Pinging (I think) with 87 octane

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Schurkey

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First check for trouble codes, stored, pending or current. Then look at live data on a cold engine that is not running.. Make sure the coolant temp is near ambient. Make sure the MAP is reading close to the barometric pressure.
Excellent detail. "Not running", but key-on. (KOEO, Key On Engine Off) Otherwise the computer is "dead" and you don't get any info on the scan tool. I write-down all the codes along with a quick description, and whether they're current codes, history codes, "Pending", "Failed this ignition cycle", etc. If there's LOTS of codes, I'm not opposed to clearing them and seeing what comes back. (Instantly, or during the test-drive, or during extended driving.)

If equipped, an intake air temp sensor would also read near-ambient temperature, or somewhat higher if the sun is beating down on the hood raising the air-cleaner temperature.

TPS should read Zero.
Typically shows a small voltage. Above "zero", but not much above. If you slowly depress the throttle, the voltage should smoothly/proportionally increase with no drops or spikes in the voltage. At WFO, the scan tool may indicate that the computer is in "clear flood" mode.

Then start the engine.
KOER--Key On, Engine Running.

At idle, engine cold, I'd expect zero knock sensor "counts". You'd have to put the engine under some load to get signal from the Knock Sensor--which would be something to look for during the test-drive after you've warmed-up the engine and looked at the stuff listed below.

Electrical system voltage shown on the scan tool should be reasonable. You'll likely have data showing an automatic transmission is in Park/Neutral vs. in gear. There may be data showing whether the A/C is commanded "on".

The MAP sensor should read around 20 in/hg vacuum, some scanners read it as absolute pressure. Baro being 30 in/hg or so and 20 in/hg vacuum being around 10 in/hg absolute pressure.
MAP = Manifold Absolute Pressure.

For old guys like me, that are used to "vacuum gauges", the MAP sensor signal is "backwards". And just as you explained--whatever the MAP shows for pressure, is subtracted from barometric pressure. The result is the "vacuum" us codgers are used to dealing with.

I guess some scan tools convert the pressure to a vacuum level for you. None of mine did that.

As the engine starts to warm up the CTS should rise and the short term fuel trims will become active. A range of -10 to +10 with some fluctuation is pretty common during initial warm up before the long terms become active. The front 02 sensors (Bank 1 & Bank 2, Sensor 1) voltage should have a nice swing to them from around 0.100 to 0.800 volts or so and be switching steadily.
I'd have said "switching rapidly" rather than "switching steadily". But the concept is the same. The sensor better swing from "low" to "high" and back. Depending on the vehicle and the scan tool, you may have a display of "cross counts"; the speed that the O2 sensor goes from high to low, or low to high. Older vehicles may be in the single-digits at idle, newer vehicles tend to have higher cross-counts; but in any event the higher the number, the better. O2 sensors get "lazy" with age, they don't switch rapidly. Low cross-counts or a graph showing slow switching may be indicating an O2 sensor at the end of it's service life.

As the engine warms up beyond 140F, the long term fuel trim will enable and the long terms should start to follow the short terms. I would expect to see them in the -10 to +10 range as well with Zero being ideal.
The scan tools I'm used to display the number, not the percentage. As with so many "digital" things, there's a 0--256 scale with 128 as "neutral", lower numbers indicate lean-command (computer reducing fuel compared to 128) higher numbers indicate rich-command (computer increasing fuel compared to 128) While the scale is technically 0--256; in actual use it's unlikely to see the extremes of the scale, things tend to be in the range of 100 to 150.

If I'm right about percentages vs. numbers, -10(%) (less than) 128 would be roughly 13 numbers--115. +10(%) (more than) 128 would be 141. I like to see things within +/- 5% on stock vehicles, but sometimes that's not achievable. Yes, the quality of the fuel (quantity of alcohol, and other factors) matters in terms of rich/lean command.

At idle the MAF should read around 1 gm/sec for every liter of engine displacement.
Thanks for that. Easy to remember, easy to test for.

As you accelerate the engine the MAF reading should smoothly increase. If you snap the throttle it should rise sharply.
Yes. And I think this covers the sensors that input data to the computer; except for the Vehicle Speed sensor which you'll have to test-drive to check, and the various sensors related to ABS, traction control, transmission, etc.

