Please Help. Sudden Huge MPG Drop After Mechanic Worked On ...

Not that this will solve the problem, but this should point you in the right direction. It sounds like your car is stuck in 'cold' mode. When a car starts, temp sensors tell the engine computer that the car is cold, so the computer runs a cold mode program. This program basically has the car running very rich, so you get lousy mpgs in cold mode. As the car warms up, the computer eventually swithes to normal run mode, where it now relies on the O2 sensors to get the ideal feul and air mixture for optimum operation, and hnce better mpgs lower rpms and better power.

That 'hitching of a trailer' feeling follows this path. Your car is warm, but the computer still thinks it's cold, so it still runs the cold mode program, and running cold mode on a warm engine is even worse than cold on cold. Running rich really loses power now.

I think your feul injectors may never have been the problem and you need to find a new mechanic.

Hope this helps.

CD

Wrong/cheap injectors and not replacing all of them as a set. First, unless you used factory injectors and the originals are in perfect condition, you now have a mismatched set of injectors that very likely deliver different amounts of fuel to each cyl. Also many of the aftermarket injectors spray like a squirt gun rather than a fan spray pattern. Until these are replaced with a -set- of good/factory injectors, I doubt you'll ever get the car to run right. Sounds like he ran into a mixture distribution problem with the few "new" injectors and tried to cover it up by richening the fuel mixture.

Also what sort of tuneup parts were used? Bosch platinums can make these cars run like total crap as well. You need to find someone who knows about these old straight 6 datsuns, like a Z-car shop.

Thanx for your reply. Two of the injectors were leaking fuel onto the engine creating a smelly, not to mention a hazardous condition. So, they had to be replaced, no question. The same thing happened two years ago with two other injectors, so this time I told them to do the remaining four. One of them turned out to be faulty electrically, or so he said. By the time he figured that out, too much else was touched. I doubt that replacing the other parts, however unnecessary it was, is the cause. Something else was touched, changed, or manipulated in some way (OR) the faulty injector is still bad despite the mechanics efforts to fix it himself. When the weather is very cold, it spits out a ton of smoke, never hits the fast idle and is very rough (RPM about 1000-1100 constantly, hot cold you name it). You can floor the car and it barely moves. Today, it did the same thing, stalled out, and I've not been able to restart it at all, even after waiting in 1/2 hour intervals. Cranks, sounds very close to catching, but never does. Fortunately, I was at home when this happened. But, it looks like I'm screwed now. Winter is only starting.