Stalling troubleshooting

[red1980F150]

Hey guys,

I could put this in the new members forum - I picked up at orangish-red (originally gray) 1980 F150 with a 302 and auto (original sticker denoting transmission code is gone, probably a c6?) in May 2020. I'm only the second owner! The founder of the company I worked my first professional job bought it new in 1980. It's very clean, but is starting to need cab corners.

Through the summer it ran really well, pretty much all I did was change the oil and air filter, though it seems I had a lot of crank case pressure so I probably should have changed the PCV valve sooner (did it today). Then I didn't drive it for about a month and a half.

Next time I drove it, it seemed to run okay at first. Then when warmed up it would stall at stops and when I dropped it into D or R. Initially I suspected vacuum leak but the hoses are good, though obviously not quite stock (EGR isn't hooked up, smog pump is gone, etc.). I've found two likely scenarios based on my searching various documents and forums:

This guy seems to say his needle got stuck and it was just getting too much fuel (can I try tapping it with a wrench like I see so often in car shows?). Symptoms are IDENTICAL, down to the high idle in N.

https://www.ford-trucks.com/forums/868397-what-are-the-symptoms-of-a-blown-power-valve.html

Then this thread on this forum suggests bad power valve and Gary gives detailed advice on how to test

http://forum.garysgaragemahal.com/Bought-my-1st-FORD-tp15773p15776.html

I decided I might as well order a new fuel filter too since they're $2, and got a similarly priced filter for the crank case vent hose on the driver side since the old one was... the dirtiest filter in human history, maybe original.

I'm youngish for the carb crowd and don't have much experience with them, though I'm used to working on my own stuff. My last truck was a 93 (RIP) with a 302 and I did quite a bit to that so I'm weirdly better with electronic stuff (have a great story). So I'm definitely trying to learn how to diagnose and treat carbs... have a lot of interest. I think the power valve and needle sound like good places to start, but want to see if anyone has other advice.

Thanks in advance.

[Gary Lewis]

Well, I'm not sure what to call you. "Red" probably applies to the truck. But that's all I have at the moment. So, maybe you could create a signature that not only includes info about your truck but also includes your name? Info on how to do that is in Bullnose Forum/Forum FAQ's.

Yes, you were to post first in the New Members Start Here folder as that will give you the best chance of having seen our guidelines. And since we hold people to them it is important that you have a chance to see them and aren't blind-sided. But, if you can assure us you've seen them then we'll overlook the issue.

But while we are doing the new-member thing, where's home? I ask because we have a map (Bullnose Forum/Member's Map in the menu) and we could add you if we knew your city or zip.

Now for the carb. Yes, you can rap on it, but unless it is a Stromberg 97 it isn't likely that'll work. But I don't think it is a stuck float/needle. I think you may have a vacuum leak. Too much fuel usually causes the engine to bog down rather than running faster at idle. But a vacuum leak almost always causes a high idle.

If you happen to have a 300 six then I'd guess the carb-to-manifold nuts have worked loose. If not, then you may well have a cracked or loose vacuum line.

So, tell us more, please.

[red1980F150]

Well, I'm not sure what to call you. "Red" probably applies to the truck. But that's all I have at the moment. So, maybe you could create a signature that not only includes info about your truck but also includes your name? Info on how to do that is in Bullnose Forum/Forum FAQ's.

Yes, you were to post first in the New Members Start Here folder as that will give you the best chance of having seen our guidelines. And since we hold people to them it is important that you have a chance to see them and aren't blind-sided. But, if you can assure us you've seen them then we'll overlook the issue.

But while we are doing the new-member thing, where's home? I ask because we have a map (Bullnose Forum/Member's Map in the menu) and we could add you if we knew your city or zip.

Now for the carb. Yes, you can rap on it, but unless it is a Stromberg 97 it isn't likely that'll work. But I don't think it is a stuck float/needle. I think you may have a vacuum leak. Too much fuel usually causes the engine to bog down rather than running faster at idle. But a vacuum leak almost always causes a high idle.

If you happen to have a 300 six then I'd guess the carb-to-manifold nuts have worked loose. If not, then you may well have a cracked or loose vacuum line.

So, tell us more, please.

Thanks Gary.

I did read the guidelines, and went and did so again just to be sure

I went ahead and created a signature, which hopefully I can add to over time to help. I'm in the Springfield Ohio area, 45504.

I bought a vacuum gauge because of this issue (a leak was my first thought too) and it was reading about 21". I think I need to retest though because I'm not 100% sure the choke was completely off. The gauge was at operating temp but had only just gotten there.

I didn't know what I was doing and first and assumed any open hole was a leak so I started capping things that were open, like the bowl vent which had no hose on it. I'm guessing I could go take that off. Obviously I still don't really know what I'm doing, but I started reading the documentation here for most of the day today and that has helped.

The truck still has the stock 2bbl (2150 ?). The vacuum hoses seem fairly healthy, not dry rotted and old, I think the previous owner kept up on it, so I couldn't find an obvious problem with cracked hoses. Though there could be a loose hose, I suppose.