Depending on the computer/vehicle, you'll also be looking for various computer outputs. There may (or may not) be data relating to spark advance/retard, EGR operation, AIR diverter valve operation, fuel flow through the injectors, electric cooling fan(s) commanded "On", etc. Newer vehicles' computers have more information available than older, less-sophisticated computers provide.

Overall, very well done. Thank you.

We haven't talked about "Bi-Directional Control" but I don't have time now. I have to accomplish stuff before sundown.
 
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L31MaxExpress

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Excellent detail. "Not running", but key-on. (KOEO, Key On Engine Off) Otherwise the computer is "dead" and you don't get any info on the scan tool. I write-down all the codes along with a quick description, and whether they're current codes, history codes, "Pending", "Failed this ignition cycle", etc. If there's LOTS of codes, I'm not opposed to clearing them and seeing what comes back. (Instantly, or during the test-drive, or during extended driving.)

If equipped, an intake air temp sensor would also read near-ambient temperature, or somewhat higher if the sun is beating down on the hood raising the air-cleaner temperature.


Typically shows a small voltage. Above "zero", but not much above. If you slowly depress the throttle, the voltage should smoothly/proportionally increase with no drops or spikes in the voltage. At WFO, the scan tool may indicate that the computer is in "clear flood" mode.


KOER--Key On, Engine Running.

At idle, engine cold, I'd expect zero knock sensor "counts". You'd have to put the engine under some load to get signal from the Knock Sensor--which would be something to look for during the test-drive after you've warmed-up the engine and looked at the stuff listed below.

Electrical system voltage shown on the scan tool should be reasonable. You'll likely have data showing an automatic transmission is in Park/Neutral vs. in gear. There may be data showing whether the A/C is commanded "on".


MAP = Manifold Absolute Pressure.

For old guys like me, that are used to "vacuum gauges", the MAP sensor signal is "backwards". And just as you explained--whatever the MAP shows for pressure, is subtracted from barometric pressure. The result is the "vacuum" us codgers are used to dealing with.

I guess some scan tools convert the pressure to a vacuum level for you. None of mine did that.


I'd have said "switching rapidly" rather than "switching steadily". But the concept is the same. The sensor better swing from "low" to "high" and back. Depending on the vehicle and the scan tool, you may have a display of "cross counts"; the speed that the O2 sensor goes from high to low, or low to high. Older vehicles may be in the single-digits at idle, newer vehicles tend to have higher cross-counts; but in any event the higher the number, the better. O2 sensors get "lazy" with age, they don't switch rapidly. Low cross-counts or a graph showing slow switching may be indicating an O2 sensor at the end of it's service life.


The scan tools I'm used to display the number, not the percentage. As with so many "digital" things, there's a 0--256 scale with 128 as "neutral", lower numbers indicate lean-command (computer reducing fuel compared to 128) higher numbers indicate rich-command (computer increasing fuel compared to 128) While the scale is technically 0--256; in actual use it's unlikely to see the extremes of the scale, things tend to be in the range of 100 to 150.

If I'm right about percentages vs. numbers, -10(%) (less than) 128 would be roughly 13 numbers--115. +10(%) (more than) 128 would be 141. I like to see things within +/- 5% on stock vehicles, but sometimes that's not achievable. Yes, the quality of the fuel (quantity of alcohol, and other factors) matters in terms of rich/lean command.


Thanks for that. Easy to remember, easy to test for.


Yes. And I think this covers the sensors that input data to the computer; except for the Vehicle Speed sensor which you'll have to test-drive to check, and the various sensors related to ABS, traction control, transmission, etc.

Depending on the computer/vehicle, you'll also be looking for various computer outputs. There may (or may not) be data relating to spark advance/retard, EGR operation, AIR diverter valve operation, fuel flow through the injectors, electric cooling fan(s) commanded "On", etc. Newer vehicles' computers have more information available than older, less-sophisticated computers provide.

Overall, very well done. Thank you.

We haven't talked about "Bi-Directional Control" but I don't have time now. I have to accomplish stuff before sundown.
Excellent addition to detail.

