Nissan Frontier Vibrates Going Uphill P0400

Maintenance/Repairs
1

2003 Nissan Frontier with a 4cyl engine, just over 300k.

It vibrates and starts chugging anytime it’s under a small load, like going up a hill. Cruises nice and smooth on level ground or going downhill. Feels like a misfire, but idles perfectly and had new plugs/wires installed a few month ago with no problems.

So there’s no service engine light, and no codes set, but when I plug my scanner into it the code P0400 appears and disappears randomly on the screen but never sets itself in the computer.

My question is, where is a good starting point? Any components known to go bad in the EGR system? And would a bad/stuck EGR valve cause these symptoms?

Thanks!

PS - there is also a code set for the catalytic converter, it was catalyst efficiency below threshold but I don’t remember the exact code. Any way this could be part of the problem, or related in any way?

2

It could be that with an EGR fault the ECM is trying to retard the timing due to a looming pre-ignition rattle and that is the cause of the misfire or surge.

Given the 300k miles on the truck, a compression test should be done to make absolutely certain that you’re dealing with a good engine. A dropping cylinder could cause a problem like this also.

3

@nw2012

If your cat is plugged, your engine can’t breathe properly and you’ll have lousy power

Just something to consider

4

Thank you, I’ll keep both of those in mind as I’m working on the truck.