autom8

This is my first post. I have a 1996 Cabriolet with a 2.8 12V motor. It has approximately 115,000 miles on it. When I first got it a few weeks back, I replaced the spark plugs (which turned out to be "sparknubs") and its air filter. This made quite a bit of difference in performance. I feel that this car should have more bottom end torque than I am getting though (1500-3000 RPM). I suspect that the previous owner used regular unleaded gas and, because of it's age, probably has quite a bit of gunk in the injectors. So far, I have fed it three tanks of 93 octane gas with Techron injector cleaner with no noticeable improvement in performance. Long story short: Although there is good juice in the top end, the bottom end seems to be severely lacking. It starts right up, the check engine light is not on and having VAG'd the car and there are no codes. Does anyone out there think that replacing the fuel injectors, fuel filter and fuel pressure regulator might solve this problem? For a V6, this car should be making more power. Thanks.

Rusty Spokes

Our 12v V6 engines are not hot rods..for sure. But they do have power enough for cruising. You said you scanned the OBC and there were no codes..which is very good. Is the car OBD2? Did you use a Ross-Tech VCDS?

If you have a bad injector(s) or an air leak..you should get a CEL..so assuming all that is fine..could be the OBC has not reset from the conditions prior to your tune up..it takes a certain number of re-starts (I don't recall how many). If you have the radio code..you could disconnect the ground from the battery for a while and see if the OBC re-sets.

A fuel filter is always a good idea..but I don't think that is the problem. The same goes for the pressure regulator or injectors. It can get expensive just putting parts on the car. without measuring fuel pressure or observing the injectors spray pattern (with great care)

Do check the vacuum lines and the big plastic intake housing..where it joins the manifold..be sure it is snug there at the big rubber gasket that joins those two parts together. There are some rubber bushings in metal pins down there..be careful and don't drop them..they disappear into another dimension always.

Has the timing belt/water pump been changed? I ask as some will use paint marks to try and set the cams rather than use the cam tool (cheap on Ebay) If the cam timing is off then the engine never quite runs right. Poor low end performance is one of the symptoms of cam timing being out of whack The engine will run and not throw a CEL if the cam timing is sort of close. Easy to enough to check with the cam bar tool and spotting TDC on the front crank pulley. Pulling the cam wheels to re-set the timing is more involved. Paint on the cam wheels or timing belt is a clue.

autom8

Rusty Spokes,

My car is OBD2 and I used the genuine Ross-tech scanner. As it turns out, the news is good. I found a frayed vacuum line running from the manifold to a Y-splitter that goes to the fuel pressure regulator and a place under the MAF (vacuum canister?). Having replaced those rubber hoses, the car runs stronger and shifts much more crisply. Before it would take a lot of pedal to make the car downshift. I think that my problem has been solved. I'm definitely going to replace all of the rubber vacuum lines this weekend. Every hose is the old German cloth braided stuff that is color coded to the plastic lines. In this case, the line was green.

The intake housing seemed too easy to slip off but it was too dark to inspect the rubber gasket. I think that I will replace this part as well. Do you have a good source for these (and other B4 Audi parts)? The pins managed to stay in this dimension though. Thanks for the warning.

As for the timing belt; it was changed by the previous owner. I haven't inspected it for paint marks though so that is on my list as well.

Thanks for the quick reply!

Rusty Spokes

That intake housing being loose on the rubber gasket can be a problem. The quick fix is find some old phone cord, like RJ14 and remove the rubber gasket. Cut about 14 inches and insert the cord inside that gap on the rubber gasket. It thickens the clamping on the intake housing and prevents an un-metered air leak there.

TurboEverything

Definitely check out ALL your vacuum lines. Mine had about 4 that were cracked or not even connected at all. Simply installed some new hoses and she definitely ran a little better, but not any better than I think you want it to be. Like Rusty Spokes was saying, these 12v v6’s are a tank of a motor. They aren’t very fast. Enough to spin all 4’s in the dirt or snow? Yeah sure. But you aren’t going to spin tire on pavement without the wheel cut and the clutch dropped. Mine has 245k miles on it and it still has good power even though rings are starting to go and things are starting to leak a little. Not a huge deal to me though as a 2.7 swap is in the near future