Locomotives run badly

1.How about some model numbers of the trains you are running?

2. Conventional or command control?

3. Type of track and transformer?

4. Wire size and # of track connections?

I think that the advice given above is spot on, yet I would start with question #4 first.

Having just built, with the help of the Members, a large 5x10 layout, using used track and older postwar  engines, I had the same types of sporadic problems that you are having.

So, I put 8 sets of power wires into the tracks, evenly spaced, using sets of 18 gauge wire.  I pulled every track section apart to inspect the pins, and if they were rusty or corroded I pulled them and replace them with new pins.    If a piece of track looked poor or the openings in the rail ends looked too old or stressed, I replaced those sections.   I then went section by section and tightly crimped every track joint, using a set of O Gauge crimp pliers.  And, I made sure that I really screwed the track sections down into the board tightly, although you probably only need two screws per track section, one in each end, staggered.

Guess what?  All of my sporadic running problems totally disappeared.

If you only have one set of power wires running to your tracks, then it only takes one poor connection between dozens of rail pin connections,  or one poor soldering spot in your power attachment, or one end of a track section being loosely screwed to the board, to give you running problems.

Now, with just an oval, you probably don't need 8 sets of power wires, but I would definitely do 3 sets. 

(No, the metal rollers don't need to be  replaced after a few hours.  They should last for years.)

Hope this helps.

Mannyrock

Some engines are simply more susceptible to power (voltage) losses than other engines, so the fact that some run fine does not necessarily eliminate power losses as a cause and, based on your description of what is happening, that is the first place I would look.

Cleaning the track, rollers and wheels is a good start but the easiest way to discover power issues is to take (or purchase) an inexpensive digital voltmeter (DVM) and turn the knob to AC volts (probably 200) and then take the meter probes and touch them to each section of track on your layout (red probe to center rail and black probe to outer rail) and observe your readings. If there are areas of the layout that show decreased voltage readings from what you have your transformer set at or are markedly lower than other sections, you've found your problem and can add additional power connections around the track and re-test.

If the DVM readings show correct and consistent voltage readings all around the track then you have eliminated power loss as a potential issue and the problem lies elsewhere.

You cleaned the pickup rollers and the track, but you also need to clean the wheels since they are part of the continuity equation.

You asked about pickup roller replacement.  They should not need to be replaced until after many, many years of operation.  But they do need to be lubricated to keep them rolling smoothly.  A drop on each side of the roller.

@BamaRider posted:

My track is a oval 4x8, no switches or anything complicated.

Units will idle with sound and lights, but give it the gas it will lurch and shut down.

So some things are easy to check. Do you have a lighted car or caboose? Do you have a meter?

You can test the rails for power around your loop to see if the power is dropping out. A better test is when there something drawing power near where your testing. That shows if there's some poor connection.

So is this track screwed down permanently? Has it been taken apart? What brand and exact type of track?

Lionel Fast track for example just requires some squeezing to restore good contact at the connections.

What type of wire and how many connections?

Have you lubed each engine properly? Look at the manuals!