Hey all!! This is my first post on this site and I hope that the wealth of knowledge that I have seen on here can help me out.. I have a 94 Z A4 with 155K miles that I am having a few issues with. First, about 2 years ago I hit about 8inches of water on the road and flooded the engine.. I got it started and running fine afterwards but ever since my idle has been screwy.. On cold starts it will idle at 5-600 RPM's but when it warms up it idles at 1500-1700 rpm's. I replaced that TPS and IAC with no changes. Annoying, but I can deal with it.. Anyone have any ideas for a fix??... Now, last Tuesday leaving work I lost all oil pressure. I rolled to the nearest parking lot and let it idle a bit to see if it was just the gauge or actually no pressure. Sure enough the lifters ticking started so I shut if off immediately and grabbed the car trailer. This past Saturday, I pulled the pan off and it already has a Melling M55HV oil pump on it that the prev. owner must have installed. I looked up inside the engine and everything seems to the fine with the oil pump drive gear and it had the metal coupler from the shaft to the pump itself. Could there be any other options of failure other than the Melling pump? I have always run Mobile1 5W30 and everything looked clean internally. I have read on another forum that the preferred pump is the Melling 10554 high volume pump. Is the consensus the same on here? Also, what oil do you guys run in your cars? I am at a standstill on what the issue could be because I would think if it were the cam or crank bearings the pressure would have dropped slowly and not immediately. Open to any ideas!! Let me know!!!

 

I think the consensus is usually to not run a high volume pump on a stock pan.

 

Run a mechanical gauge to verify the OEMs accuracy. Then go from there, but truth be told it sounds like rebuild time. Just because things look to be good doesn't necessarily mean they are.

 

Well, when it goes back together it will DEFINITELY have a mechanical gauge installed. Just ordered the Melling 10554 std. pressure pump because I still will be running the stock pan, new pickup, and I went with the new K&N oil filter to pick up any metal that worked loose. I think that I am going to run 10W30 Mobil1 instead of the 5W30 that I was running to hopefully take up any new extra bearing clearance (lol). I think it will be fine since it gets stored for winters. Any other inputs will still be accepted!!!

 

10w-30 is NOT necessarily thicker at operating temps. Matter of fact with M1 the 10w-30 is often THINNER than their 5w-30.

I would refill it with a cheap oil because you are unlikely to be able to use the oil long as oilpump failures are next to unheard of and you have made no effort to find out what the real problem is.
After that if by some chance that all works out well and you want a thicker oil Castrol Syntec 0W-30 labeled made in germany is a pretty consistently thick 30weight oil.

With the 5w- and 10w-30 thing you are confusing cold flow and hot viscosity and failing to understand that the hot viscosities are a RANGE and as a rule M1 tends to be thin for it's ranges. You put a few miles on it and M1 0w-40 is hardly any thicker than the Castrol Syntec 0w-30 or an Amsoil which tends to be at the thick end of the ranges.

Far as the idle I would get hold of a scanner and see what the IAC is commanded to do.

 

Did you pull the intake and check the drive stub? That would be the most likely failure spot with an HV pump. A 10554 is SV not HV.

 

I had the same problem, and like shoebox said, I lost the drive stub. I also found a hv pump in mine.

 

Thanks guys for the input! I am kind of shooting from the hip here so if I failed to do any basic troubleshooting I apologise..
Shoebox, is the drive stub the black thing that goes in the block where the distributer used to go that holds the drive gear against the cam? I am going to your site soon and hopefully you have a component view of it.
Keep 'em coming!!

 

Yes that is what they are talking about, and yes HV pumps commonly destroy them.

 

It's in the cam swap guides...

 

sweet... looks like when I get the bottom end buttoned up, I will be tearing apart the top end... Im thinking its a good time for a cam swap.. Where can I get a new drive stub, if that is the problem?!? Summit, Jegs type of places?

 

It is a dealership piece though some guys find a new gear to fit but I think they still need a little machining.

If you are serious about a cam swap don't bother buttoning up the bottom oilpan has to be pretty much dropped at the front to pull the timing cover.

 

Part number for this oil pump drive is: 1103868

 

And then there is the brass drive gear issue that further complicates things. The drive gear on the cam should match the hardness / same material as the gear on the oil pump drive shaft. There are difference in some aftermarket gears.

 

There was a false prophet selling cams with the wrong gears for a few years so there are some out there, though if you use a competent cam source it wont be a problem.