2000 Mazda series 4×4 auto.. Engine missing under load..

[TNHighwayman]

2000 4x4 Bseries auto with 130k miles.

In overdrive, while going uphill at highway speeds, the engine (maybe tranny?) will miss. If I floor it, it misses worse.

Still happens, but happens much less when not driving up hill (load).

No check engine lights.

I uhooked just the positive batt. terminal (unrelated incident) right before this started. Someone said unhook battery completely for 5 min and that might reset computer? This sounds like a longshot.

I dunno.. thanks

 

[MaicoDoug]

Resetting the ECM? Not a bad idea. Q: why did you disco the + batt terminal anyway?

Try listening to your AM radio for the ignition system arcing when this misfire is happening. That should help rule out that, next would be a fuel delivery issue. Did you move some wires around from their normal resting position? A little more info on exactly what was happening before this happened including washing under the hood? Forensic analysis is not just a TV thing (in real life there is much more drama).

 

[TNHighwayman]

Thanks for the reply. The truck wouldn't start cause it had a short in the battery cable, so I wiggled it to get power, then started it.

After that, the issue started. Im going to unhook and reset the PCM later today.

No washing, no cable wiggling (other than battery)

 

[pjtoledo]

what engine, how many miles on plugs 'n wires?

 

[Uncle Gump]

Once we know engine size... I'll move this to the appropriate engine forum. You'll likely get more answers there.

 

[TNHighwayman]

what engine, how many miles on plugs 'n wires?

Plugs and wires replaced by previous owner (just bought truck), so he claimed.

I will inspect them later today.

Engine is the 6cyl. 4.0

 

[Mechrick]

In overdrive, while going uphill at highway speeds, the engine (maybe tranny?) will miss

You can start it up at night, open the hood and look for arcing. Or mist the wires down with water in a spray bottle and see if it gets worse.

If the engine is extremely lean you could get the same symptom, but I would think it would trip a light at this point.

 

[ekrampitzjr]

Check the wires to make sure they weren't installed on the wrong plugs/wrong spot on the coil pack.

 

[TNHighwayman]

It's getting worse. Going to reset ECM, replace fuel filter, plugs, wires tomorrow.

Any other simple things ti replace while I'm at it?

The distributor box under the plugs looks old/original. What are the odds it's an issue with that?

Not throwing a code, so not sure what a mechanic could do. Could they run it on a diagnostic machine to troubleshoot?

 

[TNHighwayman]

It really only happens and worsens at highway speeds 60+. Rarely at slow speeds.

 

[Kira]

Any change in operational routine?
For example: Had this vehicle been used for local driving on cheap gas then summoned to high speed service?
It might balk due to clogged injectors.

Any "air rushing" noises?