New to me 2000 K2500 missing at idle, occasional stalls

[someotherguy]

Ok, EGR seems unrelated. I had the distributor wire unplugged still from earlier. Just plugged it in after idling for 5-10 minutes, instantly had a horrible idle. What does this mean? You called it a cam position sensor, but it most certainly is the 3 pin connector at the base of the distributor

That is absolutely the cam position sensor. My best guess at why it runs better with it disconnected is that it's going into a limp mode of some kind when the data from that sensor is not present. Getting the proper scan tool on this truck and setting the cam retard angle is important at this point and it may even need to go through a crank relearn procedure. If you keep guessing at what's going on you'll end up in the same position you imagine the seller was.. frustrated and gave up on what's wrong with it. JMHO

Richard

 

[Nicman201]

That is absolutely the cam position sensor. My best guess at why it runs better with it disconnected is that it's going into a limp mode of some kind when the data from that sensor is not present. Getting the proper scan tool on this truck and setting the cam retard angle is important at this point and it may even need to go through a crank relearn procedure. If you keep guessing at what's going on you'll end up in the same position you imagine the seller was.. frustrated and gave up on what's wrong with it. JMHO

Richard

Absolutely right. This article explained it all to me.

Installing and Setting a Vortec Distributor Correctly - GM Truck Central

How to correctly install the distributor and set the timing for a Vortec L30/L31

www.gmtruckcentral.com

Luckily I have EFILive and a scan cable. So tomorrow I will be grabbing my laptop and seeing what's up with that cam offset

 

[Carlaisle]

If it runs better with the camshaft position sensor disconnected than when it's connected that's basically proof positive the timing is off. As someotherguy said, it's defaulting to limp mode. Be sure to check all of your grounds. Those can play all kinds of havoc with electrical gremlins. It also wouldn't hurt to make sure the plug wires are on the distributor correctly. The Vortec 454 distributor does not use the same routing as the older Chevy big blocks. Was the cap replaced with the distributor? If not, that's another potential issue to investigate if the problem remains after verifying the timing and checking the grounds.

According to this https://torque-bhp.com/wiki/Dials Torque can display timing.

 

[Nicman201]

Good news? I could not find CMP offset in Torque, but the app called Car Scanner on Android seems to have it. It was at 4.9 at 1,000 rpm.

 

[stutaeng]

If the fuel pump relay is working right, "no oil pressure" won't prevent the engine from running.

Doesn't matter about OBD II or Vortec.

Far as I know, the oil pressure sensor doesn't communicate with the computer. Just the fuel pump and the instrument cluster.

I drove my 4.3 Vortec with a oil pressure gauge hooked up to where the oil pressure sender hooks up...was monitoring the oil low oil pressure and forgot about it, LOL. After about 2 weeks I remembered and unhooked it. IIRC, the guage needle just went the left or right out of the scale. I can't remember if the check gauges light came one. But check gauges light had already come on, that's why I was checking the pressure.

Probably wasn't wise. It was in the summer so temperature was hot... Rubber hose could of ruptured.

 

[Dravec]

Is it blowing black smoke out of the tailpipe? My 454 is, due to the well known injector leak issue. That's extremely high on my list of priorities to buy and replace on mine.

Being out of work for 2 months makes buying parts hard...

 

[Nicman201]

Is it blowing black smoke out of the tailpipe? My 454 is, due to the well known injector leak issue. That's extremely high on my list of priorities to buy and replace on mine.

Being out of work for 2 months makes buying parts hard...

Nah no smoke that I can see. My scanner app shows that the cmp offset is over almost 2° positive. Haven't had a chance to loosen the dizzy and wiggle it around yet.

 

[Nicman201]

Nah no smoke that I can see. My scanner app shows that the cmp offset is over almost 2° positive. Haven't had a chance to loosen the dizzy and wiggle it around yet.

Got it set to +0.67 at 1000 rpm. Already sounds better. Will do more extensive test driving when I fix the brakes lol

 

[RokRoland]

I am putting my two cents out there even if my experience comes from a '89 with a 350. Some things that have not been mentioned yet are:

- Lambda. My TBI had a really old Lambda sensor. It would run great from cold until the engine warmed up enough for it to start using the lambda readings and adjust fueling based on that. After the temperature was at 1/3 on the gauge or so, it would start to run more sluggish and sometimes throw a CEL. A new lambda sorted this, even though the fueling doesn't seem as crispy in closed loop mode. The fact that your thermostat was broken or removed and the car wouldn't warm up fully, but still ran pretty well, might point into this direction too.
- Coil. My truck has 160000 miles from new and was on the original coil. Other parts like dizzy, ignition modules, plug wires had been replaced before but the coil had definitely sat in its mount since Detroit, 1989. I ordered a new part from Rockauto and installed it. The idle misfilre which would happen every 5 seconds or so was totally gone after that. The module I used was supposedly a high output unit, a Standard brand, called Blue Thunder, or Blue Oyster, or Blue Whatever, honestly I can't recall. Seems to have been a good investment anyway. I didn't have any definitive symptom which led me to replace the original coil, but ageing gets to everything. Experience from working on 80s motorcycles tells me it's easy to spend days hunting a fueling issue which is due to an aged coil which gets intermittent as it warms up, so I tend to replace those on the bikes as a matter of course if there's any running issues, and applied the knowledge to this context with success.

I hope you get your 454 cured from its present state. The investment for these parts is small, so consider them also.

Edit: Oh and as someone above said, check and clean all grounds, that's a really important starting point and can not be emphasized enough.

 

[Nicman201]

I am putting my two cents out there even if my experience comes from a '89 with a 350. Some things that have not been mentioned yet are:

- Lambda. My TBI had a really old Lambda sensor. It would run great from cold until the engine warmed up enough for it to start using the lambda readings and adjust fueling based on that. After the temperature was at 1/3 on the gauge or so, it would start to run more sluggish and sometimes throw a CEL. A new lambda sorted this, even though the fueling doesn't seem as crispy in closed loop mode. The fact that your thermostat was broken or removed and the car wouldn't warm up fully, but still ran pretty well, might point into this direction too.
- Coil. My truck has 160000 miles from new and was on the original coil. Other parts like dizzy, ignition modules, plug wires had been replaced before but the coil had definitely sat in its mount since Detroit, 1989. I ordered a new part from Rockauto and installed it. The idle misfilre which would happen every 5 seconds or so was totally gone after that. The module I used was supposedly a high output unit, a Standard brand, called Blue Thunder, or Blue Oyster, or Blue Whatever, honestly I can't recall. Seems to have been a good investment anyway. I didn't have any definitive symptom which led me to replace the original coil, but ageing gets to everything. Experience from working on 80s motorcycles tells me it's easy to spend days hunting a fueling issue which is due to an aged coil which gets intermittent as it warms up, so I tend to replace those on the bikes as a matter of course if there's any running issues, and applied the knowledge to this context with success.

I hope you get your 454 cured from its present state. The investment for these parts is small, so consider them also.

Edit: Oh and as someone above said, check and clean all grounds, that's a really important starting point and can not be emphasized enough.

Yeah after making sure the cmp offset was in the correct range I'm still experiencing drivability issues. It's sputtering on acceleration sometimes the idle gets weird too.

Still need to check fuel pressure and these grounds. Where are they on this motor? Back of the cylinder head? Where on the frame?

It only seems to have this issue when it's fully warmed up. And it's not happening all the time. It just acted up when I left the drug store but once I got the gas station and let it idle for a bit, it drove the rest of the way home with no hesitations or anything. Very intermittent.