Gas difference?

Hello everyone. So lately my tacoma 98 2.4L has been making loud rattling noise when i accelerate. i use regular 87 gas. it kept happening for one month until i put 91 grade gas in it by mistake. It runs hella quiet now and starts up way better than before. i'm happy upagrading gas fixed it. but my question is why did it start happening at first place? it never made any noises at 87 grade fuel before. what could be the cause of it?

 

Did you buy all the fuel at one station ??

Quite possible the tank is getting water in or the strange blends of gas you get out there was blended wrong .

I use 87 all the time .

The thing is the ECM should have adjusted the timing to the point it would not knock .

Are you getting the MIL on at all ??

 

yes. i've been using gas from same Mobil station since past 3 years. no CEL or MIL . started off with little rattle and got to big RATTLE in over a month.

 

I did reset the ECU couple times but no luck.

 

Could be miss fires. Time for a tune up. The biggest reason to use high octane in naturally aspirated engines is due to ambient temperatures. If this occurred on a really hot day I wouldn't think much of it.

 

EGR valve would be something to check

 

Welcome to my world. I've been having a clacking problem under load for at least 2-3 years, really bad in summer months and/or with the AC on. Never found a fix. A member here tried a bunch of things, new MAF, etc (see thread link below), but couldn't track down the problem. I took it to the dealer and they blamed the cat heat shield, which I'm not buying.

Higher octane gas will help briefly but once your ECU figures that out and adjusts the timing, you'll be right back to the clattering again.

https://www.tacomaworld.com/threads...nd-hesitating-from-idle-no-load.406638/page-4


Also FWIW my plugs show no sign of excessive ping.

 

Spark plugs going bad?

 

i had to change radiator couple months ago because it cracked. i do feel the engine overheating but it doesnt show on cluster. i took it to dealers. they said it was runnig normal. and nothing was wrong with it. i guess rattling and other sort or noises arent that big of a deal for them.

 

thanks for bringing that up. i had to change that too. no lick there either.

 

I second the idea of doing a tune up...when was the last time you changed out your spark plugs? Spark knock from bad plugs sounds exactly like pinging/pre-detonation which would account for that rattling sound you're hearing.

No reason a naturally aspirated Tacoma should require high octane fuel unless something's wrong. It's a band-aid not a solution

 

checked them. they look almost new. but i'll try new ones. i got a set laying around.

 

sparks plugs and oil was changed around 6 months ago.

 

Using the higher octane makes it go away ??

Interesting that would rule out something loose just causing a rattle that sounded like knocking

 

i thought it was something loose too like exhaust heat shield or something. ended up spending the whole day under the truck trying to find something lose. nothing at all.

 

9.6 static compression is not low. Isn't the manufacturer spec 87? This truck will absolutely ping n/a if it's hot enough. And I can't even with that band aid comment. Octane is one of the biggest limiting factors of IC engines.

 

He said he was filling up with 87, which is the manufacturer's spec. If he's having to use high octane fuel now because it's not running right on what it's supposed to run on (87), how is that not an issue?

Resorting to 'oh well, I guess I have to fill up with 91 from now on' doesn't sound like a solution to the problem for me. There was talk in another thread about this same issue; that the ECU will eventually adjust to the higher octane and the underlying problem causing the pinging will cause it to return. That sounds like a temporary solution to me. That's all I was saying.

 

pinging or pre-ignition is the fuel igniting before it is supposed to by the spark plug. If the EGR valve is flaky, meaning it doesnt flow enough exhaust gas back into the intake to reduce the combustion temp then it just might ping. Carbon build up raises the static compression ratio, ignition timing too far advanced, wrong plugs... we could go on for forever on the possibilities.

 

i agree. its not the solution. toyota dealership just ignored the fact that it was rattling. i gona have to get it tuned up by one of my old mechanics. hopefully that fixes it. As glamisman said, theres bunch of possibilities.

 

Rattling and detonation are 2 different things. An engine will advance timing up to a certain point and no further. You can put a bajillion octane in and it will still advance to the exact same point. If it detects any predetonation it will back the timing off. Regardless of the cause of the detonation you should never hear it happen if everything is working correctly. Unless the engine runs out of adjustment room and you're still detonating that is. You'll just lose power as the timing goes further and further retarded.

Excessive carbon build up can create hot points that will cause detonation, lots of things can. Adding octane may bandaid it but you need to find the actual problem, assuming it is actual detonation and not some other noise.