Hi all, this is one for the mechanically minded. Please read carefully.
I will do my best to describe the problem.
The car is a 1995 Mitsubishi Magna TS 2.6L carb model
sedan, 5sp manual with 378,000km.
When the engine is cold (i.e. within 5min of initial start-up), and under light to moderate acceleration, the car will start to severely kangaroo-jump usually around 70-80km/h in top gear. It will do this in lower gears and speeds as
well. Normally to temporarily overcome this problem, I would push the clutch pedal in, let the engine recover (it will usually climb to 2,500 RPM), pump the accelerator a couple of times and then resume driving. This process can repeat a few times in a short period. Actually it will do this *sometimes* even when the engine is warm (not hot), but more when it is cold. However, when the engine is hot and when driving on flat roads, even under heavy acceleration, the engine performs flawlessly. BTW, I have confirmed that the choke valve opens when the engine is warming up in the driveway.
Then the other side of the saga is this. When climbing a very steep (20% gradient) road, the car again will start badly kangaroo-jumping and then completely die. But the strange thing is, is that I can restart the engine normally. That is, the engine will start immediately without pumping the accelerator. Now, this is all happening when the engine is hot and the choke is open.
In January we decided to get the engine rebuilt because it was getting tired and I mentioned to the mechanic that I suspect this particular problem is carburettor related and I asked if he could look at it.
Well, he got the engine rebuilt fine but admitted he did not look a the carb. I wasn't amused. And after having to fix a couple of other things after him, I have decided not to entrust the car to him again. So I'm trying to get this problem solved on my own or going to somebody else. I do have moderate mechanical experience so I'm not a complete dumbass =) but this problem really has me beat. I am suspecting the carb. float/needle valve. I have repaired carbs before on older vehicles, but have never encountered this problem.
I replaced the fuel pump just under two years ago, so I don't think this is the cause. I also blew out the fuel lines/return lines and installed a new fuel filter. The air filter is also still serviceable. All the vacuum hoses are currently connected properly in their particular order. Actually I had to correct the hoses because the mechanic muddled them up when reassembling the engine. The result was that the air conditioner idle-up was not working. I had to follow diagrams in my service and repair manual to re-route the hoses and fix the problem.
So, after spending $4000 I have a virtually new engine (which I am pleased with), but still the same old problem which is not getting better.
I hope this makes sense. I don't think I have left anything out.
Any help will be greatly appreciated.
Thanks, Tim.