I started the sea foam treatment today when I got it to idle.

 

Fuel Pressure for D?C is supposed to be 49 psi I believe.

Also, random misfires and not being able to rev past a certain point can also be a clogged Catalytic converter as well. It can cause multiple cylinder misfires and keep the engine from revving as the exhaust can't get past the cat and backs up into the cylinders.

 

good point AIM you beat me to the punch. I recently had my cat checked at Wharton County Tire in Wharton, TX for only $10. Roy make a small hole in each of the inlet pipes going into the cat about a couple of inches in front and then one aft of the cat about the same distance away. He had one of the mechanics get in my truck and start it , he then stuck this measuring device that resembled the cross between a temp probe and a tire gauge into the top inlet hole and had the mechanic rev the engine up high, he repeated this step for each hole and rechecked it a couple of times. He told me my cat was in great condition with only 1Lb of back pressure. He then welded the holes closed and checked for leaks. He said in some cases the back pressure is so strong it would blow the gauge out of the holes. Hopefully this helps.

 

You guys are geniuses. "If it wasnt for losing such dam fine enlisted men, I would promote the both of you to officers"

Seeing your post last night got me thinking, I've been looking for an excuse to purchase the harbor freight Infra red thermometer, if not now when... While u guys were beating each other to the punch, I went to U tube and found out how to check the other 3 ignition components IAC, MAP, TPS. All I needed was a small hand vacuum pump to proof the MAP. So I added that and a S&^% load alligator clips to the HF shopping list. I'll post the how to and results on those tests in a later post.

I started the truck let it warm up a little and ran him up to 1500 rpm (all u can get with out break down) Using my new toy I measured the front of cat ~400F then moved to back of cat ~200F!. Went to tail pipe (never thought to do that before) prety weak exhaust flow. Checked my ford explorer temperatures were almost even front to back. My new plan is to remove the front O2 and limp it to Cat Man Do, that is of course unless the brain trust has a better idea...

Thanks again fro your help

 

Here the scoop on testing the sensors a lot less expensive than replacing with new component. For further info go to utube and search "IAC valve test"

Component:
Throttle Position Sensor (TPS) - Remove engine harness plug from sensor, Put digital multimeter to the 20K ohm scale, connect one lead of the meter to the center prong of the TPS and the other to outside prong of sensor (the sensor has three prongs doesnt seem to matter which outside one is used). Now open and close the throttle while watching the the meter u should see a smooth run up and down in resistance, there can be no gaps or breaks where u lose the reading. If the resistance is constant your good dont buy a new TPS. I also taped the sensor with a screw driver while holding the throttle open to make sure the resistance didn't jump around.

Manifold Absolute Pressure (MAP) Sensor: The sensor has three prongs: 5vdc, output to Powertrain Control Module (PCM) and ground. remove sensor from Throttle Body (TB), connect the sensor to the engine wiring harness plug, and attach a digital volt meter (~20vdc scale) to the middle green wire of the MAP sensor engine wiring harness (I used an alligator clip to pierce the insulation about 2" back from the plug so I could tape it later) . then connect a hand operated vacuum pump ($20 harbor freight) to the MAP vacuum port. Turn key to the on position dont start the engine, observe the volt meter readings as u apply vacuum to the MAP. My readings: 0 inHg = 4.73vdc, 5 inHg = 3.83 vdc, 10 inHg = 3.07, 15inHg = 2.13 vdc & 20 inHg = 1.23 vdc. Let it sit at 20 for a while (30 seconds) to make sure it holds, also tap to make sure the reading remains stable. Sensor should show ~ a 1 volt difference per 5 inHg of vacuum. I declared mine good based upon the above results.

Idle Air Control (IAC)" The IAC is a small motor that operates a plunger in the TB to control engine idle air flow. The IAC has four prongs (connection points) two are 12 vdc for the motor and two are a set of contacts (I think as I could not get mine to run and operate the contacts) anyway the test is to apply 9 vdc using a small 9 volt battery to the motor and observe plunger operation, reverse the polarity and the motor will run in the opposite direction (Plunger in - Plunger out) . If motor runs and contacts open and close ur good.
there are a few on truck test like putting on max ac while at idle, the idle speed should increase if IAC is working right. My test was not good so I might spring for an IAC after I get back on the road.

thanks again for the help, this is a great site!

 

Pulling the front sensor sounds like a plan. You entered some excellent troubleshooting information above. I'm bookmarking it for future use.

 

Thanks for the info and the compliment. This old combat Marine appreciates it. We don't often get to many thanks so Semper Fi and OO-RAH!

 

Got the cat replaced, truck runs nice.
End of story.

 

there is actually two other ways to test the IAC and the TPS

TPS- back probe the connector with it plugged in, turn the truck on and check the voltage. have your multimeter set to 20v dc and put the negative in the left wire (theres only 3) and the posative in the middle wire, it should read 5 volts. pull the posative and put it in the right wire and it should be somewhere around 1 volt, rotate the throttle and you should see it smoothly climb up to 4.5 to 5 volts, if it does then you're good, if it goes over 5v then there is a problem and if it doesn't increase smoothly (1.2, 1.3, 1.4, 1.5 etc...) then there is a problem.

IAC- remove it (2 torx screws) and leave the connector plugged in. then have a partner turn the truck on, when the key gets turned you should see the plunger move up and down, if it stays up or down and doesn't move then you have a problem. also if you twist or push/pull on the plunger you can break it and you'll have to buy a new one anyway and the test will be for nothing. the iac and the tps both cost about 40 bucks at the parts store.

also on a side note, you can get a decent temp gun at advance for 20$.