How to pinpoint cause of surge and stall with OBD2 device?

Maintenance/Repairs
,
1

Hi All!
2007 Nissan Versa 1.8 DOHC 126Kmiles automatic.
No recent check-engine lights.
I have a basic OBD2 diagnostic scanner. How can I use that to pinpoint the following problem?

Last couple days, experienced intermittent light rpm surges in stop-and-go traffic, including surges (kind of like the car revving itself lightly) and also one stall when stopped at a light. So far, it’s only happening when warmed up, and even then just intermittently. No CEL, at least not yet. No problems at speed. It might be a bit sluggish with acceleration, but I’m not positive.

I’m assuming that it is NOT a vacuum leak because it’s intermittent.
I’m assuming it’s NOT a clutch/transmission issue, since surges also happened when stopped at a light. Correct me if I’m wrong on either of those assumptions.

Symptoms seem similar to symptoms of a bad idle air control valve, but my understanding is that this car has ETC instead of IAC.

Would like to be able to narrow possibilities down to avoid fishing expedition with parts and labor. Anything to watch for on my OBD2 scanner?

2

A dirty throttle body can cause that type of problem.

However, a DTC doesn’t usually show up when the throttle body is dirty.

So, you can’t rely on a scanner to tell you if that’s the case.

Tester

2 Likes
3

My first thought was also to clean the throttle body.

One thing you could do with the OBD 2 tool - if it will put out and save live data - is to drive it around while recording data. Record, at minimum engine load/rpms, throttle position, and the fuel trims. See what the fuel trims are doing during those “episodes.”

1 Like
4

Are you still seeing lean fuel trims with this car? Did your fuel pump fix this?

Have you checked for a crack in the air tubes between the MAF and the throttle body?

1 Like
5

If it is easy to do, like by removing the intake air boot, take a close look where the edge of the throttle butterfly valve meets up with the throttle bore. Do you see any gunk or corrosion there? If so, it may be causing the throttle valve to partially stick. That is a relatively easy job on my cable-activated-throttle Corolla, but don’t know for your Versa.

1 Like
6

Thanks all. Sounds like consensus is “check–and might as well clean–throttle body”.

Mustangman, yes, a new fuel pump solved earlier issue of dipping fuel pressure (which I had measured by attaching a fuel pressure gage). Engine has been running great since then (last couple thou miles I guess) until this problem. When I disassemble tube from MAF to throttle body, I’ll check around the tube for cracks/leaks.

Question for all. At some point in time, does it make sense to just replace throttle body with its attachments? Or will they last say 200K miles with occasional cleaning?

7

You replace the throttle body only when it gives an indication that it needs to be replaced.

They usually last the life of the vehicle.

Tester

1 Like
8

This morning cleaned butterfly valve, and later took car for long drives. No more wonky rpms, surges, or stalls! Thanks for guidance, fellows!

BTW, inspected tube between MAF and throttle body. It was intact.

3 Likes