I just had the same problem with my 89 p/u when I got it it would ping excessivley was a dog going uphill couple weeks later completely died ended up being the fuel pump fading out then finally died threw a new pump,strainer,and bracket in and runs great no more pinging better throttle response

 

Ok, you need to make sure your knock sensor is actually working. I have zero confidence that it is. You should get a CEL if the sensor is missing, which you obviously get. There is a second code which also triggers a CEL for "knock system malfunction" but it's not stored in memory like the missing code is. The manual says it's an ECU related code, but who knows. Otherwise there really isn't a code that tells you that you've hit the limits of what the ECU can advance to.

I suppose if you've got a lean condition you should be picking it up downstream at the O2 sensor. However, since you can unplug the sensor and works fine in limp mode, I would assume that the computer isn't reaching the limits of the timing adjustment. It seems like you're in this nebulous area where the ECU thinks your sensor is good but it's not actually detecting knock.

Just for clarity, the pinging only starts after your engine has warmed up, that is, entered closed loop control?

 

Lol I had one do the same thing it was the ground to the fuel pump it would run it but it was weak so under a load it would go lean and knock

 

In hook your fuel line turn the key on take the top off the Mafs push the arm back so the fuel pump turns on plug the fuel line with your finger it should be hard to stop the fuel if its not and you just hear the pump running either bad power ground or pump

 

Jerry, that is correct. I have also tried a second knock sensor I had and the result was the same.

 

Thanks Jeff, I hooked up a fuel pressure gauge after replacing the fuel pressure regulator thinking that was it. Pressure is solid.

And here I thought this thread to be long and forgotten!!!!

 

I don't know if your model year has a fuel pump pulse regulator on it or not, but mine had a similar problem and the pulse regulator had broken internally and was not providing sufficient fuel for the task. Check with your dealer to see if you have one, or if it has since been replaced by a banjo bolt.

Jeff

 

BTW, my pressure at idle was perfect It wasn't until it started getting under lad that it would act up at first. Finally the truck would only idle. Is your problem still with you?

Jeff

 

I don't think I made my concerns obvious enough. Your knock sensor is not detecting knock. The computer must be seeing enough signal to figure out it's there, but you're obviously not getting enough signal that the computer actually sees knock and backs the timing advance off enough to fix it.

There is a simple (in theory) test you can do. If you have the capability to monitor ECU voltages while driving, you can watch the ignition timing advance signal. When you start to ping you should see that move down.

The problem, whatever the root cause might be, is that your ECU isn't retarding the timing when the engine pings. The root cause isn't bad enough that the engine can't fix it by backing timing off all the way (if so, you'd ping even in limp home mode). Remember, the Electronic Spark Advance system works by advancing timing as far as it can until the engine pings. The knock sensor detects the ping and then the computer "remembers" the timing advance value and sets that as the upper limit. IF YOUR KNOCK SENSOR DOESN'T DETECT PING YOU'LL ALWAYS ADVANCE TO FULL.

No other problem can be easily diagnosed before you figure out why your knock sensor isn't working.

 

How about replacing knock sensor or swapping in a different ecu.

 

Hey Jerry, I truly appreciate your input and makes perfect sense, I will give the monitor the voltage at ecu a shot. (FYI) I have swapped out the ecu, knock sensor and checked for shorts in the circuit. So far everything checks out, I even pulled apart the wiring harness and its solid. Just about every part on this thing is new and I had all but gave up on fixing it till the thread fired up again. Here's a bit of new info for you, seems that when its cold out in the morning (phoenix az here so about 40-50 currently) it does take a bit longer for the pinging to start even after warmed up) Maybe something else?
Anyways, thanks again Jerry.

 

Did that already G, thanks though for the input.

 

hey you live in Phoenix right?? the IAT sensor is telling it to lean right as underhood temps must be through the roof??? do you have an aftermarket air filter assembly on there ??or stock maybe try to get cold outside air in there?? or but a resistor across the right wires (sorry can't remember which ones they are on the mass air!) to a colder setting somthing like 5k ohms or something you'll have to look it up in the manual ! sorry if u have tried this but I live in Canada so I get colder air! lol

 

I wish mine was just pinging like my Corrolla but its something like piston pins or something?? but apperantly mine was rebuilt like 5000 ks before I put it in soo ya wonder if planing these heads or blocks is bad for these engines!??? I have better power than my previous v6 runners soo??? lol

 

No update, threw out the back.....again, will be a few weeks.

Merry Christmas Everyone and a Happy New Year

 

happy new year!

 

Just out of curiosity, is Snortin Norton a reference to the Combat Commando's?

 

Back from the dead guys, just a super quick update...3rd knock sensor is the charm guys, runs like a champ. Thanks for everyone's input and the time you put into reading this.

 

Its the Runners name actually I remembered that it was something to do with the army but whatever the truck by the name on its own lol ! BobbyBouche glad that you got it nailed!! were you buying used sensors or aftermarket by any chance they don't like aftermarket I find!

 

"Second Guess" is now on day two and still no ping. I had used two used knock sensors that I'm guessing where in the same shape as the factory one, just not bad enough to set off the cell light. Bought a new one from RockAuto and now runs like a 1994 22RE. So now gonna throw the crawler cam back in it and wear out some tires.