Failed Emmisions

[BONeil]

I just brought my 91EB in for emissions testing. I failed on the CO portion at 25oo rpm. The rig is basically stock. The only mod that I have done was to add holes in the air box. Could this be the problem? I have just replaced most of the emmision parts trying to track down a over rich condition that ended up being the fuel pressure regulator. The nifty little hand out that they gave me when I failed says that a failure of this type requires professional diagnosis and repair by a qualified tech. I can't believe this to be true.

Can someone help?

Thanks.

 

[Maniak]

If you were running over rich for a while you may have cooked your o2 sensor(s). Our 92 explorer failed and I replaced the 02 sensor (we only have 1 on our 92) and then it passed.



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Mark
mark@legendz.com
http://mark.legendz.com
Off-Road and Motorcycle Information, Pictures and Movies

 

[BONeil]

Here a little more info that I hope might help someone give me an idea of what to look at. Gas mileage really sucks right now. Don't know what I'm getting but $5 a day to go 30 miles to and from work isn't good. Everything seemed fine before I had the tranny rebuilt. The truck sat for 2 month prior to this. When first starting in the morning it just doesn't like to run. Just touch the gas and it dies. After it warms up it seems fine but just doesn't have the power that I think it should. The check engine light doesn't come on at all. Now if the O2 sensor was bad from what I know everything should run fine until the system goes in to close loop. Right?

So what could cause this problem that isn't in the close loop?

Someone please help.

Thanks

 

[Maniak]

Yes, if the O2 sensor is bad it should run ok until it gets into closed loop.. so that means it might not be the o2 sensor..

They symptom you descirbed (problems running when cold) sounds more like the AIC (Air idle control).. or is it IAC.. I can never keep it straight.. anyway.. here are some things to try to see if this is your problem.

If you have A/C.. wait until the motor is wamred up.. then turn on the AC.. if the idle goes up the AIC is working.. if not it may not be working.. Another test is to disconnect the AIC (the connector).. if the idle goes down the AIC was working...

The AIC is shaped like a cylinder on the driver's side of the intake plenum. It is held on by 2 10mm (or 8mm bolts).. If I remember correctly the part is around $70.

Mark

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Mark
mark@legendz.com
http://mark.legendz.com
Off-Road and Motorcycle Information, Pictures and Movies

 

[rock883]

Hey I'm pretty sure your problem is the fuel pressure regulator. I just fixed mine today and my gas mileage has skyrocketed! I drove about 70 miles today and it used less than a quarter of a tank. Its a fairly easy fix. I had to drain the radiator coolant so that I could take the upper hose off to reach one of the bolts but that bolt was the hardest part about the job. It took me about an hour to drain the radiator and get the regulator off. Then the next morning I ordered the part, and got it today and put it in in about 15 minutes or so.

 

[DrewP]

Having personally failed the emissions test in NM numerous times, I have a few suggestions for you to try. Did you only fail CO or did you also fail hydrocarbons? Sometimes if you are running too rich you will fail both...or your hydros should be high at least.

Anyway, try changing your oil, put in new plugs and ignition wires, replace your air filter, fill your tank up with some good gas. Then drive your car on the highway for at least 50 miles and take it to be tested right away.

It's a cheap and easy thing to try.

Good luck.

 

[DrewP]

Having personally failed the emissions test in NM numerous times, I have a few suggestions for you to try. Did you only fail CO or did you also fail hydrocarbons? Sometimes if you are running too rich you will fail both...or your hydros should be high at least.

Anyway, try changing your oil, put in new plugs and ignition wires, replace your air filter, fill your tank up with some good gas. Then drive your car on the highway for at least 50 miles and take it to be tested right away.

It's a cheap and easy thing to try. :>

Good luck.

 

[Explorerdude]

Hey,
Just wanted to add my two cents...

I don't recall if the 91 has a mass air flow sensor on it or not but if it does read the following if not I don't know what to tell you.

