I just have an ideling problem. It started when I put 93 octane in the car. I was wondering what the octane rateing was for this car and I was also wondering if it would cause my crappy idleing. At idle my car will either stall, or come really close to stalling. The whole car shakes and transmission shakes at idle. I have to rev it up around 1500 often. Its a stock KA24DE motor. Bad spark plugs maybe? Injectors? Non of this happened though until it was filled with 93, anyone else had this happen to them? Please and thank you :bigthumbu
Idleing problem/ Octane?
- Thread starter slidewayz240sx
- Start date
Octane is the resistance of gasoline to ignite under compression. The higher the octane the less its likely to cause detonation aka pinging. N/A cars usually requires a lower Octane unless the motor has HIGH COMPRESSION pistons. The reason turbo cars need high octane fuel is because the compressed air the turbo produces is hotter so it raises the combustion temp which can cause the gasoline to preignite, and because your cramming soo much air into a tiny chamber.
Detonation can destroy a motor if to much timing is advanced.
Also on a regular N/A with no performance mods using a higher octane fuel will leave Carbon desposits in the head which will rob power, because higher octane requires more energy to combust so if its harder to ignite than obviously it wont burn so easy which leaves deposits.
So you used a higher octane you pretty much wasted money, and robbing power.
The misconception people think is that the higher octane provides performance gains, Not true like I said Octane is the resistance to combustion by compression. Higher Octane allows you to advance more timing which will yield more performance from the motor but doesnt mean the gas is giving you the performance.
Its like the misconception on Standalone ecu's. Standalones do not add power they just unlock the power the motor is already capable of. It's like using a crack program to release a demo program to its full version.
Detonation can destroy a motor if to much timing is advanced.
Also on a regular N/A with no performance mods using a higher octane fuel will leave Carbon desposits in the head which will rob power, because higher octane requires more energy to combust so if its harder to ignite than obviously it wont burn so easy which leaves deposits.
So you used a higher octane you pretty much wasted money, and robbing power.
The misconception people think is that the higher octane provides performance gains, Not true like I said Octane is the resistance to combustion by compression. Higher Octane allows you to advance more timing which will yield more performance from the motor but doesnt mean the gas is giving you the performance.
Its like the misconception on Standalone ecu's. Standalones do not add power they just unlock the power the motor is already capable of. It's like using a crack program to release a demo program to its full version.
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Haha thanks. Yeah, 711 gas pumps are confusing. Im so used to the octane being 87,89,93 from left to right, so I push the center button for 89 and as im pumping i realize that 711 puts 93 in the middle *smacks head* son of a bitch...
I would experiance spark knock under 1500 rpm while i was NA If i did not run 93 octane, anywhere else in the revrange it was okay. Has your idle rpm changed from 87-93 (it shouldnt have).
Is your idle stable? How many miles have you driven on the 93?
BTW FYI, my 1996 owners manual suggest premium fuel for maximum performance. KA ecu will advance ign timing if no knock is present. I got better fuel mpg and gained horsepower in my imagniation when i ran 93.
wait you said this happened afer you went to a 711 gas station. I wouldnt call 93 the bad thing, i would call it bad gas in genral. Run this fuel damn close to the bottom of the tank, refil with a couple gallons, run that out, then fill it up. Im pretty sure its bad gas. Has the engine performance dimished while driving it? WOT performance the same?
Is your idle stable? How many miles have you driven on the 93?
BTW FYI, my 1996 owners manual suggest premium fuel for maximum performance. KA ecu will advance ign timing if no knock is present. I got better fuel mpg and gained horsepower in my imagniation when i ran 93.
wait you said this happened afer you went to a 711 gas station. I wouldnt call 93 the bad thing, i would call it bad gas in genral. Run this fuel damn close to the bottom of the tank, refil with a couple gallons, run that out, then fill it up. Im pretty sure its bad gas. Has the engine performance dimished while driving it? WOT performance the same?
My idle is normally around 750-800 rpm. Sometimes it runs fine and other times it fluctuates between 800 and 200 then just dies. I do think it might just be bad gas. Im getting new spark plugs/ ocatne booster/ injector cleaner and gonna play around with that. I put about 3/4 of a tank in of 93 and have drove about half a tank. So that leaves me with a quarter tank of 93 still in there. Ill drive it low and then put the ocatne/ injector stuff in. Thanks for the help Puma/ Rick....now Rick...I have another question...step by step instructions on replaceing a clutch with tools needed =)
S13 Slide
Driver
running higher octane in a stock car will yeild power, this is where the knock sensor comes in, since higher octane is entering the combustion chamber it allows the ECU to advance the timing alittle bit more, which means more power. the carbon deposits will be there no matter what fuel you use its part of a motor being a motor.
