Even when components look in great shape, they can be bad. SureTrack community member AUTO TECH INC USA had an Audi A4 in their shop that had a low speed misfire. All the obvious parts were checked or replaced. They posed the question to the community, and with the help of fellow community member ericsautomotive, they were able to resolve the issue.
The following Real Fix summarizes the interaction between them in the community that led to the solution.
Vehicle
2005 Audi A4 Quattro 1.8L
Title
Engine Misfire, Replaced PCV Hose
Complaint
Engine misfire at idle and at low speed. At high speed, it runs great.
Diagnostic Steps Performed/Parts Replaced
Computer diagnostic ONLY shows multiple misfire on 1,2,3,4 cylinders. Compression test shows 170 PSI on all 4 cylinders. Vacuum leak test ok, New spark plugs, new ignition coils, and new fuel injectors. Can the ECU create this misfire.
Best Answer from Community Member ericsautomotive
Remove the oil cap with engine running. If engine stalls, check the PVC system for issues. I’ve seen a lot of those valves fail and cause this symptom.
Cause
New PCV valve. PCV Regulator Valve and all vacuum hoses look great, but the vacuum hose from PCV Valve to intake manifold was collapsing on the inside of the hose intermittently creating vacuum restriction and creating engine misfire.
Correction
Replaced defective vacuum hose. Engine runs like new again. Problem solved.
SureTrack® is a powerful value-added feature available with select Snap-on diagnostics tools. It offers an exclusive combination of expert knowledge and detailed parts replacement records, all wrapped in an interactive community.
Want more? Click here for more information on using SureTrack.
Looking for diagnostic tools? Click here to request more information on Snap-on diagnostic tools.
New or Expired SureTrack users: Click here for authorization key instructions.
