Emission light came on for the first time

[Quik LS]

well now that we are talking about this.. I dont see the fuel causing the coils to go bad.. Maybe if it was a fuel that burned alot SLOWER it could cause the coils to go bad for the fact that the amperage to the coils would have to increase to allow a strong enough spark to over come the plug gap and the cylinder compression and fuel resistances to burn... But i dont see that happening from a fuel that burns faster

again - saying on topic - misfires. the lower octane fuel 'may' be causing his misfires. He 'may' be having a coil issue not related to the octane.

however in post #13 - you seemed you did not grasp why lower octane fuel causes misfires. It seems that you do now.

Now if the mis-fires are bad enough - it could damage the plug - and then the mis-fires is more constant than just fuel octane - but not likely. It's not likely that mis-fires due to lower octane cause coils to go bad - but that is not how this post started. He started with mis-fires, you pointed at coils/gaskets, I pointed at octane, you stated octane can't cause coil issues.... but the real post was about mis-fires...

 

[Quik LS]

Actually the V6 gen1 also has VCG issue too...

I had misfires around the same mileage OP has (maybe 5-10k more).. replaced VCG and coils.. problem solved

and i always use 91+

Cool - you don't hear a lot about the issue with V6s - maybe not as many members with them. Was there oil getting into the plug wells?

 

[tireman]

My V6 is like that

My 01 V6 is like that too. Put in 87 octane and it runs like a dog. Always use 93 octane and never have a problem. At 87 octane I thought I would blow the engine, terrible rough engine when under load.

 

[lincoln00]

see with my Gen 2 V8.. it runs great with 87 or 91.. i have ran both.. only difference i noticed was a little ping on off idle acceleration... no ruff idles or anything, maybe it has to do with the Gen 2 running the CAN system.

 

[jumpman6235]

Cool - you don't hear a lot about the issue with V6s - maybe not as many members with them. Was there oil getting into the plug wells?

Yea, i didnt change it myself, but after my mechanic did he told me there was oil in them. I have heard of other v6's having this issue too.. your right though not too many members here have v6 so it doesnt get recognized as much

 

[LEOV5]

Whenmy LS with the V6, was in the shop for bad coils. I had showed them the oil on the rear of the valve cover under the intake manifold. Replaced that with 2 new coils and she runs great. and even shifts alot smoother. So yes, I would say that the V6's do have the leaking valve cover problem. I also agree with Quik, that over time you will run a HIGH COMPRESSION engine with lower octane fuel. It won't happen with the first tank of gas, but give it time and you bet. Plugs, pistons, rings, valves, something is going to go bad.

 

[lincoln00]

i am going to try the pcm reset...if i turn the heat on without AC there is a smokey smell with a hint of raw gas(not too bad)

well now that the codes are gone you will never know what was wrong iwith it.. until you run that monitor again and it fails... im so glade everyone told him to reset his PCM...

now its alot harder to figure out what plug/coil went bad... well i guess you might as well replace them all

 

[lincoln00]

Whenmy LS with the V6, was in the shop for bad coils. I had showed them the oil on the rear of the valve cover under the intake manifold. Replaced that with 2 new coils and she runs great. and even shifts alot smoother. So yes, I would say that the V6's do have the leaking valve cover problem. I also agree with Quik, that over time you will run a HIGH COMPRESSION engine with lower octane fuel. It won't happen with the first tank of gas, but give it time and you bet. Plugs, pistons, rings, valves, something is going to go bad.

not from 87 when 91 is what is recommended.. 3 octane points isnt going to cause catastrophic failure...

 

[lincoln00]

Whenmy LS with the V6, was in the shop for bad coils. I had showed them the oil on the rear of the valve cover under the intake manifold. Replaced that with 2 new coils and she runs great. and even shifts alot smoother. So yes, I would say that the V6's do have the leaking valve cover problem. I also agree with Quik, that over time you will run a HIGH COMPRESSION engine with lower octane fuel. It won't happen with the first tank of gas, but give it time and you bet. Plugs, pistons, rings, valves, something is going to go bad.

not from 87 when 91 is what is recommended.. 3 octane points isnt going to cause catastrophic failure...


10.75:1 isnt "HIGH compression" its just higher then normal... say 9:1

 

[Quik LS]

well now that the codes are gone you will never know what was wrong iwith it.. until you run that monitor again and it fails... im so glade everyone told him to reset his PCM...

now its alot harder to figure out what plug/coil went bad... well i guess you might as well replace them all

Not very constructive.

If there is a real problem - the codes will come back. If it was simply octane - it could take a tank of 91+ to settle it out, but then it's gone. Resetting the PCM is free and something anyone can do - so why not try it. If it come back - then get it read.

 

[lincoln00]

I know it wasn't octane.... I just did a search on Google about octane ratings and compression ratios, Everyone has there opinion... I found a link about some guys saying anything over 10:1 compression needs 96 octane... its all in the driving still of the owner of the car.

yea and with a car with a non continuous monitors like the ford motor company it could take months for that monitor to run and show him what cylinder was screwing up...

