Engine juddery, loss of horsepower.

[None_zero]

5 minutes ago, datzenmike said:

The TVV was referred to as the 'brown thing'. The VVT variable vacuum transducer is for the EGR which is (I hope) disconnected.

Yeah if you refer to the pictures I posted a few minutes ago both egr and vvt are on my work bench 

[datzenmike]

Depends if this was a mileage option Z20 or a Z20 from the A10 car.

 

The mileage option Z20 has a higher compression and has a knock sensor on top edge of the block under the intake. Inside the cab is circuitry to retard the ignition timing when knocking is present. If this is that Z20 there's going to be problems as I doubt this circuitry was included.

 

 

Look on the front, maybe the front sides for the head casting number. A Mileage Option Z20 head will have W04 cast into it.

[None_zero]

31 minutes ago, datzenmike said:

Depends if this was a mileage option Z20 or a Z20 from the A10 car.

 

The mileage option Z20 has a higher compression and has a knock sensor on top edge of the block under the intake. Inside the cab is circuitry to retard the ignition timing when knocking is present. If this is that Z20 there's going to be problems as I doubt this circuitry was included.

 

 

Look on the front, maybe the front sides for the head casting number. A Mileage Option Z20 head will have W04 cast into it.

Yes I recall that we did determine this previously because of some confusion over the placement of oil pressure sensor vs knock sensor I'm going to double check now but I'm certain it is......

And it is

Edited February 26, 2023 by None_zero

[None_zero]

And here is the knock sensor which I also kept. It has been disconnected since before I owned the truck

Edited February 26, 2023 by None_zero

[datzenmike]

This means on top of everything this is a high compression engine that relies on the knock sensor to tame the pinging. Oh well, try running 3 degrees of advance or try higher octane gas.

[None_zero]

4 hours ago, datzenmike said:

This means on top of everything this is a high compression engine that relies on the knock sensor to tame the pinging. Oh well, try running 3 degrees of advance or try higher octane gas.

I have noticed in the past if I run plus it runs better. Premium and it's rough regular it's not smooth and plus seems to do the best. But no way i going to run anything but regular in it getting 9 miles a gallon. And it has run better in the past than it was yesterday. I haven't really messed with it today. I needed a little break 

[datzenmike]

[None_zero]

So let's talk this through a bit. Because I've never got the feeling that the person who had the truck before the guy who had it before me didn't know what he was doing. The guy who had it before me didn't really know what he was doing and I definitely don't know what I'm doing... but having said all that.. do you think the fuel pump and filter were changed to compensate for something like higher compression and no knock sensor to regulate it? I've said many times on here that the cylinders lack compression though because it inches down hill while in gear... so Maybe regular wear has reduced the compression... I mean how big of a difference are we talking about?

Edited February 27, 2023 by None_zero

[datzenmike]

The original fuel pump probably failed and that was a cheaper option. All the pump does is deliver fuel to the float chamber. It has nothing to do with how the engine runs other than delivering fuel.

[None_zero]

I think in my own mind which means a very poorly educated guess. Is that the trouble was and is in the carburetor. And most of the other stuff is things I've done trying to avoid replacing or rebuilding the carburetor, that I shouldn't have done and so we end up with this laundry list of corrections and adjustments a mile long. I keep coming back to the idle mix screw for one thing.  Also I'm curious is that muted combustion likely the result of pinging which is ... over advanced timing right?

Edited February 27, 2023 by None_zero
Said the wrong thing

[None_zero]

And then there is the tachometer. And if I'm setting my timing off a faulty reading then the odds of ever getting it right have to be next to nil .... how does the tach take its reading? From the distributor?

Edited February 27, 2023 by None_zero

[None_zero]

Let me just focus on one thing at a time though so let's go with the carburetor. What about the diaphragm controlling the secondary throttle valve if it's faulty would that cause fuel to flow into the secondary value even if the primary valve was screwed closed because it diesels big time despite the fuel cut off solenoid being functional. (I assume that's what the fsm refers to when it says "anti dieseling solenoid) vacuum actuated booster... does this refer to the vac advance i guess?

Edited February 27, 2023 by None_zero

[None_zero]

Ok I'm just gonna read for a while because I am answering my own questions I think 

[datzenmike]

Keep the FSM in the bathroom and read there. Garbage out... information in.

