Holden Ute Range

It’s very likely you have at least two distinct things going on here. While it’s not uncommon for the contents of a car’s radiator to appear murky or dirty, that’s not usually something that would trigger a check engine light. If the radiator is filled with tap water (not a good thing) then it can soon become rusty and dirty to the eye. It will still cool the engine, but you’re much better off with the correct type and grade of coolant to protect the engine from corrosion.

As far as the check engine light goes, you could be looking at literally hundreds of causes for this. The check engine light is telling you that something is not quite right and that you should have the car scanned at a workshop. That way, the computer can tell the mechanic exactly what’s going on and what needs to be checked, repaired or replaced. Until you do that, you’re effectively flying blind.

People often complain about the complexities of modern cars, but the ability to plug a diagnostic probe into a car and have the vehicle tell you what’s wrong with it is, indeed, worthwhile progress.

Any excess smoke from a diesel engine can mean a too-rich mixture. So are you certain the injectors are the correct ones for that engine? Has a sensor been bumped during the replacement process that is not sending the right signal to the computer that controls the injection on a modern turbo-diesel?

Also, cold-start problems in an engine like this are often traced to the glow-plugs. These are crucial to warming up the cold engine internals so that combustion will take place. So perhaps a check of the glow-plug wiring is in order as this could have been disturbed while the injectors were being replaced.

Has anything else been changed or replaced as part of this process? Has the engine been sitting for an extended time (allowing the fuel to go stale)?

The reason you can’t start the engine in second gear is for safety reasons. Car makers fit what’s called a Neutral or Park switch, which means the engine won’t crank unless the car is in Neutral or Park. That prevents the car starting in gear and taking off.

If the lever’s connection to the transmission has failed or become excessively worn, you can get the symptoms you have because the lever won’t select Neutral or Park. And therefore the engine won’t start.

However, it’s highly questionable that this is connected to the limp-home mode. That’s usually caused by a problem with the driveline that threatens to do more damage if you continue driving. The gear lever problem sounds more like a simple mechanical issue. Did both things happen at the same time? If not, they’re very probably not related.