I’m working on a 1995 Bronco XLT 4x4 5.0 E4OD I just picked up. It was drinking coolant and transmission fluid at first, so I ran a KOEO and got 172, 211, and 628. Since I don’t work on automatic transmissions I took it to a local shop. They agreed that it appeared to be the torque converter, and replaced it, rear main seal, and transmission seals for $840. Next, I replaced the thermostat, temp sender, water pump, some hoses, radiator cap, and distributor. I also flushed the rust out of the cooling system with a chemical flush. I should note that while installing the distributor I decided to try 11* of timing, which the engine appears to like. I also found that the ground wire to the intake manifold was disconnected and fixed that. I also discovered multiple bolts loose on the driver side exhaust manifold, 2 disconnected O2 sensors in those manifolds with no wires to plug into, and multiple bad welds where the exhaust was chopped off before the cat to make duals. They even increased the pipe size and just filled in the difference with bad welds.

After all of this I have:
157 – MAS lean – First time this code came up

172 – H02S Lean – I thought this was associated with the messed-up exhaust before the 157 code came up.

542 – Fuel pump secondary circuit fault – I have also had odd fuel gauge readings like slow rise and sudden big drops down. There have been two instances of the engine shutting down when the fuel level shows some. This was attributed to the 211 code the first time, but now that it has happened again and this code has arisen I am beginning to wonder. I plan on testing the fuel system pressure.

628 – Excessive converter clutch slippage – It has a hard shift into drive or reverse, especially when it’s cold, but mostly smooth shifts the rest of the time. The fluid level appears to vary with no leaks or additions. Do you think the pump is going out? See next. I would like to have all the codes except this one cleared before I take it back to the transmission shop.

I am also concerned about the size of the tires on the truck. She is wearing 31x10.50R15. The tag on the rear end says 3L55, so I’m guessing she has a 3.55 final drive. Wouldn’t this combination increase the work load on the transmission? What would be the best final drive ratio if highway driving and MPG were your goal and you wanted to keep the same size tires?

It was too late to run the KOER tonight but I do plan on doing it tomorrow.

Thanks!

 

If your O2 sensors aren't hooked up I can see the 172 code. I would think your computer would be in "limp" mode or a standard setting mode, but not sure how that works on these. I have a 1992 manual and there are differences. First I don't have code 157 in my emissions manual.

172 says, 172rc Lack of Oxygen Sensor (HEGO) switches, indicates lean

542 says, 542oc Fuel Pump circuit open-EEC Processor to motor ground

628 says, 628o Converter Clutch error

r=Engine running
o=Engine off
c=continuous memory

You're on top of it and have the codes, just wanted to show what my manual said for comparison.

I have the Innova tester and I can't do the KOER test until I clear the codes from the KOEO test. Will yours let you do the KOER test?

I would work on getting those O2 sensors hooked up and see what codes I have then. HTH.

 

Thanks for the response!

I also have an Innova tester. The manual says to not perform a KOER until you have fixed and cleared the KOEO codes, but it will still let me.

The problem with the O2 sensors in the exhaust manifolds is that there are no wires to plug them into.

All of my codes so far are C. Sorry, I forgot to add that in my initial posts.

 

Wow! I don't know how that will work unless the PO "fooled" the computer.

Maybe my tester will let me go on. Just didn't realize it.

Maybe you can find the wires in the bundle, I don't know.

Man, hope you get it.

 

Could be as simple as a bad connection at the solenoid pack. This connector is on the passenger side of the transmission. There should be a removable metal cover/heat shield to get to the connector.

Most OBD-I trucks of this era have a single O2 sensor located near the converter(s). Starting in 1995 there were some weird offshoots that could very well have two O2 sensors as part of a California emission package.

Take a close look under the truck to see if there is actually only the one O2.

 

Thanks for all the feedback!

I will check the connector on the transmission, but I'm pretty sure the pump is going bad. It is starting to leak fluid again and has a very hard time maintaining 80 mph.

I was able to get some pics that should help.

Here is the driver side exhaust manifold


And the passenger side


Here is the welded exhaust and you can see where the one connected O2 sensor is in the H pipe.


And the leaks from the transmission




I am planning on replacing the exhaust, probably starting with the exhaust manifolds, and changing to a 3.73 final drive ratio. Since this thing rarely goes off road I plan on using just a limited slip diff in the rear. Should the front be a limited slip as well? My other plans are upgraded sway bar bushings and end links, upgraded tie rods, upgraded front brakes, replace rear brake shoes and hardware, replace crankshaft seal, and the sixliter mod. I am considering a rear disc brake upgrade.

I am planning on doing a vacuum and fuel system pressure test this week. I have turned the timing back to 10* for now. The cooling system is fully bled and running in top shape. Hopefully I will have more info to relay soon.

Thanks all!

