Vortec 454 idling problem

[JSlezak83]

I had a similar idle issue turned out to be a very easy fix. PCV hose from passenger side valve cover to manifold was disconnected.

Prior to me buying the truck, the manifold gaskets were replaced, and I guess they may have just forgotten to connect that hose.

I posted this a month or so ago and at least one other person had the same thing. It’s worth a check, and in the same neighborhood as the TPS.

 

[RawbDidIt]

Unlikely things do happen, so don't discount it, but I'd put it at the bottom of the list. Although I did just have my oil pressure sender give out right after an oil change, so these things can happen.

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I had a similar problem with mine too. The boot to the PCV was cracked. Makes me super careful when I inspect vehicles now. A $10 part can cause quite the headache.

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[8T7K5]

The o2 sensor code has been there for a while, since before I started replacing things. I think, given how tired and abused this engine is, I'll be better off and money ahead if I do a rebuild. It's sat for at least 6 months that I know of and on top of the rough idle, it's got a miss that I can't identify. Granted I'm not a mechanic and have limited knowledge of working on engines but it seems like given what I've replaced-new plugs, cap, rotor, wires, everything fuel related minus injectors-it shouldn't run like it's got a miss.

 

[454cid]

The o2 sensor code has been there for a while, since before I started replacing things. I think, given how tired and abused this engine is, I'll be better off and money ahead if I do a rebuild. It's sat for at least 6 months that I know of and on top of the rough idle, it's got a miss that I can't identify. Granted I'm not a mechanic and have limited knowledge of working on engines but it seems like given what I've replaced-new plugs, cap, rotor, wires, everything fuel related minus injectors-it shouldn't run like it's got a miss.

I think that would be a mistake. Their are tons of people that do the welp, might as well get a new engine, and then can't get that one running correctly, either.

 

[RawbDidIt]

The o2 sensor code has been there for a while, since before I started replacing things. I think, given how tired and abused this engine is, I'll be better off and money ahead if I do a rebuild. It's sat for at least 6 months that I know of and on top of the rough idle, it's got a miss that I can't identify. Granted I'm not a mechanic and have limited knowledge of working on engines but it seems like given what I've replaced-new plugs, cap, rotor, wires, everything fuel related minus injectors-it shouldn't run like it's got a miss.

What code is it throwing specifically? I don't know much about the 454, but I know basic mechanical theory. I'd start by figuring out which cylinder is missing. Pull the plugs and see which one is fouled. You should be able to see a fuel problem in a cylinder by looking at the plugs. Black means rich or oil fouling, yellow usually means lean. Physical damage is usually timing related, or neglect. If they're brand new and damaged, that would lend towards timing. If you can't read them because they all still look new, run the engine and unplug one spark plug at a time, if it runs rougher, you've got the wrong cylinder. Once you've found the cylinder that's causing the issue run a boroscope into it and see what it looks like. The plugs may be brand new, but the cylinders have been there since day one, they'll have the same telltale signs of damaged rings, lack of spark, or lack/surplus of fuel. The O2 code can give you a hint as well. If it's getting proper fuel and spark but there's oil fouling the plug, you won't ignite, and you'll get a rich code, if the port is dirty, or the injector is fouled you'll get a lean code (I'm pretty sure the 454 is TBI, so there should only be 2 injectors, this pretty much rules out the injectors if only one cylinder is missing). If your timing is off, it's not likely to affect only one cylinder, so check that last. You mentioned that it was sitting for 6 months. Did you run the same old fuel in it when you restarted, or did you siphon the old stuff and put in fresh fuel? Old fuel can do some nasty things to an engine, you've already replaced the pump and filter, if you find carbon fouling on any of the new plugs, I'd run the vacuum test and see what you come back with, could be a plugged port, or a sticking valve, either way you're going to have to pull the intake and heads and give them a cleaning. Don't use the fuel additives, they'll just do a half ass job, and throw all that carbon into your catalytic converter and exhaust system and cause problems there.

https://images.app.goo.gl/aVSkXQ6JCmLx99xv5

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[454cid]

...(I'm pretty sure the 454 is TBI, so there should only be 2 injectors...

Only the early 4.3L V6 was labeled "Vortec" when it was a TBI engine. The Vortec 454 has 8 regular injectors.

