knockem Posted June 13, 2021 Report Share Posted June 13, 2021 So I have the EPC light coming on on my Lupo. Start the engine and it fires up immediately. And if you hold the revs then it revs normally for about 3 seconds then the EPC light comes on and it does. I've had my vagcom on it and get 18047 - accelerator position sensor 1/2 (G79/G185) P1639 35-10 implausible signal - intermittent. I've cleaned the throttle body and the brake lights still come on. Charged the battery to full. Any help as to what to check with the vagcom would be greatly appreciated as I'm now scratching my head Thanks in advance Quote Link to comment Share on other sites More sharing options...
mk2 Posted June 13, 2021 Report Share Posted June 13, 2021 If it is the pedal sensor, it might simply be a loose plug...? I'm pretty sure ALL Lupos and Arosas are drive by wire, as in there's no physical link between the engine and the pedal. (ok, i think there were a few early skoda factory versions that have a regular cable throttle). The throttle pedal (accelerator) sensor is above the pedal box and IS a right pain to get to. Quote Link to comment Share on other sites More sharing options...
knockem Posted June 13, 2021 Author Report Share Posted June 13, 2021 4 hours ago, mk2 said: If it is the pedal sensor, it might simply be a loose plug...? I'm pretty sure ALL Lupos and Arosas are drive by wire, as in there's no physical link between the engine and the pedal. (ok, i think there were a few early skoda factory versions that have a regular cable throttle). The throttle pedal (accelerator) sensor is above the pedal box and IS a right pain to get to. Thanks for the reply. It's looking like it's the sensor. Just wondering if I could have disturbed something as I did a gearbox replacement 3 weeks ago and was all fine before that and lasted a week after? Is there anywhere on this forum or online that shows how to get at the pedal sensor as laying in the footwell it just looks impossible without taking alot of the dash out or something. Does Haynes do a manual? Thanks again. Quote Link to comment Share on other sites More sharing options...
ObjectiveAway Posted June 13, 2021 Report Share Posted June 13, 2021 What happens if you turn electric throttle valve with fingers while engine is runing? Quote Link to comment Share on other sites More sharing options...
ObjectiveAway Posted June 13, 2021 Report Share Posted June 13, 2021 I think your engine should run with closed throttle as well, and this is IMO fault (because 3sec and engine shuts down) Quote Link to comment Share on other sites More sharing options...
knockem Posted June 13, 2021 Author Report Share Posted June 13, 2021 19 minutes ago, ObjectiveAway said: What happens if you turn electric throttle valve with fingers while engine is runing? I tried pushing it open but it seems to not want to turn. I have run vcds 060 throttle valve reset and it moves it lovely and passes the test. 19 minutes ago, ObjectiveAway said: I think your engine should run with closed throttle as well, and this is IMO fault (because 3sec and engine shuts down) So I can get the car to idle kind of by not touching anything after starting the engine the EPC light comes on and then it hold idle for more like 10-15 seconds before during but it hunts around from around 700rpm up to 1300rpm and sounds like it's missing but only after the light comes on. Quote Link to comment Share on other sites More sharing options...
mk2 Posted June 14, 2021 Report Share Posted June 14, 2021 Check your crank sensor. Unlikely, but one of the most common causes for engines to sputter and die is a dodgy crank sensor. But ultimately, it's either no fuel or no spark. The symptoms sound like fuel starvation, but I don't think it is. Quote Link to comment Share on other sites More sharing options...
knockem Posted June 23, 2021 Author Report Share Posted June 23, 2021 So after pulling the pedal box and swapping out the position sensor it has solved nothing. So now I'm stuck. Is there any measuring blocks on the vcds that I can look at to find some thing out. Weirdly noticed today that the measuring block for engine coolant was sitting at 120C would that cause limp mode with no throttle pedal? At a loss now. Quote Link to comment Share on other sites More sharing options...
mk2 Posted June 23, 2021 Report Share Posted June 23, 2021 Yeah, could be a temp sensor also. Should be around 15-20 when cold first thing in the morning. From memory, there are two temp sensors- they should provide the same reading when cold. Ah, just thought- it might be a power bus fault- often caused by a dodgy power relay (that provides engine loom power). Or even ignition switch - also a common fault. You'll need a voltmeter for that. Quote Link to comment Share on other sites More sharing options...
Skezza Posted June 24, 2021 Report Share Posted June 24, 2021 You scanned it yet? Could be a damaged MAF sensor still plugged. Wouldould cause this issue, or an air leak also... Both would indeed light up EPC light, if you have no EML. Quote Link to comment Share on other sites More sharing options...
mk2 Posted June 25, 2021 Report Share Posted June 25, 2021 Just had a thought... in one of the measuring blocks, you can see the % throttle applied when you put you foot on the pedal. Do you get 0-100%? If it's intermittantly 0 then a value, it could be that the voltage on the power rail to the sensor is dodgy. Most common cause is fuse/relay or a plug. This is an unusual fault... Quote Link to comment Share on other sites More sharing options...
knockem Posted June 29, 2021 Author Report Share Posted June 29, 2021 So the throttle pedal sensor was definitely a fault as it has a big notch as you turn it but after installing new second hand one and starting the engine I got big smell of burning wires so i shut it straight down. fault read again I got a new code saying ignition coil 1 short to earth and low egr signal so had a look in the engine bay and found the earth wire to the coil was red hot and the insulation Burning/falling off. I had changed HT leads plugs and this cheapo ebay coil when I got the car about a month ago because of a missfire which turned out to be broken down leads. so dug out the old coil and hey presto perfectly running engine. So lesson learnt do buy cheap ebay coil pack. I reckon its gone bad and somehow sent HV through the throttle pedal sensor and fried it. Now all I have to put it all back together again. oh and buy a newish engine loom. Thanks for all the help and suggestions @mk2 and @Skezza and @ObjectiveAway Quote Link to comment Share on other sites More sharing options...
mk2 Posted June 29, 2021 Report Share Posted June 29, 2021 That aint right. The loom fuse should have popped. Burning red hot wires means at least 30A. The fuse is rated at 10. The ECU turns off output drivers at about 2.5A. The HT feeding back into the loom reminds me of a cluster i fried in a polo breadvan. Checking the plug leads, a spark jumped straight onto the rev counter feed; Dead instrument cluster.... d'oh. 1 Quote Link to comment Share on other sites More sharing options...
knockem Posted July 7, 2021 Author Report Share Posted July 7, 2021 Reviving this post now haha. So I had 5 days of trouble free driving and then this morning it did the same thing. I haven't fault read it again yet as I am typing this from work but it was extremely similar break down just down the road from my house as before. It has rained over night and I can't remember if it was raining the last time this happened. How annoying is it to find a loom break/short to earth as that's what I'm thinking this is now? I really wanted this Lupo to work out but this is turning into a pain. Quote Link to comment Share on other sites More sharing options...
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