90Luminator Posted October 20, 2005 Report Posted October 20, 2005 Hey guys, I found that when I use 87 octane in my 90 eurosport, I hear a faint "valve ticking" in top gear. However when I put 93 octane in, the sounds go away. The manual states that 87 is the recomended fuel but I get the odd sound. Am I going crazy? Has anyone else experienced this odd sound. And yes I keep the car in check, just put in new plugs and fuel filter. Thanks -Andy Quote
90Luminator Posted October 20, 2005 Author Report Posted October 20, 2005 what's spark knock, and can it be fixed? Thanks Quote
3pt1lumina Posted October 20, 2005 Report Posted October 20, 2005 my 77 chevelle does that.. I have to use a higher octane (93 instead of 87). On my chevelle, it is predetination. Basically, the cylinder is firing before the piston reaches TDC, resulting in pushing the piston down prematurely, which results in unusual wear ontop of the piston. (this is what my shop teacher told us anyways) I dont know if this will fix it, but installing a cooler running thermostat will get rid of this. (it did in my dad's 77 monte carlo) so i'm gonna give that a shot in the spring. basically, just run 89 or 93 and dont worry about it too much. Quote
19Cutlass94 Posted October 20, 2005 Report Posted October 20, 2005 You could try a higher octane fuel. Alot of times pinging and desieling are caused because your not using a high enough octane fuel. Even though you dont have that problem, if you say 93 works, Id keep using that. Quote
TeeJay3800 Posted October 20, 2005 Report Posted October 20, 2005 It should never be necessary to run anything higher than 87 in a 3.1. If it pings (knocks) burning 87, you should do a top end clean and run some fuel system cleaner. Quote
99RegalGS Posted October 20, 2005 Report Posted October 20, 2005 my 77 chevelle does that.. I have to use a higher octane (93 instead of 87). On my chevelle, it is predetination. Basically, the cylinder is firing before the piston reaches TDC, resulting in pushing the piston down prematurely, which results in unusual wear ontop of the piston. (this is what my shop teacher told us anyways) Predetonation is not a correct term. There is Pre-ignition and Detonation (knock). What you have described though is Pre-ignition, which is VERY bad and can cause a lot of damage very quickly if substained for any length of time. I think what the other members said is the correct problem which is Detonation (knock). Detonation happens after TDC and after the spark plug fires. For more infomation please read this. http://www.streetrodstuff.com/Articles/Engietonationne/Detonation/index.php Quote
Prospeeder Posted October 20, 2005 Report Posted October 20, 2005 the diesleing is when the motor keeps doing with the power off right? i here thats really bad because the oil pump isnt running and will cause alot of damage Quote
19Cutlass94 Posted October 20, 2005 Report Posted October 20, 2005 yupp, motor keeps running with the power off, because its burning all the unburned fuel. Quote
gp90se Posted October 20, 2005 Report Posted October 20, 2005 Hey guys, I found that when I use 87 octane in my 90 eurosport, I hear a faint "valve ticking" in top gear. However when I put 93 octane in, the sounds go away. The manual states that 87 is the recomended fuel but I get the odd sound. Am I going crazy? Has anyone else experienced this odd sound. And yes I keep the car in check, just put in new plugs and fuel filter. Thanks -Andy I would first chnage the fuel filter, and use a bottle of berrymans fuel injector cleaner in the fuel (FOLLOW THE DIRECTIONS TO A T). Either run a bottle of seafoam or GM top end cleaner thru the plenum and replace the plugs with delcos. there is no reason a 2.8 shouldnt run mint on 87 octane at all. the diesleing is when the motor keeps doing with the power off right? i here thats really bad because the oil pump isnt running and will cause alot of damage thats a whole other issue usually a timing or power backfeed issue but never seen it on a w-body, so im not going to get into that right now. Quote
digitaloutsider Posted October 21, 2005 Report Posted October 21, 2005 Can a fuel injected engine even have dieseling? Quote
3pt1lumina Posted October 21, 2005 Report Posted October 21, 2005 my 77 chevelle does that.. I have to use a higher octane (93 instead of 87). On my chevelle, it is predetination. Basically, the cylinder is firing before the piston reaches TDC, resulting in pushing the piston down prematurely, which results in unusual wear ontop of the piston. (this is what my shop teacher told us anyways) Predetonation is not a correct term. There is Pre-ignition and Detonation (knock). What you have described though is Pre-ignition, which is VERY bad and can cause a lot of damage very quickly if substained for any length of time. I think what the other members said is the correct problem which is Detonation (knock). Detonation happens after TDC and after the spark plug fires. For more infomation please read this. http://www.streetrodstuff.com/Articles/Engietonationne/Detonation/index.php oh man, thats what I get for taking a free auto course.. thank you for the clarification!! Quote
Jcrow Posted October 21, 2005 Report Posted October 21, 2005 Dieseling happens in carburated cars because they can keep getting fuel, You cant suck fuel out of a fuel injector! Quote
maybe2fast Posted October 21, 2005 Report Posted October 21, 2005 who did you buy the car from? maybe it has a premium chip! Quote
sdwhite Posted October 21, 2005 Report Posted October 21, 2005 A lot of times detonation is caused by carbon buildup in the combustion chamber. The carbon get's hot enough that it ignites the gas in they cylinder before it reaches the top of the compression stroke and before the plug fires. It can be caused, in earlier vehicles, by having your timing advanced too far. Dieseling happens in carbed vehicles only partially because it can continue to get fuel. It happens mostly because there is still something igniting the gas. Quote
TGPilot Posted October 21, 2005 Report Posted October 21, 2005 It should never be necessary to run anything higher than 87 in a 3.1. If it pings (knocks) burning 87, you should do a top end clean and run some fuel system cleaner. I did not read the rest of the posts...but this is a very good diagnosis without actually hearing the car or running a datalogger on it. As long as there are no other issues with the car's valvetrain and you are positive it is only heard with lower octane gas then most likely you have carbon build-up on the tops of your pistons. This in turn causes the compression ratio to increase enough in the cylinder(s) that the lower octane gas knocks just like if it was a higher compression engine that required high octane fuel. Quote
TGPilot Posted October 21, 2005 Report Posted October 21, 2005 i here thats really bad because the oil pump isnt running and will cause alot of damage You heard wrong unless you have some fan dangled electric oil pump. If the motor is turning so is the oil pump in any car I have ever worked on/built/rebuilt. Now if the motor "BackCranks" (runs backwards) from a backfire and then starts to diesel while running backwards then yes you will lose oil pressure because it is running backwards. But that is hard to do with a carb engine because the air then rushes out of the engine through the carb instead of through the exhaust. 8) Quote
GP1138 Posted October 21, 2005 Report Posted October 21, 2005 I thought "Dieseling" was when the engine turned backwards, and that's what they were referring to. Quote
TGPilot Posted October 21, 2005 Report Posted October 21, 2005 I thought "Dieseling" was when the engine turned backwards, and that's what they were referring to. http://www.misterfixit.com/diesling.htm http://mgaguru.com/mgtech/engine/ro101.htm Quote
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