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What could be causing my car to ping/knock?

 
Old 07-17-2001, 04:34 PM
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Rick86
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I have been having a problem with my car pinging, I have verified timing, replaced cap/rotor, sparkplug wires, using 92 octane fuel, dyno operator said I was to lean, but would not lend any suggestions. Knock counts were varified using AutoXray. Car only pings with agressive acceleration and does not ping at cruise. Car runs in normal coolant temps. Any ideas or areas to look at. TIA
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Old 07-17-2001, 05:17 PM
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How about a list of mods. It is hard enough to troubleshoot when not in person, but nearly impossible when you don't even know what you are troubleshooting.

Let us know and we can probably help more, but I would start by checking fuel pressure at WOT. If it drops off, replace the filter. If it still drops off, replace the pump.

Again, let us know more about your setup.


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Old 07-17-2001, 05:18 PM
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I have a similar problem. I was told by Dave Emanuel in his CF column that I should have a custom chip burned to correct errors in the timing curve.

Since you are running lean, you may need a new O2 sensor. Does your AutoXray show lean at part throttle or only at WOT? That is, in closed loop or only in open loop with the BLM on cell #15 and value = 128.


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Old 07-17-2001, 05:39 PM
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65Z01, I have all of those numbers written down at home, but from memory, car does go to open loop at WOT, O2 reading approximate were 913 at start of run and dropped to 871 at end. Mods include mild cam, K&N, open air lid, rear screen removed from MAF, dynomax mufflers, fuel filter changed 10,000 miles ago, NO CODES showing, dyno'd at 190 rwhp, 290 rwtq (and it was pinging the whole time, operator refused to run it anymore after two runs, said he didn't want to be liable if my motor blew). Knock counts steadly climbed when I tested (I could also hear a rattle, so its not false knock). I plan on taking it in to be looked at, but the shop is always busy, maybe they'll be able to get to it this week? I just want some more ideas or areas to look at while I'm waiting on the shop. Thanks
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Old 07-17-2001, 05:57 PM
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Rick86, I don't hear ping, I just see knock counts and retard degrees on my AutoXray. Since you can "hear" ping, maybe you should replace the knock sensor, I don't think you should be able to hear ping if the sensor is working properly.

Try a 160 deg stat and fan sw to bring down chamber temp. This should reduce ping tendency.

What is base timing and TPS setting? Both will effect your timing curve.

Since you are leaning out at WOT and high RPM try an AFPR set to maybe 4lbs higher than your stock FPR. Anyway you will know when it's dialed in from AutoXray BLM cell values and O2 readings. You will see BLM cells 1-14 with values below 128 at part throttle (closed loop); and O2 sensor readings in the low 900s at WOT in open loop.

Sounds like you could also benefit from a custom chip to dial in your fuel and timing curves. But try some of the above first, they're a lot cheaper.

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Old 07-17-2001, 06:17 PM
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Thanks 65ZO1, my base timing is set at 6 degrees (with est disconnected) TPS .56 at idle and 4.33 at WOT. I was searching archieves section and have a question about the EST. When I disconnect the EST I don't get a check engine light also with my AutoXray it does not show timing or retard, but months ago when I used a friends scanner (not AutoXray) it showed timing and retard? Could my problem lie with the EST? If so do you/anyone know how to check if the EST is working properly?
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Old 07-17-2001, 09:23 PM
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cured my pinging on accelleration by replacing the water temp sensor.
i had no codes flashing!
must have fooled the ecm is all i can figure.
$7.00 fix from autozone
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Old 07-17-2001, 11:13 PM
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hey rick!
good to see ya, its been a while. sorry to hear that you still have that ping. since the dyno day i have replaced wires and coil and added an adjustable fuel pressure regulator- to help with my lean problems. I don't know if it is helping or not but my car sure feels good. i need to dyno it again to find out.

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Old 07-18-2001, 09:19 AM
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You need to get a scanner that shows all the info on it. The cam may want less timing and the custom chip may help. The EST should code when disconnected.
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Old 07-18-2001, 11:36 AM
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Hey guys thanks for the help, last night I checked the timing and disconnecting the EST wire or leaving it connected the timing stayed the the same (right at 6 degrees), also still no trouble light or stored codes showed up. I'm know believing that my car is getting to much timing or something is up with ESC or ECM. I'm still waiting for an appointment to take the car to the shop.

Hey Rich, does your AutoXray read the timing and retard?
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Old 07-18-2001, 12:41 PM
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That's odd. It should've set a code with the wire disconnected .

FWIW, I had the same problem. I found that my main cat had fragmented and plugged my rear Y-pipe. I also did the TB bypass at about the same time. I removed the obstruction and the ping is gone. I can run 90 octane now if I want whereas 93 before would still not keep it from pinging.

Randy

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Old 07-20-2001, 11:56 AM
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Update: I have found out that my check engine light does not work. When I disconnect the est wire I do get a code 42, but no light, I also disconnected the ESC and again no light, but code 43. According to one book I should have 5 volts at the EST wire, I have 0 volts. 5 volts tells the distributor to take commands from the ECM, 0 Volts indicates wire is disconnected so base timing can be set, and tells distributor to ignore ECM commands.
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Old 07-20-2001, 05:43 PM
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I got tired of chasing my knock retard problem and, after hearing no ping at ALL, I realized it was engine/exhaust noise causing the false signals.

I inserted a 1/4 watt, 4.7K resistor in the EST line.

Now I get no knock retard, no ping, no code and the engine pulls like crazy.

My thanks to the thirdgen.org board for the tip.

Of course you can always have the amount of timing and/or the rate of timing increase modified by reburning the PROM.

From what I've a read 871 mv 02 reading in PE (Power Enrichment)mode is fine. The posts I've seen say shoot for 850 mv, which is slightly leaner than what you're running in PE.

Of course, the posts also say don't depend of 02 readings to tune A/F ratio since the sensor is too slow, but it's better than nothing, right?

My thinking is: If you don't hear any knock or ping, no code, the plugs have good color (clean cut inspection) and the 02 reading is 850 or higher in PE, then you probably have a false knock problem.

To be one the safe side though, I'd rule out any other cause of the knock retard before resorting to the resistor fix.

Jake

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