Have a greddy catch can, used seafoam, changed plugs, fuel filter, had stock maf replaced under warranty, added a maft to get my lt's to a negative state. Even with - lt's I still get up to 7 degree's of kr at part throttle. I use mobil gas , 91 here in ca and even tried some 76 100 to mix with the 91 and still kr and pinging. I have no codes coming from the predator. I can't use the predator tune because then I get 10 degree's of kr and tons to ping even at wot and part throttle. I am using the STOCK MAF so ignor the sig. Only mod to the direct flow lid.

 

Sounds like your car is sick lean. Does it hesitate as well?

What was the last thing that you did to it before it started doing this?

 

The stock MAF should not require the MAFT to get right.
Maybe go back to basics, drop the MAFT, reset the PCM,
let the LTFTs stabilize and then use your Pred to eyeball
the LTFTs over the driving envelope. If it's still crazy lean
then there may be some air leak that needs to be chased
down. You might do a fuel filter change if you haven't,
maybe even invest in a discount fuel pressure gauge just
to look at rail pressure over parked RPM range, see if there
could be some line kink, pump wiring or other delivery issue
showing up as early fuel fade.

 

Sounds like you have a major vacuum leak.An 02 has low timing to start with and in no way should have knock,expecially at part throttle.

 

I am now 100% stock and still have part throttle pinging and kr. I have changed the fuel filter already and have added a vacuum gauge to help with mpg which has helped and the guage drops to 0 at wot and reads 22 at idle. I have tested the fuel pressure at idle but not upping the rpms. I will have to try that tomorrow. One weird thing tonight I noticed driving on the highway is while cruising one of the long trims was reading 0.00 and only would read - when accelerating. My pinging all started when I got the predator but even then the first couple months I had no ping with that. Then the first ping I had was when I put the stock tune back in to take the car in for dealer service. When I reinstalled the predator tune the ping went away. Then it started pinging alot. I have had the dealer check for codes too and nothing.

 

I would check your injectors for proper operation and if that doesn't work, try getting your computer reflashed. You may have some bad data in there.

FWIW most of the tuning devices (hypertech in particular) out there don't really flash the PCM back to stock. Usually something or another is left behind. The only 'true' way to get back to a stock PCM is to have it reflashed by a Tech2 at the dealer.

Good Luck

 

mine is a 02 and completely stock computer and i get kn at part throtthe up to 5* sometimes

 

I've heard that when you load the Predator tunes
all of your LTFT and STFTs get zeroed. This may
account for why you get a brief period of no ping;
if your eventual trimmed state is leaner then 0 is
(relatively speaking) rich and suppressing ping for
the moment.

It is possible to have a natural 0.0 LTFT happen;
just long odds.

What does your ECT sit at?

 

My ect is around 190 on the highway and up to as high as 224 yesterday in town. Stop and go. I had lots of pinging then with the higher ect. However even with low ect's and low iat's the ping is there at times and the kr is always there. I had the dealer reflash the pcm, at least that's what they told me when they scanned for codes. The dicks charged me $42 dollars to do that. In what way can I check the injectors. Listen to them with a piece of hose? What sensor's give the long trims readings? The thing lastnight with the 0.00 on one has never happened before. Any way to test the 02's too? I have a multimeter tester. Can I test for voltage or something?

 

Got to get those fans set to run earlier, use the Predator
and set FAN1 to something like 185 ON / 183 OFF and
FAN2 to 198 ON / 196 OFF; this will have your low speed
fans running full time as soon as the engine gets up to
thermostat controlled temp and the high speed will be
a "backstop" if your low-speed fan can't keep up with
the heat thrown by high output operation. There is
nothing wrong (like missing) with your "chin spoiler"
plastic air dam, is there?

LTFTs are a PCM computation over time, have to watch
them with the Predator real time display, they are based
on O2 switching action. The Predator will also scan for
codes, "forget" (spelled with a u,c,k) the dealer for that.
Predator real time display also shows your O2 voltages, a
happy sensor at cruise will bounce madly and at WOT will
show you a high (850-930mV or so) output. Some of these
params you have to scroll down a ways, to see. Lots of
useful info there though that you need to build a mental
map of, to find your way out of this maze.

 

That sounds right! A couple of months ago I added a 160 thermostat and I still had pinging. A few weeks later I added a FAN CONTROL switch from SLP and I always use it for city driving. Get this.... with the cost of gasoline as crazy as it is, I'm using 87 octane and my Z doesn't ping anymore

 

I will set the fans lower today.

 

Your engine temps don't sound that bad. They are right in the emmissions required range. Lowering your fan temps may help your problem, but I don't think that IS the problem.

Did the reflash do anything at all? Did your LTerms budge after the reflash. Did the car stop pinging for a brief time?

You have light mods and the car should run fine with the stock program back in it. If the car is still pinging after the reflash, then 99.9% it's not the computer and it is time to start looking for hardware.

If I were you, I would stay on the stock program until the problem gets solved; its just one more thing to eliminate. You don't have anything in your sig that is going to drive your a/f to the nether-regions and cause pinging.

Assuming that your computer is now stock.....

We'll run through stuff that can elevate your cylinder temperatures first.