I have a 94 Explorer XLT that I had a what I think to be a similar problem with... Although I passed emissions I was getting several "funny" codes. I had a check engine light come on so I took my truck into the mechanics and found that the codes my truck was giving me was one for too rich of fuel , one too lean of fuel and several other code of which I don't remember. The first thing my mechanic did was to change my O2 sensor. He did that and it seemed to fix the problem for a couple miles than my light came back on. I took it back and to make a long story short I had to take my truck to the dealorship and they told me that they reccomended me to change my MAF. I told them that I'd take care of everything means they wanted like 300 bucks for a new sensor!! I ended up cleaning my MAF and it fixed a bunch of problems... not to mention it took care of the light!! SO... After you replace your plugs wires oil and the like, try cleaning your MAF and see what happens... Now when you clean it don't forget to clean the sensor itself. Mine had a ton of carbon build up on it. If you look at the write up on this website about how to clean your Mass Air it explains everything. If you need any help just contact me I've done it before. Hope this helps....

Happy Wheelin,

Joe Dead Link Removed
94 Explorer XLT
4" Superlift Suspension
33X10.50 BFG AT KO's
Flowmaster II Cat-Back System
KKM Tru-Rev Intake

 

[BONeil]

Well I finally got some spare time to work on this.
I changed the oil, filter, plug wires, and air filter. I also plugged up the holes I had added to the air box thinking maybe there was too much cold air getting in when it was cold.

Last week I tried pulling codes and got a 21 which is coolant temp senor out of range. Since I had already replaced this before, I changed the thermostat since I've had the truck 2 years and never changed it but had noticed that it seemed to be running cooler than it had.

After all of this I started it up and if I touch the gas it dies. When trying to restart it you have to floor it to clear all of the gas out.

Once its warmed up it seems to run fine. I checked the air mixture sol. on the side of the intake and when I disconnected it there is a drop in RPM so I would think that it is working.

Pulled codes again after this and it still shows that the CTS is out of range. Is it possible that the new one has gone bad already? I still have the old one and as soon as I have a chance I'm going to put it back in and see if this help.

Its seems that my truck has not run right since I got it back from having the tranny rebuilt. Is there anything they could have done when they removed or reinstalled the tranny that could cause something like this to happen?

Anyone have any ideas what I should do next?

Thanks in advance.

Scott

 

[Ira]

Scott,
Just a couple of things that ran across my mind while reading your last post. First of all, there are different sets of codes. Which ones are you checking? The one KOEO (key on, engine off) is your stored codes. They are there from the time it first senses a problem until YOU reset them. In other words, if you replaced the CTS 2 years ago and did not reset the codes, it will still be stored in memory and you will continue to get this code.

The other common code set is KOER (key on, engine running). These are NOT stored codes. These codes WILL reset each time the key is turned off. This is a problem code that is in effect while the engine is running at this time.

I would recommend resetting the codes and then driving it for a while and rechecking the codes. You may find you have a different code than what you have had yet.

Another thing I thought of, make sure both vacuum lines are still connected on your airbox. They have a tendency to come off if you don't get them pushed on very well.

Good luck.

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Ira
91 XLT 4x4
What do Playboy and National Geographic have in common? Just a couple of the places I will never get to visit

 

[BONeil]

The code I was looking at was the KOER ( engine running test) Engine off test gives my all systems are good with no stored codes. The vacuum lines are connected to the air box as this was my first guess of where the problem could be. Hopefully this weekend I can get to changing the CTS out to the old one( good thing I never get rid of an old part unless I know for sure its bad) maybe this will fix the problem.

Thanks for the advice.

Scott

 

[BONeil]

Well its finally fixed. Problem was the new Collant temperarue sensor went bad. Replaced it with the original (good thing I never throw away any part unnless I know for sure its bad)and I don't geeet any codes. While I had it out I took an ohm meter reading on it and the bad on was reading 1meg ohm. The good one was reading around 20k ohms. Tapping the bad one on my vice and the reading changeed into the good range. Too bad I bought it 6 months ago or I'd be bringing it back to Pep Boys for a new one. Doesn't really mater since I have the original one. Never thought that one could go so quickly.

What a difference it makes on gas mileage. Got over 100 miles on less than 1/4 tank. Also there was a dramatic difference in the emmisions.

Thanks to everyone for you comments and suggestions.

Scott

 

[ex91]

hey 91's do have a MAS