Rich backfire with Loss of Power

[Deathacus]

Right, almost made it to Colorado. '94 MTX, she's got a rough idle, loss of power, and a pretty consistent backfire. Gets worse under load, set cruise control at 75 and she's just fine after a moment. Oh, and she's quite hot.

There is no CEL, and pulling codes look fine. There was a memory code for low voltage on the coolant temp sensor and the MAF, I cleared those and they havnt come back. May have been a weak battery triggering those. Resistance on the ECT was like, 25 ohm or kohm or whatever on a cold engine on a 75-80 degree day

 

[BaySHO Performance]

You could have a bad plug or wire. Check for spark using one of these:

https://www.amazon.com/Calterm-66331-Tru-Spark-Adjustable-Sensitivity/dp/B000JFHMPC?dib=eyJ2IjoiMSJ9.gCsV55MeRYeHCe4FtE6ACInH3NHHkRB4HPLGN92d_CtCW9lS3L83nfclGVHOBAz0-Rc_-PP1Gnd7uK-2vKoboAwHdZiIfjTNLPL9KC6zMFciPSyBGokAEgTUpRVP-rKCACk6LH4w-uGXTFm1-JGscYMTQoksjlJGzVI26tFQ8ZegKslBav75tejvl7EQcc-a-Mqa3GzvwNsciXfJTuvfAf3Tnr53QmECc22mg-4I39LrYTmTeLHlGe6dLhxXJgBLbrcA51pqBK-Lwm4nftR8B3l-Frbo8A9nVq3OZmzyyZ8.lZx_3Ey-rKYFgtVnzK1ikc5rrI_xyyPX5HGJNo2PaUc&dib_tag=se&keywords=calterm&qid=1784574363&sr=8-1

The engine didn't get wet by any chance? Water in the plug wells would cause a loud backfire. The backfire could easily have destroyed a cat. If the rear cat blew, loss of power would result if a piece of it got stuck in the catback. If the front cat blew, you run the risk of pieces getting sucked back into the engine, scoring the cylinder walls beyond repair.

So I suggest removing the Y pipe and checking the cats. If no black sand, A long flexible pick up tool can be inserted to make sure they are still OK.

 

[Deathacus]

The car did eat a shit ton of wet mud, but didn't see anything in the plug wells.

 

[BaySHO Performance]

The car did eat a shit ton of wet mud, but didn't see anything in the plug wells.

So the plugs must have been dry. However, a plug wire could have got wet. That could have caused a misfire. Do you recall the time relationship between the car getting muddy and the car starting to misfire?

 

[Irish Pride]

He didn't mention spraying down the engine at the car wash before the car show last week. I don't know if that is when the misfire started or not but there was verifiable water in the plug wells.

Did you ever swap the plugs and wires as suggested?

-Chad