help diagnose these symptoms

[NickDawson]

Hey folks,

I've been tinkering on my own quite a bit and learning as I go. The truck is running but there are a few things that make me suspect something is not quite as it should be:

• High revs when started and choked - some may recall my idle problem, after cleaning the fuel lines and carb jets, my solution was to increase the mixture screw. I've since backed it off a bit, but its still revving high (by ear), if I lean it any more, it stalls at idl
• Soft brakes- they are still effective, but softer than they were a few weeks ago. At a stop light my foot slowly creeps towards the floor. One pump fixes that
• Puttering sound when letting off the gas - particularly in low speed/ high torque situations like shifting from 1st into 2nd and 2nd into 3rd. Letting off triggers a rapid two or three "puffft" sounds from the exhaust
• Reduction in gas mileage - I haven't filled up yet to do the calculation, but its noticeably burning a lot of gas

So my uneducated guess is some kind of vacuum problem. I've been studying the vacuum gauge on my dash and determined that its probably worthless... it idles on the low end of idle, and dips to "drive" when I accelerate, and "decelerate" when I take my foot off the gas...
But wouldn't a vacuum problem be a proper DX for my break and idle issues?

I felt around the line between the master cylinder to were it meets a metal pipe (i'm sure there are more appropriate terms) I didn't feel any leeks - so what is the right way to trouble shoot vacuum? Do I just yank every hose and replace it? Seems cheap and easy enough. Do I need a vacuum gauge of some kind?

I have not pulled plugs to see if it is in fact running rich. We have a family event this weekend to which I would really like to drive the Rover. I'm worried that once I pull a plug it may never run again. Is there any trick to that?

As always, thanks in advance.

[LRMAN]

This sounds a lot like too rich a mixture. Check the plugs. They are very easy to get out and in again.

The brakes sound scary. I would not drive this truck until you get this fixed. Could be bad brake cylinder, bad seals on master.

[Dino]

High Revs at Start- Could probably mean your carb should be cleaned

[robert wood]

The early NADA SIII had a very wierd distributor that actually retarded the spark at higher vacuum. This was something to do with emission control but IMHO did nothing but make the motor run poorly. Take a look at your distributor and if the diaphragm assembly points forward towards the radiator buy yourself a new distributor with the diaphragm pointing towards the firewall. My personal favorite type is the Ducillier one.

If the distributor has been replaced with one as described above check that the advance/retard is actually working. You can do this by sucking on the tube and seeing if there is movement within the distributor.

If all is well with the distributor and you still get some popping when running downhill the timing may be a bit too far advanced.

Ray

[NickDawson]

Thanks guys

I'd continue to lean it out, but it stalls.

I'll check the plugs and distributor tonight - its not a NADA truck (UK import with a new-to-it 2.5L motor)

[Sputnicker]

I don't think your symptoms are all related to the same root cause.

Fast idle is probably too much choke (you only need enough to idle smoothly and not stall) and/or poor adjustment of the choke cable/linkage.

I doubt that you have a vacuum leak, but you can check by sticking a hose in your ear (no, this is not intended as an insult) and probing with the other end of the hose. You will hear a loud sucking sound when you get close to a vacuum leak.

The brake issue is serious and you should address it immediately. There is another recent thread on this. Look for leaks at all of the wheels and if you don't find anything, it is your master cylinder. A vacuum leak would give you less power assist from the servo (i.i. you need to stomp harder on the pedal) , but if it's going to the floor, you have a hydraulic leak.

My guess on the exhaust noise is either an exhaust leak or too rich a mixture. What you are hearing is unburned fuel igniting after it enters the exhaust system.

By the way, the mixture adjustment on the carburetor only works for the idle circuit. The mixture at speed is controlled by jets and is not adjustable (without changing jets). A rich mixture can also be caused by a carburetor fault like a leaky needle and seat or float level too high. An old-school, low-tech way to check mixture at speed is to get the engine nice and warm (make sure the choke is off), run at speed for a while (mile or two), turn the engine off (don't let it idle), coast to a stop (in a safe place) and pull the spark plugs. If they are fuzzy and black, or slightly damp and black, it is too rich. Optimal mixture is a very light brown, or no noticeable deposits on newer plugs.

Good luck.

[NickDawson]

I don't think your symptoms are all related to the same root cause.

Fast idle is probably too much choke (you only need enough to idle smoothly and not stall) and/or poor adjustment of the choke cable/linkage.

The brake issue is serious and you should address it immediately. There is another recent thread on this. Look for leaks at all of the wheels and if you don't find anything, it is your master cylinder. A vacuum leak would give you less power assist from the servo (i.i. you need to stomp harder on the pedal) , but if it's going to the floor, you have a hydraulic leak.

My guess on the exhaust noise is either an exhaust leak or too rich a mixture. What you are hearing is unburned fuel igniting after it enters the exhaust system.

Good luck.

Thanks Sputnicker
I'll admit, I was hoping they were related. All the the issues with the truck started on the same day.

I'll continue to work on the idle adjustment - but I'm guessing that was not that appropriate fix for my stalling problem. I suspect the jets are correct since it ran for 4 weeks with no problem.

Interestingly, the choke control used to pull all the way out, where I could see the cable - in the last week its been much tighter and more effective and my cold start light is working again.... regardless, having already tinkered with the idle mixture setting I'm guessing that it has something to do with this.

As for the breaks - I've kept my eye out for leaks - nothing around the wheels - would I see it without taking tires off?

Here's my usual question: how complicated is break work/ master cylinder? I'm constantly worried about getting into a project and rendering it undriveable

again, someone remind me this is what I signed up for and again please leave out the part about UK imports

[LRMAN]

Brake work is not complicated. A simple pump pressurizes the lines that in turn expands a hydraulic cylinder pushing brake shoes against a machined drum.

You could easily have a faulty flexible brake line. I have seen symptoms similar to yours from that. It could also be a bad brake cylinder or master cylinder. If one part of the brake system is failing then other parts are going to soon also. Don't risk your life on some basic parts.

Don't try to fix what you have. Replace all wheel cylinders, All flexible brake lines, all pads and either a new or well rebuilt master cylinder. Having the drums turned or replaced is a good idea. Flush everything and then fill and bleed. I think you will notice a difference.

If anything I have said seems complicated you may be better off trusting this to someone more experienced.

[bmohan55]

Nick, I just did all my brakes, it wasn't that hard and very educational. Replaced the Master cylinder and two wheel cylinder, turned the drums (replaced one) and new pads. Our hosts have a great "how to" in their tech section on brakes. Check the rubber lines too.
Go with a new master cylinder if needed as it's very difficult to rebuild one correctly.

[NickDawson]

Does replacing the master cylinder require replacing the servo too?
The rest seems like a stomachable price and after reading the green bible last night an approachable project (although I'm still fairly unsure about draining and bleeding the system)

I'm also not 100% sure there is a leak ... I drove around last night and put them to the test... 30mph to a dead stop = worked fine several times...
foot on the break on a hill for several minutes = truck never moved, but my foot did very slowly creep down... Although I guess in the end its sill to try and talk myself out of something that could be a safety issue.

Took it in for Va state inspection last night, secret thought is that having someone else drive it might help confirm the diagnosis. I asked them to pull all 4 wheels while on the rack, regretting that I won't be there to see it, but for $20 its worth my time to check each one in the 100 degree heat wave we are having. Of course, this assumes that they would have a clue what they are looking at.

I'll keep everyone posted - thanks for the tips.

The idle problem is still lingering, but as near as I can tell, its only manifestation is poor gas mileage