 

[RawbDidIt]

Only the early 4.3L V6 was labeled "Vortec" when it was a TBI engine. The Vortec 454 has 8 regular injectors.

Thanks, couldn't remember if/when they upgraded the injection system for the big block, never owned one myself. Is it the same injection system as the small blocks, or are there larger injectors, different electronics, etc?

Either way, this doesn't change the diagnostic process much. Look up the code, at the very least it'll tell you what bank of cylinders is giving you hell, then pull the plugs on that back, and see what you find. This probably isn't something that requires a full rebuild, but depending on the problem you may want to if you're already ripping the whole thing apart.

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[8T7K5]

I appreciate the replies. So the back story is this thing was sitting up in a field, according to Carfax I'm the 4th owner. Some time between the original owner and me it was neglected pretty badly. Came from Iowa, even has an engine block heater which is something I've never seen on a gas engine. I bought it knowing it was going to need work, as in the entire interior redone as well as getting rid of some surface rust on the outside. The guy I bought it from said it wouldn't start. Towed it home, put in new plugs, wires, cap and rotor and a battery and it fired right up but still sounded like it had a miss. Ran a compression test, all cylinders were around 140-145 except #7, which was at about 125. When we had pulled that plug, it was really bad carbon fouled. I had some help from my ex father in law who has built engines and knows a lot more about them than I do. After getting it going with new plugs he said it still sounded like it had a miss. Hooked up my trusty OBD reader and connected to my Torque Pro app and it showed the crank position sensor was bad. Changed it, it was still running rough. It had been parked at his house so I drove it the couple of miles or so to my house so it would be easier to work on. This was my first actual road test of it. When I tried accelerating, it cut out bad so I figured it wouldn't hurt to change the fuel pump (gas gauge wasn't working so I figured the sending unit was bad) and fuel filter. I'd noticed a gas smell coming from under the hood, so I thought maybe it was a leaking injector or regulator or one of the lines going to the fuel rail. Regulator was the "easiest" of those to change so in order to do that and not want to pull out what remaining hair I have, I took off the upper intake. I figured since I'm there I might as well change the valve cover gaskets since they were leaking. Replaced the regulator and noticed that the line going into it was wet so I'm sure I found the source of my gas smell. Changing that out eliminated the smell and after replacing the pump, etc my cutting out issue was gone as well.

Got the new upper intake gaskets on and mistakenly used RTV on it. This caused a huge vacuum leak so off it came as well as the RTV. New gasket, no sealant, no vacuum leak (from there anyway). I regret not replacing the injectors now as I'm concerned my "miss" could be a bad injector and I'm pretty sure they're the original ones but now that I've done it twice, getting the upper intake off and getting them swapped out might not be so bad. Road tested it again and while it didn't cut out anymore, it still felt gutless. Mashed on the skinny pedal a little and while it didn't bog down, it just didn't want to go. After replacing the upper intake gaskets a second time, once it got up to operating temp it started doing the up and down idle. Prior to that, it was idling a little high at about 1k but once it warmed up, rough idle and it was getting hot enough to make the fenders hot. Changed out the thermostat, flushed the radiator, my heat problem was fixed but it was still idling up and down. Ran my OBD scanner again and the following codes showed up-P0102, Mass or volume air flow circuit low input; P0122, throttle/pedal position sensor/switch A circuit low input; P1345 Powertrain; P1406 Powertrain. Changed the throttle position sensor, let it get to operating temp, my fluctuating idle is gone but it idles high at around 1100 or so and it's still throwing the code for the TPS.

So that's where I'm at, with the elimination of one problem and 4 more popping up. I'm seriously way past the extent of my knowledge on all of this. I really want to get this thing going but at this point, I'm not sure I've got the ability to get it done. I appreciate the help!

Edit-code P1406 is apparently related to the EGR valve, which I deleted and put a block off plate in its place.

