Well, some new pieces to the puzzle. (242,000 mi)

I tried pulling on the throttle linkage a few minutes after starting the truck. The idle immediately returned to around 700RPM. I think this is the source of my high idle. Extra air is getting into the engine because the butterfly valve is closing/seating correctly. I saw a thread about adding a thin washer w/ a 3/8" hole. I'm going to do this mod. BTW, my MAF was running above 5g/sec at idle and the second I pulled on the linkage, the idle dropped and the MAF returned to the correct range of 3.3-4.7g/sec. So I'm going to give this mod a go tomorrow.

Unfortunately, I'm now experiencing major losses of power when driving. Very odd. First the problem presented itself as a delayed response when I'd step hard on the gas peddle last week. Today, I cleaned my MAF (replaced 1'18) and added seafoam to the gas at the highest recommended concentration 2oz/gal. Took it for a drive and within about 15min, pressing on the gas peddle was having no effect on RPM or acceleration. At slow speeds, as the engine attempted to respond to the gas pedal, the truck lurched at times and then eventually stalled. It would start right up. No issues starting. Happened a bunch of times as I attempted to get home. I added more gas for fear I added too much sea foam and am letting it idle in the garage for a bit. I found at times, keeping the RPM high, helped while driving down the road.

My guess is a fuel delivery problem: fuel pump or injectors. What's your best guess?

Appreciate the insights!

Sometimes when your vehicle has too lean of a mix the ECU will retard your ignition timing to prevent damage and as such you'll lose loads of power (this is what "limp mode" is and is very often triggered during P0171. However, it's usually only present with a CEL if I'm not mistaken). Does it keep coming back or is this now happening with a clear dash?
A decent way to check your injectors is to grab a long screwdriver or socket extension, and put your ear on one end and the other on the injector. They should all sound relatively the same, a slight variance can be attributed to age/wear but anything real noticeable is obviously a red flag. If your fuel pump was going out, a different code is almost always thrown (P0080 or something). If it was fuel related my first guess would be the filter but it sounds like you've pinpointed it to the throttle - however I wouldn't be surprised if you maybe weakened some old varnish in the filter and made it's way to the injectors, from the Seafoam.
Personally I think Seafoam is pretty weak. I recommend either RedLine SI-1 or the new BG44k Platinum. Both are terrifically strong, and I practically attribute them to having valves cleaner than my dinner plate at almost 300k. Seafoam itself is nothing but isopropyl alcohol and naphtha suspended in pale oil. I'd recommend trying the TB mod, and if that doesn't fix it then change out your fuel filter and throw in some of the aforementioned cleaners. (I never do just one treatment, usually 2-3 tanks for good measure). Start cheapest and work big.
Edit: How do your spark-o-lators look? I assume they're probably fine but it's another cheap place to start. Mine were practically lacking an electrode and still zapping good enough to run

Just replaced the fuel filter (OEM) in May. I already have the injectors so I'm going to put them in. The goal is to get the high idle and this new problem resolved so that I can put a supercharger on (as long as compression is good). But don't dare attempt the supercharger project until i get these problems resolved once and for all.

I had the P0170 CEL today and cleared it before I took the truck for a drive. Throughout today's acceleration/lurching issue, the CEL remained off. It's still off as the truck idles in the garage.

Appreciate the fuel additive insights. Wasn't aware!

Update. Replaced fuel injectors and installed the new throttle body. truck drives like new. The low idle issue is gone. But I don't think this was what was causing the sudden engine dying. Turns out I had two electrical issues. The ppsitive battery terminal was shot and the alternator was bad. What little charge the battery was getting was quickly consumed and as sokn as the battery voltage dropped, the truck exhibited the previous problems (lurching/engine died). Replaced the battery, started the truck and disconnected the battery. the truck instantly died.

have the cs144 and the adapter plug. installing this week. psyched to get these issues behind me!

now, one last issue. I'm still smelling gas. not as strong now. I'm going to replace the spark plugs with the ones id use w a supercharger as I prepare for that.

so 3 potential things to check I guess: catalytic converter, headers/manifold or charcoal canister? anything else I should check?

how does one know if the charcoal canister is working? could that throw a p0170?

I have zero rust. no leaking fuel. engine is running great. idles perfectly. both o2 sensors new. the ecu was reset. I'm pretty stumped.

Usually if there is a problem with the EVAP system you’ll get a leak code (small or large) or the readiness monitor won’t set.


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Do you smell any sulfur? If you have an exhaust leak (before or at the cat) it should smell of both gas AND rotten eggs. If you don't, and your fuel rails look alright, I would look into the charcoal canister, as fuel odor and poor performance are both big signs of one failing. Do you notice a drop in MPGs?
In case you haven't already, sniff around he canister while running. Probably will be impossible with the all the wind stirred up by the fan but worth a try. If you don't have any codes thrown or pending codes related to the charcoal canister itself, I would assume it's probably a bad purge valve that isn't functioning properly when told to. I believe the proper way to test charcoal canisters is with a vacuum pump/gauge but I'm not totally sure. Just my 2 cents

yes, I've had a drop in mpg's. I was attributing it to the e-rated ko2's. hmmm.

no sulfur smell at all. is the purge valve part of the charcoal canister?

Yes, the purge valve is what allows the vapors in the canister to be recirculated back into the engine instead of wasted into the wind

P0455 relates to charcoal canister issues.

checked my notes. the purge valve was replaced in '18. is there a way to test it?

I got that code last week, bought some Maf cleaner, stripped one of the screws but was able to clean it in the box as best I could. It didn't look dirty though. I replaced the upstream o2 sensor last year on the 43 code and it seemed to fix that. Is vacuum leaks my next move? Where all do I check for those? if that doesn't do it, I'll probably have to bring it to have the professional figure it out.

I had this code for about 2 month and replacing parts like maf sensor, bank 1 coil, valve cover gasket, intake gasket and what fix it was the o2 sensor=bank 1 sensor 2. which I had replace about 3 years ago

Last year my 02 threw the same code. Replaced the gas cap and cleared the code. Hasn't come back since