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Random (and significant) loss of power MKV

loss power problem r32 mkv mk5

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#1
tanito87

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Hi Everyone, i am a happy owner of an Audi A3 3.2 DSG which i bought 3 months ago, which is virtually the same as the Golf R32. (R32 didn't arrive to my country so it's the closest thing i could findd).
It has a few mods on it, p flo type air intake, cat back exhaust decat, and engine + dsg remap.
The car is always loaded with shell v-power. No crappy fuel, and it has no ECU errors.

I have noticed in the last month some serius drop in perfomance,really significant in fact, car couldn't get past 125mph, and very difficult to get to that speed, but what its funny, is that its random, and it's not just top speed. 1st and 2nd gear are more ar less equal every day, but from 3rd gear, it is slow, really slow.

Maybe i turn it on in the morning, you can feel it's whole power, turn it off, come back two hours later, and it feels like a 130hp car. (this is an imaginary situation, it can happen when i first turn it on, during the whole day, just a few minutes, dry, humid, day, night, heat or cold)

So what i am going to do next is to log MAF sensor, Intake temperature sensor, lambda sensors (please someone tell me if it has lambda or wideband), and timing, to try to determinate what it's causing it.

But as hasn't been so long since i own the car, and i coulnd't find any info i thought thay maybe i could ask to an experienced forum in this engine, maybe is an issue which is already known in the engine and i don't have to struggle to find the solution.

Thank you very much.

#2
mp302007

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When it's in the "off mood", is there any difference in engine sound, does it rev out ok or is it more lumpy? Being intermittent sounds like a sensor or actuator issue but the ecu should give fault codes for these.

Should be related to either air, fuel or spark (compression being mechanical). Air could be maf or throttle (unlikely). Fuel could be flow or pressure (pump or filter blockage, or fpr (unlikely). Spark could be crank position sensor or plug gaps (unlikely) or coil packs. Not an exhaustive list but process of elimination might help.

#3
tanito87

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When it's in the "off mood", is there any difference in engine sound, does it rev out ok or is it more lumpy? Being intermittent sounds like a sensor or actuator issue but the ecu should give fault codes for these.

Should be related to either air, fuel or spark (compression being mechanical). Air could be maf or throttle (unlikely). Fuel could be flow or pressure (pump or filter blockage, or fpr (unlikely). Spark could be crank position sensor or plug gaps (unlikely) or coil packs. Not an exhaustive list but process of elimination might help.


Thanks for the answer, No, the engine sounds is not different when its not working properly.
Compression is discarded, the power loss wouldn't be random
Spark plugs are new and gaps were regulated, coils are supossed to be new (according to previous owner), but can the the coil packs cause such a poor perfomance?
I forgot to buy the fuel filter the last time i serviced the car so i will change it soon, and see if it improves.
I cleaned and checked the throttle body last week trying to eliminate alternatives.

So my main options right now it's the MAF or IAT sensors since how the car reacts look like it's an AFR problem. Coil packs now that you mention it, but i think that coil packs would cause a progressive loss of perfromance, not random.
I will also run a fuel pressure test

#4
mp302007

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In retrospect, the fuel filter and pump are unlikely if the symptoms are intermittent. However, if a coil pack or two are degrading, or the connectors are loose/corroded then the engine will "miss" when running. This should be noticeable as lumpy running. If you can whip the plugs out when the symptom occurs at least one of the plugs should be wet with unburnt petrol. Unlikely if there is no noticeable difference in noise.

That leaves crank sensor or perhaps temperature sensors (water and air). I think the inlet air temp is part of the maf, but I could be wrong. Some more info here...
http://www.golfgtifo...p?topic=94783.0


#5
DubNurd

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You really need to scan for codes, and look at the live data while driving to see what changes.

Throwing parts at it can be very expensive, and still have no result.

                                                          
 
Allan
 
My non-Golf .:R32
29361330218_1f724845b0_o.jpg
 


#6
tanito87

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Hi guys, i took it to the dyno and make some logging, It made 217whp to the front wheels (disconnected haldex, and no way to measure BHP because of the DSG gearbox) but that day it was running well. Anyway i will send you the loggings and if anyone can look at them great.
I think that the mafs reading are a little bit low, and appearently there is something wrong with one of the lambda sensors.
No Codes in the engine module
Street log: https://drive.google...iew?usp=sharing
Dyno log: https://drive.google...iew?usp=sharing

I have enabled comments on the doc so it's easier to spot something anyone can find

And again, thank you all





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