misfire issue

[91eagle_tsi_awd]

i did a search but couldnt seem to find my problem.

my car has been misfiring when i downshift for a while now.i didnt have a thermostat on the car so i put one on the other day.now when the car reaches normal operating temp. and i turn it off and wait like 10 mins to try to start it back it shuts off and when i rev it ,sounds like its running on 3 cylinders ,huge misfire.it also does it sometimes at idle ,starts to misfire really bad,sputters and sounds like it wants to shut off.dont really know what the problem is so i dont know where to start looking.when it does this and i rev it seems to go a while after a little while.anybody have any ideas what it might be??

car has
msd spark plug wires
nkg plugs

also the base timing on the car is not set ,its been like for a while and i never had this problem till now.

 

[DSMcrazy3]

It may have those plugs/wires, but how long has it had them? That is usually the problem when it comes to misfire, but timing could be another culprit, also fuel, are there any fuel upgrades done?

 

[91eagle_tsi_awd]

spark plug wires are maybe about 4-5 months old,about 2000 miles on them as well as the plugs.car still has the stock fuel system.i also have all my emissions eliminated .i tried to put it on the set timing but i cant get my damn timing gun to flash.on my second timing light because i thought the first one i bought was defective so i exchanged it and this one doesnt flash either hooked it up the way vfaq tells you but i had no luck

 

[91eagle_tsi_awd]

i forgot to mention ,my af gauge seems to die out when i downshift ,like the voltage from o2 sensor is really low.thats when i have my misfire.but as far as the car sputering when it cools down for a while i have no clue what that might be.it wasnt doing that without the thermostat in the car.

 

[Patterson]

i forgot to mention ,my af gauge seems to die out when i downshift ,like the voltage from o2 sensor is really low.thats when i have my misfire.but as far as the car sputering when it cools down for a while i have no clue what that might be.it wasnt doing that without the thermostat in the car.

Is that a wideband O2 sensor? if it's not, don't go by that. They are basically a blinking light. Plus, you'll always be lean with you downshift and are off the gas. I bought an autometer A/F gauge, i like it because it looks pretty cool, but I think i'm going to get a real wideband O2 hear in a bit

 

[91eagle_tsi_awd]

no i dont have a wideband but i soon as i get a new job thats the next thing on my car.

 

[Patterson]

sorry, i hit the wrong button!
it is definately an ignition problem. pull the plugs to see if they are burning correctly and make sure that they are still gapped to spec. In addition, is the CEL on? if it is, get the code so that way you can isolate the problem.
I had a similiar problem with my car. My third cylinder was misfiring and i couldn't figure it out. I ended up breaking out the Voltmeter and checking the resistance of the coils. I then found my culprit!

 

[91eagle_tsi_awd]

my cel is not on.ive been wanting to change my coil for so long .im going to swap it out with a friends and someone also told me to change my cas.so ill try that if the coil isnt the culprit

 

[ddavisaf]

What sort of recent maintenance have you done to the vehicle?
If you havn't tried it, rotate the CAS 180°.
Check the resistance of your coil pack, both primary and secondary coils.
Ohm the plug wires and make sure they're in spec.
Inspect the plugs to make sure they're not fouled.
Make sure you're running NGK BPR6ES plugs gapped at .028".
Make sure your fuel filter isn't clogged.
Make sure your injectors aren't clogged.
Run a boost leak test.