Sometimes, what is seemingly a complex problem can have the simplest of solutions…if you know where to look! Such is the case with this Audi Quattro “power loss / misfire” problem. Let’s say you have the owner of a 1992 Audi Quattro standing at the front counter. He says his car has developed a loss of power and occasionally misfires on acceleration. Of course, the first thing you think of is that the fuel filter or air filter is plugged or maybe an ignition part is bad. Or maybe…
Then you find out that the owner has just replaced the fuel filter, air filter, spark plugs, ignition wires, distributor cap and rotor – with Audi factory parts, and he seems to be mechanically adept. Now the plot thickens. The next logical question you pose to him, as you scratch the stubble of your burgeoning goatee, “Did this problem start before of after you replaced those parts?”
You were secretly hoping he was going to say “after” weren’t you? No luck – The reason he replaced the parts was because he thought a thorough tune-up would eliminate the existing problem. “Rats!” you think. “It’s NOT going to be one of those easy to diagnose jobs.”- Or is it?
Looking at the technical service bulletins (TSBs) in your automotive information system (online or disc-based), you find a TSB that describes his vehicle’s symptoms perfectly. According to Audi, some 1988-92, Audi 2.3 liter, 5-cylinder Quattro’s may exhibit a loss of power and/or an engine miss because of low fuel flow. The cause is a restriction at the inlet banjo bolt on the fuel distributor. (See diagram.)
The culprit, in this case, is a mini-filter inside the banjo bolt that can become partially or completely clogged. This filter was supposed to be replaced every 7,500-miles. Sometimes these filters were overlooked, the parts departments quit carrying them or they became prematurely plugged due to a high amount of contaminants in the fuel tank.
The fix is to replace the old banjo fitting (with filter) with a new type. The illustration below shows the difference between the two.
If the hex head of the banjo bolt has a raised shoulder (A), it contains a mini-filter.
Replace mini filter with a new type banjo bolt. (Part No. N0210712)
The hex head of this banjo bolt (B) does not have a raised shoulder and does not contain a mini-filter. This is the one you want to use.
Taking a print out of the TSB to the car, you quickly identify the old type banjo fitting. After installing the new style banjo fitting, you test-drive the car and the problem is solved. Unfortunately, the owner spent a lot of money replacing parts that might still have been serviceable. On the other hand, when he finds out what the problem was and how you professionally diagnosed it, he probably will give you all his future repairs. Now wasn’t that easy?