New member here...I look forward to many a night on this forum.

I purchased my 1995 F-250 (with the small V8 and 5 speed manual) about 2 years ago. Last year when I had to take the truck in for emissions here in Arizona I failed. I had done all the pre-maintenance that I normally do to help a vehicle pass, e.g. oil change, spark plugs, air cleaner, etc. I also replace an O2 sensor that my check engine light was flagging. The engine light cleared and has never come back. In fact I used to get the light only when I was cruzing at highway speeds for a length of time. Once I shut the engine off and started it again. It would be gone and only come back if I got on the freeway again. After replacing it, this has not happened again. Despite my efforts, I did not pass the emissions test so I took it to a "reputable mechanic" and he installed a second cat and "tweeked" the settings and took it through for me. It passed!! When I picked it up, he told me to hurry and fill the tank to dilute what he added. Still don't know what that was!

Fast forward... I failed big time this year...only 6 months after he passed the truck for me (I was very late on getting it tested last year). I thought with a new second cat I would have no problem. Boy was I wrong. Here are the numbers (passing numbers in parenthesis): idle - HC 773 (300), CO 8.05 (4.00), Loaded - HC 504 (300) CO 11.86 (3.00). All this with passing with almost ZERO emissions only six months before!

The truck has always ran fine even in its current state. The only thing I noticed while driving it recently was the AC started going out and would only come back when I changed the RPMs abruptly. Oh, and power does seems to be lacking a little. A vacuum issue...? Could this be related to the emissions problem?

Another piece of the puzzle, the previous owner replaced the stock air cleaner and housing with a KN set up. Could this play a role?

Sorry for the long first post but I am now sitting with a truck I can no longer legally drive.

Help would be much appreciated.

 

Hi LCconvert, welcome to FTE!

I'm not that familiar with the EEC-IV system that your truck uses, but there is a procedure to check for trouble codes. That would be the first step to determine what's wrong.

This forum is for the '99-present Super Duty trucks, so I'm going to send this one to the '87-'96 F-series forum, you should get some more help there.

 

The something may of been alcohol .
The K&N can disrupt the airflow past the
Mass Air Flow sensor and cause a fuel issue.
When you took it in did you keep it running while you waited?
You want it to not cool down and the alcohol in the gas line dryers
can help. You can get that in the stuff for de-iceing fuel like
Heet Products, Gas-Line Antifreeze, Water Remover, Premium Fuel Line Antifreeze, Injector Cleaner | Gold Eagle
HEET. But be careful.


Sean

 

Yes, I kept it running while waiting for the test. So I guess I can sum up the issues as poor power, ac cuts out randomly and starts back up only after abruptly changing the RPMs, and of course the very poor emissions results (see above). I don't know if these are related but I sure hope so.

Maybe I should try and source a stock air cleaner assembly and get rid of the KN. Would that be a good start?

thanks!!

 

After thinking about it some more, it might be running rich. Could the MAF sensor cause that? Could a vacuum leak cause that as well?

 

Dirty MAF or vacuum leak will cause it to run LEAN.

High HC's are rich.

Check the fuel pressure at idle. You might have a bad vacuum line going to the fuel pressure regulator or bad vacuum regulator and the pressure is too high. It should be around 28-30lbs at idle, 38-40 under load.

If it's 38-40 at idle, that means no vacuum is making it to the fuel pressure regulator, or the regulator itself is stuck open or leaking vacuum.

When you say the ac cuts out, do you mean you get warm air from the vents, or the vents themselves turn off?

 

It sounds like you have a lot of unburned fuel to me. Clean your MAF sensor, clean your K and N, and check for codes. It's been a long time since I owned an 87-96 truck, but I'm sure the procedure to run the code test is stickied in your forum or something

 

What he added to your tank was either E85 or denatured alcohol. I have heard adding up to 5% of that to gas will help with emissions. You don't want a lot in there, the E85 may degrade some of your lines. So just enough to pass, that's why he wanted you to go fill up with gas and dilute what was in there.

 

It is like the vents are turning off, the airflow goes to almost zero. The only way I have found to get blowing again is to release the gas pedal and step on it again. Then it starts to kick in again.

 

The a/c issue is common on fords it's taking the air from the dash and venting it thru the defroster. Check for vacuum leaks. Or take it off of max air.
My 95 ranger is the same way

 

The first thing to check about the AC is the little white vacuum line on top of the AC box under the hood... They are known to deteriorate (sometimes they just crumble when you touch it) and cause this problem.. Just get some rubber vacuum line and slip it over the good portions of the white line. I doubt this is causing your other problems, but any vacuum leak is too much, so it can't be helping.....

 

I have never fixed this issue, it has been sitting ever since I failed emissions over a year ago...I know...pathetic! I do occasionally drive it around the block but not much more.

Is it worth sourcing an original air cleaner system and get rid of the K&N? Or is it not likely contributing to my issue?

thanks

 

After looking at the K&N set up there is no MAF sensor that I can see. I also checked my manual...I am not sure my 5.8 is supposed to have a MAF sensor. Could this be true?

Can a MAP sensor cause my emission problems? (See readings in first post)

 

There is no MAF on a 1995. It uses a MAP sensor, it doesn't get dirty like a MAF.

I'm sorry I can't help further. All I can say is that it's time to go over the emissions with a fine tooth comb. Check all the hoses for cracks and breaks. Especially in AZ, I'm sure pretty much every plastic hose is brittle and cracked if not broken off.

Get the hoses figured out and move on to the next thing.

 

Running that rich could mean it is stuck in cold mode or some default. What thermostat do you have? Are all the sensors hooked up? If the computer thinks it's cold all the time, it's going to run rich.