VW Lupo Diesel: Glow Plug Warning Signs & Smoke Alerts

Had a similar situation with a 2001 VW Polo diesel. The symptoms match what you describe, constant preheating lamp, flashing check engine light, and exhaust smoke under acceleration. The heating element control unit was indeed the culprit in my case. The plug connections had corroded over time, causing inconsistent signals to the glow plugs. This led to incomplete fuel combustion, which explained the smoke and engine misfire symptoms. This is typically a serious issue that needs prompt attention, as continuous driving with faulty glow plug control can lead to vehicle stalling and potential engine damage. The repair involved: Testing the glow plug control unit, Cleaning all connector pins, Replacing corroded wiring harness, Verifying proper voltage at each glow plug Worth checking the actual glow plugs first though, they are easier to test and less expensive to replace. If those test fine, then investigating the control unit and its connections would be the next logical step. Suggest having a professional diagnostic scan before any repairs, as similar symptoms can also indicate injection timing issues.

Thanks for the detailed response about your Polo issue. The symptoms really do sound identical to what Im experiencing with my Lupo. Since cold start problems are getting worse, I might need to get this fixed soon. Curious to know, do you remember roughly how much you ended up paying for the full repair? Also, has everything been running smoothly since the fix, or have you noticed any other engine light issues?

The repair turned out to be exactly what I suspected, a faulty glow control unit connection. Got it fixed last month for 95€, which covered fixing the cable connections that had deteriorated over time. The diagnostic test confirmed it was just the wiring to the control unit causing the problems. The good news is that since the repair, the engine light has stayed off and cold starts are perfect again. No more smoke from the exhaust when accelerating, and the diesel engine runs much smoother overall. The glow plug preheating system now works as it should. It was a relief the issue was just a connection problem rather than needing to replace the entire control unit, which would have cost significantly more. Worth getting these symptoms checked early, waiting too long can lead to more expensive repairs down the line.

Its been two weeks since I got the repair done and Im really glad I followed through with fixing it. Found a reputable mechanic who specializes in diesel engines and the whole experience was much better than my previous repair encounters. The diagnostic test confirmed it was indeed the glow control unit causing all those warning lights and smoke issues. Total bill came to 280€, a bit more than expected but included a full system check and cleaning of all connections. The mechanic showed me the corroded parts and explained everything clearly. The vehicle runs perfectly now, no more warning lights, clean exhaust, and starts right up even on cold mornings. No engine misfire or vehicle stalling issues since the repair. Looking back, I probably should have dealt with this sooner, but at least its sorted now and I know what to watch for in the future.