Hey guys, so it appears my car's condition is getting worse as I try to diagnose problems (first car and not a mechanic). This is going to be a long post because I want to make sure I give as much information as possible, if anyone can give advice it would be greatly appreciated.
Engine is 1.8T 20V AUQ (Cupra FR) with a decat and RAMAIR intake.
When I first got the car it was idling rough on first start, and this was gradually getting worse. I eventually replaced the MAF sensor under the advice of a mechanic as unplugging it while idle seemed to make the engine run smoothly. I got a BOSCH MAF unit (not just the sensor because I didn't know you could just change that yet), and I was happy with the car's performance.
After noticing an oil leak the mechanic suggested a rocker gasket change in an attempt to scan the problem from the top down. I agreed and he changed this for me and fitted some spark plugs I had bought too. At the same time I got the two front wheel bearings changed as they were really bad (making a lot of noise).
The car was alright after that but then I noticed the main problem I had all this time was how rich the car was running. Despite the fact that there's no cat, I wouldn't expect that much petrol smell. I get a strong smell from exhaust on and off for a few seconds consistently. There is also a petrol smell coming from the front of the car (I think, although it could be wafts from the exhaust). EVAP Canister is ticking but I've read that this is normal for VWs. I'm assuming since EVAP system is under vacuum it wouldn't be causing the rich condition?
The mechanic scanned the codes back when I changed the MAF and got:
- Brake Switch (F) Implausible Signal P0571
- Catalyst System Bank 1 Operation below threshold P0420
- Fuel Trim Bank 1 (Mult) System too Rich P1127 Intermittent
- Pressure Drop between Turbo and Throttle Valve P1297 Intermittent
There was an additional "System too Lean Intermittent" code the first time it was scanned but it didn't come back after it was deleted.
So, wanting to do some investigation myself, partly out of wanting to solve it and partly to save money. I did some research and caught on to the idea that the Pressure Drop could be causing the Rich condition, as air that had been accounted for could be escaping. Not having a full picture I checked what I thought I could, starting with the tubes near the top of the engine; DV and N75, as well as the inlet to the throttle body. They looked fine as far as I could tell. I have a jack and some stands but I have not been brave enough as of yet to get under the car to check the pipes around the turbo and towards the intake.
I cleaned my air intake and that didn't really change things, although it was very dirty.
I then took off the DV itself and checked if it was holding air by pushing the valve up, placing my thumb on top and checking if there was suction when releasing the valve and my thumb. It seemed fine (again I don't really know what I'm looking for nor do I really have the tools or experience). I put the DV back on and started the car, it sounded rough as usual and the petrol smell was there, idling at ~792 and dipping slightly every few seconds. I thought I'd try disconnecting the MAF sensor to see if it made a difference and it didn't seem like it did until I reconnected it and the idle started dipping to ~500 every few seconds, in the same rhythm as before.
I left it for the night and this morning thought I'd try to see if the throttle body is dirty as this is a suggested cause of the problem and something quite simple to do.
I unscrewed the clamp and took off the large inlet pipe that connects to the throttle body, I looked inside and the plate had some carbon build up on the edges but it didn't seem that bad to me. I thought I'd wipe it with a kitchen towel to see if it was something that just came off or not, as I'd likely want to get some cleaner if it seemed like a problem. I wiped and some of it came off no problem, so I thought I might clean it at some other point but not a priority.
I reconnected the pipe and screwed the clamp back on as tightly as it was originally.
I then started the car and it sounded terrible... like it was stalling the whole time and the idle RPM was erratic. I didn't panic too much as I'd witnessed this before, I went over to the MAF sensor and unplugged it, thinking this might be causing the problem. Nothing changed however so I plugged it back in and turned off the car.. Not wanting to damage anything in the engine.
Now I'm writing this. I'm kind of at loss for what to do. My first instinct is to call a mechanic, but I also want to understand what's going on.
Firstly, I don't have the tools to do a TBA. I was thinking maybe when wiping I offset it somehow, so a clean and alignment wouldn't go amiss.
Secondly, I haven't checked my MAP sensor. I don't know where it is or how to check it. If someone could explain this to me I would appreciate it. I don't really know how the ECU knows that there is a pressure drop.. What sensors are involved in this and where are they located? I know the difference between the MAF and the MAP would throw something, but what about after the MAP?
Third, would a simple ECU reset via disconnecting the negative for a while help?
I've been using this diagram https://farm5.staticflickr.com/4035/4411150985_e2ba604b2a_o.gif to get a better understanding of how everything is working, but so far my understanding is very surface level, and looking at the actual car is a different beast altogether. (VW why so many tubes everywhere?
