A 2001 Vw Eurovan presented to our shop with initial diagnostic trouble codes P0341 and P1347, indicating problems with camshaft timing. Initial inspection using an oscilloscope to check the correlation between the camshaft and crankshaft signals confirmed that the engine timing was indeed off.
Upon removing the valve cover for a closer inspection and to examine the timing chains, we were confronted with an extreme case of engine sludge. The valve cover and visible internal components were coated in a thick layer of sludge, resembling hardened wax. Due to the severity of the sludge and the timing issues, the customer authorized a complete engine rebuild. The engine was removed and sent to a machine shop for a thorough overhaul.
Following the engine rebuild and reinstallation in the Eurovan, a new issue arose. The engine now exhibited a rough idle and was setting code P0346, specifically pointing to a camshaft position sensor problem. Interestingly, this issue only occurred at idle; the engine ran smoothly and powerfully at higher RPMs.
To investigate the new code, we returned to the basics and scoped the camshaft and crankshaft position sensor signals at the Engine Control Module (ECM). Comparing these signals to known good waveforms, we observed that the exhaust camshaft signal appeared to be approximately 18 degrees out of phase. Further investigation revealed that disconnecting the Variable Valve Timing (VVT) solenoids had no effect on the camshaft position sensor (CMP) signals, which should normally change if the VVT system is functioning.
We consulted with the machine shop regarding the camshaft timing. They expressed confidence in their timing setup during the rebuild but confirmed the extreme sludge they encountered. The machinist reported washing the engine components multiple times and manually scraping away significant carbon buildup, describing it as having a candle wax-like consistency. Despite their cleaning efforts, they acknowledged the possibility of residual carbon deposits remaining within the engine block.
Suspecting that residual sludge might be contributing to the ongoing issues, particularly with the VVT system, we decided to perform an engine oil cleaning procedure using BG EPR (Engine Performance Restoration) oil cleaner. We ensured the engine oil reached full operating temperature and allowed the cleaner to circulate for an extended period. After the treatment, we inspected the engine oil filter, which was relatively new (less than 100 miles). The filter contained a considerable amount of black debris, consistent with carbon deposits. However, the BG EPR treatment did not resolve the rough idle or the P0346 code.
Further examination involved removing the CMP sensor 2 to inspect the reluctor wheel on the camshaft. We observed that the reluctor had some independent movement relative to the outer face of the cam gear. Referring to a VW Self-Study Program, we confirmed this is normal operation. The reluctor is designed to bolt to the inner rotor, which is connected to the camshaft, and is not directly fixed to the outer housing of the cam gear. This observation led us to believe that the cam gear/actuator itself was likely not seized or sticking.
The lack of response when disconnecting the VVT solenoids strongly suggests a malfunction within the VVT system itself. Given the history of severe engine sludge, it is highly probable that residual carbon deposits are still impeding the operation of the VVT system, despite the new solenoids.
To definitively confirm the mechanical camshaft timing, the next step is to remove the valve cover and physically verify the timing marks. Past experience with a 24V VW Eurovan exhibiting similar symptoms, which were ultimately resolved by cleaning gummed-up VVT solenoids (even though the solenoids are new in this case), reinforces the suspicion of sludge-related VVT issues. While considering more aggressive sludge cleaning methods, such as BG’s comprehensive sludge cleaning kit, a thorough verification of mechanical timing is the immediate priority to ensure the engine rebuild was correctly assembled and to guide further diagnostic steps. This case highlights the persistent challenges presented by severe engine sludge, particularly in relation to VVT system functionality in engines like the 2001 VW Eurovan.
