Pinging....Knock Sensor?

[Chaser]

Has anyone else had problems with the jk pinging/knocking? I've just spent the last two nights under the truck chasing a pesky rattle I was getting when the engine was warm and under load. Yesterday in desperation I filled up with 98 octane and surprise surprise no more rattle. My very limited knowledge on the subject suggests it might be a faulty knock sensor or throttle position sensor. What do you guys reckon?
Anyway its going back to Jeep on tuesday.
Are you guys able to run on standard fuel without knocking? I hope its not another Jeep thing as they are starting to become overwhelming to a first jeep owner. Cheers in advance!

[carvesdodo]

Have a read of your owners manual.

If its like a TJ or XJ manual ... It will mention pinging and knocking as a result of using a low octane fuel.

Petrol is like tyre pressures ... you match it to the vehicles use ... not a misconception about running costs.

[Chaser]

Not sure there is a "misconception" about running costs. Premium fuel costs significantly more for a negligible increase in mileage. As far as I'm aware a 20+ year old pushrod engine design isn't exactly pushing the envelope in terms of technology and shouldn't require are higher than standard octane rating. Especially in winter......

[carvesdodo]

Originally Posted by Chaser

Not sure there is a "misconception" about running costs. Premium fuel costs significantly more for a negligible increase in mileage. As far as I'm aware a 20+ year old pushrod engine design isn't exactly pushing the envelope in terms of technology and shouldn't require are higher than standard octane rating. Especially in winter......

sighhhhh ......

Whats the metricated american owners manual suggest you should be running ???

Does it mention pinging / knocking as a result of lower octane fuel use ???

Wasnt making a point about engine variations ... was making the point that the info you might want could be in that probably, unopened little book in your glovebox.

[SeaComms]

My 2000 model Subaru Forester used to get much varied fuel economy with differeing grades of fuel. For an average fill up of around 45 litres, driven distance would vary from 300 to 500+km. I just sold this car a few weeks ago with 336,000km on it, so had a few trips round the block under its belt to base the findings on that I have summarised below. The Jeep on the other hand only has just over 2000km on it so far and all on standard unleaded so I can't comment on it yet...

I found using standard unleaded fuel from different service stations would vary my travel from 350 to 450km around town. The worst for the Suby I found to be the Woolworths/Caltex servos, none in particular, all seemed just as bad as each other.

Dropping to 10% ethanol under pretty much any brand would drop me to around 300 to 350km max.

Premium from the Woollies/Caltex would give me around the 400 to 425km, same as regular from most other servos.

Premium from most BP and Shell would give me around 450 to 475km around town (On the highway this would stretch right out to close to 600km).

On average, the cost difference in premium fuel worked out less than the improved mileage, so cost per km was less (with the exception of Woolies/Caltex, the difference in cost from standard to premium with their fuel was greater than the improvement in distance travelled).

It should be noted that I did ocasionally get pinging in the Suby, but only ever on the Woolies/Caltex fuel, which leads me to believe it probably has a lower octane level than actually rated which coincides with the noticed decrease in fuel economy.

As mentioned the Jeep only has 2000km on it so far and its being used as the misses's daily drive. She is not as ******** as me when it comes to making note of fuel amounts and mileage etc so it will be a while before I can see what if any differences fuel makes to it.

[Chaser]

"Your engine is designed to meet all emissions
regulations and provide excellent
fuel economy and performance when using
high quality unleaded gasoline having
an octane rating of 87. The use of premium
gasoline is not recommended. The use of
premium gasoline will provide no benefit over high
quality regular gasoline, and in some circumstances may
result in poorer performance."
From the unopened book in my glovebox. This leads me to summise that there may be something amiss.

My experience differs from yours Seacomms. Two cars ago in a Mazda six I noticed very little improvement in fuel economy probably a max of 30-45 km. My previous car was 95 octane only so it has been a while though.

[Chaser]

and on the next page:
"Light spark knock at low engine speeds is not harmful to
your engine. However, continued heavy spark knock at
high speeds can cause damage and immediate service is
required.
Poor quality gasoline can cause problems such as hard
starting, stalling and hesitations. If you experience these
symptoms, try another brand of gasoline before considering
service for the vehicle."
My apologies....