Once its pumped up leave the gauge on till morning im sure my 94 held all night.

 

Install a fuel pressure gauge. Cycle the key on and off to get the highest pressure. The spec is 43.5 psi. 41 psi is too low, 47 psi is too high according to the FSM.

Start the car, it should read 3 to 10 psi lower than what it read in the test above.


Think of how it works. With the engine running at idle you have full vacuum to the pressure regulator which lowers the fuel pressure. At WOT you have no vacuum to the regulator, same as if you disconnect the vacuum at idle.

And after doing the first test again, the pressure will drop an unspecified psi (not more than 10 I'd suspect) then hold.

This is the first step, if it falls within spec it should be ok.

 

Thanks for walking me through it. It's starting to make more sense.
Here is what I found out tonight:

Key ON, pump running - 43 psi
pump stops - 41 psi
Then at 5 minute intervals - 39,35,31,27,23,20,17,16,15,14,12 psi
1 hour later - 12 psi

I'm leaving it on tonight for antfarmer2 to see if it holds until morning.
Tomorrow, when I can start the car up and rev it without bothering anyone, I will do the running test as you said and check the pressure. I will make sure to pull the vacuum from the fuel pressure regulator and see how/if it changes. If you think I need to test it while driving, I will do that too.

 

Update 2:

I checked spark plugs and spark plug boots and all are secure.

Today, I learned a lot more about the EGR and secondary injection systems, trying to find a possible cause for my recurring oxygen sensor failure. I found a thread discussing how a compromised Secondary Air Injection system can lead to sputtering or after-fire during deceleration due to cold air being sucked into the hot exhaust pipes. I get a lot of sputtering, so I did more research and found a post about Secondary Air Injection check valve failure. It makes sense to me that if the valve remains open, then cold air can be sucked straight into the exhaust manifold causing both a lean reading and the sputtering. So I did as the write up said and cleaned both check valves with carb cleaner then some WD40, hoping that they will work properly now.

My plan for tomorrow morning is to first listen to the car dead cold for any exhaust leak around the manifold.
Next, I will replace the O2 sensor that is throwing the lean condition code, which is probably coated with carbon, so that I can get the car running better (at least temporarily). I want to avoid possibly damaging the catalytic converters due to the car being so rich (thinking it's lean).
I will also verify fuel pressures with the car running and after removing the fuel pressure regulator vacuum line to hopefully rule out the fuel system as a cause.

Thanks everyone for all the help so far. I will update again tomorrow.

 

Sounds like a leak compared to mine on the fuel pressure keep us posted and becarefull shutting the hood with the gauge some have cracked their windshield.

 

I am going to pick up a vacuum pump tomorrow to test the EGR solenoid and the evaporator purge solenoid, which I did not know existed until now. Thanks!

 

I think your fuel pressure drop is too much.

 

Update 3:

This morning, I started up the car when it was cold and used my funnel-hose stethoscope to listen for exhaust leaks around the manifold and heard no tapping sounds.
Next, I replaced the oxygen sensor (picture below), which was coated in carbon as I suspected. I test drove the car afterward and it has its normal amount of power, since I've known it anyway, and no Service Engine Light.
Finally, I checked the fuel pressure with the car up to temperature and running:
At idle: 35 psi
Removed FPR vacuum: 45 psi and a hissing sound from the FPR.
Shut off engine: 38 up quickly to 42 psi and held there for a few minutes.

On the way home from work today I will pick up a vacuum pump so I can better test the EGR and evaporator purge solenoids for leaks and anything else you guys can think of. Thanks for sticking with me. I hope to get to the bottom of this soon

 

If you have a cylinder misfiring it will show as lean and add more fuel. Remember it is an oxygen sensor, it does not see the extra fuel in the exhaust, only the unburned oxygen. Pull your plugs and read them.

 

Alright, I will do that and post a picture when I get them out. I'm guessing they will be covered in carbon like the oxygen sensor was. But will this be the source of the problem or side effect, like the oxygen sensor failure is? Could a vacuum leak or pre-O2 sensor leak cause a lean condition, increasing fuel at the injectors and fouling the spark plugs/o2 sensor? Is there anything else I should check that could cause these symptoms?

I appreciate the help. I'm learning a lot from you guys and hope to get my car running well soon.

 

If you can get it good and dark look for arching and sparking under the hood. and when you pull the plugs out check the gap there can be a little puck that can come off

 

Alright, I pulled out a couple plugs and here is how they looked. I pulled them all out not too long ago to check the gaps (I hadn't gapped them the first time, believing the "pre-gapped" on the box - which they were pretty close), and I remember them all looking about the same. I can tell there is some carbon build up, but not enough to interfere with spark it seems. I don't know much more about reading these, so what do you think? Should I go buy another set?

 

UPDATE 3:

This morning I tested the EGR solenoid and the evaporator purge solenoid, and I think they are both leaking!

I put the vacuum pump on the purge solenoid with the car off and it did not hold vacuum at all. Everything I've read says it should be closed when off and open when the computer sends it power. So, I'm going to replace that.

I pulled off the EGR solenoid and it too leaked vacuum (slowly but significantly). I hooked it up to the battery and it clicked on and open (held no vacuum at all), so I suspect it should be holding vacuum without power to it. For that reason, I'm replacing that as well.

That could be two sources of vacuum leak causing me to run lean and richen up my air/fuel mixture and subsequently foul my oxygen sensors. Does that sound right to you?
Now, there may be more vacuum leaks I don't know of so I may (carefully) test that with propane or carb cleaner before I call it a day.

I am going to pick up both solenoids and an oxygen sensor for the right bank as I presume it is fouled and going to cause me problems sooner than later. So I'll have replaced both at the same time and can monitor them better down the road.

I'll update with the results. I'm heading to the parts store now, so let me know if you have any other suggestions and I'll just run back over there.

antfarmer, I need to check for arcing tonight when it gets dark. I may get one of those light bulb sensors too that test that spark is getting to your plug from the boot.

Have a nice Saturday everyone, Evan

 

UPDATE 4:

So, I replaced the passenger o2 sensor, so both are new now. I also replaced the evaporator purge solenoid, which was faulty. I just test drove the car, and man it has some power back! Probably more than it ever has since I've owned it..

Now I am concerned about that EGR Valve and Solenoid. The valve trickles down on vacuum when the car is off, and it holds no vacuum with the car on. I looked at the link provided earlier and followed the directions below. If these are right, then I think the EGR valve I bought is bad. The solenoid may be too, but I'm not sure if it is supposed to hold vacuum or not. Anyone know?

Edit 10/09/2015:
I have had no further issues with O2 sensors going bad. I believe my problem was either leaking fuel injectors, the evap purge solenoid, or changing one O2 sensor instead of both. Since I have fixed all these issues, it has been 4+ months without a code.