)
Does anyone have some suggestions before I call someone?
Sorry for the massive wall of text, but yeah, I need help on this one
.
Engine is 1.8T 20V AUQ (Cupra FR) with a decat and RAMAIR intake.
When I first got the car it was idling rough on first start, and this was gradually getting worse. I eventually replaced the MAF sensor under the advice of a mechanic as unplugging it while idle seemed to make the engine run smoothly. I got a BOSCH MAF unit (not just the sensor because I didn't know you could just change that yet), and I was happy with the car's performance.
After noticing an oil leak the mechanic suggested a rocker gasket change in an attempt to scan the problem from the top down. I agreed and he changed this for me and fitted some spark plugs I had bought too. At the same time I got the two front wheel bearings changed as they were really bad (making a lot of noise).
The car was alright after that but then I noticed the main problem I had all this time was how rich the car was running. Despite the fact that there's no cat, I wouldn't expect that much petrol smell. I get a strong smell from exhaust on and off for a few seconds consistently. There is also a petrol smell coming from the front of the car (I think, although it could be wafts from the exhaust). EVAP Canister is ticking but I've read that this is normal for VWs. I'm assuming since EVAP system is under vacuum it wouldn't be causing the rich condition?
The mechanic scanned the codes back when I changed the MAF and got:
- Brake Switch (F) Implausible Signal P0571
- Catalyst System Bank 1 Operation below threshold P0420
- Fuel Trim Bank 1 (Mult) System too Rich P1127 Intermittent
- Pressure Drop between Turbo and Throttle Valve P1297 Intermittent
There was an additional "System too Lean Intermittent" code the first time it was scanned but it didn't come back after it was deleted.
So, wanting to do some investigation myself, partly out of wanting to solve it and partly to save money. I did some research and caught on to the idea that the Pressure Drop could be causing the Rich condition, as air that had been accounted for could be escaping. Not having a full picture I checked what I thought I could, starting with the tubes near the top of the engine; DV and N75, as well as the inlet to the throttle body. They looked fine as far as I could tell. I have a jack and some stands but I have not been brave enough as of yet to get under the car to check the pipes around the turbo and towards the intake.
I cleaned my air intake and that didn't really change things, although it was very dirty.
I then took off the DV itself and checked if it was holding air by pushing the valve up, placing my thumb on top and checking if there was suction when releasing the valve and my thumb. It seemed fine (again I don't really know what I'm looking for nor do I really have the tools or experience). I put the DV back on and started the car, it sounded rough as usual and the petrol smell was there, idling at ~792 and dipping slightly every few seconds. I thought I'd try disconnecting the MAF sensor to see if it made a difference and it didn't seem like it did until I reconnected it and the idle started dipping to ~500 every few seconds, in the same rhythm as before.
I left it for the night and this morning thought I'd try to see if the throttle body is dirty as this is a suggested cause of the problem and something quite simple to do.
I unscrewed the clamp and took off the large inlet pipe that connects to the throttle body, I looked inside and the plate had some carbon build up on the edges but it didn't seem that bad to me. I thought I'd wipe it with a kitchen towel to see if it was something that just came off or not, as I'd likely want to get some cleaner if it seemed like a problem. I wiped and some of it came off no problem, so I thought I might clean it at some other point but not a priority.
I reconnected the pipe and screwed the clamp back on as tightly as it was originally.
I then started the car and it sounded terrible... like it was stalling the whole time and the idle RPM was erratic. I didn't panic too much as I'd witnessed this before, I went over to the MAF sensor and unplugged it, thinking this might be causing the problem. Nothing changed however so I plugged it back in and turned off the car.. Not wanting to damage anything in the engine.
Now I'm writing this. I'm kind of at loss for what to do. My first instinct is to call a mechanic, but I also want to understand what's going on.
Firstly, I don't have the tools to do a TBA. I was thinking maybe when wiping I offset it somehow, so a clean and alignment wouldn't go amiss.
Secondly, I haven't checked my MAP sensor. I don't know where it is or how to check it. If someone could explain this to me I would appreciate it. I don't really know how the ECU knows that there is a pressure drop.. What sensors are involved in this and where are they located? I know the difference between the MAF and the MAP would throw something, but what about after the MAP?
Third, would a simple ECU reset via disconnecting the negative for a while help?
I've been using this diagram https://farm5.staticflickr.com/4035/4411150985_e2ba604b2a_o.gif to get a better understanding of how everything is working, but so far my understanding is very surface level, and looking at the actual car is a different beast altogether. (VW why so many tubes everywhere?
)Does anyone have some suggestions before I call someone?
Sorry for the massive wall of text, but yeah, I need help on this one
.
