Hi guys, hoping you can shed some light on a problem im having with a VS i bought. The previous owners were friends and told me the fuel consumption was terrible. Since buying it i have noticed that the temp rarely goes above 1/4 and takes forever to get there. Only once has it gone to 1/2 and that was in heavy traffic. There is black soot around the exhaust tip and over the back of the car. Hesitates for a second when accelerating from a stand still about 70% of the time. The car is a 96 SII, 255k's, only mod is a sports exhaust. I've done a fault check which gave code 12
Code 12 means everything is ok! I would say you have a stuck thermostat!! replace it and you should be right:thumbsup:
Has to be either coolant temp sensor (the one that tells the ECU the engine is hot/cold and/or the oxygen sensors. First do the CTS.
I've done some reading and found info on this O2 sensor earth problem that many VS owners have experienced, could this be the problem? I have checked out the wiring to the LHS O2 sensor and there are 4 wires, which one is the earth wire which must be fixed? there is a connector, the four wires going in are- black-purple-black-pink going to connector from loom ---------------------- connector tan -purple-brown-brown from connector to O2 sensor Hope that makes sense
It's the heater wire that interferes with the signal, not the earth. Cut the pink wire on the RH sensor. First I would do the basics, plugs, leads, air and fuel filters. Putting a bigger exhaust on the VS makes it worse for economy anyway, extractors get a bit back, but don't expect any better than 13-15kms/100 city driving.
Ok i've fixed it, when i pulled the thermostat out it had 82* on it, i bought a 91* one. I cleaned out the plenum and TB, put new airfilter in, pulled the eng fuse to reset ecu and added some injector cleaner to clean it all out. It now gets to 2/3, idles perfectly and has no flat spot:w00t: Was talking to my mate who i bought it off and he said he had a coolant service done 4-5 weeks before they left Perth for Adelaide as they were towing a trailer and its around then that the economy got worse. He was spittin chips as he sold it due to the economy and he thought the donk was stuffed. Thanks guys!
Less back pressure. More flow might be good for high speeds but in a real world situation you need that back pressure to get you moving from a standing start. That's why you see fools putting 3" exhausts on a stock 304 V8 and then wonder why they have no go in them.
Well that is interesting. My muffler from the cat converter back was totally shot about 5 years ago. An exhaust place had a special on rebback 2.5" exhausts and told me that I would get better efficiency with the 2.5" exhaust, so they talked me in to fitting one of those - It was cheaper than the Lukey anyway! It is hard too say whether economy got worse - the thing I have noticed since putting that exhaust on (and it may be conincidental) is the exhaust is always heavily sooted up, and the back of the car gets caked in it (more than is normal from my observations). I have had the injectors serviced, changed O2 sensors, changed coolant sensors and the economy has improved but not the soot. So is Not_an_abba_fan saying that the 2.5" exhaust could be the problem? Or is it just that the exhaust flow is slower out of a large exhaust, so soot is not ejected out as fast allowing it to accumulate in the exhaust and and the back of the car?
when i got me 2.5 inch cat back redback for me v6 vs i never noticed a decrease in economy...i actually got it down to 10.7L/100 around town. but im averaging 12-12.5/100 around town. not sure about highway as i hardly ever drive long distance. these figures are going by from when i fill up at servo (same servo) this isnt light driveing either altho the exhaust guy said that id notice bugger all difference in economy but would notice more noise (duh!) and better response.
A common misconception to do with exhaust is back pressure. Back pressure is a bad thing. A large exhaust can actually have more back pressure than a smaller one. The key factor is exhaust velocity. The faster you can get the exhaust moving the better. Each exhaust pulse has a low pressure point behind it so it helps to draw the next pulse along with it. If the exhaust is too big then the pulses slow down causing the next pulse to hit it and this is what creates back pressure. The engine will use more fuel to create a bigger bang to force the exhaust out of the tail pipe rather than the exhaust doing the work. This is why larger exhausts will carbon up and have a lot more soot than a smaller one. So by going to a smaller diameter pipe, the exhaust will travel faster and have less back pressure. It isn't about how much exhaust gas you can move, but how fast you can move it.
Thanks mate, I have been searching for an answer to this significant soot problem for a while.:thumbsup: I'll go back to a good quality standard exhaust when this one burns out.
