Barak Reis

Hello sabino, I changed fuel filter when I did the pump. I bought pressure tester last night, got some errands to run today then test. Only code it’s ever thrown is 32, I can duplicate it when driving normally, but’s it’s easier when cruise is on. I read some information on when the computer tests that circuit and it is easier to maintain in cruise. When I changed the egr valve, it and all the passageways were clogged with carbon buildup, maybe I did not get it all. One day wanna look at exhaust ports to see if same is present, but first things first. Also I have tested the new valve and it’s operating properly. But the lack of back pressure in cruise on freeway might cause the computer to say the valve is not where it thought it should be. Thanks for the help. It’s appreciated.

Barak Reis

Hello gents, so I checked all the grounds except for underdash. Most were in bad shape. Took almost 2 hours to get the one behind the block. Problem still exists.

However I was flushing the radiator because I have had some issues, what came out was like mud. After we filled iit over heated fast. No water was making it up to intake and stat. we finally found the plugs on bottom of block, and we had to poke out the crud. I believe it was the dex cool that was mud when I got the truck. Other side was knock sensor, this stuff was baked on the tip. This crap was baked on everything. Saw it when I did intake manifold. Thought it was carbon buildup. Of course the connector crumbled in my hand. So I need probably change sensor and definitely change connector. Then test fuel pressure. Can I try and run it without knock sensor connected see if it duplicates problem? Is there a ground that goes from driver side frame to block? I could not find one. It’s running at 180 degrees right now. Ac on full blast, it was hitting 240 on the regular before.

I will try and update tomorrow. Got a busy day.

Sabino56

Wow, I've never had experience with something like that. Definitely something that needed fixing. I would imagine there other passages in block constricted too? Maybe someone with experience has ideas on if anything else should be done.

As as far as driving without knock sensor - I think it’s ok as long as engine isn’t knocking bad - for testing. I’m pretty sure only thing knock sensor is used for is to retard timing to prevent knocking.

Barak Reis

Me neither Sabino! My son and I flushed this block for an hour, I was in disbelief. I have read some articles on dex cool, and it’s tough to get rid of, even if your water is crystal clear. It’s a chemical thing where it bonds to the metal. I am going to to a flush that basically “strips” the electrons from the metal surfaces and frees them up to exchange with another coolant. Thank goodness for google.
I was reading up on the knock sensor. Your right, but it depends on vehicle, and computer. It can dumb down an engine, by retarding, it can make it hard to accelerate. I’m not knocking as far as I can hear. Running at a cool 180. Still gas gauge is off, so I am going to try and get those grounds under the dash before I check fuel pressure. Also when looking for grounds found a fuel pump relay, want to check it, and look for my 12 volts there before I drop the tank.
Thanks for hanging in there with me!

Sabino56

Just to make sure - I assume you know but you don’t need to drop tank to check fuel pressure. Check just after fuel filter, there. If you unclip lines from holder there you can get enough space to insert the fuel pressure adaptor fitting.
The fuel pump should come on for about 3-5 seconds with key in on position before starting. Check while it’s idling and while you nail accelerator to make sure. It doesn’t drop under higher demand

Barak Reis

I thought I could check the pressure there, but I am not sure where to check the voltage?

Sabino56

Personally, I wouldn’t worry about the voltage unless you found the fuel pressure too low. Is there specific reason you want to check it? Or just trying to be complete? If just checking off items - too much work to drop the tank for a voltage check unless you have a specific problem you are chasing.

Barak Reis

I see, really just wanting to check things off the list.

Barak Reis

Ok so I had to run to a friends house late tonight, Sunday, Long day, did not get to work much on the truck. However since it was cool I had my son hop under the truck and pull off the connector for the knock sensor, Figured it could not hurt. Well issue almost disappeared. Little studders here or there but much less issue. Finally got the code to pop up, but hade to loosen em up around a wet corner to do do it. Still not 100% that’s all there is only because it was still
doing it a little. That could have been cuz it was still only around 180 degrees and the temp sensor wan probably retarding the timing. I will need to change the connector,. How
do I test the wire? Can I use a butt connector to splice into wire?

Sabino56

Not sure why you need to change connector? it's broken?
Regardless - w.r.t. knock sensor. You said coolant passages where blocked with crud. Did you remove knock sensor also and see if coolant came out? I don't know if actually true, but I've read in one of the blogs that sensor needs to be in water jacket to get accurate readings of knock.
2nd - if you are thinking the knock sensor could be a problem and you haven't replaced it/it's old/no history on what's in there, I'd replace it with an ACDelco. Memory is they aren't expensive. Again, I don't know if true -but I've read off brands may not work as well. On Rockauto, you can order a new connector for a few bucks at same time and splice that into existing wire.

That said - you said that the blocked passages were also causing engine to run hot, the thermostat wasn't opening or something. I don't have experience with what problems that can cause but 2 thoughts
- The ECM monitors coolant temp to decide when to go into closed loop. If it's not getting a good reading from the coolant sensor it can cause problems. There are two coolant temp sensors - one for the dash gage and one for the ECM. One is on tstat and other is by cylinder 1 on drivers side of block. I'm pretty sure the one on side of block is the one which the ECM reads. If passages have been crudded up - you may want to remove that sensor and see if coolant comes out. I've never removed one so not positive it's in water jacket but would think it should be.
- The ECM reads the knock sensor to retard the timing to prevent knocking which can damage the engine. If you were running really hot - it could be the engine was knocking and the ECM was retarding timing to try to stop it. In other words, maybe it was doing what it was supposed to do and core problem may have been over temp in engine. So now, with engine running cooler its not knocking as much and ECM isn't having to retard the timing as much. Could be the knock sensor isn't the thing which was/is causing the problems - just the engine running to hot? Did you run it after fixing the cooling problem with and without the knock sensor? or only without the knock sensor?

It can be hard, at least for me, to figure out what is causing what in these engines when the ECM may be getting erroneous input from some sensor - or maybe something else is wrong and the ECM is attempting to correct for it.
I did have a problem once where a bad knock sensor was throwing bursts of erroneous knocks and causing the engine to stutter on acceleration. I fixed it with a new ACDelco sensor. However, the only way I actually figured out what was actually going on and that it was a bad knock sensor was to log the data stream from ECM thru the ALDL connector. I could see sudden bursts of knocks with old sensor which went away with the new sensor under same driving conditions. Just because there was a burst of knocks it didn't necessarily mean the first sensor was bad - it could have been that something in engine was actually knocking.
It's a bit of an investment in time but may be worth it if you plan on keeping the truck for a long time. Tunerpro is free/donate software and you can either build a cable or buy one from Moates.

Whatever, at this point - I'd still follow thru on a fuel pressure test.