I have a '96 B body LT1, half the time it pings like crazy in the higher RPMs. It doesn't always do this, but it does happen a lot. The knock sensors don't make it stop either, it will ping until I let off the gas or it shifts. I also have a slight misfire at about 5% throttle, which is also about half the time. I changed plugs and wires and fuel pressure is at 39-46psi (idle/WOT) when this is happening. I am thinking opti, but I don't see how an opti can over advance the timing? Thanks for any opinions

 

Loose parts (rotor, maybe optical pickup?) in opti could advance/retard timing intermittently. So could carbon traces, I think.

 

You said you had a b-body motor but did not mention the car. If it is in something else are you using the b-body timing tables?

Honestly though valve float was the first thing that came to my mind. The b-body springs are pretty weak, with some miles on them guys have documented float as early as 4800rpms.

 

Has the engine been modified in any way? Has the stock programming been changed? As Dwayne asked, are you possibly using an aluminum head timing table with the iron head B-Body engine? Have you verified that the PCM is pulling timing with the knock retard system? Have you verified the knock sensor is functioning correctly? If you can hear "ping" and the PCM is already pulling the 15deg of knock retard it is capable of, you've got a serious problem.

 

The car was bone stock no mods and was pinging with 99k miles. I have added F-body Maf, cold air, and a PCM4Less tune. I have only owned this car for a month, so don't think I have been driving around with it pinging like this for a long time. Another thing I noticed is that sometimes when I start the car it sounds like a high compression car that doesn't have a timing retard, but that has only happened like 3 times, so nothing is consistant. I was going to just replace the opti, but if someone thinks timing chain or something like that, then I will do that while I am changing the opti.

Is there a way to lock out timing so I can rev the car up and down and watch for fluctuations in timing?

 

Are you running Premiuim Unleaded fuel? If It's pinging as much as you say I'm suprised you still have pistons left. I put a hole in a Forged TRW piston from pinging...

 

It doesn't seem to matter what grade I use, it has pingged with 92 octane. Like I said it isn't consistant. I can hit it on the freeway and it will be fine, slow down and do it again and then it will ping.

 

Usually you can hear if your car pings if you put it say say 6th gear at slow speed (about 1k rpm) and give it some gas give it a hard load and you'll hear it ping.

 

When pcmforless did the tune, was he aware you were running iron heads?

 

Yes I mentioned it has iron heads on the sheet. It pinged before the tune, when it was bone stock down to the paper filter.

I am thinking opti, but if someone on here has had an issue similar to this and has other suggestions, I would like to address or check those at the same time rather than pull the car down over and over.

 

From the hard starting, coupled with the pinging, it sounds like its got too much advance. Hard to think of anything that would alter the timing other than the distributor.

Is there any chance you have a huge buildup of carbon in the heads, increasing the compression ratio? What is the typical coolant temp when the engine is operating?

 

It is possible, I ran some cleaner through it already (SeaFoam, TB cleaner). I don't have a numerical guage, but it operates 1/4 way up from the bottom, and I have never seen it reach the middle of the guage.

 

Aside from all the other advice, Also replace the fuel filter if you haven't already....I've seen clogged ones do some funny things including bad pinging even while a fuel pressure gauge was showing plenty of pressure... pressure is not always indicating of the actual flow volume.......That may not be it but when a car tends to ping in the upper rpms, many times it's a serious fuel flow issue.....and it's only a 15 minute deal to replace the fuel filter so it's a cheap easy thing to try.......Joe

 

What is the difference between pinging and knocking?

 

"Ping" is generally used to describe pre-ignition, where the heat and pressure of the rising piston cause the A/F mixture to auto-ignite BEFORE the spark fires. "Knock" is generally use to describe a second flame front that auto-ignites from the heat pressure of the spark induced flame front.