Hi guys, hope everyone is having a great summer so far. I wanted to ask for help troubleshooting what happened to my 2004 6 speed today. I was cruising on the freeway and had noticed the CEL light come on and then quickly turn off. Drive ability remained unchanged for next 20 miles until I was one exit away from my destination. The CEL blinked and then stayed on and all of sudden the rpm’s dropped to zero with no power to the engine. I managed to safely coast it to the side of the freeway and then proceeding to turn off the ignition. I waited for about a minute and then turned the vehicle on and drove it alongside the freeway outside border with the flashers on until I got safely into a parking lot after the exit.

I would imagine it was on limp mode as there was no power and wouldn’t let me rev past 3k and 25mph. As I waited for the tow truck to come; I disconnected the battery for 10 mins and then rested the ECU by pumping the brake 15 times to see the needle bounce back and forth confirming reset. I turned the vehicle ignition and it turned on like normal with the rpm’s at regular range. I decided to drive it around the parking lot and rev’d it with no issues and change to power!? Since I have AAA and had already called in the tow; I decided not to chance it so proceeded with having the car towed.

When I got home and plugged in my ODB scanner, I didn’t get any CEL’s on the history as the computer was reset (even in the stored option screen). Here’s my thought process, the engine is back to running normally and there is no CEL’s triggering when I leave the car idling. I don’t want to drive the car until I check/change the spark plugs and coils (I have spares). What else would you guys recommend I check/ change before taking it on a test drive? I also checked the engine oil level to see if coolant was mixed in along with the radiator fluid which is at normal fluid level and free of contamination as well.

 

Did the rpm drop to 0 while the car was still moving? As in.. was the engine turning but the tach showed 0?

 

From what I remember, yes it was. There was no power and it felt like I was in neutral as giving it gas did nothing and all I was doing is rolling and slowly loosing speed as I made my way from the far left lane to the right lane.

 

So if the engine was turning but rpm read zero, your ECU either isn't turned on or has lost connection to the dash or to the ESS. Loose battery terminal or ground? See if you can clean and snug them down.

 

i routinely check and clean the battery terminals along with the ground wires since I am running a sound system. The music didn’t skip a beat so I know the battery connection didn't trigger off. To be honest, I am starting to think the rpm’s stayed on and I just believed they went off since the engine was basically dead and the car was only coasting and not allowing me to accelerate.

 

Fuel pump

 

I was also going to say fuel delivery could be it. Maybe constant highway driving cooked something. He says he revved it driving around the parkinglot though so doesnt sound like the usual cutout at higher rpm.

Another similar sounding issue was when my throttlebody was dying it closed and had a similar effect where i lost all power and the throttle did nothing. Normally with the key on you can wiggle the throttle pedal to hear the TB opening and closing, but I couldn't. Sometimes power cycling off and back on after a minute would fix it. Sometimes I had to disconnect the battery for a minute.

 

Seen them fail pretty much as he described a few times. The engine dies just driving along then later fires right back up again only to die again soon after.
Have also seen them cutout as you describe so .........

 

Thank you guys very much for the help. I will drive the car on my 30 minute commute tomorrow. I will be taking my ODB scanner and also keep to the right of the highway in case I experience the same issue. The fact that I reset the ECU didn't help as I was left with no CEL code. If this happens tomorrow, I will take a pic of the CEL on the ODB scanner to share with everyone. I am hoping I can repeat the same as yesterday and be able to drive home after rather than get towed again. I don't believe the fuel pump has ever been changed on the vehicle as well.

 

It's a maintenance item ...supposed to be changed every 100,000(ish - not sure of exact interval) kms. So If you have that many miles/kms on it you should change it regardless of whether that is your issue or not.

 

I drove the car yesterday 30 miles each way for my commute without a single issue. The odb scanner didn’t pick anything up as there was no CEL that came on. I have ordered the fuel pump from Rock Auto. I bought the Delphi brand as they sell the pump complete with housing. I have had good experiences with Delphi products so decided to go that route instead of the OEM Mazda one that was 3-4 times the price.

 

Fuel pump issues can manifest morw when the tank is near empty. Fuel cools things down

 

Agreed, i have the bad habit of waiting until the gas light comes on to fill up. The reason for this is because I run premix and find it easier to drop in my 8oz plastic container i carry instead of measuring the amount. I plan to start filling up at a quarter tank going forward and simply adding 3/4 of the plastic container so I don't run into any issues with the fuel pump.

 

*Problem Solved* I replaced the fuel pump a few weeks ago and have not experienced this issue or any CELs since then.