Ok I give up...

[blueroo]

So for quite a while I have had this rather annyoing problem with my car. It's most prevalent in second gear. Basically when I hit around 3300-3800RPM the car seems to "pop" like it's hitting a rev limiter.

Now, I'm not going to post the exact speed on here as forum rules prohibit it, if you have an idea of what the problem might be PM me and I'll tell you the speed. Anyhow, going up to the mountains a couple months ago the car would not go past x speed. I tried backpedaling but to no avail, it just wouldn't go past x speed. Two days later coming back from the mountains it went 13mph faster than x speed and still felt like it had plenty of room to go.

I've replaced:

-distributor
-dizzy cap
-dizzy rotor
-plugs
-coil
-PCV valve
-breather cap
-air filter style
-air filter element
-fuel filter
-gas cap
-exhaust manifold gasket
-exhaust flange gasket

I've adjusted:

-ignition timing
-valves
-curb idle
-A/F screw

The only things I haven't replaced:

-carb
-fuel pump
-oil pump
-spark plug wires


I'm at a complete loss as to what it could be and it's annyoing when it happens as it makes it sound like I don't have a clue how to drive. Any suggestions?

 

[CZLN6]

Howdy Blueroo:

What are the conditions when the condition occurs? Is the engine hot?

How old is the fuel pump? How many miles on the cam? What I'm getting at is a weak fuel pump delivery. enigne heat makes it worse. It can be the fuel pump getting tired, the eccentric on the cam that pumps the pump getting flat? If it doesn't happen when the engine is relatively cool, like just after start up, but happens regulary when the engine is hot, fuel delivery is likely the problem.

If it happens at heavy lugging check the float level in the carb. In either case, you might try raising the float level to assess what happens.

Adios, David

 

[rbohm]

8) it does sound like a weak fuel pump to me, or another possibility is a clogged fuel line.

 

[BIGREDRASA]

1.) Fuel pump. 2.) Clogged fuel pickup strainer.

My mantra is to attack the cheapest problem first. Pull out the sending unit from the gas tank, and make sure the pickup is clear. (Cheapest.) Replace fuel pump (Not as cheap.) I also believe that, with these old motors, you might as well change certain things, before they leave you stranded in the middle of nowhere.

 

[Bort62]

I'm curious as to why you can't post the speed

 

[page62]

I'm curious as to why you can't post the speed

He's probably exceeding the speed limit, which tends to be quite low in Penna...

 

[BIGREDRASA]

I'm curious as to why you can't post the speed

He's probably exceeding the speed limit, which tends to be quite low in Penna...

:nono:

 

[pedal2themetal45]

I always thought the speed limit was as fast as you could get away with. 8) Can you say WOT

 

[BIGREDRASA]

In the old days, many states had "Prima Facie" speed limits. The limit was the "Safe and Prudent" speed for conditions. The signs were there to tell you what was prudent under ideal conditions, and you could be busted for doing the posted limit in foul weather.

 

[mach1 mark]

Try changing the voltage regulator, I believe that's what it's called, the little black box that's next to the radiator.
At high speed my engine acted the same, I changed the voltage regulator and it fixed the problem. I got the idea from an article in "Mustang & Fords".

 

[mustang6]

Try changing the voltage regulator...At high speed my engine acted the same, I changed the voltage regulator and it fixed the problem. I got the idea from an article in "Mustang & Fords".

Really? I am curious what the reasoning behind this was. I would think that the first symptoms of a malfunctioning regulator would be in high battery draw functions like engine starting and headlights, not a relatively low draw system like ignition (unless you are running a MSD or something).

I'm not saying ignition isn't his problem (I would be questioning both his ignition advance and fuel delivery in this situation), but I wouldn't have guessed voltage regulator in the top 10 items to check so I am curious.

 

[Bort62]

I'm with ya Mustang6.

However, a faulty voltage regulator could cause problems at high RPM high alternator output that caused the overall system voltage to drop, leading to problems with the ignition.