I'm happy to grab some pictures tomorrow. I'm not sure what additional information will help the most so let me know if there's something that would be especially helpful.

If high crank case pressure could be a clue... I have it. It seems most like that's a separate issue, to me, but perhaps worth mentioning. The ported vacuum switch also has no caps and nothing attached to it, I found that earlier today.

[ArdWrknTrk]

Thanks Gary.

I did read the guidelines, and went and did so again just to be sure

I went ahead and created a signature, which hopefully I can add to over time to help. I'm in the Springfield Ohio area, 45504.

I bought a vacuum gauge because of this issue (a leak was my first thought too) and it was reading about 21". I think I need to retest though because I'm not 100% sure the choke was completely off. The gauge was at operating temp but had only just gotten there.

I didn't know what I was doing and first and assumed any open hole was a leak so I started capping things that were open, like the bowl vent which had no hose on it. I'm guessing I could go take that off. Obviously I still don't really know what I'm doing, but I started reading the documentation here for most of the day today and that has helped.

The truck still has the stock 2bbl (2150 ?). The vacuum hoses seem fairly healthy, not dry rotted and old, I think the previous owner kept up on it, so I couldn't find an obvious problem with cracked hoses. Though there could be a loose hose, I suppose.

I'm happy to grab some pictures tomorrow. I'm not sure what additional information will help the most so let me know if there's something that would be especially helpful.

If high crank case pressure could be a clue... I have it. It seems most like that's a separate issue, to me, but perhaps worth mentioning. The ported vacuum switch also has no caps and nothing attached to it, I found that earlier today.

High crankcase pressure would explain an oily vent filter.

Are you sure the line between the PCV check valve and the intake manifold is clear?

That seems like a lot of blow by.

Does your truck have a tach?

When you say you have a high idle, but it's just gotten up to temp, perhaps the carb is hung up on the fast idle cam?

It couldn't hurt to examine/clean all those external linkages.

A blown Powervalve usually has a truck struggling at low rpm's and clearing up as the revs increase.

Also common is bucking and popping on deceleration.

Is the EGR vacuum line capped off or is the EGR actually missing and a plate in its place?

An EGR that's stuck open a little could cause a stall at idle when the transmission is engaged.

 

[Gary Lewis]

Thanks Gary.

I did read the guidelines, and went and did so again just to be sure

I went ahead and created a signature, which hopefully I can add to over time to help. I'm in the Springfield Ohio area, 45504.

I bought a vacuum gauge because of this issue (a leak was my first thought too) and it was reading about 21". I think I need to retest though because I'm not 100% sure the choke was completely off. The gauge was at operating temp but had only just gotten there.

I didn't know what I was doing and first and assumed any open hole was a leak so I started capping things that were open, like the bowl vent which had no hose on it. I'm guessing I could go take that off. Obviously I still don't really know what I'm doing, but I started reading the documentation here for most of the day today and that has helped.

The truck still has the stock 2bbl (2150 ?). The vacuum hoses seem fairly healthy, not dry rotted and old, I think the previous owner kept up on it, so I couldn't find an obvious problem with cracked hoses. Though there could be a loose hose, I suppose.

I'm happy to grab some pictures tomorrow. I'm not sure what additional information will help the most so let me know if there's something that would be especially helpful.

If high crank case pressure could be a clue... I have it. It seems most like that's a separate issue, to me, but perhaps worth mentioning. The ported vacuum switch also has no caps and nothing attached to it, I found that earlier today.

Jim is right on all points.

As for the vacuum gauge, it really won't show that you have a vacuum. Typically a vacuum leak makes the RPM go up and that makes the vacuum reading go up. But having the fast idle cam still on due to the choke being on or the linkage stuck can up the idle as well.

Yes, you should have a 2150 so you can read that documentation if you haven't.

And, you are now on the map.

[red1980F150]

High crankcase pressure would explain an oily vent filter.

Are you sure the line between the PCV check valve and the intake manifold is clear?

That seems like a lot of blow by.

Does your truck have a tach?

When you say you have a high idle, but it's just gotten up to temp, perhaps the carb is hung up on the fast idle cam?

It couldn't hurt to examine/clean all those external linkages.

A blown Powervalve usually has a truck struggling at low rpm's and clearing up as the revs increase.

Also common is bucking and popping on deceleration.

Is the EGR vacuum line capped off or is the EGR actually missing and a plate in its place?

An EGR that's stuck open a little could cause a stall at idle when the transmission is engaged.

Thanks Jim, great idea to check the line for a clog, I might never have thought of that. I checked it after work and it was clear, so no dice there. I do have too much blow by though, I'm hoping it's something fixable and not more severe, but I don't remember the truck leaking at all when I first got it... which has changed significantly.

The truck doesn't have a tach or an oil pressure gauge, which is unfortunate given the current troubleshooting (not coincidentally, I bought a set of gauges last night! - summit racing has a really good deal on the intellitronix gauges ).

