Matthew Henderson Posted August 21, 2022 Report Share Posted August 21, 2022 Hi, I've got a 2001 1.0 MPI, and I've replaced the egr about a week ago, because we were getting egr errors on starting the car, even after clearing the errors, so we replaced it, and I am now getting the p0408 error after 10-15 mins of driving, cleared the error keeps appearing, any tips for trying to stop it, cheers in advance Quote Link to comment Share on other sites More sharing options...
mk2 Posted August 21, 2022 Report Share Posted August 21, 2022 Does it use any oil? I'm guessing you checked all the obvious like temp sensor, coils, plugs, leads, inlet air leaks etc... Quote Link to comment Share on other sites More sharing options...
Matthew Henderson Posted October 1, 2022 Author Report Share Posted October 1, 2022 Sorry for delay but no doesn't use much oil and coil leads intake all good. Replaced the egr valve and seems fine for a while and sometimes after a run (maybe an hour's) it's fine and then it will come on when you start the car Errors are p0408 and p0141any feedback gratefully received. Thanks Quote Link to comment Share on other sites More sharing options...
Matthew Henderson Posted January 22, 2023 Author Report Share Posted January 22, 2023 (edited) Hi Again - Ok so problem still not gone away, So far the post cat lamda sensor replaced with new one, egr valve replaced with new one, removed and cleaned the inlet manifold to egr breather pipe, and have managed to clear the P0141 code, but not the P0408. After clearing the P0408 code, (With OBD Reader) the car will run fine with no issues, and no lights on the dash, we have driven the car for 2.5 hours no issues at all, but if you were to switch the ignition off after running the car and then re-start the car (Warm, maybe a few minutes later), the check engine light comes back on (P0408). The only other thing that has happened is that I ran the car to work from cold (No check light on dash after clearing code) some 15 miles, left it at work for 8 hours or so and then drove back home again with no check light!......but once back home and a few minutes later started it again and check light came on! and so the cycle carries on. don't understand .....grrrr, just to say that we have checked the usual suspects, leads, coil are all good, but haven't changed the coolant temp sensor on the radiator. Anybody have any other suggestions, short of a bigger hammer? Many Thanks Matthew Edited January 22, 2023 by Matthew Henderson Quote Link to comment Share on other sites More sharing options...
mk2 Posted January 23, 2023 Report Share Posted January 23, 2023 Yeah, temp sensor. Any wierd engine problems with ALL vdubs between 1998 and about 2007, first step is swap the temp sensor. There have been hilarious YT videos about it. But they're not always the culprit... One place collected so many broken sensors, it filled a big bin. Like 5000 sensors! Quote Link to comment Share on other sites More sharing options...
Matthew Henderson Posted January 30, 2023 Author Report Share Posted January 30, 2023 On 1/23/2023 at 10:15 AM, mk2 said: Yeah, temp sensor. Any wierd engine problems with ALL vdubs between 1998 and about 2007, first step is swap the temp sensor. There have been hilarious YT videos about it. But they're not always the culprit... One place collected so many broken sensors, it filled a big bin. Like 5000 sensors! Cheers for that. I did buy and replace the temp sensor, but the problem still persists.. Anybody have any other ideas Quote Link to comment Share on other sites More sharing options...
mk2 Posted January 30, 2023 Report Share Posted January 30, 2023 When warmed up, can you see any engine data? Like O2 voltage, temperatures, ignition advance numbers etc. Quote Link to comment Share on other sites More sharing options...
Matthew Henderson Posted January 30, 2023 Author Report Share Posted January 30, 2023 Hmmn - No that's not anything I can access I'm afraid. Anything else I could try It's just odd it only happens once the car is restarted when warm, but can be driven all day with no Engine management light once reset via the reader! Quote Link to comment Share on other sites More sharing options...
mk2 Posted January 30, 2023 Report Share Posted January 30, 2023 Hmm. You say you changed the EGR valve and control solenoid. Have you tried shorting the two wires together, only because I'm wondering if there if an open circuit to the solenoid in the plug or wire. It says circuit "high", which I'm wondering if it really means open circuit. 🤷🏻♀️ I'm almost guessing now. It's the hot or cold start that stumps me. Or perhaps it might be because the EGR isn't working, which causes the wrong values to be measured at the air flow/map sensor (or whatever sensor is being used). So when cold, the engine is running in open loop- O2 sensor not working yet, and all the ECU numbers are basic running, not corrected. So any error is ignored. But once warmed up, it senses that something is wrong, and flags a fault. But it might just run a check during transition from cold, open loop running to warmed up, closed loop. Have you checked that the EGR valve moves when plugged in. I can't remember- is it vacuum activated or just electromechanical on that engine? Might be the vac line...? Quote Link to comment Share on other sites More sharing options...
