VW Bora Rough Idle Fixed: Throttle Body Guide

As someone with moderate experience working on VWs, I dealt with almost identical symptoms on my 2005 VW Golf, sounds very similar to your situation. The main symptoms were a rough idle and stalling, which pointed to a vacuum leak in the system. After some diagnostics, the workshop found a deteriorated hose connection from the vacuum pump to the air valve. These vacuum hoses often become brittle with age and can crack or split. The repair involved: Complete inspection of all vacuum hoses, Replacement of the defective connection, Testing the throttle body operation, Clearing the check engine codes Total cost was 175€ and completely resolved the idle problems. The car has been running smoothly since the fix. Before suggesting specific solutions, could you share: Current mileage, Any recent repairs or maintenance, Whether the check engine light stays on constantly or flickers, If the rough running happens only when cold or also at operating temperature These details would help determine if your issue matches what I experienced or might be something different in the air intake system.

Latest service was done 2 months ago at 82287km. The check engine light actually flickers rather than staying constant. After reading your input about vacuum hoses, I checked more carefully around the manifold pressure sensor area and noticed one of the hoses feels quite soft and shows small cracks. This could explain the intermittent engine stalling and rough running issues. The engine runs poorly both cold and warm, but gets notably worse after the engine reaches operating temperature. This seems to align with your vacuum hose theory, as heat would make the damaged hose expand and potentially leak more. Given the age of the car and similar symptoms you described, I will have the vacuum system thoroughly checked, particularly around the air supply components where the hose shows deterioration.

Thanks for those extra details, they really confirm what I experienced with my Golf. The flickering check engine light combined with deteriorating hoses matches exactly what happened in my case. The fact that your symptoms worsen at operating temperature is a classic sign of vacuum leaks affecting the air intake system. The soft, cracking hose you found likely isnt the only one affected. In my repair, what started as one visible vacuum leak led to discovering two other compromised hoses that werent immediately obvious. The heat cycling over years makes all these hoses vulnerable at about the same mileage point youre at. Since your symptoms mirror mine so closely, Id strongly suggest having all vacuum hoses inspected and replaced as a set. On my Golf, trying to replace just the visibly damaged one didnt fully resolve the engine stalling, it took a complete vacuum system overhaul to get proper air flow restored. One tip from my experience: have them check the connections at the intake manifold extra carefully. My vacuum leak actually originated there but showed damage further down the line. The repair cost should be similar to what I paid (175€), assuming no other issues are found during the inspection.

Thanks for the detailed follow-up. After reviewing your vacuum hose experience, I took the car to my regular workshop today. They confirmed multiple vacuum leaks, just as you predicted. The main culprit was indeed the cracked hose I spotted, but they found two more deteriorated hoses near the throttle body that were causing additional air intake problems. The manifold pressure readings were fluctuating wildly due to these leaks, which explains the inconsistent idle problems and engine stalling. The total repair came to 190€, slightly more than your case, since they also had to clean the throttle body while doing the vacuum system work. The car now idles perfectly and the check engine light has stayed off. The rough running is completely gone, both in cold starts and at full operating temperature. Really appreciate the advice about checking the entire vacuum system rather than just replacing the one visible bad hose, you saved me from having to do the job twice.