:q:q:q:q NYC and me my self both ahd bad misfires and we didn't even get a code after a blinking CEL but this guy had a solid CEL.. he had a good chance at saving money....

 

[Quik LS]

not from 87 when 91 is what is recommended.. 3 octane points isnt going to cause catastrophic failure...

when will you give it up.... how many ways can you be shown facts, and still refuse to say that 'maybe' you were wrong and actually learned something. This is the 5th or 6th time?

seriously

 

[97stscaddy]

I had showed them the oil on the rear of the valve cover under the intake manifold. Replaced that with 2 new coils and she runs great. and even shifts alot smoother. So yes, I would say that the V6's do have the leaking valve cover problem.

That's a totally different type of leak which NO car is immune to. The common issue with the V8 is that the O rings that go around the plug holes are :q:q:q:qty, they dry out and pour oil into the plug wells and drown the plugs. They eventually fill up with oil which seeps into the coil which then kills it.

Quik I'm trying to wrap my own head around the whole Idea of a misfire caused by lower octane. What it sounds like is that the lower octane is causing the fuel to combust before the spark occurs. Which would technically be a misfire. But last time I checked 10:1 compression is not enough compression to cause 87 octane to spontaneously combust without a major heat source or spark. So clue me in please, because I still think its coincidence that a coil has failed while he just so happens to be running regular gas.

Everyone has there opinion... I found a link about some guys saying anything over 10:1 compression needs 96 octane... its all in the driving still of the owner of the car.

Post up that link. A properly maintained and tuned engine with 10:1 compression should be able to run just fine on 87. For instance:

A real world example is the Northstar engine from 1999 to 2000. The 1999 engine was a 10.3:1 compression ratio. It was a premium fuel engine. For the 2000 model year, we revised the combustion chamber, achieved faster bum. We designed it to operate on regular fuel and we only had to lower the compression ratio .3 to only 10:1 to make it work. Normally, on a given engine (if you didn't change the combustion chamber design) to go from premium to regular fuel, it will typically drop one point in compression ratio: With our example, you would expect a Northstar engine at 10.3:1 compression ratio, dropped down to 9.3:1 in order to work on regular. Because of the faster burn chamber, we only had to drop to 10:1. The 10:1 compression ratio still has very high compression with attendant high mechanical efficiency and yet we can operate it at optimum spark advance on regular fuel.

I know for a fact that the 4 cylinder in the 98 Toyota Camry has a 9.5:1 compression ratio, and they run on 87 with no trouble.

 

[Quik LS]

Well - it has a lot to do with the design goals of the engine.

the camry is targeted at the family hauler segment so to be able to use 87 octane is very important, even if they traded a few extra hp to do it.

the LS was targeted as a luxury sport sedan, therefore performance was more important than being able to use 87 octane, and all of it's competition (in the day) used 91+ as well.

There are a lot of factors that determine what the minimum octane rating can be used in an engine - not just compression.

For example - if you have an engine that normally uses 87 octane and give it a performance tune - usually mean you mess with the spark and maybe some fueling - you often end up having to run 91 to reap the benefits of the tune. Advancing the spark is the most common reason - since you begin to 'lead' firing within the rotation cycle from where is was normally.

Even silly things like attitude play a big role in minimum octane rating. I grew up in the Rockies - and you could only buy 85 or 91 - instead of 87 and 93. The reasoning was that the higher altitudes allow less air density to be drawn into the cylinders, which then reduces compression in the cylinder - meaning that you can run lower octane fuel without knocking. But if you took that same tankful of 85 from the mountains to a place at sea level - you would start knocking (bad thing).

With the original poster of this thread being form Florida - he 'may' be more likely to knock with 87 than someone from a higher altitude state. Especially in an engine that was designed to use 91+. Now if he could retard the timing enough - he 'may' be able to run 87 without a problem - but pay for it with a loss of performance. and then there is the 'emissions' side of this....

when tuning performance cars - often we tune it using 93 (which allows for the most spark), which means once we are done - the owner is usually stuck using 93 (since they are performance-minded they make this trade). Some then fill up with 100+ octane and we go through another tuning cycle - and create an even more agressive tune - which they only use at the track and when running 100+ octane.

make sense?

 

[jcavz24x]

I have driven about 50 miles and the light is still off but it runs the same.it has a rough idle and stutters at an even speed...but.. at WOT it feels normal and accelerates like it should..there it started to have harder shifting.

before, it would mainly stutter at acceleration which i believe was the 87. now that there is 93 it does not.

sounds like coil or plug? im thinking bad gas caused mifire and then affected the plug(s) which now dont work at all.

 

[jcavz24x]

as soon as a get a change im going to have the plugs pulled

 

[Quik LS]

if you are going to change plugs - change the PCV as well - it's a $2 part that always fails on the V6 - and it's under the intake, a pain to get to - so if you are pulling the intake for the plug, swap PCV as well.

The symptoms of the a bad PCV are very similar to a bad coil - stumbles on idle (since that is where the engine needs high vacuum and the PCV will not allow it).

