Celica Forums General Discussion General 91 octane causing idling problems?

Well, lately my GT has had problems idling, particularly after braking to a stop (I have an auto and it almost felt like the car would stall on me). I brought it my mechanic and he put in some fuel injector cleaner and a bunch of other cleaning stuff in my car (if it had to do with intake, it got cleaned) but the problem never really went away.

I normally fill up with 91 (let's not discuss the merits of this in this thread) and on a whim last night decided to fill up with 89. To my surprise, I haven't had any idling problem at all in the last two days. I even went driving around town to random places for about an hour and a half last night to try and recreate the problem, with no "success".

Is it possible for 91 octane to cause even the slightest idle problem in the GT? What conditions would have to be present to aggravate such a problem. My guess is that without playing with the timing you couldn't take advantage of 91 in a GT and thus could cause a bad idle, but I'm not a serious expert. Any thoughts on this?

let me clarify the idling problem. It idled very low and rough, normally I'd be above 600 and closer to 700 but I'd be consistantly under 600 and occasionally the tach would flutter and dip under 500.

oh crap.. i fill up with 91 octane.. no probs yet tho! (and ya lets not discuss the whole octane thing.. it's MY money i'm burning anyway)

umm bro trying cleaning the throttle body.

that's what my mechanic did. and I'm tempted to do it again myself.

throttle body, IAC, fuel injectors, valves, everything got treated and cleaned. and still the problem persisted. I'm going to go with three tanks of 89, and see if I still have a problem. If I still do, then I'll go down to 87 for three tanks, and if that doesn't do it then i'm cleaning my throttle body myself, getting a new airfilter (which I don't need, but i'll do anyway), and clean the inside of my stock intake, and if that doesn't work, i'll do a 3S-GTE swap j/k

if after three tanks of 89 I don't have a problem, I'll go back to 91 for three tanks. If it doesn't come back, then...

I have tried 91 from different stations without any change. I might consider a 4th tank of 89 from a different station too. Does anyone think this is a distinct possibility, that my gas could be causing my problems, or am I just wasting my time?

BTW: GT drivers, I'm noticing no difference between 89 and 91

hey i have the same problem and i fill up my gt auto with 91. a few weeks ago at a red light my car felt like it was going to stall but that was the only time the idle was really noticeable. whenever my dad takes the car he'll fill up with 89 and i noticed the idle isn't as bad. As for the difference in 89 and 91, Kim accidently filled up with 89 and he noticed no difference, neither do i.

I'm still willing to bet that my idling problem is a combination of 91 and a few other factors (you think a grounding kit could help?), hopefully my little experiment will tell me more.

i heard some people complain about this before. I have a GTS so I have to use 91 octane

my auto gts does this

all gts have to use 91 octane?

There is no need to put 91 octane on a GT. You're just throwing your money away. GTS on the other hand, requires 91 octane.

octane is dependant on the compression...the GT has a 10: 1 compression whihc only requires 87. the gts has a 11.5: 1 which requires 91.

use the right gas for the right car and you should be good.

91 = gts nothing less.. but on a gt it's pointless from what i know.. maybe your ecu is tryin to adjust to your changes in fuels.. try a ecu reset?? who knows

Crap, did not know that. i've already filled up the tank twice with 87

^^^you gotta make sure you fill your GTS with 91. otherwise you'll experience knocking sounds from your engine.

Can't you people read?


I'm not asking you which gas to use, I'm asking if 91 octane can cause an idling problem in a GT. If you say yes, explain your answer.

and we are telling you the correct fuel to use for your engine. you even blatantly stated that your idling problem was cured when you went with a lower rating. it really doesn't take a genius to figure this out...

I think it's entirely possible.

91 octane is much higher than what is required in a GT. We all know octane rating refers to how difficult it is for the fuel to burn. I'm going to go out on a limb and say some of that 91 fuel isn't being burned by your engine. Since idle speed is so near to the point at which the engine would stall, I think robbing the engine of some of its fuel (which is basically what you're doing if some of the 91 isn't actually being burned) could cause it to idle rough.

what I meant in the bold part is that I don't need to be told what the proper fuel for my engine is, I've read the manual forward, backward, and upside down, and I've read every gas thread in the last six months.

if you had read some of my other posts, you would notice that I suspect that 91 could be causing the problem but in conjunction with other problems.

You still haven't answered my question. Can 91 cause an idle problem in the GT? If yes, how/why? What other conditions could/need to be present for this (i.e. what else could be wrong with my car). I've used 91 for about 5 months with no problem, until this started.

please answer my question. that's the whole reason i started this thread.

thank you rev

so you're telling me you read up on what fuel is required for your engine. you then put a diffrent type of fuel for it. then have a problem with it. then are asking what was wrong with it to begin with??

Eh, let's be fair. Nobody actually listens to the crap Toyota puts in the manual. How often does it say to change the oil? It's either every 6k or 8k miles, I forget which. Yet, 90% of people still change it every 3k because they don't trust Toyota. Toyota wants to make the cost of maintaining the vehicle the recommended way appear as low as possible, because it attracts buyers. They also don't want their cars to run for 200k miles, because it takes away business.

That being said, I'm fairly certain in saying that only bad things can come from running 91 in a GT.

Eh, let's be fair. Nobody actually listens to the crap Toyota puts in the manual. [/quote]

he said he read threads about it. he just basically pwned himself and is ashamed to admit it.

*sigh* lots of people have put 91 in their GT, and until this thread, I've never heard of anyone having problems, while almost everyone noticed a difference. I had no reason to believe I would have any problems. and I didn't have problems for about five months.

If my car performs better, and I see no harm in doing it, then I will do it to my car. It's the same reason people have CAIs, exhausts, headers, etc. just slightly different.

not a single gas thread I've read has ever said that 91 in a GT will be bad for the engine, only that it doesn't need it.

well, you don't need a CAI either...but people do it.

CAI improves the performances of the car. putting 91 octane on a GT does not.

^^ I think that's what I meant when I said "Let's not discuss the merits of this."

Look, the answer is simple. If you suspect the 91 octane is causing the problem, then quit using it. If the problem goes away, then problem solved. If not, then take it in and have it checked out.

Can 91 octane cause the idling problem? Possible, because it is wrong grade for the GT. And that's what we are trying to say.

umm...when did I ever say my engine was knocking? and I think i've already stated that for the time being, I'm not using 91.

tony, just leave this alone. he's hard set that he is right. at least his question was answered...even though in our eyes it was answered several times...

Doesn't that GTS manual say to use 97 octane or something crazy like that

That's the research octane number. It's equivalent to 91 at the pump.