[None_zero]

Oh boy. Sooooo let's say that hypothetically this caution. Had not been observed when cleaning the inside of the carburetor and that perhaps someone did scratch and or nick the jet...  what would be the result. Asking for a friend 

 

[datzenmike]

Jets come in various sizes for tweaking the fuel mixture. You would have to gouge it out with a drill before it would affect anything..... uh you know to keep the primary and secondary jets separate???? They have the same thread and will interchange. Generally the primary is marked in the low 100s and the secondary is around 160. It might run with a 160 in the primary side but be extremely rich. Easy to mix them up.

[None_zero]

I haven't removed them ever but I have gone down into that area with brushes and flat metal pieces trying to clean the crap off it. I mean my friend has done that...

[None_zero]

The only thing I've felt confident enough to do with the carb before now was clean it. Adjust the set screws on it and fix things that were visibly broken on the outside like the linkage on the back from the choke to the diaphragm or once the screw somewhere on that same assembly had backed out and vanished and I replaced it. Other than that I'd never even seen the float till you told me to open it up because I was always worried I'd take it off and then not have some replacement gasket or other that I'd need to reassemble it 

[datzenmike]

 

[None_zero]

Ok up date time; did a thorough cleaning of distributor cap and rotor. Pulled all the plugs and sprayed the fouling off of them and checked the gap. Discovered that the one I'd swapped out was .039 gap while all the rest were .032 (changed it back to the other one since that wasn't the problem anyways. Raised float back up close to where we raised it to before. Attached manifold vacuum to ab valve. Replaced a few vac lines that were likely leakers. Cleaned the carburetor. I didn't do all this at once but rather in stages with driving in between. Result: shuddering is gone from engine (I believe at the end it was the overgapped plug and the corrosion in the distributor that was making it do that. Compounded by the fouled plugs) engine no longer runs rich (if anything it's a bit too lean I may try some small choke adjustments to sort this out. Truck ran great today. Power was back acceleration was good. Fuel efficiency is up from where it was but still hasn't reached my target mpg. (Was getting 9 mpg, now getting 13 mpg, target is 18 mpg) more mpg would be nice but I'm attempting to manage my expectations. If the plugs remain unfouled over the next few days I'll change the oil and filter. That should help some. And I need to fix the... camber I think is the one I need to change. (The top of the tire tucks in toward the engine a little) but over all it already feels like a new truck. Thanks for all the help through this adventure in keeping Betty alive and in shape. And any other suggestions on bumping that gas mileage up I'd love to hear. Of the initial problems the only ones that remain are the tach (which seems improved somewhat) still reads a bit low at low rpm (maybe just reads low all the time) and the idle mix screw is still bottomed out to get the best idle.  

Edited March 1, 2023 by None_zero

[None_zero]

I've been studying the carburetor in the fsm and a lot of other stuff also but focused on that a lot to try to understand every aspect of its functionality. I do feel like I'm still leaking vacuum somewhere possibly at the carburetor mounting plate but haven't checked any vacuum levels yet 

Edited March 1, 2023 by None_zero

[NC85ST]

One way to check for vacuum leaks is by spraying carb cleaner around the suspected areas with the engine idling. A change in the rpm’s will show where a possible problem is.

[None_zero]

Ok thanks for the tip. I saw on another thread (I think it was wayne) saying to spray the base of the carb with starter fluid. But I assumed it was just so you could watch for movement of the liquid I didn't know to pay attention to rpm shifts 

[None_zero]

I've been experiencing some shifts in performance, it seems like she drives much better and gets better mileage in the morning. Of course my commute to work does include a fairly sharp drop in elevation so the return trip has some decent hills to drive up. But it's not like it's uphill one way and down the other for the entire drive. Maybe the short drive I make at lunch without much warm-up time is affecting the performance on the longer drive home a few hours later?

[datzenmike]

Vacuum leak and idle.

 

An air leak lets in air and leans out the mixture.  This is worse at idle where intake vacuum is highest and most affected. The leak is fixed... it doesn't leak more as the engine revs up so what affects idle has little effect when driving. That small fixed amount of air leaked in is mixed with a huge volume of air and fuel and is not noticeable when driving. If it was noticeable when driving the leak would be so large it wouldn't idle and might not even start.