Hi. I'm new to this forum and was hoping someone had some ideas. This is a long story so please be patient and hold on. I bought this truck in 97 and have used it quite heavily and now have 252 000kms. About a week after I took it on yet another heavy load test 1000 in the box and 1500 behind, not including the heavy trailer (no signs of anything going wrong- strong and powerful) the engine started sputtering on the hwy- loosing power then kicking in again etc. I made it home but was anxious because my new employer wanted me at work dam it! He told me to put some gasline antifreeze in (it was the first frost of the season) and continue the 2 hour trip to meet him. I kick myself now because I got back in my truck, followed his instructions and continued. It coughed and sputtered all the way- but I made it. I left it at mechanic #1 who didn't have the proper diagnostic equipment but replaced the fuel filter and said it seemed a little better and indead it did seem different. After a few minutes it started doing the same thing again. At idle it would run, roughly mind you, and if I stepped on the gas it would just want to die before increasing in rpms. I left for home (2hours) and the engine overheated on the way, the temp. gage only showed slightly warmer than normal so I didn't worry. I made it home and took it to Mazda.
The dealer (mechanic #2) put it on the diagnosis, of course, and told me after that they were 99 percent sure that the head was either cracked or warped because the engine had over heated. Their diagnosis was: coolant low-3 litres, engine oil low, rad fan clutch inoperative, plugs contaminated, engine running rich, low compression, suppect head cracked, worn rings and colapsed pistons, converter plugged, front pipe and inter.pipe broken, o2 senser inopertive, fuel presure leaking down, possible cause leaking injectors or leaking fuel pump.

Now I thought, it's dead and went to sell it (with full disclosure of course) The guy who bought it from me came back a day later and said he had good news and bad. He decided that he didn't want it because of an unexpected financial situation. The good news was that he said he knew what the problem was- a new radiator cap! So, off we went to Canadian Tire and picked one up. It seemed to make it run better but I think that it was just a separate problem. Being the nice guy that I am I took the vehicle back. This was a year ago and I've since had it to another mechanic (mechanic #3) who said that the fuel pump presure was 4lbs cold and 38 and 42 running, the compression is 170, 150, 190, 142. He checked the relay it was fine, switched the regulator from his truck same truck, same problem. He thought that it needed decarbonization and a valve job and I should check the fuel pump.

I've since checked the fuel pump, it turned out to be a GM pump that some other mechanic had stuck in 30 000 k's previous. I tryed another pump just like it and same problem. I've also, replaced the wires, plugs, rotor, checked the coil etc. and still same problem.

The last 2 mechanics said they didn't think that my head was cracked or anything like that as there is no sign of anything in the oil and ever since I replaced the rad cap no leakage of coolant. Last fall I ran the truck for two weeks- about 1000 kms because I really needed it even though I would only get 150 kms on a tank and it ran consistantly- it was just hard to start and keep running but once it ran it continued. Now after sitting the winter, I can't even get it running.

The truck was running perfectly before this problem surfaced over a year and a half ago. Since I'm a little stubborn (ok...maybe a lot) I really want to find the problem. Thought maybe next to blow out the gas lines? Check the injectors for leaks? Put in new seals?

Can I put in my neighbors 1990 automatic 2600i engine with automatic transmission even though mine is a 1992 manual? Can you tell I'm not a mechanic?

Any ideas? Maybe just some headaches after this read?