Topic: Does anyone else have to use 89-93 oct?

[01amberfirewv]

When I run 87 in my Jeep the engine makes some nasty noise when the peddle hits the floor.  I took it to the dealer after I got it and they said they did not notice it.  I took it back and they said oh, yea thats spark knock and the best thing to do is alternate 89-93.  I didn't mind then because gas was only $1.00 a gal but now that the prices are jumping through the roof it is getting expensive.  

I have heard that I could have a carbon build up.  I have also heard that my timeing needs adjusted.  This problem is very evedent when I use 87 and I hear it all the time.  With 89 I only hear it under heavy acceleration such as getting on an uphill interstate on ramp or when I do not down shift to pass.  With 93 it is gone.

[trailblazer95]

Your timing is computer controlled.  EVERYTHING on your TJ is computer controlled and leaves hardly anything up to you to adjust, which can be good, and bad.  If you've got carbon buildup, just use some fuel injector cleaner or fuel system cleaner.  

You're wasting your $$ on 89-93 unless you're running some supermodified engine.  I had to run 93 when using a supercharger, but other than that, the engines are optimized to run on 87.

[StefanBidi]

Seafoam!!!  My Nissan had the same issue, and after I seafoamed the engine I can barely notice it.  There's still a knock, but only when under extreme load, like going up a hill (which is multiplied since I have larger tires on the truck as well).  I had knock on acceleration as well, but now that's gone.

[01amberfirewv]

Seafoam!!!  My Nissan had the same issue, and after I seafoamed the engine I can barely notice it.  There's still a knock, but only when under extreme load, like going up a hill (which is multiplied since I have larger tires on the truck as well).  I had knock on acceleration as well, but now that's gone.

I have never heard of seafoam, what is it?  Also I know that my naturaly asperated engine shouldn't need it but I have also heard that spark knock or detination can ba harmful to the engine.  That is why I still run 89 but I do hate spendning the money

[shotgun]

Seafoam is a combination fuel / oil additive.

http://www.seafoamsales.com/motorTuneUpTechGas.htm

All of the methods of use and stated benefits sound the same as putting the same amount of atf in the same locations.

[Jeffy]

Yeah, but you won't get the cool white cloud with ATF.

There should be no reason you would need to run Plus or Premium in a MPFI 2.5L.

[StefanBidi]

Yeah, but you won't get the cool white cloud with ATF.

That's true!  And seafoam is also OBDII safe (which means it won't clog up the cat).  It smokes A LOT for the first 2 miles, then very little for 10 miles, and you can't help but laugh when people come up next to you and give you dirty looks.

[01amberfirewv]

There should be no reason you would need to run Plus or Premium in a MPFI 2.5L.

I have had many people tell me that but still havent figured out why I do.  I have tried injector cleaner, octain booster, redlining it etc and they are all temporay fixes and not as effective as running higher octain.

[trailblazer95]

let me ask you this, is it a kind of clattering/knocking noise when you hammer the gas down in the higher gears, like 3rd-5th?  my girlfriend's TJ has the exact same problem... it stops when you let off the gas.  pretty much we've just learned to drive around it.   It's been to the dealer and they've pretty much just told us the same thing.

[01amberfirewv]

let me ask you this, is it a kind of clattering/knocking noise when you hammer the gas down in the higher gears, like 3rd-5th?  my girlfriend's TJ has the exact same problem... it stops when you let off the gas.  pretty much we've just learned to drive around it.   It's been to the dealer and they've pretty much just told us the same thing.

Yea thats it but it is hard to drive around here because of all of the hills on the interstate.  My brothers 2.5 also does it but not as bad as mine.

[Jeffy]

Well, 2.5L's have had one problem that not too many people notice.  The PCM stumbles when under a slight load at higher speeds.  This was a problem with my YJ for a while.  It would be 100% repeatable, too.  Slight hill, bring the RPM's to around 3000 and hold. Felt like a tank of bad gas but the gas was fine.  Every once in a while the engine shoould misfire and you can really feel the drop in power.

I think it's gone with my new ignition.  Although I doubt I have any carbon buildup since I do run it up to 5000rpm.

[YJmechanic]

I work at a jeep dealership.  Any dealer should be able to do a complete fuel system cleaning.  It doesn't cost a lot maybe $50.  What we do is take the tb off and clean all ports including removing the ais motor and tps.  Them run treatment in the tank , and finally draining the fuel rail, disconnecting the fuel pump and hooking in a machine to run 100% consentrated cleaner directly through the injectors then back to the tank.  I notice a big improvement to all the jeeps I have done in this way.  You could do this yourself but you have to find a hookup for the decompression valve on the fuel rail.  All the other things you can do yourself with normal auto parts store cleaners.

[jwrape]

Have you thought about transmission gear chatter? My AX15 that I just installed chatters pretty good when the accellerater is at the point where you are accellerating but not hard. Kinda where the gears would have some play in them because I am not accellerating nor de-accellerating.
Gear chatter is VERY common in Jeeps and I know there are a few different gear oils that can reduce it. Syncromesh is one of them.