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Help me before I get pi$$ed at this thing.

W7NB

W7NB

1/2 ton status
Joined
Nov 9, 2006
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Location
Springtucky, OR
So here's the story - 90 Blazer with stock 350/700R4/241. Chassis has 232k miles but who knows how many miles on the engine. Still has good compression and burns no oil to speak of.

Problem was it would ping like crazy when I got on it, so I sarted down the list of things the factory manual says to check. I started by replacing the cap/rotor/wires/plugs and setting the timing - yes I disconnected the wire. It's at 0 degress in bypass mode and runs around 4 before connected.

Still pings. :mad:

Checked the EGR valve, which did need replacing as it was VERY sticky. Replaced the O2 sensor just because I already had a new one - stuck with the single wire since it's stock manifolds. Replaced the fuel filter.

Better then it was, but still pings. :mad:

Took a look at the fuel injectors with a timing light and find the pattern is a little puny and has a few drips. Buy a reman TBI setup since it was decent price but in the process of installing it I end up breaking off the clip that holds on the 700R4 TV cable. :doah: Oh well, I needed to change the tranny fluid anyway, right?

Replace the TV cable and take it out for a drive. Notice three things right away.

1. Shifts are much crisper an at a little higher RPM then before. Guess the old cable needed replacing anyway.

2. I GOT RID OF MY STICKY THROTTLE!!!:laugh: That has annoyed me for quite a while, but I'm not sure if it was the throttle body or the TV cable causing it.

OH, Yeah















3. IT STILL PINGS:angry1: :angry1:

So my mechanic checked the fuel pressure for me and it's fine 13.8psi. He suggested the harmonic balancer either may have spun or it may not be the right one. I'm going to run the engine up to TDC with a dial caliper this weekend to check and see if the timing mark matches.

Beyond that does anybody have any suggestions? I'm about ready to pull all two of my remaining hairs out about this. The truck runs ok for a DD but any heavy wheeling or towing my boat makes it ping bad enough I'm afraid I'll tear it up.

So all you experts break out the questions or suggestions. I'll be home all weekend and will check whatever folks think would be worth trying.
 
Knock sensor won't allow it to ping unless you have a SERIOUS problem. Check that. are you not getting any codes?
 
Also bear in mind that the ecu allows it to pink very lightly.
 
ideas off the top of my head:

1 bad knock sensor?

2 air/fuel ratio: i'd say point the finger at a lean condition.

-weak injectors not supplying enough go-juice to compliment the rush of air volume at WOT, causing detonation.
-or, vac leak around manifold or throttle body.
-o2 sensor

3 for the sake of argument, lets say the motor has 232K also. there could be a lot of carbon in the cylinders that's hotspotting and causing detonation. does it ever deisel when you shut it off?
 
Check foe trouble codes!!!! If it is pinging you should definatly have some.
It will be easer for people to help you if you post the codes.
heres how if you dont know:http://www.troublecodes.net/GM/
Your ALDL connector is under the dash next to the steering column.
 
vortec said:
ideas off the top of my head:

1 bad knock sensor?

2 air/fuel ratio: i'd say point the finger at a lean condition.

-weak injectors not supplying enough go-juice to compliment the rush of air volume at WOT, causing detonation.
-or, vac leak around manifold or throttle body.
-o2 sensor

3 for the sake of argument, lets say the motor has 232K also. there could be a lot of carbon in the cylinders that's hotspotting and causing detonation. does it ever deisel when you shut it off?
Click to expand...

All great answers - so in reply.

1. New knock sensor

2. Why lean with new TB and injectors? Fuel pressure 13.8 and good looking spray pattern - better then the old injectors. Vacume 29.5 to 30mm HG and steady at idle so I doubt I have any serious vacume leaks - someone correct me if thats not a valid test and I need to do somthing different. Brand new O2 sensor.

3. This is possible. The motor does not diesel when I turn it off even after a long drive, but I don't think that eliminates carbon build up issues. Anybody have suggestions for how to get rid of them?
 
Thunder said:
Check foe trouble codes!!!! If it is pinging you should definatly have some.
It will be easer for people to help you if you post the codes.
heres how if you dont know:http://www.troublecodes.net/GM/
Your ALDL connector is under the dash next to the steering column.
Click to expand...

Only code I have had was originally for a bad TPS that I also replaced. I had it hooked up to a code reader today while I was driving and it did not show any codes. I would expect it to throw some sort of a code if it could not correct the timing enough to prevent ping but no luck - I also get my foot out of it as soon as it starts and that may be why the computer does not throw a code.
 
Well, I just started getting the Code 22 again. Does this mean I got another bad TPS or do I have a voltage or connection problem somewhere else? I'm going to pull it off in the morning and take it back unless someone has other ideas.
 
Any other thoughts?

This is kinda making me cranky because I want to go wheel but don't want to tear the motor up.:(
 
W7NB said:
All great answers - so in reply.

1. New knock sensor

2. Why lean with new TB and injectors? Fuel pressure 13.8 and good looking spray pattern - better then the old injectors. Vacume 29.5 to 30mm HG and steady at idle so I doubt I have any serious vacume leaks - someone correct me if thats not a valid test and I need to do somthing different. Brand new O2 sensor.

3. This is possible. The motor does not diesel when I turn it off even after a long drive, but I don't think that eliminates carbon build up issues. Anybody have suggestions for how to get rid of them?
Click to expand...

Go to your friendly GM man and get some Top Engine Cleaner. Follow the instructions on the can. After treatment you should be good to go :waytogo: Also check to make sure you have the correct heat range plugs installed.
 
If you keep getting TPS code after replacing it. You may have a open grounded wire somewhere in the circut. Check the TPS connections look for a broke or grounded wire. Check the ECM and make sure everytning is plugged in good.
 
MaxPF said:
Go to your friendly GM man and get some Top Engine Cleaner. Follow the instructions on the can. After treatment you should be good to go :waytogo: Also check to make sure you have the correct heat range plugs installed.
Click to expand...

And MaxPF gets a gold star!!!:bow::bow::bow::bow:

I talked with a guy I know who turns wrench at a GM shop. He said either get the GM top end cleaner or go over to a local parts place and get Seafoam engine cleaner.

So I pick up a can - it says to use the pcv intake on the TBI to suck the cleaner into the engine and use 1/3 of a can, then shut it off and let it soak.

Well, being the typical backyard knothead wrench turner I use 1/2 a can and let it soak, then run it out and do it again. You should have seen the cloud come out of the pipe when I started it up after!

I wait for the smoke to clear and take her for a drive...















AND THE KNOCK IS GONE!

I get a little ping if I hammer it, but otherwise it runs fine. I'll post up if anything changes but it looks like I'm cured. So now if I can get rid of the driveshaft vibration I'll be ready to play!:D

 
Glad to be of service. :wink1: If your buildup was really bad it may be worth it to run another can through there. That carbon buildup can be really stubborn, but the top engine cleaner will eventually get it out of there. Also, after you do another treatment (or now if you choose not to) it would be a really good idea to change your oil :waytogo:
 
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