I just purchased a '95 f150 with 302 and e4od tranny. It has 162,000 miles on it. I've been looking it over and going through some of the stuff. I've no where near gotten though all of it, but so far I have been puzzled by one thing in particular.

This truck doesn't have a conventional exhaust system. It does have the stock manifolds, but then there looks to be an aftermarket y-pipe with an O2 sensor tied into it. After that is a glass pack followed by dual exhaust. There's no cat or the air tube that I've seen on other models like this.

The O2 sensor has two wires, and I thought that was kinda strange since I've been reading that it should have four. Well, I borrowed my brother's scanner and hooked it up this afternoon. Turns out the computer isn't even reading the O2 sensor. It's staying in open loop and there's no voltage being generated from it. However, I've already verified that the engine generally runs pretty well and gets reasonable gas mileage (15-16 highway at 55-65 mph).

I also pulled the plugs when doing a compression test and they didn't look rich at all (actually kinda lean). This does not compute in my understanding of how these things work. There's no check engine light on either, although we did pull a 332 (EGR flow insufficient) code and 411 (cannot control rpm), as well. I think the idle problem is coming from a bad IAC valve. I noticed it was disconnected, and when I plugged it back in the idle went up a bit too high.

Also, the compression test I did showed the following marks:

1. 148, then 152 after cranking a few more times
2. 149, then 162 after cranking a few more times
3. 123, then 125 after cranking a few more times
4. 126, then 145 after cranking a few more times
5. 155
6. 158
7. 171
8. 165

What happened is I tested cylinders 5-8 first. I allowed each to crank the same amount of times, and then took the reading. When I got to #1 on the other side it only read 148, so I (for kicks and giggles) cranked it a few more times with the pressure from the previous cranking still in the system. I did that for #'s 1-4, and on # 3 I did a wet test as well. The numbers didn't change much on #3. Cylinders 3 & 4 seem a bit weak. Engine runs fine and shows 18-19 inches of vacuum at idle with very little movement.

I will say that overall the truck seems slow compared to another one that I recently was able to look at that actually had higher miles. They both are extended cab short box with 302 and auto tranny, 3.31 gears. The only difference is that mine has the e4od and the other one has the 4R70W. Somehow I think there's a chance every thing is not running quite right with mine, and I need some advice on what might be going on with it.

Also forgot to mention that the fuel pressure is good/normal from both tank's fuel pumps. The computer said that the timing was at 12 degrees. I understand that 10 is where the factory put it even though some run it up to 13-15. I haven't yet inspected the cap/roter, but I have verified that there's no crossfiring/grounding due to no firworks under the hood in the dark. The spark plugs are worn but not too bad (Motorcraft) and the plug wires are 8mm.

To summarize:

1. Can't figure out why the computer is not reading any voltage from the oxygen sensor, staying in open loop, yet getting reasonable gas mileage. Spark plugs are showing that it's not running rich. Also, there's only two wires protruding from the O2 sensor, but I haven't yet traced them to see where they go to.

2. Seems to have weak compression on cylinders 3 & 4, yet engine idles and runs smoothly.

Thanks.

 

Well, I'll be darned. An eagle's view (close-up) of something is best. The O2 sensor is a 4-wire. From the top it looked like two until I crawled underneath and looked specifically at it and realized there were two more wires hiding beneath the top two.

I also hooked up the voltmeter to it and confirmed that it was sending out a voltage signal and that that signal was switching back and forth. Why the computer scan didn't show that and why it says it's staying in open look I would sure like to know the answers to.

 

Some guesses
You COULD have a coolant temp sensor, or possibly an air temp sensor ( if you have one) that's bad. Then it will never go into closed loop because the computer doesn't know if it's warmed up.

I would think that would give you a code

One cylinder does seem consistently weak.

I'm not sure about 95s. Are they still TFI ignition? If they are, you have to disconnect the SPOUT connector to check the base timing -- you didn't mention that you did that.

hj

 

I will be getting a Haynes manual soon, and then I'll start testing the sensors to make sure they're within specs. I suppose I was short sighted by assuming the "open loop" had to do with the O2 sensor.

Timing wasn't checked in the conventional method with the spout thingy and timing gun. I simply read what the computer scanner was reading. I'm assuming it would be the same figures, but I don't know. Anyone care to comment on this one?

 

What scanner did you use and where did you connect it? The reason I ask is because the info you gathered with it generally isn't available from the OBD-1 system which this truck should have, so that makes me think that either you actually have a '96 truck with OBD-2 or the data from the scanner is wrong and can be ignored.

 

Well, I borrowed my brother's scanner. It's one of the good ones that has the various attachments to work with Fords, Chevys, etc... Brand name, I don't know. I've used it before to monitor certain vitals on my wife's '94 Saturn, so I know it's capable of reading O2 sensor voltage on OBDI vehicles.

As to where I plugged it in: the self test port on the inner driver's side underhood right next to the firewall.

 

Sounds like your scanner was good enough to tap into the ' data stream ' that some Fords apparently had -- don't know much about it.

But, if you do have the TFI style ignition, you have to disconnect the SPOUT to get the 'base timing', no matter how you check it.

The reason is that it disconnects the computer from the timing control. If you don't disconnect the SPOUT, the computer will probably be causing a slight shift in the timing.

hj

 

OK that's intersting. Still the device may not have interpreted some of the data correctly so it's possible there is nothing wrong with the truck. We now know the there is a proper O2 sensor connected and it seems to get the expected milage so there's not likely to be any major electronic problem. I suggest pulling the codes, if you get an all clear 11 or 111 then that confirms there are no sensor issues. See "doing a self test" at www.fordfuelinjection.com to pull the codes without any special tools.

 

Thanks for the replies. There are a couple codes. One of them has to do with the egr. I'll have to pull that off and make sure it's not plugged. The IAC is the other one. Probably need to replace that.

I don't fully understand the timing issue with the spout connector, but I'll read up that since I'm sure there is plenty of info. I do have a timing gun, and I'll check it that way in due time.

I plan to put in a vacuum gauage and a AFR (air-fuel ratio) gauge shortly to help "monitor" things.

I'm brand new to the F150 world. So, lots of learning to be done.

 

Forgot to mention that I can get 17 (maybe 18) mpg with this thing at 55 mph and no load, just being careful on the throttle. With a loaded 5x10 trailer that weighs a couple thousand pounds it'll do 12.5-13, once again at 55 mph. I figure that's within specs.