Hey -- I have a NA S4, and I am having some issues with my oil pressure, or the oil pressure gauge... I wouldn't know.

The following happens: Every time I start the engine (doesn't matter if the engine is cold or hot), oil pressure goes up on the gauge, to the first line over zero. As I start to drive, the needle starts to go down very slowly, and about 5~6 minutes later, the needle stays here:



... and maybe it moves up very slightly, but that's it.

Car runs overall fine, except it idles a bit erraticaly when hot, on hot weather.

So, I know what everyone will say -- "Check the oil pressure sender and the cable".

Ok -- what should I check for? And... if that doesn't solve the problem, what else should I check? Maybe the fuel filter is clogged? What else would you recommend?


Any info/feedback will be greatly appreciated!

-D

 

...I don't think the fuel filter being clogged would do that.

Your oil pressure sender is probably the cause. I don't know how to check it; I had mine done by a professional. Anyways, the erratic behavior you describe sounds almost exactly like mine when my pressure sender was bad.

 

So a bad oil pressure sender can **** up an FC's idle?

 

sounds like you have two different problems. The oil pressure gauge probably has nothing to do with the idle. As for checking the oil pressure sender, make sure that the connection is clean and not corroded or covered in oil. There is only the one wire that connects to the sender.

As for the idle it could be a lot of things. Start with the most simple, clean the air filter, check the spark plugs, fuel filter.

 

Will do.

So, the sender itself can't be wrong?

I have a new air filter installed, and next week I'll be receiving new NGK plugs, NGK plug wires, fuel filter, oil filter and a complete belt set

 

Sorry, I missed the erratic idle part of your first post. My bad.

The cheap, easy first step is to check your spark plugs. My car has about 20k on a rebuilt engine, and it seems to foul the spark plugs fairly consistently, always runs and idles better after new plugs. After that, I'd try running some techron through the car, clean your fuel injectors.

Sweet! sounds like you'll be eliminating a lot of potential causes of the problem. If that doesn't fix it, just run some techron through the car on a full tank of gas to clean the fuel injectors.

If that doesn't fix it, you're looking at probably a blown engine or bad fuel pump, but I can't imagine that actually being the case.

 

Wow... a blown engine?

The car pulls fine and runs great... it's a stock NA S4, with only 65k miles... my only "problems" are the erratic idle and this oil pressure gauge thingy...

 

Could be a vac leak too. TPS failure could also cause sparatic Idle.

In fact there are a good many issues that cause bad idle.. Does it pulse up and down at all?

 

It cycles in a pretty rythmical way...

http://www.youtube.com/watch?v=XhZdaM5c5Vk

Cooler weather makes it much more stable... and it looks like it gets worse and more prononced as the engine gets hotter.

Maybe it's a cooling issue? The water temp needle has never gone over half the gauge (on a S5 cluster).

I just ordered a new OEM thermostar and a rad cap...

 

That doesn't sound blown.. So I kinda doubt that it is..

Could definitely be bad TPS settings. Heres a good read from the FAQ bad idle:

http://www.teamfc3s.org/info/articles/idle.html

Also do a search for TPS adjustment. Or just go read up on it in the FSM.

 

I adjust it on a weekly basis...

The thing is, seems like every time I check it with an multimeter, it's off... I always have to adjust it.

Adjusting the TPS helps, but it doesn't really solve the problem.

Maybe I should wait for the new sparkplugs, wires, belts, filters, thermostat and stuff, get them installed and see if things change.

 

I doubt that anyone will say "Check the cable" and if they do, throw things at them.

Your sending unit is probably tired/worn out/or a UAW member.
In either case, a new sender will most likely fix your problem.

 

Just an odd suggestion could it be because he has an S5 gauge setup in an S4 or doesn't that matter?

 

Not really.

 

If it keeps falling out of adjustment you could have a bad TPS.

Good plan. Don't spend money you don't have to.