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View Full Version : EPC light and power loss at cruising speed/coasting only when cold.



autocross16v
11-01-2010, 04:39 PM
Whenever it gets below 45-50 Deg. F my car has been hesitating while driving occasionally and has died on me a couple of times. However today it was colder (about 28 Deg. F) and was cruising at about 60mph on my way to work with cruise on when I lost power (idle fluctuated between 1000-1300) and the EPC light came on. As usual no throttle response and after I turned the car off and back on it was ok. Still hesitated every now and then but the EPC light didn't come back on.

I haven't done anything to the car recently and the only code I have is the typical 17743 - Engine Torque Monitor 2: Control Limit Exceeded
P1335 - 35-10 - - - Intermittent.

After looking at common causes online I guess I am just looking for any insight. It just seems odd to me that it happens at low throttle percentages and only when it cold out. It runs just fine when above 50 or so.

Any help would be appreciated.

quattro_mds
11-01-2010, 07:28 PM
Check your plugs. I was running hotter plugs (Iridium) instead of good ole fashion copper and had the same cut out problems, could not figure it out of a long time. Then I changed the plugs to see what the difference between copper and Iridium and bam no more cut outs. Just a thought... If not there my be other gremlins lurking

walky_talky20
11-01-2010, 08:21 PM
This was a code I hadn't heard of before, so I did a little searching about it. The consensus seems to be this an engine load related code. That is, for some reason the engine load is not being calculated properly. Usually this seems to be due to faulty MAF sensor or a boost leak/boost spike situation.

I would assume if it is killing the engine this would be a safety response related to the Drive By Wire system. For example, the engine load is getting higher and higher, and you back off the throttle. The ECU starts to close the throttle plate, but the load goes higher still. It closes the plate more, and despite this, the load value continues to increase. Seeing as it can no longer safely control the engine in response to the accelerator pedal, it throws a fault, shows the "EPC" warning light and cuts fuel. The whole problem here could just be a MAF that is reading too high due to a large boost leak or faulty MAF itself. This is just my assumption as to what is going on based on your description and my research into other instances of this code/issue. This is just conjecture and not based on my personal experience with this code...which is none.

I suppose the first thing I would do is log the MAF to see if it looks good. In your case I would do the normal 3rd gear pull as well as steady state cruising which provokes the code. Next I'd log the boost and make sure everything is working there. You can also check your DV while logging boost. Just let off the throttle all at once (slam the throttle plate shut) while at full boost and make sure the Actual Boost measured by the MAP sensor doesn't spike too high. A boost gauge will not show this spike, only the MAP sensor which is in front of the throttle plate.

Next, you want to look for vacuum and boost leaks. A helpful tool here is the long term fuel trims. If you part throttle fuel trim is very negative, it is highly likely you have a boost leak. If you idle fuel trim is very positive, it is likely you have a vacuum leak. Of course you should also do a visual inspection of the manifold and intercooler hoses as well, and a boost leak test if you can. You should also check the DV manually by sucking and blowing into it's vacuum line. It should hold vacuum and not pass any air when blown into. If the diaphragm is ripped, it will fail these tests.

Hope that gives you some place to start.

autocross16v
11-02-2010, 03:36 PM
I have replaced the MAF about a month ago, and have copper NGK plugs in there since the beginning of the summer.

It is weird because it will do this with cleared codes and if I drive easy (no boost) it still will act up. It doesn't always die, but it will always hesitate under deceleration usually when it is cold out.

I just find it weird that it only does it when cold. I will do some logging tonight when it gets colder and see what I find.

I was hoping someone would have experienced it but I appreciate your input and hopefully we can put our heads together with some more info and figure something out.

autocross16v
11-26-2010, 06:52 PM
Well an update on this. I have been datalogging with VagCom whenever I can and it is cold enough out and have come up with nothing. Everything seems to be right on par with what it should and nothing weird happens when it cuts up. I have probably logged over 240 minutes of driving and used markers so I could find it and so far nothing.

Another scenario that causes it to act up more is when I hit bumps or go around sharp corners such as on/off ramps. Again it only does it when cold out, more common below 35 deg. F. I haven't quite figured that one out and it will do it on a full tank of gas as well. I have checked just about every connector that I could to ensure that it is tight and not wiggling but nothing.

It is still not consistent and it has developed into cutting out when I try to start out from a stop light/sign.

Any suggestions or has anyone ever heard of/had an issue like this?

walky_talky20
11-26-2010, 09:06 PM
Are you still getting the Torque code? If it seems to be temperature dependent, have you logged the coolant temp at all?

If the MAF values look good, the only items that are sticking out to me are the crank sensor (engine speed sensor) or the ECU. I suppose some issue with the wiring harness, or a bad ground is always an option as well. My father has a Volvo S60R and it has a random stalling issue and it will even fail to start up again sometimes. He has found that knocking on the ECU housing fixes it, so we've diagnosed it to be a faulty ECU/bad solder joint. We believe the ECU was chipped and that was the cause of the problems (bad solder job). He barely drives the car, so hasn't worried about fixing it yet.

I guess the next thing I would do is try another ECU. I think it's probably the easiest thing to try. I happen to have a spare '01 1.8T ECU (018 M box) and I'm not terribly far from you (Erie, pa area). I would need it back, but I don't mind loaning it to you for a while if you cover the shipping. PM me if you're interested.

autocross16v
11-29-2010, 05:55 PM
No I am not getting the torque code. Actually the only code I get occasionally and meant to post this up was a "17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 35" code.

I really have a feeling that the too lean code is contributing to this problem. But so far everything I have looked at makes sense. Coolant temp, air temp, MAF, Injector pulse time, 02 sensors. I replaced the MAF about 2 months with a new Bosch unit from ECS. This cleared the misfire codes I was getting and cleared the same system too lean code I have now for awhile. It has come on randomly.

The MAF readings I am getting are good and consistent, and peaks out at appropriate reading. I don't know I am going to do some more searching around. I really appreciate your help.