S13 Slide said:
um buddy your ecu doesnt know when you put in a higher octane so it leaves the timing the way that its always been. Your ecu has set parameters so it doesnt constantly advance timing until it detects knock, the only people who do that are experienced tuners.Also your knock sensor is only effective until 3000rpms after that, the ecu wont accept the signal because after 3000rpms the motor produces so much noise that the knock sensor will give false readings.
As for carbon desposits yea it might get their but why aid it? Only use the gas octane thats recommended by the manufacturer.
So NO adding higher octane does not yield performance, you have to manually adjust the timing to take advantage. Your stock computer will not compensate because their is no sesnor that detects the grade of the fuel. The only thing that might happen is the O2 sensor might read rich if the fuel wasnt burnt completly and lean out the motor.
Also the only vehicles that can distinguish different fuels is Flex Fuel vehicles because gasoline and alcohol resonate at a different frequency but still cant determine the grade.
if you read the gas cover in your 240 it will say premium fuel recomended for maximum peformance so im pretty sure its ok to put 93 in a 240 i do it all say and my car runs fine
S13 Slide
Driver
pumaking said:
hook up a timing light to your motor and rev it up, even at a certaint rpm the timing is jumping around to find the best degree, now unhook your knock sensor and see what happens....the ECU goes into safe mode and runs the timing retarded so theres no chance of knock, also loss of power, that was one of my ECu codes that came up along with my TPS and CTS i fixed all 3 of them and wow the differeance is HUGE.
Trust me the ECU dose detect Knock. how else do you think the S2000 2.0 Liter produces somewhere around 240hp?
pumaking said:
Exactly the reason most cars which run 93 will yield bigger MPG compared to a lower grade.
Also, running a higher octane will allow for more HP...why else do you think high HP turbo cars run race gas?
Anyway, Nick, I didnt' read all of the thread but if I had to take a guess at why you are having problems at idle I'd say check your MAF and see if that is the problem. All you need to do to check is disconnect it, cover the port and see if the car will run better at idle...this is the only method that I really know of other than visually inspecting it...
Let me know if you want some help...I'm free all weekend.
I'd also say run that injector cleaner through anyway...
S13 Slide said:
Wow you seriously didn't read what I said did you.
LIKE I SAID a ECU has predetermined parameters. If you look at a map in the ecu you'll see the timing table it specifies what amount of timing will be at that parameter for example at idle you might get 1000rpms x 34kpa will have like 39* advance timing.
As for the timing jumping thats called Interpolation. The reason it jumps is because youd have to a have a big ASS map in order to have it in one location. If you ever looked at a tuning software while tuning you'll see the point on the map where it'll specify where the motor is at, it fluctuates because the ecu determines other factors like engine temp, air temp etc etc. The motor will never stay at for example 2354rpm it always bounces so the ecu usually changes every 250rpms or less depending on how good the code is, so thats why it changes, not because the ecu is continuing to advance for best performance.
But the predetermined parameters the ecu will not go over that, unless you have a shitty code than your motor will go bye bye.
ok what does removing the knock sensor have to do with anything. I told you ususally after 3000rpms the ecu doesnt listen to the knock sensor because after 3000rpms the motor produces so much noise that it would constantly retard timing. And if your under 3000rpms and remove the knock sensor ofcourse it will retard timing. So your point is invalid.
Again reading comprehension is king.
Here are some links to disprove you guys and back me up.
http://www.state.mn.us/mn/externalDocs/Commerce/Gasoline_Octane_Facts_102902052227_OctaneFacts.pdf
http://auto.howstuffworks.com/question90.htm
http://www.co.suffolk.ny.us/webtemp3.cfm?dept=3&id=2049
http://advanceautoparts.com/english/youcan/html/ccr/ccr20030201fs.html
David A said:
if you look at the links I provided you'll see that higher MPG with higher grade gas is a Myth. Fuel Economy is based several factors not just the gas.
The reason why High HP turbo cars and regular high hp N/A cars need high octane is because Turbo: compress air and pack air in the combustion chamber so if your compressing air into that chamber, and the motor compresses that air more on the compression stroke your heating the air up more which will cause detonation so you run a higher octane to battle detonation. N/A cars use a higher compression ratio for the pistons thus compressing a lot of air on the compression stroke which creates a tremendous amount of heat. Have you ever seen how a diesel engine works, it creates power power by igniting the diesel fuel with compression, and diesel engines have a high compression ratio usualy 17.7:1.
So no High Octane does not give power, it just allows you to run higher compression and advance timing which is where the power comes from. The higher octane only allows you to achieve that because it doesnt detonate.
I'm not trying to come off as an asshole I'm just trying to educate you guys.
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