Mazda Forum - Mazda Enthusiast Forums

I don't know if it custom to give a new person hello to the forums here or to just get to brass tax. So I would like to say thank you to anyone in advance who takes the time to read this and offers any advice or knowledge they have. My area of expertise is with PC's and so this is all somewhat new to me. I am from the American Midwest and I am really trying to fix my Daughters truck.

I looked through the forums. I have done a huge amount of research, testing and work.I can't find this specific problem anywhere and I am going to be forced to sell this truck in less than a month If i don't find a solution...It was a present for my daughter too. Right now I am loaning her my car. So here we go:

Mazda B2600i 2.6 liter the ECU is marked "G618". It is fuel injected and it has an automatic transmission. I will give any other specs I can determine upon request.

The truck was driven about 12 miles along the highway one night after running fine for months, it was turned off that night and the next day it would not start on its own.

First the symptoms:

The truck will not provide codes

The truck will never start on it's own. Spraying starter fluid in the throttle body where the intake air hose mates up to it, replacing the hose, tightening it and turning the key will start the truck every time. (I Don't put starter fluid where it will cross the MAF)

It will not idle on it's own after it is started. I must hold down on the gas peddle just enough to keep the rpm's in the 1500 range until it warms up ( can go higher with the rpm's but not much lower) . Once it reaches operating temp it will idle on its own at 750 rpm's in park without issue.

In idle after it is warmed up the engine is very responsive to the gas peddle and will increase in rpm's according to pressure with only one problem : a slight touch will cause the motor to stall. A full (or at least a heavy ) press of the peddle will cause the engine to raise in rpm's accordingly.

Once the truck is placed into gear, (I stress it must be warmed up fully or it will die the moment you do so) The rpms drop to just about 600 and the idle becomes very rough. If the gas peddle is very slightly touched the truck will die. If the gas peddle is pressed about 1/6 to ¼ of the way the truck accelerates, poorly. I have to let off the gas very lightly to help the truck shift as well, it will shift, but it does it at around 2000 rpm's if I let up a little, but at about 2500 if I don't. The shifting is smooth and it goes into gear smooth.

Pressing past about ¼ of the way down on the gas causes the truck to start struggling, pressing about an 1/16 on it will cause it to die. In between I can get some use from it, it will go and I do drive it... with difficulty.

There was backfiring occurring, that stopped when the MAF was replaced.

The exhaust smells rich.

Now the steps we have taken:

The coil was tested and it's strong and functioning properly. All of the plugs are firing and there is current in all of the wires. There is no “flashing” when under smoke and/or in the dark. The distributor looks good and the plug leading to it is solid. Since Idle in park is fine it does not seem to be a timing issue.

The mass airflow sensor was replaced.

The battery was replaced.

The O2 sensor was replaced.

The catalytic converter was removed and replaced with a straight pipe.

The fuel filter was replaced.

The truck was drained of gas and refueled several times now.

All repairs and replacements were done after the problem started.

The intake air charge sensor was pulled and tested, under heat the resistance drops accordingly the wire leading to it with the key in the on position was reading 4.8 volts.

The water temperature sensor was tested, under heat the resistance drops accordingly the wire leading to it with the key in the on position was reading 4.75 volts.

The throttle body was pulled and cleaned. The solenoid in the throttle housing was cleaned with MAF cleaner and seems to operate fine. The fuel pressure was checked, the spray pattern of the injectors as well as their pressure was checked, the fuel pump was checked. All tested out fine.

I cannot get the throttle position sensor off of the throttle body housing it's stuck, tight. But what I can see from research makes me think that is not the culprit but I am open to being wrong about that if anyone else thinks it could be.

I am not a mechanic and this has been a crazy undertaking so far, but I feel like there is some piece of specific info I am missing that might solve the problem.

My back is against the wall, if anyone can postulate any reason that this might be happening I would dearly appreciate it because it has me in a really bad spot.