 

Today I picked up a vacuum test kit and a fuel pressure tester. After relieving the fuel pressure I noticed the Ford connector in the fuel pressure test kit did not fit properly. It feels like the threads inside the brass connector are stripped out. I'm glad I just rented this kit.

This knocked a good deal of my plan out for the evening, but I was able to get some testing done with just the vacuum test kit. The fuel pressure regulator changes the engine when the vacuum line is removed and reattached. I did notice a 5lb per 30 seconds loss after getting to 22lbs. Is this indicative of a problem?

Next I tested the evap canister and found no vacuum would build on the side with a green and black vacuum line leading from it. When hooked up the actuator connected via the black line would move, so I followed the green line to the Exhaust Valve Regulator. I got the same 19lbs on the EVR side of the green vacuum line. I hooked the vacuum pump up to the upper port on the EVR and a gauge on the lower. Every squeeze of the pump resulted in a matching jump and immediate drop in the gauges. No vacuum would build. I reversed the order and found the same results. This leads me to believe the EVR has gone bad. Could this cause some of my error codes? I think this could be the cause of 157 and 172.

We will see what tomorrow brings.

 

The EVR is a controlled vacuum leak. Some good reading here: Fuel Injection Technical Library » EGR Vacuum Regulator (EVR)

I believe the FPR should hold vacuum longer than what you listed. Inspect the vacuum port of the FPR for signs of fuel.

 

I appreciate the link! According to the Haynes Manual, if you connect a vacuum tester to the supply port and a gauge to the to EGR port you should be able to create a vacuum on the supply side and have no vacuum showing on the EGR side. The new and old one both failed this test, but I got a new code saying the new solenoid was bad on my KOEO test right after installation. After swapping them out the code went away.

The testing method in your link will probably work. I will try that next time I work on it.

The last time I worked on it I did install the new EVR, as stated above, and get to actually test the fuel pressure. After the EVR situation was settled I had only code 172CR, which is not a surprise.

Here are the fuel pressures I recorded:

KOEO = 10psi
KOEO + EEC connector fuel pump on trick = 40psi
KOER = 32psi
KOER fuel pressure regulator vacuum removed = 41psi
KOER fuel pressure regulator vacuum re-installed = 32psi

The fuel pressure regulator was loosing 8" of vacuum in 30 seconds with the engine running. Also the KOER fuel pressures are a bit on the low side. Could these mean there is a small leak in the fuel pressure regulator? I did not see any fuel in the vacuum line.

I can only find a vacuum leak on the white line coming out of the thermactor box thing. It does not appear to be very large, but I will get it replaced with the proper line soon.

 

In my experience if the Fuel Pressure Regulator (FPR) will not hold a vacuum that means the diaphragm is leaking, which means unmetered fuel would be sucked into the intake therefore the O2 sensor would sense a rich condition. Seems odd you get a lean code.

Look at the vacuum port on the FPR very closely by sight and smell.

 

I got the 172 code cleared by just changing the O2 sensor. The exhaust manifolds having extra O2 sensors that were not connected delayed this simple fix. Now the only code I have is 311R. I have read where others get this code when the FPR starts to go. Considering I have already measured what appears to be a slow leak in the FPR, I will be changing it out.

Tomorrow at 8am I have to go get new tires because I had a rear tire delamination at 75MPH on the interstate in downtown ATL Friday. She earned her name, Bronco, during that experience.

 

Wow! I assume and am glad no one was hurt! Good job figuring it out so far!

 

Thanks! It took a lane on either side to get her settled, and I think the guy that was driving next to the tire that let go needed new pants. I managed a 20 minute tire change on a tiny shoulder with a wall and a drop down if I needed to run. Monday I found out the tires were 13 years old and the spare was original to the Bronco, aka 1994 production.

I got to say that I do love the new tires!

Bfgoodrich All Terrain T/A KO2

 

Ha! New pants! We have those tires on my wife's 1998 Suburban. They look good. May get them on my 86 F250.

My Bronco has the earlier KO's. They get noisy at 60 MPH. Are the KO2's better?

The gent at my favorite tire store told me my tires on my 1986 are pre 2000, need to change them soon, for the same reason you had.

 

I have not noticed any excess noise, but it feels a bit loose compared to the more street design of the previous tire. I also have not checked to see what pressure they set them at. Add in the need for new tie rods and bushings and I can't judge much right now. Give me a week to get some things sorted and I will report back.

I do agree with you on the look! The sidewall is pretty aggressive. I actually chose this tire because it has a pretty good snow rating. This truck lives at my family's vacation house in Helen, GA. Her main purpose is to get out of Helen and back to civilization if there is ever a large snow storm up there.

The expiration date for a tire that has done nothing but sit in a warehouse is 7 years. If your tires are pre 2000 you need to change them soon.

My 628C code came back, so she will be going back to the shop that did the transmission work. If the pump is going out would you have changing trans fluid levels? It seems like I get it right and check it a few days later and it's high. All cold tests.