5.7L TBI still Pinging-I'm stumped

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obsetter

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I have a 1994 Suburban with the 5.7L TBI engine. I have spent a lot of time trying to diagnose a pinging problem that persists. The ignition system including related sensors have been replaced with new ones.

Pings the same using 87 or 93 octane, Same with bottle of octane boost

I set my base timing to 0 Degrees with the electronic spark control disconnected. Tan/Blk stripe wire below glove box.
I checked for trouble codes-non.

Replaced: Complete reman. distributor, cap, rotor, plug wires, plugs, ignition coil, oxygen sensor, knock sensor, coolant temperature sensor, egr valve, egr valve selenoid, MAP sensor, Engine Control Module, new fuel pump, fuel filter, TBI fuel pressure regulator, Throttle position sensor, new thermostat

Tested for vacuum leaks, non found
It runs very good, drivability very good.
spark plugs look good
With the ESC wire disconnected effectively dissabling the advance system, no pinging persists but very poor power.
I can only think it may be a shorted wire? I pulled the 10A fuse at the fuse block for the ignition/engine control module then testing for voltage 22mV ignition off, 12 volts ignition on no start
disconnected the harnesses to ECM then checked voltage at fuse. 0V key off, 1 volt? Key on no start. Why the one volt?
I would appreciate any help or comments, this is driving me to get a diesel which supposed to ping
 
what spark plugs are you using, make and number? What temperature thermostat are you using? How many miles on the engine?
 
I have Autolite 25's and don't know on the thermostat. I bought both at NAPA. They looked up the vehicle.
Here is some info on the 25's:

Copper Core
Heat Range Chart Location
D13

I'm not sure on the temp for the thermostat. I do recognize with the new thermostat. when warming up from sitting overnight, it seems to take a long time to open. The temp gage goes almost the 210 then suddenly opens. After this it moderate the temp. nicely approx. 1/4 mark of gauge.

The engine has 41,000mi original
thanks for your help
 
The factory plug is a AC CR43TS which does not convert to 25, it converts to 23. Your plug maybe too hot. To avoid the guesswork of proper cross reference, I would put the original plug back in, CR43TS.
 
I will get the suggested spark plugs and report back.
Thanks Zora
 
zora said:
The factory plug is a AC CR43TS which does not convert to 25, it converts to 23. Your plug maybe too hot. To avoid the guesswork of proper cross reference, I would put the original plug back in, CR43TS.
Click to expand...

It may well be that the plugs are too hot, but the 25's appear to be the plugs recommended for your truck. I put a set of "Bosch Platinum Plus Spark Plugs 4007" in my '94 about 4500 miles ago and they work fine and still look brand new (now that I corrected the too-rich problem).

Your thermostat seems a bit odd in that it doesn't open until it's reached 210. My '94 has never seen that temperature even in the dead of summer. You may be running too hot, which could cause pinging.

Does it ping even before it warms up?

Your "shotgun approach" to the problem probably resulted in a lot of unnecessary $$ spent. The good news is that you have a low mileage truck with a lot of new parts. Of course, the fact that the mileage is so low likely means you didn't need most, if not all, of that stuff.

If your plugs aren't too hot (and they don't seem to be since they are the recommended plugs -- go on the AutoZone site and see for yourself) and your truck isn't running too hot due to the thermostat, then it would seem that your problem could be spark advance. You can probably have that checked out by an appropriate shop, or you might even check it yourself with a timing light. Watch how far the spark advances as you have someone rev the engine and compare what you find with what is to be expected (if you can find the specs).

The only other thing I can think it could be is excessive carbon built up on the pistons. This can cause pre-ignition detonation and resultant ping.

I doubt that's your problem, especially since your mileage is so low; but it is a known condition for pinging, particularly in high mileage vehicles.
 
When you replaced the cap and rotor did you notice if the distributor weights moved freely? T-Max is correct that Autozone comes up with a 25 but if you put the original plug in on this site, CR43TS, it comes up with 23.

http://www.sparkplug-crossreference.com/
 
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zora said:
When you replaced the cap and rotor did you notice if the distributor weights moved freely? ***
Click to expand...

I believe that he has the same distributor as I have (since we both have '94's) and if so, then as per your prior post in my thread, there aren't any weights in there.

http://chevyforum.org/chevy-forums/showpost.php?p=47439&postcount=19

As to the plugs, some other sites I consulted also gave the 25's as the plug to use. Still, if the manufacturer recommends a cooler plug, moving to a cooler plug might help with the problem. I suppose each vehicle is somewhat unique and perhaps his would like a cooler plug?

I wonder where my Bosch 4007's come out on that point. I don't seem to have any pinging problem at all even tho' I suspect that my base timing is a bit advanced. I'm still working on cleaning the timing tab so that I can see precisely where I've set the timing. But at this point, I suspect it's just a tad advanced (but probably not enough to really matter).
 
Where/how did you test for leaks? Intake manifolds are regular culprits for pinging.
 