Matthew Henderson Posted January 30, 2023 Author Report Share Posted January 30, 2023 (edited) Cheers for your help mk2.......... Yes the EGR has been replaced with a new one and its electromechanical rather than vacuum, so although I haven't replaced a control solenoid, I assume that would be part of the electrical EGR unit, please correct me if i'm wrong but haven't seen any obvious solenoid lurking in the engine bay. I get your point with regard to an open circuit when cold and warm etc but would that not be a permanent issue given that the car can run warm with no isssues until switched off and back on again. From cold - Turn ignition on - clear the error code with scanner - start the car (Light off) - run car as long as you like - no EML, and once warm (Possibly 2 hrs of driving) still no EML light, but if you were to switch engine off and then restart, the EML will come about 2-3 seconds after starting the engine and so the cycle repeats. I have also found that from cold - clear the code - drive to work (30 mins) - leave the car for 8 hours - start the car - drive home with no EML Grateful for your assistance thus far Could it be something to do with the Cat possibly, but again why when its restarted Edited January 30, 2023 by Matthew Henderson Quote Link to comment Share on other sites More sharing options...
mk2 Posted January 30, 2023 Report Share Posted January 30, 2023 Nah, not the cat. You'd get a different message. Ok, i don't think it's any ignition component. Or any fuel component, like injector, regulator or pump. The ECU is measuring the exhaust gases mix, and it's convinced that the cat upstream O2 sensor is fine. Not sure how smart the ECU error checking routine is in that model, but it can mess with the mixture by firing just one of the injectors (at a time) during normal running to find faults, by enrichening the fuel air mix- then a split second later see the resulting change at the sensor. All hidden from you. It can try all the injectors and if it sees the same result for each one, then chances are the injectors are fine and the O2 sensor is fine. So then it knows that the fuel system is working ok. But it knows if the EGR is playing up by watching how the mix changes as the exhaust gases heat up. So it thinks there's an issue with EGR.... or at least that's what diagnostics is telling us. So what is meant to happen is that the exhaust mix is meant to richen up a bit when EGR is activated (not as much fresh clean air is being allowed into the engine, so the exhaust "should" get slightly richer). Helps reduce NOX emissions. So maybe the exhaust mix isn't getting richer? I'm thinking aloud here. Maybe there's air getting into the engine via a manifold leak somewhere, or a pipe or a dodgy brake servo (through the vacuum pipe). Perhaps all the sensors and electromechanical actuator thingies are all just fine and there is actually something wrong with the engine. But something small enough that you'd not notice it. 🤷🏻♀️ I really have no idea at this point. Quote Link to comment Share on other sites More sharing options...
Matthew Henderson Posted January 31, 2023 Author Report Share Posted January 31, 2023 Yeah I kind of see what your saying and having another look can’t see anything obviously leaking is the any obvious/easy to check the inlet manifold as they are plastic and I guess given the age of the car could be a potential? Quote Link to comment Share on other sites More sharing options...
mk2 Posted January 31, 2023 Report Share Posted January 31, 2023 The old trick is to use gas (lpg/propane) down a thin pipe, very slight gas flow, so you don't blow up everything. When you get the gas flow pipe near the suction leak, the revs go up a bit when idling, but only for a moment, as the ecu will instantly try and throttle back the engine. It sucks in gas instead of air through the leak. Or use a stethoscope. Or simply disconnect every single pipe going into the manifold and block them off. That will eliminate pipe leaks. Mk4 golf engines were(are) known for their crap leaky plastic inlet manifolds as well. Sigh. Quote Link to comment Share on other sites More sharing options...
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