This thread was saved without dates. "Around Aug 2004" is estimated from neighbouring threads.
I have posted this a couple of times without the problem being solved.
At the moment I am getting 5km/L gas milage and its getting worse. Any input will be appericated for this, I would like to start restoring/modifing the lovely S12 But all the money is going on petrol.
A bad oxygen sensor is a common cause of poor mileage.
Also the coolant temp sensor (the ecu one not the gauge one) and a bad thermostat are common. Could be a number of things really MAF, bad compression, etc. But i would start with the easy things first.
check for leaking injectors or fuel leaks too.
Hmm... other suggestions have been good... Clogged cat can hinder things as well... I'm getting about 22m/g at the moment... I think that's about 8km/l. So 5km/l would be about 13m/g. Yeah, that's pretty bad. You a lead foot, or just a putter?
I'd check the condition of the engine first before replacing any parts/sensors.
Do a compression check and let us know what the result is.
Hi guys/girls thanks for the input,
Alrighty here goes
done compression test all over 150psi I couldnt get a good seal when testing so air was escaping around the tester 150 was the lowest 165 was the highest with air still escaping.
disconnected the exhust from bottom of down pipe before cat seemed more slugish than with it connected
It doesn't matter if Im lead foot or going light on the gas I still get about the same milage, It changes about 20km on 18L of fuel.
Ive checked the injectors mechanically and electrically they are working fine, Ive had a look for fuel leaks but couldn't see any but Ill do a full inspection to make sure.
tested coolant temp sensor and wiring for it all ok, replaced thermostat the old one was stuck open but it hasn't made any differance except get warmed up faster. Done a check on the MAF seems to be working fine, even replaced it made no change. even when I dissconect the MAF the revs go abit higher but has soon as I go to give it some gas it dies and wont start with the MAF dissconected.
the O2 sensor has not long been repaced with a NGK one from sparkplugs.com, even when the new one went in it made no diiferance.
20M/G is about 12km/l
A problem that I ran into a few years ago on an Alfa that was getting real bad milage was a lose connection to the coolant temp switch. The sensor was good and the wiring was good. It just had a bad connection.
The ecu kept the car in a "full cold" run even when hot.
The car ran fine but it just sucked gas like there was no tommorrow. 4mpg worth.
right gone through and checked the fuel lines no leaks, I even disconnected the fuel preasure regulator so the fuel lines had more preasure in them while checking.
The connection to the temp sensor is ok cause I did the testing from the ECU end and could see the resistance canging with the temp of the motor
does it smoke? How good does it drive? If it's actually using all this gas it can't possibly be running right.
ok...
So the injectors are ok
The O2 sensor is new
The MAF was replaced
I'm assuming the car comes up to tempature
have you checked the air filter, and fuel filter? How's the ignition. good wires plugs and coils?
No it doesnt smoke but there is alot of soot on the tip of the muffler, and no it doesnt run right either in idle you can see the motor ocasionally do like a miss and rock from side to side, when driving it it bogs itself so it is quite slugish and I can also feel the car surging when crusing sometimes.
the air filter was replaced with a pod filter not long ago and is still clean
fuel filter has aslo been replaced with a Z32 one just before the pod filter went on
replaced coils and power transistors
checked HT leads, cap, rotor and plugs replaced faulty bits Yes I know they need to be replaced but they are working
thanks people I really appreciate the input keep the ideas coming
my 86 did this shortly before it kicked the bucket (not to get your hopes down) are you hitting boost?
do you have an A/F gauge? If so where is it at idle, cruise and WOT? If it's an LED it'll probably be all they rich so I hope you have an analog one
Alright so far we've got
Air filter ok
fuel filter ok
no fuel leaks
injectors are fine
ignition is fine (plugs need to be replaced?)
O2 sensor is new
MAF was replaced
Car comes up to tempature? (never confirmed that)
Before my final suggestion I'd look at vacuum lines, induction work, intercooler (if you have one) for vacuum leaks. I know you probably already checked those but that's all I can think of besides this.
If your injectors are for sure 100% not leaking a drop of fuel, absolutely fine, no way in hell they could be faulty and you are absolutly sure there is no fuel leaks. I'd look at the ECU. Even if you were running flat tires all the time you couldn't get gas mileage this bad unless something is seriously wrong. If all of these other components are good what's left :dontknow: ?
A 2002 tacoma i looked at had this problem. It turned out a transistor in the ECU that turned #4 injector on and off had shorted. Intermittently grounding the injector making it squirt fuel 100% of the time.
Ive gat a AF gauge and yes its digital, Ive had it out of the car for a couple of weeks now but I hooked it up the other night and it sat on 1 bar below rich and just sat the in idle, I took it out before using the car again so unsure what WOT measure is, guessing that it will be rich as well.
the car comes up to temp fine sits between 1/4 and 1/2, never gets to half way.
gone through all the vac lines replaced some, also dissconnected and block vac lines with no change so I reconnected them
no I dont have a intercooller in yet, gone through all the induction lines replaced broken air intake line from MAF to turbo, also checked turbo to manifold so many times its not funny that connection is fine as well.
trying to organise another ECU to try out to see if its the ECU on the blink
the codes I get are 14, 22, 23, 24, 31.