 

[lincoln00]

yea and while your at it... run 87 octane agian... it will still run the same i guarantee it....LOL

ok ill admit the car is suppose to use 91 octane... But i will also say that 87 octane will not damage anything... and will not cause a misfire or coil and or plug failure..... like i have been saying.

87 octane will not cause a misfire.. it will increase NOx output... but will not cause a misfire...

All i see you base your fact on is compression, when there is more involved then that.. like I said before

I'm not going to say i'm wrong when i know these cars will run fine with no PROBLEMS from RUNNING 87 octane!

oh and your comment on the Altitude proves my point even more... There is more involved then compression when it comes to getting the right octane rating!!!!

 

[Quik LS]

87 octane will not damage anything... and will not cause a misfire

87 octane will not cause a misfire.. it will increase NOx output... but will not cause a misfire...

do you agree that running lower octane will increase the chance of 'pinging'?

 

[lincoln00]

With the original poster of this thread being form Florida - he 'may' be more likely to knock with 87 than someone from a higher altitude state. Especially in an engine that was designed to use 91+. Now if he could retard the timing enough - he 'may' be able to run 87 without a problem - but pay for it with a loss of performance. and then there is the 'emissions' side of this....



make sense?

your not making sense... first you say there is all this things that make octane important... then you say the engine is made of 91+, there is to many variables to say a engine HAS TO RUN 91+!!!!!!!!!!!

Know i wont make you admit your wrong!

 

[Quik LS]

It seems I have accidently embrassed you. I applogize for that - it is only my intention to correct the information and offer what I know. I learn a lot on forums and from others, I also share things that I feel I am knowledgeable about.

I am not trying to make you understand how engines work, why/how octane ratings matter, tuning - I certainly am no expert, I do know a thing or two on the topic.

Rather than continue to drive the point to you, and you refusing to acknowledge some very fundamental concepts - and simply ruin this thread - I'll offer to continue this out of public's eye and on PM - if taking it off the public stage will make you less defensive.

 

[The Hotness]

Here...


Simple version: Our cars require 91+, they wouldn't require it if it weren't required.

If you don't put the required fuel required by your manufacturer then your just a cheap bastard and you shouldn't be driving an LS.

Period.

When I first bought my car I was unaware of this, and ran a couple of tank through. I wondered why my car lacked power, after running premium I was surprised at the results. I especially loved how this car reacted when I ran 100 octane unleaded. Smooth and way more power, even bumped my MPG to 27 freeway.

Needless to say I didn't buy this car because of economy or cheap gas.

Based on the logic of others, you might as well as not use synthetic oil. Might as well use SuperTech. I hear WalMart sells it for about a $1/quart, means you could change your own oil for about 10 bucks. I personally spend about 50, but that's because I am trying to protect my investment and follow the requirements my car company asks.

 

[jumpman6235]

if you are going to change plugs - change the PCV as well - it's a $2 part that always fails on the V6 - and it's under the intake, a pain to get to - so if you are pulling the intake for the plug, swap PCV as well.

The symptoms of the a bad PCV are very similar to a bad coil - stumbles on idle (since that is where the engine needs high vacuum and the PCV will not allow it).

^^^^^^^
DO IT!!!.. this is also a guaranteed failing part you will need to replace

good lookin Quik.. i forgot about this pest

 

[97stscaddy]

make sense?

Yes I understand all of that, that part about compression ratio vs octane was directed at Lincoln00.

What I was asking is how does burning 87 octane fuel in an engine that was designed to use 91+ cause a misfire?

 

[LLCoolLS]

Quality of gas at different gas companies

I have always run 91 octane from day one. The problem I had was not related to the octane/grade of the gas, but the quality of the gas from different gas stations. I live in Toronto. I was filling up with 91 at Esso (Owned by Imperial Oil) for the first six months and found the engine idling rough and struggling to say idle; and would misfire on acceleration. I got a flashing CEL and got a multiple misfire code (Cylinder 3). The car needed a tune up anyway so I changed all the plugs to hybrid platinum/iridium plugs, and changed the #3 coil ($50 CAD from Ford). It helped a little but the rough idle and misfires still occured (just less often).

Coincidentally, I was at Ford to have my tires switched, and I overheard the service advisor speaking to another customer with an F-150 that was experiencing the same problems.

Now, this can be a coincidence because I know the LS engine is originally a Jaguar, but hear me out.

The advisor asked the guy where he fills up. He said always at Esso. The advisor then immediately told him to stop filling up there because he had just gotten a memo that morning from Ford head office notifying him that Esso gas may be harming Ford engines.

After hearing that, I drove the car till empty, and filled up with 91 at Petro-Canada (Partnered with Chevron, Mobil, & Gulf), and tested it out. After about 100 kms, the car purred without a single hiccup. It ran (and still does) smoother than ever.

Sorry so long, but I thought I'd share this because it solved my misfire problem. Again, this can be a coincidence, but it just seems not in my case. Changing gas stations saved me lots of aggravation.

Just thought you guys might want to consider that.