How many times have you checked all of the obvious parts associated with a trouble code, but they look perfect? Even when parts look like they are in great shape, they can be bad. One SureTrack community member was faced with this issue while working on a 2005 Audi A4 Quattro 1.8L. The customer was complaining that their engine was misfiring while idling but ran well at a high speed. Let’s see how this technician, with the help of another SureTrack community member, found his way out of this dilemma when trouble codes and disguised good-looking parts just weren’t enough for a fix.  

The Diagnosis

The technician started by running a diagnostic test and found there were multiple misfires on 4 cylinders. He followed up with a compression test that showed a 170 PSI on all 4 cylinders and a vacuum test, which all proved to be okay. After also replacing the spark plugs, ignition coils and fuel injectors, he still could not find a solution. This is when he turned to the SureTrack community for advice.

A fellow community member suggested removing the oil cap while the engine was running to see if the engine stalls, and check the PCV system. The technician was finding that the PCV Regulator Valve and all of its vacuum hoses appeared to be fine. He did find that the vacuum hose between the PCV Valve and the intake manifold was collapsing on the inside of the hose, intermittently creating vacuum restriction and creating engine misfire.

The Fix

The technician replaced the defective vacuum hose, and the engine runs perfectly. This technician’s story is proof that not all part inspections can be done with a quick glance of the exterior. Luckily, with the help of a SureTrack community member, one more customer left happy.

Real Fixes from Mitchell 1’s SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read the Real Fix in the Mitchell 1 ShopConnection Blog.