My 95 cobra pings under hard acceleration running 93oct. and timing at 13deg. Something wrong there? starts pinging at around 4K. What do you guys think i should do? i know stock is 10, and i do remove the spout before i change it.
Pinging
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BlackVert
15 Year Member
my guess is that you have some carbon buildup on your pistons that is increasing the compression ratio enough to make it ping.
seafoam is supposed to help that sort of thing ...
or backing the timing down a little might make a difference
seafoam is supposed to help that sort of thing ...
or backing the timing down a little might make a difference
desertcox05
New Member
maybe your HB has slipped and your not really at 13 deg.
what's the water temp when it does it. Mine would ping like that after sitting in traffic on a hot day
what's the water temp when it does it. Mine would ping like that after sitting in traffic on a hot day
99FiveOh
10 Year Member
Yeah, what's the mileage on your car? What all have you replaced since you owned it? Be specific...
85K mi. upr cai,offroad x flowmaster super 44 catback,ac/delete, smog bypass. The temp never gets over halfway, only on really hot days setting in traffic it will get up some. just pings under WOT after 4K rpm
Pinging often occurs from an EGR failure. Might want to check your EGR out. They have a tendancy to get full of crap and go bad.
Kurt
Kurt
earleys94gt
Active Member
99FiveOh
10 Year Member
Well, I have double your mileage, but I had this problem and changed everything, checked everything... nothing seemed to help. I seafoamed the engine too, nothing. My problem turned out to be the distributor shaft. the bearing was so worn out that the reluctor wheel was smashing into the PIP sensor and thus damaged it. Fixed the dizzy, replaced the PIP and was good to go.
You probably don't have this problem since you have low miles, but in case someone finds this thread with the same problem, it might help.
You probably don't have this problem since you have low miles, but in case someone finds this thread with the same problem, it might help.
I had the same problem about 6k ago, roughly 161k. Changed to premium fuel and seafoamed it. Seemed to do the trick. Just my 2 cents.
What miles are you at? Just curious if this recurring problem with our cars so I don't end up spending a ton of money trying to figure it out.
What miles are you at? Just curious if this recurring problem with our cars so I don't end up spending a ton of money trying to figure it out.
99FiveOh
10 Year Member
blksn955.o
Founding Member
If its happening at high load/hard excel its not the EGR as it turns off/closes either way at WOT (failing open would only cause a richer mix that would help reduce ping). Now if it was doing it at say 50-70mph at cruise on the hwy EGR would be a big possible option if it fails closed you will get a lean A/F and cause a low load ping/bucking (also common if EGR is deleted and not shut off in the tune).
As common as our HB's fail it is worth checking out for sure as you may be running 18-20* at the ball and not even know it if its spun/going bad. A solid tune up for the 94-95's if purchased now should include plugs, wires, cap, rotor, fuel filter, air filter, and a new HB.
One thing to remember our 94-95's run HOT from the factory. One thing I noticed putting in a 190 stat and turning the fans on to match those figures keeping it cooler stopped the ping.
I have 10.33-10.6 comp on a iron head gt40 motor, run the stock rad., live in a area that gets 100-110 temps with 90+% humidity in the summer and have ran 32-33* total timing (28 is stock IIRC). I have even ran 91 with no issues at 32*. Datalogged temps and autometer guage show 192-194* as well. 20-30* colder than stock will help greatly to stop ping.
As common as our HB's fail it is worth checking out for sure as you may be running 18-20* at the ball and not even know it if its spun/going bad. A solid tune up for the 94-95's if purchased now should include plugs, wires, cap, rotor, fuel filter, air filter, and a new HB.
One thing to remember our 94-95's run HOT from the factory. One thing I noticed putting in a 190 stat and turning the fans on to match those figures keeping it cooler stopped the ping.
I have 10.33-10.6 comp on a iron head gt40 motor, run the stock rad., live in a area that gets 100-110 temps with 90+% humidity in the summer and have ran 32-33* total timing (28 is stock IIRC). I have even ran 91 with no issues at 32*. Datalogged temps and autometer guage show 192-194* as well. 20-30* colder than stock will help greatly to stop ping.
99FiveOh
10 Year Member
blksn955.o
Founding Member
After, as it was the combination of going with a colder stat and moving the fan turn on points that I saw the issue stop.
99FiveOh
10 Year Member
First off, it's common knowledge that GT40 heads with their different combustion chamber design don't lend themselves to detonation nearly as bad as their E7TE counter parts.
Second, you have tuned your car, so you can't really say you're getting away with x amount of timing when you have tuning ability. For instance, you have to be able to tune the car somehow to adjust the fan turn on temps. I'm not sure how you modified your fuel and spark tables, but to my understanding it is one of those values that is programmed into the T4MO computer that promotes pinging in the first place.
So obviously if you combine a tuning device with a "less likely to ping" cylinder head, of course you can run more timing and be safe. As it stands, If I set my timing to anything over 10* it'll ping like crazy! And I do have a new balancer and just about everything else as well.
Second, you have tuned your car, so you can't really say you're getting away with x amount of timing when you have tuning ability. For instance, you have to be able to tune the car somehow to adjust the fan turn on temps. I'm not sure how you modified your fuel and spark tables, but to my understanding it is one of those values that is programmed into the T4MO computer that promotes pinging in the first place.
So obviously if you combine a tuning device with a "less likely to ping" cylinder head, of course you can run more timing and be safe. As it stands, If I set my timing to anything over 10* it'll ping like crazy! And I do have a new balancer and just about everything else as well.
Two passes on nitrous works better than Seafoam. Nitrous burns so hot, it clears almost everything out.
Kurt
Kurt
blksn955.o
Founding Member
Valid points yes, but 10.3 to 10.6 comp on an iron head will probably make up for any chamber difference of a 8.8-9.0 gt40 or E7 headed combo. Just to be totally open I did polish the chambers a bit to help further with det. Also IIRC the OP has a cobra that has those gt40 heads so it is if anything an even more apple to apple comparison.
On the tune side. When I first got it setup it pinged (before tweecer). I ran the stock gt maf and cobra j4j1 file factory and a modded T4mo with only changes for the inj. slopes. NO other changes both with the fan settings lower to match the stat I had already installed and that was it. Factory timing an fuel tables VERY basic changes just to get down the road and capture some datalogs to make more changes.
Now in my situation the stat alone actually made things worse. It overheated like a MOTHER. I had to wire up a manual fan switch until I got the tweecer (about a year or two, also ran before headwork on box stock gt40's) to control the fans as they were not syncing up it seems. As soon as I reset the fan settings the entire combo ran dead consistent in the temp dept. and the ping went away.
99FiveOh
10 Year Member
blksn955.o
Founding Member
Go moats QH...I am REALLLLLLY thinking about selling my tweecer.
I have heard about some new auto tune functions coming out that automatically adjust the tune on its own! REALLLLY cutting edge
I have heard about some new auto tune functions coming out that automatically adjust the tune on its own! REALLLLY cutting edge
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