So estimating a high idle is totally by ear, but fairly obvious in this case. I'll look at the documentation to make sure know what I'm looking for and check out those linkages. The one thing I can say is that when the choke is on the truck never stalls, the problem only comes about when it's warmed up and the choke is off.

The EGR is just capped off, it's still present. Actually, until I capped it yesterday it was just sitting with no hose or cap. What do you guys think about removing it? I've seen the arguments for using it to cool the charge, not sure if it matters on these old engines... plus mine could have already been unhooked for decades at this point.

[Gary Lewis]

Thanks Jim, great idea to check the line for a clog, I might never have thought of that. I checked it after work and it was clear, so no dice there. I do have too much blow by though, I'm hoping it's something fixable and not more severe, but I don't remember the truck leaking at all when I first got it... which has changed significantly.

The truck doesn't have a tach or an oil pressure gauge, which is unfortunate given the current troubleshooting (not coincidentally, I bought a set of gauges last night! - summit racing has a really good deal on the intellitronix gauges ).

So estimating a high idle is totally by ear, but fairly obvious in this case. I'll look at the documentation to make sure know what I'm looking for and check out those linkages. The one thing I can say is that when the choke is on the truck never stalls, the problem only comes about when it's warmed up and the choke is off.

The EGR is just capped off, it's still present. Actually, until I capped it yesterday it was just sitting with no hose or cap. What do you guys think about removing it? I've seen the arguments for using it to cool the charge, not sure if it matters on these old engines... plus mine could have already been unhooked for decades at this point.

Still sounds like it could be a vacuum leak. You may be a good candidate for the smoke test. Read here: http://forum.garysgaragemahal.com/Vacuum-leak-detection-effective-and-inexpensive-td11511.html. That will usually find vacuum leaks that you might not find another way.

But you can also spray brake or carb cleaner around in suspect areas. If there's a vacuum leak the cleaner gets sucked in and burned, which speeds the engine up briefly. But be away that the cleaner can melt paint, so be careful.

On the EGR, when they work they are good. When they don't they are bad. But you can't just block the EGR valve off and not have other problems. The inert gas slows the combustion process so when the EGR valve is supposed to be open the ignition advanced significantly to get the final combustion to be at the right time. So if you disable the EGR you should re-curve the distributor or you can have pinging.

[ArdWrknTrk]

Thanks Jim, great idea to check the line for a clog, I might never have thought of that. I checked it after work and it was clear, so no dice there. I do have too much blow by though, I'm hoping it's something fixable and not more severe, but I don't remember the truck leaking at all when I first got it... which has changed significantly.

The truck doesn't have a tach or an oil pressure gauge, which is unfortunate given the current troubleshooting (not coincidentally, I bought a set of gauges last night! - summit racing has a really good deal on the intellitronix gauges ).

So estimating a high idle is totally by ear, but fairly obvious in this case. I'll look at the documentation to make sure know what I'm looking for and check out those linkages. The one thing I can say is that when the choke is on the truck never stalls, the problem only comes about when it's warmed up and the choke is off.

The EGR is just capped off, it's still present. Actually, until I capped it yesterday it was just sitting with no hose or cap. What do you guys think about removing it? I've seen the arguments for using it to cool the charge, not sure if it matters on these old engines... plus mine could have already been unhooked for decades at this point.

I think you need a regular carb spacer because you likely have a leak there.

[red1980F150]

Still sounds like it could be a vacuum leak. You may be a good candidate for the smoke test. Read here: http://forum.garysgaragemahal.com/Vacuum-leak-detection-effective-and-inexpensive-td11511.html. That will usually find vacuum leaks that you might not find another way.

But you can also spray brake or carb cleaner around in suspect areas. If there's a vacuum leak the cleaner gets sucked in and burned, which speeds the engine up briefly. But be away that the cleaner can melt paint, so be careful.

On the EGR, when they work they are good. When they don't they are bad. But you can't just block the EGR valve off and not have other problems. The inert gas slows the combustion process so when the EGR valve is supposed to be open the ignition advanced significantly to get the final combustion to be at the right time. So if you disable the EGR you should re-curve the distributor or you can have pinging.

Yeah, this all make sense. Just learning what I have and thinking it through... since the throttle is closed at idle and that prevents air from getting in, of course a leak would speed up the idle because extra air is getting past the throttle blades, right? Would the stalling at stops then be because there isn't enough vacuum left to adjust the timing correctly?

The EGR comments make sense too. I guess it might be interesting to hook a line up to it and see how the truck reacts. I read somewhere yesterday that one can test it's functionality when the truck is running with a brake bleeder vacuum, which I have. I should dig that article up (might be on here?). *Edit - found it - http://www.garysgaragemahal.com/egr-system-description--testing.html

In any case, you have given me some good homework and a few things to try, I very much appreciate it.

[red1980F150]

Still sounds like it could be a vacuum leak. You may be a good candidate for the smoke test. Read here: http://forum.garysgaragemahal.com/Vacuum-leak-detection-effective-and-inexpensive-td11511.html. That will usually find vacuum leaks that you might not find another way.

This is awesome.