16 replies to this topic

[Josh18]

Hey guys I am scratching my head with this. Since I got my Legacy about six months ago it has had a random and previously infrequent complete loss of power. I have had misses from coil packs before and its not like that, its more like its losing all spark or all fuel for a second. It seems to be getting worse lately. It only really does it when Im cruising at 80 to 100 with light throttle and highish load. Now it is losing power for longer and more often I have worked out if I move the throttle when it does it, it will recover. If I keep my foot the same it also seems to recover after a second or so, both times with a bit of a jerk, and it might do this a couple of times in a few seconds then be  fine for the rest of the drive. Its really annoying as apart from that the car drives really well, and I seem to have sorted all of the normal TT woes.

So far I have fitted a new fuel pump, returned from a nasty ebay fuel pressure regulator to stock genuine one, changed the front O2 sensor (which seems to have improved economy a lot but still on the first tank). I have a MAF sensor on the way from Import car parts because it did actually give me a MAF code once (only code its ever given, which is frustrating). Another part I thought it could be are maybe a throttle position sensor, given it only seems to do it in one throttle position and seems to recover by moving the throttle. Then of course there is wiring ugh. But I would have thought a broken wire would give me a code. Hopefully this MAF will solve it when it finally turns up.

I have done a lot of forum searching and haven't seem much that replicates my exact symptoms. Its getting worse so on one hand I'm waiting for it to strand me on the side of the road and on the other if something actually hard fails i might be able to diagnose it!

Any help would be appreciated.

Cheers

Josh

[duncanm]

Sudden on/off sounds like electrical to me. Clean all the plugs in the engine bay and refresh all the ground points (unbolt, clean).

Another possibility, as you mention light throttle, is that the ECU thinks you're coasting (zero throttle) and has applied fuel cut. That would indeed be TPS. so maybe start by making sure those plugs are all good (including ECU end), and check the TPS voltage is in spec and ok at light throttle.

[Josh18]

Cheers Duncan

Cheers

[Josh18]

I did a bit of googling on testing a TPS and that seems fairly easy. Do you know what sort of reading I should be looking for at idle and light throttle? Also, I have cleaned all the grounds I could find in the engine bay previously. Are there any that are hiding that I might have missed, including the ECU ground (or any other important ones you reckon), Which I have read about but never explored. Ive never even looked at my ECU actually.

I do agree with you on it sounding electrical, its like its being 'told' to turn off, but some dud sensor or something. Annoying that something like this can happen and not throw a code, but I guess that's the nature of the beast hey.

Cheers

[El_Freddo]

You could remove the TPS, pop the cover off and clean up the contacts within the sensor, then glue the cover back on.

Follow the FSM procedure to reset the TPS position correctly.

Cheers

Bennie

[duncanm]

gen3 - but I doubt your's will be any different

 

 tps.png   33.53KB   1 downloads

[Josh18]

Thanks guys. I will do the test tomorrow.

I looked up the part number that should be on mine through Amayama and the one it has on it is supposed to be for a later model it looks. Physically it looks the same but I wonder if it's been changed out before. 

Duncan where would I get a copy of the FSM? Also does it have wiring diagrams for the TT in it?

Cheers

Josh

[duncanm]

Josh, I've only got a gen3 fsm.

Google and you'll find one

[Josh18]

Thanks Duncan I now have a 1995 copy which is close enough but I couldnt find a turbo one. It shows me where the engine loom connects to the body and gives me a better idea of where all the grounds should be. Looks like the engine loom ground should be on the manifold somewhere on the LH side, I'll look for that.

My new MAF turned up today so I fitted that and reset the ECU. It seems smooth but the biggest difference I noticed is that the car no longer back crackles on the over run, so something must have been out on the old one.

I will back probe the connectors for the TPS today and see what i get.

Cheers

[Josh18]

I checked the voltage of the TPS at the plug, the engine to body harness plug and the ECU plug. All seemed pretty good, no drop outs that I could get and it was adjusted right. I found that engine harness ground and will clean it up tomorrow.

I read about back probing connectors with dress makers T-pins. I got some today and have to say they work great! I made up some long alligator clip leads to check what wires went where and they worked great. The ECU pins were not what the above manual or my non turbo FSM, so I'm glad I worked that out!

I'm still going to replace the TPS because it is so intermittent and being an electro/ mechanical part it wouldn't surprise me if it was going bad.

Cheers

[El_Freddo]

If it’s not the TPS, I’d probably look into the O2 sensor next. When was the last time it was replaced?

Cheers

Bennie

[Josh18]

Hi Freddo thanks for that. I replaced the front O2 sensor only a week ago and it did seem to make a big difference to the fuel economy, but the random cutouts remained and seemed to be getting more and more frequent. I believe my new MAF sensor has cured it though. Since changing that around three hundred km ago it has not cut out once. The car also feels much smoother and on the first drive I really noticed more power low down, so much so that I had to reduce my throttle inputs. When testing the TPS I also disconnected all the connectors in that line and cleaned them with electrical cleaner so that may have helped as well.

I'm not calling it fixed yet, but the difference is noticeable so far.

Cheers

[Ordex]

Great to hear you fixed it Josh18!

 

Do you get the blue label MAF? Part number 22680AA200. And was that from ICP in the UK? They aren't cheap

 

Reason I ask is I think all 3 of the MAFs I have are busted in their own special way. One behaves identically to your description and the other two seem to run lean and lack response.

[Josh18]

Hey Ordex, yeah it was the blue label one from ICP. Good that we can still get them at least. Interesting to know that one of yours went in the same way. How long have you been getting out of them generally? Im running this one with a stock panel filter and airbox so it should have the best chance it can.

Its much better to drive now and fuel economy is also much better.

So now that that is fixed one of my front control arm bushes decided to leak out its goo. This car goes on and on! It is starting to get towards the end though I think. I bought the rear bushes, should probably to the front one too, but they all need doing, I could go on and on!

Cheers

[duncanm]

Good to hear its sorted.

 

Replacing all the bushes makes a big difference.

[Ordex]

I can't say how old any of the 3 MAFs I have are - they all came with the car. I wonder if as they age the element/resistor thingy becomes less sensitive (regardless of how much MAF cleaner you use), and they slowly lean out the car.

 

I'll buy a new one soonish, but for now I actually fixed the random cutouts by removing the rubber seal on top of the MAF, prizing off the cover, and then it was simply one of the socket connections internally had a dry solder joint!

I followed this guide I found on the SVX forums (our early TTs share the blue MAF with the SVX)

[Josh18]

Thanks for that! I read about similar things on Nissan MAFs, which are the same with a different colour label I think. I might have to have a look at my old one. Was it easy to spot?

I thought you meant you had gone through three new ones before. Im happy I bought my new one, the car drives beautifully now.

Cheers