I can get all the codes to go away except 22 and 31 (fuel pump and air con)
the fuel pump circuit on the ECU is dead so bypassed this and have the pump running on the ACC switch, its been like this for awhile and has not caused a problem at all.
the aircon has been disconnected so no problem there.
Im also looking into the compadability with the CA18DE and DET ECU with the S12 so far its looking promsing 8-)
the only way you could get the DE or the DET (the DET will be the one you want) to go in is if you changed the ignition system. Either to the DIS system (and have to use it's CAS sensor) they use or to an aftermarket system.
anybody else have any ideas that I can try
if no one else has no Ideas for me to try :dontknow: Im going to rip out the engine and throw the non turbo motor back in:lame:
No it doesnt smoke but there is alot of soot on the tip of the muffler, and no it doesnt run right either in idle you can see the motor ocasionally do like a miss and rock from side to side, when driving it it bogs itself so it is quite slugish and I can also feel the car surging when crusing sometimes.
the air filter was replaced with a pod filter not long ago and is still clean
fuel filter has aslo been replaced with a Z32 one just before the pod filter went on
replaced coils and power transistors
checked HT leads, cap, rotor and plugs replaced faulty bits Yes I know they need to be replaced but they are working
These engines tend to run rich, so I am not surprised to hear that you have carbon build up. This is largely comtributed becuase of the BOV. However the bad mileage, and the not seeing a large amount of black smoke (which would indicate super rich), could suggest that there is some sort of a fuel leak. Now the most common place for a fuel leak are the three connections at the fuel pump, or the lines themselves...Now you also said that you replaced the coils, wires and so on...have you checked to make sure that this is giving you a descent spark (I would assume you are, I'm just trying to get a better picture). Now also between shifts, I was wondering if you see a large puff of dark grey or black smoke. If you do you could have the same problem, only to a worse degree as SSChung, which we also can't figure out. Aside from the obvious I could only suggest checking all your vacuum lines, andthat sort of thing.
I have a brand new remanufactured ca18et, with all new components, except fuel injectors, fuel pump, fuel regulator....all other sensors and gaskets are new, and everything else has been seriously cleaned. Engine has about 1300 miles on it now, and I am starting to see some more and more soot in the tail pipe, and it smells a little rich too. This has just recently started, and after I began laying into the throttle a little. It runs perfect, and idles perfect, but the soot in the tail pipe is starting to concern me. I wonder if the bov is causing this?
I have a brand new remanufactured ca18et, with all new components, except fuel injectors, fuel pump, fuel regulator....all other sensors and gaskets are new, and everything else has been seriously cleaned. Engine has about 1300 miles on it now, and I am starting to see some more and more soot in the tail pipe, and it smells a little rich too. This has just recently started, and after I began laying into the throttle a little. It runs perfect, and idles perfect, but the soot in the tail pipe is starting to concern me. I wonder if the bov is causing this?A BOV WILL cause a rich situation because there is metered air that the engine thinks it is getting, but is getting shot out the BOV instead. Becuase there is no MAF on the BOV the engine will not know that it is not getting the added air, and thus it sends more fuel, which richens your mixture...but this only happens when the BOV is operating (throttle plate closed)...it won't occur if you are just driving...8)
These engines tend to run rich, so I am not surprised to hear that you have carbon build up. This is largely comtributed becuase of the BOV. However the bad mileage, and the not seeing a large amount of black smoke (which would indicate super rich), could suggest that there is some sort of a fuel leak. Now the most common place for a fuel leak are the three connections at the fuel pump, or the lines themselves...Now you also said that you replaced the coils, wires and so on...have you checked to make sure that this is giving you a descent spark (I would assume you are, I'm just trying to get a better picture). Now also between shifts, I was wondering if you see a large puff of dark grey or black smoke. If you do you could have the same problem, only to a worse degree as SSChung, which we also can't figure out. Aside from the obvious I could only suggest checking all your vacuum lines, andthat sort of thing.
I dont have a BOV yet
I have gone threw all the lines and checked for leaks found none
Its an auto so there isnt anything noticable between shifts
I have read in another post that the fuel injectors caps if they are broken or missing they can cause bad idle I was also wondering if it would cause bad gas mileage as well?
well i doubt its the caps but rather the o-rings that seal the injector in the mani.. if these are bad you would run lean cause you'd be sucking in unmetered air... so that wouldnt cause you to use any more gas then normal
alrighty heres an update Ive replaced the plastic injector caps motor ran smooth turned it off and started it again motor was running rough again:wall: , checked the spark jumping about 1.5 inches nice and blue.
The only thing I can put it down to is either the ECU running in limp mode if it has one, distributor CAS faulty or motor is screwed.
Now also the turbo is leaking oil into the intake line what effect on the engine will that have??