics,but it made no difference. The car stumbles on rapid acceleration,misses,especially coming off low RPMs. I checked the wiring connections to the camshaft position sensor also

Have your fuel injectors tested may have bad injector is injectors.

Also have the fuel pressure regulator tested .