I'd try a new thermostat. OEM temp on that I THINK should be 195. Don't buy one of those cheap ass ones from Autozone. Go to a NAPA store and get a good one. I've had too many fail right out of the box from Autozone. If you get one there, test it before installing it. Bring a pot of water to boil and drop it in to make sure it opens. Pull it out and let it cool and watch it to make sure it closes.
 
T-Max said:
* * * As to the plugs, some other sites I consulted also gave the 25's as the plug to use. Still, if the manufacturer recommends a cooler plug, moving to a cooler plug might help with the problem. I suppose each vehicle is somewhat unique and perhaps his would like a cooler plug?

I wonder where my Bosch 4007's come out on that point. I don't seem to have any pinging problem at all even tho' I suspect that my base timing is a bit advanced. I'm still working on cleaning the timing tab so that I can see precisely where I've set the timing. But at this point, I suspect it's just a tad advanced (but probably not enough to really matter).
Click to expand...

Just to update things, I pulled a couple of my plugs again (they are burning very clean) and noticed that they have "HR9 BP" stamped on them. It would seem that this means they are "heat range 9," but I'm not absolutely sure of that. I don't know what the "BP" means.

This Bosch link -

http://rb-aa.bosch.com/aa-th/en/static/produkte/zuendkerzen/zuendkerzenkunde/waermewerte.htm

Sez -

Low code numbers (e.g. 2 to 4) signify "cold" spark plugs, in other words, low heat conduction in hot engines (e.g. Ferrari).

High code numbers (e.g. 7 to 10) signify "hot" spark plugs, that is, high heat conduction for cold engines (e.g. VW Beetle).

So if my 4007's do have a heat range number of 9, that would seem to mean they are pretty hot plugs. These are the recommended plugs for my '94 Suburban 5.7L TBI, which is the same truck as the OP's.

Who, BTW, hasn't been heard from lately. (Hello, how are you doing with this problem? :))

Frankly, I seriously doubt that his pinging problem is related to the plugs at all. My #1 suspect would be advanced timing under operating conditions. I suppose if it were running really lean, that could be a cause. But inspection of the plugs should inform one as to that (plus it likely wouldn't run quite right and he sez: It runs very good, drivability very good. spark plugs look good.)
 
zora said:
using this site http://www.sparkplug-crossreference.com/convert/AC_DELCO/cr43ts the original equipment CR43TS correspond to Bosch HR6BC or HR8BC. Wish we all knew what is correct, you probably got your HR9 based on autozone?
Click to expand...

Yes, I did get my 4007's at AutoZone and yes, that's what they said goes in my truck. But the Auto Parts Warehouse site also says that's the plug to use (along with other Bosch heat range 9 plugs).

I think lots of other parts suppliers also recommend the Bosch 4007 plug for this application.

As you can see, that site lists the particulars on the 4007 plug and notes that it's a heat range 9 plug (thus confirming that assumption on my part), as is also the case with 2 other recommended plugs, the Bosch Premium Class Platinum+4 & the Bosch Super Class Platinum Plus. Both of the Denso plugs they list on the first page are heat range 20, which I assume compares with the Bosch heat range 9.

The Delco CR43TS plug is listed on the 2nd page of the Auto Parts Warehouse site's listing of plugs for this truck.

I believe the plugs that were in my truck were Autolite plugs. I will check what they are and report back.
 
Why don't you put the proper AC/Delco plugs in your engine and see what happens? They're GM designed for GM cars. I only run OEM plugs in my vehicles regardless of what I'm driving. I have AC/Delcos in my Equinox and Champions in my Dodge. If I had a Ford, I'd have either Motorcraft or Autolites in it. I wouldn't run Bosch plugs in my frigging lawnmower, let alone a car or truck I own.
 
T-Max said:
* * * I believe the plugs that were in my truck were Autolite plugs. I will check what they are and report back.
Click to expand...

Turns out the Autolites were from a different vehicle. I haven't yet located the plugs that were in this truck but I believe they are still around here somewhere.
 
1994 Pinging update
Hello and thanks for your comments. I replaced the plugs with CR43TS. No change. I have read in some of these forums about data streaming analysis. OBDI ALDA connections.
Well, today I bought old school GM Diognostics equipnent, 'Pathfinder 1993' it came with all kinds of adaptors the main unit/display and books. Now the big question is will this work for my 1994 k5.7L. Was there any changes in 1993 to 1994. I am hoping this will work so I may obtain data realtime. I saw some tables and correct limits to compare this data too. Hopefully there will be something to identify the source of pinging.
This Suburban has sentimental value to me. That is why I am putting this kind of money into.
Thanks for your input.
 
Best of my knowledge they did not switch to OBDII until 1995 so you should be OK with the equipment. Curious if it will permit you to check individual components like the knock sensor.
 
Yes,
It gives me 68 different sets of data for things like MAP, %EGR, TPS, Knock count, coolant temp, rpm,torque converter lockup, Oxygen voltage, AIC...
 
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