Engine surge issues while cruising

[Kurtis West]

Tries scowering the forums for this topic and have found similar but not so similar issues.

I have an 07 ram QC 5.7 hemi 4x4.

Couple weeks ago I noticed my oil pressure dummy gauge fluctuates now while driving and at an idle. Have yet to run oil pressure test as it seems to drive fine.

However as of last week I noticed while driving at highway speeds I'll give a bit more gas and the rpms will actually drop down before the speed increases.
This generally happens around 1500-1700 rpms.

I've cleaned the air filter (k&n)

And cleaned the throttle body.

Until recently I've had intermittent CEL light for P0420 (catalyst below efficiency)

The light hasnt come back on in over a week

Idle rpm is solid and doesnt fluctuate.

Headers and exhaust are old and have a good amount of surface rust. I'm almost positive of an exhaust manifold leak.

Could an exhaust leak or catalytic converter cause this idle issue at cruising speeds or should I focus more towards the tps, ecm, trans lock issue?

 

[Redtruck-VA]

I would check trans fluid level and fix any exhaust leaks. Then look at spark plugs..

 

[Marley]

PO420 could be several things.

Vacuum leaks, exhaust leaks, bad cats, bad 02 sensors are the main culprits.

Once the code is erased it can take a couple of weeks to reappear as the ECU runs diagnostics.....depending on how much vehicle is driven and severity of issue.

I recently deleted downstream 02's to lesson my headaches.

 

[Karlsweg]

Is it the mds kicking in and out? When mds is activated, it runs higher rpm by 200 or so. At least my 07 does lol.