96 LX d16y7
200k miles
aftermarket header

This problem started out as it would stumble and kind of die out at a stop light and sometimes in a curve or going down the road. now It is undrivable, sitting still i can rev the car real slow and it will rev up, if I jab the throttle it will bog and sometimes backfire. if you try to drive or pull off it will bog out.

When it started I had a MAP code so I changed the sensor, I have pulled and cleaned the IAC, I have changed the TPS, replaced the coil and ICM, and the main relay, plugs, wires and rotor button were done in the last 5k. The cat was melted and in bad shape so I have deleted it and installed a header.

I have rented a fuel pressure tester and have checked it, pressure is in the stock spec, 34 or so and 40 with the vacume line off the regulator. only odd thing I seen is when I rev the car slow the pressure will stay the same, if I jab the throttle and make it bog out the pressure will jump up and then back down.

I am at a loss and have no clue what else to check or try.

 

If the Cat was bad its possible its an o2 sensor problem if they have never been changed then i would suggest that be your next step. IF every thing is factory wired that is the only thing that i can think of the Key was when you mentioned header its possible sometimes on Old o2 sensors that they go bad with a little bump or if your cat was burned perhaps the 02 sensor was damaged as well. Is the vehicle running very rich? That would be another key factor.

 

The upper O2 was changed a year or so ago and the header was done about 3 months ago.

forgot to say it is not giving any codes.

 

no codes?? hmmm if thats the case it may be a Fuel filter have you changed that? it may be a Fuel pump also. Those 2 arent connected to the ECU directly. The fuel pump is but its not connected Via sensor so if its bad there wont usually be a code.

 

Check the mechanical and ignition timing. The belt may have skipped a tooth.

 

I did change the filter a few days ago.

 

Wouldn't that throw a misfire code?

 

Generally not. Backfiring is a common symptom for the timing being off. Pretty easy to check. If the mechanical timing is fine, then check the ignition timing.

I am also assuming that the plugs, wires, cap, and rotor are fine. If not, those should be checked first.

You might also want to check the fuel pressure regulator.

 

good to know> that brings up another possibility. IF your car had leaked oil or sprayed oil in the past its possible it caused what RonJ said the timing belt slipping. When you check the belt i would see if its covered in oil. If so you may have other problems on your hand. The oil pump is on the crank well just outside so you may check if you have a leak on that.

 

It would run fine just intermittent, if timing was off why would it rev slowly and be ok but not when opened up? it took a month before it got to as bad as it is now.

will be tomorrow before I can do any timing checks.

No oil leaks or spay that I have ever seen, it does not even leave an oil spot anywhere, it has always burned a little about 1qt per change and the last year up to 1 1/2 per change.


How do you check the regulator?

 

 

I have checked the regulator that way and all checked out. it has vacuum when disconnected, and once disconnected the gage reading went up.

we will check timing tomorrow.

 

also as a note,

I have checked the 3 sensors in the dizz all checked in ohm spec and none of the line were to ground.