My US fzj80 with about 220K is stumbling off idle. When I first start her up she will fast idle just fine for about 10 seconds or so and then when the fast idle drops she starts stumbling and barely running. If I try to depress the throttle she will stumble further and practically die. If I feather the throttle and play with it lightly sometimes I am able to increase the RPM above idle but even if I can get the RPM up above 2K she is still breaking up while up there.
Some background information, The car has been sitting for roughly a month while I did the oil pump seal. The oil pump seal was a bear and I had JIS bits breaking off in the screw heads (yoda should have used torx! ). The problem seems to have occurred upon the first startup after the oil pump job was complete. The truck was not perfect before I started the oil pump job. The truck would idle fine and run fine under light throttle conditions but break up if pushed hard. My plan was to stop the huge blood loss from the oil pump and then troubleshoot the WOT break up while I was using the truck daily. Alas now she will bearly idle.
So far I have:
1. Inspected all the vacuum lines and the intake rubber from the MAF to the plenum. No Visible leaks.
2. Shot starting fluid all around the intake/ vacuum lines and intake area from the MAF downstream. No change in idle.
3. Shot starting fluid straight into the air filter to see if that would make a difference in idle. Oddly it did not.
4. Inspected the wiring including the harness by the EGR. All looks good.
5. Disconnected and reconnected also wiggled various connectors to the distributor and other components to see if that would make a difference. It did not.
6. Pulled the EFI main relay in the fuse area on the driver's side inner fender while the car was running to see if that made a difference and the car immediately died.
7. Pinched the Vacuum line going the Fuel Pressure Regulator. No difference. Pinched the fuel return line from the FPR. No difference.
8. Removed the return line to the tank from the FPR and replaced it with clear tubing to a jerry can and started the engine. The fuel will flow out of the FPR at a moderate rate with some air bubbles in it.
9. Removed the Vacuum line from the FPR while the engine was running and clear tubing still connected. The fuel would stop flowing from the FPR indicating to me that the FPR is functioning properly and blocking all return fuel when Vacuum is not present. Again none of this made any difference to the way the truck runs.
10. Changed the hi-tension lead from the coil to the distributor cap which looked so so. No difference.
11. Changed the distributor cap and rotor. No difference.
12. Checked for codes. (I actually did this in the beginning but did not want to reorder my list PO300 Random/Multiple Cylinder Misfires detected. Then PO301, PO302, PO303, PO304, PO305, PO306 For Cylinder #1 through #6 Misfire detected respectively. (I said to myself No $hit Sherlock
My gut instinct from the very beginning is this is a fuel pressure issue but I don't see a way to check the pressure. The fuel pump is obviously working somewhat or else the car would not run at all. The fuel pressure regulator also seem to be working from my crude tests above but maybe the fuel pump is not making enough pressure?
With that said can anyone link me to a part that will go in between the FPR and the Fuel Rail with a schreader valve on it so I can put a standard fuel pressure gauge on the rail? Is there any other way I can test the fuel pump or drive it harder to see if that will solve my problem? just a FYI the fuel pump has already been replaced once on this truck when it had about 120K miles back in 2002 when the pump failed on me in New Hampshire at the Yankee Toys Fall Gathering.
Does anyone have any other suggestions as to where the problem may lie? My next steps to kill time while I wait for your response is to pull the plugs and take a look at them. I may even change the wires as I have a spare set on hand but I really doubt if all 6 wires could fail at once.
Thanks and regards,
John
Some background information, The car has been sitting for roughly a month while I did the oil pump seal. The oil pump seal was a bear and I had JIS bits breaking off in the screw heads (yoda should have used torx! ). The problem seems to have occurred upon the first startup after the oil pump job was complete. The truck was not perfect before I started the oil pump job. The truck would idle fine and run fine under light throttle conditions but break up if pushed hard. My plan was to stop the huge blood loss from the oil pump and then troubleshoot the WOT break up while I was using the truck daily. Alas now she will bearly idle.
So far I have:
1. Inspected all the vacuum lines and the intake rubber from the MAF to the plenum. No Visible leaks.
2. Shot starting fluid all around the intake/ vacuum lines and intake area from the MAF downstream. No change in idle.
3. Shot starting fluid straight into the air filter to see if that would make a difference in idle. Oddly it did not.
4. Inspected the wiring including the harness by the EGR. All looks good.
5. Disconnected and reconnected also wiggled various connectors to the distributor and other components to see if that would make a difference. It did not.
6. Pulled the EFI main relay in the fuse area on the driver's side inner fender while the car was running to see if that made a difference and the car immediately died.
7. Pinched the Vacuum line going the Fuel Pressure Regulator. No difference. Pinched the fuel return line from the FPR. No difference.
8. Removed the return line to the tank from the FPR and replaced it with clear tubing to a jerry can and started the engine. The fuel will flow out of the FPR at a moderate rate with some air bubbles in it.
9. Removed the Vacuum line from the FPR while the engine was running and clear tubing still connected. The fuel would stop flowing from the FPR indicating to me that the FPR is functioning properly and blocking all return fuel when Vacuum is not present. Again none of this made any difference to the way the truck runs.
10. Changed the hi-tension lead from the coil to the distributor cap which looked so so. No difference.
11. Changed the distributor cap and rotor. No difference.
12. Checked for codes. (I actually did this in the beginning but did not want to reorder my list PO300 Random/Multiple Cylinder Misfires detected. Then PO301, PO302, PO303, PO304, PO305, PO306 For Cylinder #1 through #6 Misfire detected respectively. (I said to myself No $hit Sherlock
My gut instinct from the very beginning is this is a fuel pressure issue but I don't see a way to check the pressure. The fuel pump is obviously working somewhat or else the car would not run at all. The fuel pressure regulator also seem to be working from my crude tests above but maybe the fuel pump is not making enough pressure?
With that said can anyone link me to a part that will go in between the FPR and the Fuel Rail with a schreader valve on it so I can put a standard fuel pressure gauge on the rail? Is there any other way I can test the fuel pump or drive it harder to see if that will solve my problem? just a FYI the fuel pump has already been replaced once on this truck when it had about 120K miles back in 2002 when the pump failed on me in New Hampshire at the Yankee Toys Fall Gathering.
Does anyone have any other suggestions as to where the problem may lie? My next steps to kill time while I wait for your response is to pull the plugs and take a look at them. I may even change the wires as I have a spare set on hand but I really doubt if all 6 wires could fail at once.
Thanks and regards,
John