Terrible Fuel Economy, All Usual Suspects Checked

[stolen_s15]

My R33 is getting terrible fuel economy of 190-250 with 50 city trafic 50% freeway (190 driving normal, 250 driving miss daisy the whole time), and its really starting to give me the shits. Car has usual 200rwkw mods runing a PFC tuned by RE Customs

What I have done so far:

Made sure it was not my driving

Checked accuracy of fuel guage and speedo

Replaced 02 sensor

Cleaned AAC valve

Cleaned AFM

Got RE Customs to make sure the tune was spot on, they said it is now perfect, they checked for fuel leaks and found none, they said it would not be the cat because car is not down on power at all and drives very well.

The only suggestion the had was an injector(s) could be leaking (they noted the idle is somewhat rough) and this could be causing the problem.

So does anyone have any suggestions as to what else might be causing this problem before i spend the time and money getting the injectors checked.

Cheers

[Baconer]

try replacing the fuel filter aswell, i replaced different items every few thousand kms and noticed an increase in kms from a tank each time, now im getting between 600-700km (highway) consistently from a tank (mine is stock standard though). I replaced fuel filter, O2, air filter, cat (and exhaust), spark plugs and went from 350 to where i am now (600-700)

[stolen_s15]

I'll try the fuel filter and spark plugs this weekend, migth also check the cat. Thanks for you help buddy

[Amec]

I know on Z32s if you have a faulty engine coolant temp sensor or a faulty det sensor then one or both of these conditions will cause poor fuel economy.

[stolen_s15]

Might change those sensors then also. What is a det sensor? Detonation?

[r33cruiser]

thats not tooo bad man. i used to get 500+kms per tank.

but replaced o2 sensor and upped fuel prs, because it was at 25psi.

and now i get about 300-400.!!!!

[stolen_s15]

^^^ WTF would you do that for? Any problems that caused you to do those two things?

190-250 is terrible dude, bloody terrible. I have this feeling the problem will be a leaking injector, but to replace with stock seems like such a waste of $. and I dont have the cash for some 750cc's and a retune just at the moment.

Edited December 6, 2007 by stolen_s15

[chook]

get the injectors ultrasonically cleaned would be my next move. I had mine done by a mobile injector cleaner goy, came around, took about 2 hours.

Edited December 6, 2007 by chook

[stolen_s15]

get the injectors ultrasonically cleaned would be my next move. I had mine done by a mobile injector cleaner goy, came around, took about 2 hours.

I like that idea.

What was the cost mate? Do you know if they are able to give you a report on the flow of the injectors?

Cheers

*EDIT*

Seems that around $30 per injector on site is the going rate.

Edited December 6, 2007 by stolen_s15

[Jmaac]

As above, could be a faulty coolant temp sensor (tells the ecu to run rich until the car is warm)

Another possibly is check your brake drag (jack car up and spin wheels freely). Handbrake might of dropped a spring or maybe even ceased a caliper piston??? Both happened to my VL

Edited December 6, 2007 by Jmaac

[stolen_s15]

Ok will check all of the above this weekend, will report back.

Cheers guys

[courier33]

Had same prob with my R33 GTST and turned out to be O2 sensor. Heres a couple more ideas:

Pull the spark plugs out.

If its running really rich they will look like they are really black and very sooty.

If they are ALL black then its not a leaking injector. Its more likely some sensor error or the ECU dumping fuel in for some reason.

If only ONE is black then look at that cylinder. You would notice a missfire on that cylinder.

If NONE of them are black and your getting bad economy then..... NO Idea.

BTW I had a missfire when the O2 sensor was dead. Missfired from running too rich. AFR's were 9.7 to 10.2 when cruise. 250ks to tank.

[r33cruiser]

my pesonal experience is different. before i was getting 400+kms per tank. now ive replaced02 sensor and sparkies and im only getting 250-300ish!!!!

and still stock ecu etc.

[stolen_s15]

Just finished a full tank after the ecu 'touch up' by RE customs. I manged to get 310km and 1/4 of that was done on the dyno, so it has made a decent improvement.

I CBF changing the fuel filter and checking the plugs the w/end but will do it next week and see what happens.

Nick

[Baconer]

well i just got 675km (9.5L/100km) from that previous tank of petrol, that should be some incentive to stop being so lazy and change the filters

Only just read then that yours is 200kw, mine is stock standard apart from the exhaust but that extra 50kw shouldn't cause that much different in fuel usage

[r33cruiser]

lol mate. just wondering if u meant the exhaust gave u 50kw?

[samdumbert]

When was the last time you cleaned or changed your air filter?

[Baconer]

lol mate. just wondering if u meant the exhaust gave u 50kw?

Me? I was saying my car was around 50kw lower then his (mine 147kw, his ~200)... Dunno how that could be misread :X

[stolen_s15]

well i just got 675km (9.5L/100km) from that previous tank of petrol, that should be some incentive to stop being so lazy and change the filters

Only just read then that yours is 200kw, mine is stock standard apart from the exhaust but that extra 50kw shouldn't cause that much different in fuel usage

Okay, but there is no way you have managed that in Melbourne peak hour traffic. I might drive my car to Sydney for Xmas, so I'll see if I can tailgate a truck the whole way and beat that figure

I will change the filters and plugs this week sometimes, I know I'm just being lazy. But after the work Xmas party Friday night I lost all enthusiasm do do anything but sleep it off!

[WogsRus]

dam you all i get 350km around town in tassie, no matter how i drive, and not much better on the high way.