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D3: idle-speed control valve

14K views 6 replies 4 participants last post by  E46life91  
#1 ·
Hi folks

I have just recently picked up an e46 325i 5-speed manual, unfortunately the car has already thrown me a couple of warning lights and has stored some codes. What I am experiencing is that the car starts, idles and runs perfect from a cold start, but if I am to shut the engine off hot after 10 miles, 20 miles, 30 miles or whatever and then start the engine again after 5 minutes or so the idle hunts up and down and within a few hundred yards of taking off I get 3 warning lights and the car enters limp mode. The lights are EML, DSC triangle and amber brake (!). This happens every time I start and run the car while hot, and doesn***8217;t resolve until it***8217;s cooled down. The codes stored in my C110 code reader are D3 idle speed control valve, mechanical fault. The first time it occurred I had to carry on for 50 miles or so which ended up also causing a check engine light with 2 other codes stored, these were: CA fuel trim bank 1 control limit, and CB fuel trim bank 2 control unit. Yesterday I removed the ICV and checked it, it was already moving freely but I thoroughly cleaned it out with carb and intake cleaner and reinstalled it, checking for leaks in the rubber boots and that the DISA valve was functioning ok while I was at it. Took the car out for a spin for half an hour and thought the issue was resolved, but went to drive off again 15 minutes later and the fault returned with the same D3 fault code stored. Any suggestions for what to try next or where to look? I don***8217;t want to replace the ICV without being certain that***8217;s definitely at fault. I took resistance readings from the ICV as follows:

1-2 10.6ohms

2-3 11.8ohms

1-3 22.4ohms

Was planning to try running the car with the MAF disconnected next to see what happens, would this show that the MAF may be at fault?
 
#2 ·
Anyone at all have any experience of this? Started the car from cold today and drove solidly for one hour without shutting down the engine, engine runs perfect through the entire rev range and sat idling perfect for 10 mins in the middle of this journey. No misfires or intake leaks, just smooth performance. However once back home, shut the engine down, start it up 5 minutes later and the idle hunts up and down immediately! Drove off and within 100 yards all 3 warning lights illuminate and car enters limp mode. Something isn***8217;t quite right from hot starting, if the car is running hot from its first cold start it***8217;s unaffected completely, even after running continuously for an hour. Cleared the codes and unplugged the MAF sensor and the car started fine with perfect idle, drove off and no warning lights, smooth performance. Could the MAF be at fault? The fault code is still D3 ICV but I***8217;m 99% sure it***8217;s in fine working order after checking it the other day. Is it possible to test the MAF functionality with INPA?
 
#4 ·
I will update this incase it helps someone in the future...my D3 idle-speed control valve mechanical fault code, and as a result limp mode with the 3 warning lights, were all being caused by what I discovered to be a cheap aftermarket MAF sensor fitted to the car. I replaced the MAF for a genuine Siemens VDO one and this has completely resolved the issue, no running problems whatsoever. So check your MAF sensor and avoid cheap aftermarket ones at all costs would be my advice!