Cylinder Temperatures

Lean Conditions

1) Check your LTerms: On the stock program your LTerms should vary on different throttle positions and be within +/- 10% most of the time.
2) Check your Plugs: Read the plugs for a lean condition. Pay attention to the difference between the plugs. If 7 are brown and one looks like chalk then your fueling problem is isolated to that cylinder. If all of the plugs are white then it is a universal fueling problem and you should check the MAF, and your fuel pressure
3) Fuel Pressure: Fuel pressure should be 58 psi.
4) Clean your MAF: Spray some electraclean onto the thermistors of the MAF (little doohickies that look like resistors). Make sure the thermistors are damage free and all of the associated fine-wire is in good condition.
4) Injectors: If you have the time, pull the rail off and flip it upside down while fuel line is disconnected. Have somebody turn over the vehicle......get a rag and cover your paint. As the injectors fire they should emit a fine spray that blasts over a foot from the injector. If you see one injector dripping or not firing as the others replace it.

Elevated Cooling Temperatures

1) Check your cooling level. Ensure that you are within spec
2) Ensure that your not vapor locked (somehow ). Using a 10mm socket loosen cooling jumper located on the forward side of the head. Dont take it off, just loosen it enough for water to come out. Start the car and wait for cooling to emit from it. If water never comes out then your locked. Once water comes out tighten it back down.
3) Ensure that your fans are working properly. With the car just idling in place the first radiator fan should kick on. The car temperature at stand-still should be around 210-220 deg with the stock thermostat.

Excessive Back Pressure:

1) Ensure that one of your cats aren't plugged. Pull the cat off and check for normal color and shape. If the catalyst is solid white or black (caked with soot), or deformed then you may have cat issues.


Octane and Ignition Problems

Oil Ingestion

1) Check for Oil Ingestion: Check your PCV system for oil consumption into the inlet. Does your car consume oil?
2) Poor oil ring. When checking the plugs make sure that you don't have oil on the plug. Does your car smoke at WOT, or blow blue smoke at all?
3) Make sure you are running good gas. (you said 91, good enough)

Excessive Compression
1) Excessive Carbon buildup will raise your compression to the point of detoniation. Ensure that your heads and chambers are clean. You said you ran a top cleaner.

Hot Ignition
1) Do you have the stock sparkplugs. Try changing plugs and see if the problem goes away.



That all I can think of for right now.

Good Luck

 

The injector "eyeball" testing is a good idea, one weak
one can be a single-cylinder lean pinger while the
-average- mixture is trimmed to center and 7 out of 8
are a few percent rich and don't make a peep.

 

I just checked fuel pressure at both idle and at speed and its reads about 60 psi. My lt's are around - 2,3 at part throttle and 0 at wot. This is 100% stock. I checked for vacuum leaks using a hose and can't hear any. I changed the fuel filter a couple months ago and this problem has been going on since about august last yr. I changed the plugs a month ago and they don't show signs of running lean. I have done 4 treatments of seafoam and have a catch can with inline filter. Car uses no oil, maybe 1/4 qrt every 3k miles at times. Maf was replaced 5 weeks ago after it thru a code. No codes now. Am using a fram filter so no worry of filter oil on maf wires. As far a checking for vapor lock which area am I looking for? Is it the metal coolant line that goes from one head to the other? Confused on that. If I had the money I would get a lemon law on the car. I have other issues such as a big cluck in the front when braking hard and the leather on the driver seat is cracked and I can see the foam underneath. Mind you this car only has 18k miles.

 

Should I get a 160 thermostat maybe? There is no kr or ping when the motor is cold. Once up to temp then it starts. Also if I shift gears really fast and at high rpm's when I get back on the gas after upshifting and get lots of pinging. Also after a long drive the car starts to hesitate off the line. Have to slip the clutch more. Once it bogs the car feels like it's misfiring and takes a couple secs for the rpm's to start coming back up. I'm gonna have to take the car into the dealer for the clunk when braking so I will adress this issue. My dealer always gives me the bs of no codes no problems. I'm gonna have to speak with the manager about this and if that doesn't work then Gm customer service.

 

What plugs are you using? If they are stock heat range, just for ***** and giggles, try a set of NGK TR6 gapped at .045" Just if you have a stock or stock heat range plug. Also, what kind of gas are using? Just the 91, or still trying a mix of 100/91? If you can, run the tank down and then use straight 100. Run that for a few miles, and monitor the kr, LTFTs and such.
Good luck,
Charlie

 

I use 91, Ca gas but a few weeks ago added about 1/2 a tank of 100 and still had some kr with predator tune. The plugs I'm using are Ac Delco Iridium , stock heat range gapped at .50. I certainly don't want to have to do another plug change and shouldn't since I never had a problem when I was stock before. Tonight I noticed that my spark settings on the predator were - 2% so I not 100 stock tune. Still have some predator tune in there. I would like to be able to run the predator tune again as I did the first few months I had the predator and had only .88 kr at wot and that was because I had the car leaned out a bunch. When I ran some 100 octane with the predator a few weeks ago the car ran awesome. Tonight I also checked for spark plug wire problems by looking under the hood in the dark with the car running, looking for sparks flying and have none. Also looked for glowing cats which I heard is one way to know if there bad. No glow. If I have the dealer reflash the pcm there gonna charge me a bunch for that like they did for checking for codes. I hate those bastards.

 

UPDATE : I know this thread is OLD but I had the exact same trouble that about drove me nuts. Pinging at part throttle that got worse over time, all stock 01 WS6 TA. Fuel trims looked good but I noticed bank 1 was always around +3 cruising, - 3 to at idle.
Bank 2 stayed around 0 most of time. I pulled the plugs and noticed number 3 cylinder center porcelain looked damaged. Car ran great at WOT without any pinging.

Problem was the intake gaskets were leaking slightly around number 3 cylinder. NO check engine light, no lean indications. Spraying the intake with carb cleaner etc changed nothing. Replacing the intake gaskets solved the pinging.


Hope this helps someone else chasing this problem.