But that would be slightly obscure. I certainly would not put it high on the list.

 

[ludwig]

I would think that the first symptoms of a malfunctioning regulator would be in high battery draw functions like engine starting and headlights, not a relatively low draw system like ignition

VR keeps it from spiking and troughing. Bad VR will keep the charging system from loading up the battery when it's running. It clips the spike after the engine is going and then sinks back to 11.2 volts or whatever instead of the 12V+ that tops the battery back up. Drive for 200 miles and the battery is dead. Other stuff doesn't run at full power.

 

[Bort62]

I would think that the first symptoms of a malfunctioning regulator would be in high battery draw functions like engine starting and headlights, not a relatively low draw system like ignition

VR keeps it from spiking and troughing. Bad VR will keep the charging system from loading up the battery when it's running. It clips the spike after the engine is going and then sinks back to 11.2 volts or whatever instead of the 12V+ that tops the battery back up. Drive for 200 miles and the battery is dead. Other stuff doesn't run at full power.

Right, a bad VR will result in being stranded on the side of the road.

An intermittant VR will result in occasional problems, especially with things like headlights.

I don't see either directly affecting the ignition as it will run at a much lower voltage than anything else.

IE< if your regulator was crapping out and your battery dropped sufficiently low to cause problems with ignition (at any rpm), you wouldn't be able to get it started again once you shut it off.

 

[MustangSix]

Hitting a limit at a particular rpm and load leads me to believe you are running out of fuel. One other thing I would do is to pull the fuel sender and pickup to see if the sock is clogged.

 

[66 Fastback]

I am curious how high the elevation is of these mountains and what elevation do you normally drive at.

What do you mean when you say "pop"? Is the ignition cutting out?
Does it occur at the specified rpm on level ground or is this only when going up hill under a bigger load?

Can you give carb, distributor type, timing, tranny and axle info?
Doug

 

[blueroo]

Carb: Reman 1100 (aka crap but it gets the job done)
Dizzy: Reman (and actually a good reman) LOM w/5-16" shaft and Ignitor I ignition
Tranny: T5 tag #1352-162 (3.97:1 first, 0.78 OD) <problem was also there with stock 2.77 trans>
Axle: 8inch open diff, 3.50:1 gears
Timing: I forget exact timing but I'm getting 22in vac at idle (650rpm)

As for it being a heat issue that's where it gets odd. At first startup after having sat at least 2 and a half hours the problem is really bad. As the motor warms up it goes away somewhat but not entirely.

In neutral there's no problem, only under load.

I forget elevations but when I went up it was late at night (left town at 7PM, arrived in Potter around 130AM) and it was giving me a huge fuss. Two days later coming home around late morning/early afternoon it was running insanely well

To describe it is a bit a hard. It's almost like a high speed bogging mixed with a misfire. It's not loud like a backfire though.

 

[ludwig]

If you have the carb plate on the intake manifold with the cooling hoses disconnected, hook them up again. There is something about having a consistent temp, even if it is high. Some people say this helps performance.

You might be getting some heat soak when it stands still for a short while. Then it warms up by conduction, but not consistently and not as high at night or on a cold day. The heated coolant water makes it all the same each time.

I have never had this problem but some have written about it.

FWIW, I had a carb that worked fine when it was cold, but when it got really hot, the body or the shaft or something would expand. There was an irregularity in the casting, or a piece of flash or a bump or something on one of the shafts, and it would start to pinch down on one or the other moving part that otherwise would move freely. New carb solved the problem.

 

[Bort62]

Carb: Reman 1100 (aka crap but it gets the job done)

Well, I think the evidence might suggest that it is NOT getting the job done.

 

[wsa111]

Sounds like fuel starvation & possibly valve float.
Run a fuel pressure test @ WOT.
What rpm is the engine flattening out??
Hook a voltmeter up during driving & check for over 13.5 charging voltage.
these test will reveal the problem. Bill