When I said TPS reading zero I was thinking percentage rather than voltage. 1/2 volt is pretty normal for closed throttle and 4.5 volts WFO, which corresponds with 0-100%.

Also as I was stating, I look at mostly modified stuff or swaps into pre-smog vehicles now so factory injector pulse width, ignition timing, air divert and EGR are not something I often have to mess with.
 

Erin

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I have 1997 single cab short bed 4.3/5speed. I use this truck as daily commuter for a long time, the past year or so I’ve been running 93 octane, seems to get rid of a ping (sounds like cricket chirp) when under load accelerating, and gets way better fuel mileage. I’ve read this could be egr (which I know nothing about), or it could be wrong spark plug?? I’m running e3 diamond fire just to try. I filled up with 87 lately to try and save some money but I don’t want to keep doing this if causing issues. Any guidance in troubleshooting would help a ton!
New EGR got rid of my pinging, but it has since returned.
 

Erik the Awful

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So I changed my plugs to ac Delco, and this thing drives like a different truck. Idk how long it will last because the e3 plugs I took out were nasty. Reeked of gas and black. Idk if that’s a sign of bad injectors or what.

E3 plugs are gimmicky garbage. I wouldn't be surprised if they were your problem. I can tell you that back in the late '90s I replaced a metric crap-ton of Champion Platinum plugs in Nissan Quest minivans with the correct Nippondensos. They would run like utter crap on the Champions.

But. Absolutely do your due diligence in checking everything else out.
 

L31MaxExpress

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E3 plugs are gimmicky garbage. I wouldn't be surprised if they were your problem. I can tell you that back in the late '90s I replaced a metric crap-ton of Champion Platinum plugs in Nissan Quest minivans with the correct Nippondensos. They would run like utter crap on the Champions.

But. Absolutely do your due diligence in checking everything else out.
t
Always Nissans with plug issues lol. In the mid-late 2000s, I pulled those dumb Bosch/Splitfire 2 or 4 ground electrode plugs out of more than I can count and put the correct NGK plug into them. Its like every Versa/Sentra/Altima owner put the cheapest, crappiest Walmart plug they could find in their car.

I actually had a couple of owners get defensive. I just put plugs in it, it couldn't be the plugs, you are trying to take me for $$$ for something I have already done. On and on. I was able to talk some sense into most of them though by simply asking them if the car was running poorly, misfiring before the plugs were changed. The answer was usually NO. My 2007 G35 3.5HR did not get its plugs changed until 178K miles and I only did it then because I noticed they had never been done. With the newer Nissan FWD stuff you will go through 2 or 3 CVTs before you need plugs.
 
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Schurkey

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With the newer Nissan FWD stuff you will go through 2 or 3 CVTs before you need plugs.
Who knew that spark plugs could last the life of the vehicle while transmissions need to be changed with the seasons.

Yeah, that's real eco-friendly. 'Cause transmissions take way less resources to build than spark plugs.

Next, they'll want us to buy "electric" vehicles even though the power grid can't support 'em. Or they'll demand electricity generation on a massive scale that's weather-dependent; so if the weather doesn't cooperate, we can burn cowchips for heat.
 

L31MaxExpress

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Who knew that spark plugs could last the life of the vehicle while transmissions need to be changed with the seasons.

Yeah, that's real eco-friendly. 'Cause transmissions take way less resources to build than spark plugs.

Next, they'll want us to buy "electric" vehicles even though the power grid can't support 'em. Or they'll demand electricity generation on a massive scale that's weather-dependent; so if the weather doesn't cooperate, we can burn cowchips for heat.
The stupidity is already here. That massive electric outage in TX a couple of years ago was because the Federal government would not let the power companies bring natural gas fired kicker plants on line in time.
 

Schurkey

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You're describing California and its ban on ICE vehicles
The stupidity is already here.
I'm describing the whole country under the political "leadership" of unconvicted criminals-in-charge and Appointed Idiots who should be tried for Treason and misuse of tax dollars.
 

L31MaxExpress

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I'm describing the whole country under the political "leadership" of unconvicted criminals-in-charge and Appointed Idiots who should be tried for Treason and misuse of tax dollars.
Oh trust me I know and feel the same way! A couple of them should be impeached and in prison for purposely wrecking the economy and collusion.
 
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