 

[RawbDidIt]

I appreciate the replies. So the back story is this thing was sitting up in a field, according to Carfax I'm the 4th owner. Some time between the original owner and me it was neglected pretty badly. Came from Iowa, even has an engine block heater which is something I've never seen on a gas engine. I bought it knowing it was going to need work, as in the entire interior redone as well as getting rid of some surface rust on the outside. The guy I bought it from said it wouldn't start. Towed it home, put in new plugs, wires, cap and rotor and a battery and it fired right up but still sounded like it had a miss. Ran a compression test, all cylinders were around 140-145 except #7, which was at about 125. When we had pulled that plug, it was really bad carbon fouled. I had some help from my ex father in law who has built engines and knows a lot more about them than I do. After getting it going with new plugs he said it still sounded like it had a miss. Hooked up my trusty OBD reader and connected to my Torque Pro app and it showed the crank position sensor was bad. Changed it, it was still running rough. It had been parked at his house so I drove it the couple of miles or so to my house so it would be easier to work on. This was my first actual road test of it. When I tried accelerating, it cut out bad so I figured it wouldn't hurt to change the fuel pump (gas gauge wasn't working so I figured the sending unit was bad) and fuel filter. I'd noticed a gas smell coming from under the hood, so I thought maybe it was a leaking injector or regulator or one of the lines going to the fuel rail. Regulator was the "easiest" of those to change so in order to do that and not want to pull out what remaining hair I have, I took off the upper intake. I figured since I'm there I might as well change the valve cover gaskets since they were leaking. Replaced the regulator and noticed that the line going into it was wet so I'm sure I found the source of my gas smell. Changing that out eliminated the smell and after replacing the pump, etc my cutting out issue was gone as well.

Got the new upper intake gaskets on and mistakenly used RTV on it. This caused a huge vacuum leak so off it came as well as the RTV. New gasket, no sealant, no vacuum leak (from there anyway). I regret not replacing the injectors now as I'm concerned my "miss" could be a bad injector and I'm pretty sure they're the original ones but now that I've done it twice, getting the upper intake off and getting them swapped out might not be so bad. Road tested it again and while it didn't cut out anymore, it still felt gutless. Mashed on the skinny pedal a little and while it didn't bog down, it just didn't want to go. After replacing the upper intake gaskets a second time, once it got up to operating temp it started doing the up and down idle. Prior to that, it was idling a little high at about 1k but once it warmed up, rough idle and it was getting hot enough to make the fenders hot. Changed out the thermostat, flushed the radiator, my heat problem was fixed but it was still idling up and down. Ran my OBD scanner again and the following codes showed up-P0102, Mass or volume air flow circuit low input; P0122, throttle/pedal position sensor/switch A circuit low input; P1345 Powertrain; P1406 Powertrain. Changed the throttle position sensor, let it get to operating temp, my fluctuating idle is gone but it idles high at around 1100 or so and it's still throwing the code for the TPS.

So that's where I'm at, with the elimination of one problem and 4 more popping up. I'm seriously way past the extent of my knowledge on all of this. I really want to get this thing going but at this point, I'm not sure I've got the ability to get it done. I appreciate the help!

Edit-code P1406 is apparently related to the EGR valve, which I deleted and put a block off plate in its place.

So there's a few different issues here, let's break this down.
EGR valve delete: the engine is expecting to recycle exhaust air, and you've prevented that. The code is being thrown because there is no longer an EGR. If you're going to delete it, you have to reflash the ECM to factor in the EGR delete.
The mass airflow sensor: your getting a code reading too little air is going into the engine. This would cause a rich condition. Check your air filter and intake system for blockages, if there aren't any, pick up a can of MAF cleaner or pick up a new MAF.
TPS: you may have gotten one that's bad out of the box, or another issue, namely one if the other two I mentioned, is making the ECM think that the TPS is giving inaccurate readings.
You'll be fine, these engines aren't too complex, just make sure you're actually solving a problem before you pull the trigger on a new part. With a project like this you're going to fix one problem just to reveal another until it's fixed. I had the same thing happen with mine, just be thankful it appears to be mechanical and not electrical. If you want to keep this truck I recommend purchasing some diagnostic tools. Fuel, oil, and vacuum pressure kits, a multimeter, etc. $100 in diagnostic tools will save you thousands in parts and hours of time.

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[454cid]

Will your scanner read the values, or is it simply a code reader? I'm curious on the air flow... should be a Hz and/or g/cm^3 number.

Also that P1345 means your distributor is way off. It doesn't throw a code until +/-20-ish, and the spec is +/-2 (degrees)

I got an OEM MAF from the salvage yard when I needed one.