Help! N/A pinging, need help diagnosing...
11-19-2005, 03:25 AM
#1
Three Wheelin'
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Help! N/A pinging, need help diagnosing...
Hey gang...
I have an '88 N/A that has a pinging issue. Trouble is, I'm not sure where to look next for the possible cause. At moderate/heavy throttle, she pings on 91 octane.
The car was pinging when I bought it earlier this year. Since then, I have replaced the TPS, DME temp sensor, O2 sensor, flushed the fuel system, replaced the filter and balanced the injectors, and recently replaced the H/G and T-belt (finished that yesterday).
The car is still pinging even though the head and pistons are totally clean of carbon deposits and I have brand new OE plugs. I only run 91 octane in the car, and it has a stock chip. The timing should actually be *retarded* slightly since I had 30 thousandths decked off the head to raise the compression, which should actually help fight off pinging (this is not the cause of the pinging, as it was pinging when I bought it months ago).
What are my likely/possible causes?
Are there any other external sensors I can check/replace, or could the DME itself be faulty? Or is it possible that my FPR/dampener/fuel pump may have an issue causing it to lean out above a certain load or RPM? For some reason I seem to remember messing with the TPS adjustment and having some sort of effect on the pinging, but this was a while back and I cant' recall for sure...was this my imagination or could TPS adjustment be a factor?
The car runs beautifully otherwise (aside from needing a waterpump because the bearing is shot and the waterpump pulley wobbles). I just don't know what to check next. If anyone could help I'd appreciate it! Thanks so much!
I have an '88 N/A that has a pinging issue. Trouble is, I'm not sure where to look next for the possible cause. At moderate/heavy throttle, she pings on 91 octane.
The car was pinging when I bought it earlier this year. Since then, I have replaced the TPS, DME temp sensor, O2 sensor, flushed the fuel system, replaced the filter and balanced the injectors, and recently replaced the H/G and T-belt (finished that yesterday).
The car is still pinging even though the head and pistons are totally clean of carbon deposits and I have brand new OE plugs. I only run 91 octane in the car, and it has a stock chip. The timing should actually be *retarded* slightly since I had 30 thousandths decked off the head to raise the compression, which should actually help fight off pinging (this is not the cause of the pinging, as it was pinging when I bought it months ago).
What are my likely/possible causes?
Are there any other external sensors I can check/replace, or could the DME itself be faulty? Or is it possible that my FPR/dampener/fuel pump may have an issue causing it to lean out above a certain load or RPM? For some reason I seem to remember messing with the TPS adjustment and having some sort of effect on the pinging, but this was a while back and I cant' recall for sure...was this my imagination or could TPS adjustment be a factor?
The car runs beautifully otherwise (aside from needing a waterpump because the bearing is shot and the waterpump pulley wobbles). I just don't know what to check next. If anyone could help I'd appreciate it! Thanks so much!
11-19-2005, 12:11 PM
#5
Nordschleife Master
I really dont know what the cause of this could be other than bad gas. Perhaps throw a few TUM's in the gas tank.
But seriously, Campeck is correct that the DME has a fuel quality switch. FRWilks webpage has a pretty good writeup on the basics,
http://www.frwilk.com/944dme/fqswitch.htm
I would only use this information to set it back to stock, you can seriously damage your engine by setting it to anything other.
But seriously, Campeck is correct that the DME has a fuel quality switch. FRWilks webpage has a pretty good writeup on the basics,
http://www.frwilk.com/944dme/fqswitch.htm
I would only use this information to set it back to stock, you can seriously damage your engine by setting it to anything other.
11-19-2005, 12:57 PM
#6
Three Wheelin'
Try running something like seafoam in the fuel and in through one of the vacuum lines you might have a lot of carbon build up that is causing hot spots. How do you plugs look?
11-19-2005, 07:22 PM
#7
It was my understanding that by 88 the NA's had a knock sensor that would retard the timing at the onset of detonation. Someone here should know for sure. It might then be a non-functioning knock sensor....
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11-19-2005, 09:47 PM
#8
Three Wheelin'
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No, it doesn't have a knock sensor.
This is really frustrating. I'm going to check for a lean condition tomorrow. Also, I'll check the DME.
I could theoretically run 100 octane in it all the time...I mean, at this rate, regular will cost $6/gallon soon anyway. lol.
But seriously though...I think running ~95 octane with a homebrew mix would just be masking a problem. I want to find the source. I'll let you know if we find anything tomorrow.
This is really frustrating. I'm going to check for a lean condition tomorrow. Also, I'll check the DME.
I could theoretically run 100 octane in it all the time...I mean, at this rate, regular will cost $6/gallon soon anyway. lol.
But seriously though...I think running ~95 octane with a homebrew mix would just be masking a problem. I want to find the source. I'll let you know if we find anything tomorrow.
11-20-2005, 08:04 PM
#9
Three Wheelin'
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UPDATE:
Checked AFM = OK, DME = OK. Still don't know if the pinging was being caused by an ignition advance problem or lean condition.
Threw in some cold NGK's I had (BR8ES), and the pinging went down. But these are very cold plugs and might foul quickly. NGK heat index of 8 is about equal to a Bosch 4 or 5. Stock heat range for the 944 is a Bosch 7.
Then I cranked the FQS on the DME to +3% fuel and -2.77 deg. ignition timing. Pinging went away all together, but the car was noticeably slower with the retarded ignition timing (my cam is also retarded by -3 degrees...and the two of them put together really slow the car down).
Next I side-gapped the plugs and changed the DME setting to +6% fuel and stock ignition timing. At full throttle above 4k RPM it still pings, but not as bad. If I let off to about 85% throttle, the pinging stops. Also, it's relatively warm outside so the pinging may go down after it gets cold.
Looks like I'll eventually be able to tune it so it won't ping, it's just going to take a few tricks and some time. But I'm about to park her for a week or two in order to install a waterpump, so the pinging issue will go on the backburner for a little while.
Checked AFM = OK, DME = OK. Still don't know if the pinging was being caused by an ignition advance problem or lean condition.
Threw in some cold NGK's I had (BR8ES), and the pinging went down. But these are very cold plugs and might foul quickly. NGK heat index of 8 is about equal to a Bosch 4 or 5. Stock heat range for the 944 is a Bosch 7.
Then I cranked the FQS on the DME to +3% fuel and -2.77 deg. ignition timing. Pinging went away all together, but the car was noticeably slower with the retarded ignition timing (my cam is also retarded by -3 degrees...and the two of them put together really slow the car down).
Next I side-gapped the plugs and changed the DME setting to +6% fuel and stock ignition timing. At full throttle above 4k RPM it still pings, but not as bad. If I let off to about 85% throttle, the pinging stops. Also, it's relatively warm outside so the pinging may go down after it gets cold.
Looks like I'll eventually be able to tune it so it won't ping, it's just going to take a few tricks and some time. But I'm about to park her for a week or two in order to install a waterpump, so the pinging issue will go on the backburner for a little while.