Ford Mustang Forums banner

1 - 13 of 13 Posts

·
Registered
Joined
·
293 Posts
Discussion Starter · #1 ·
I've had my Dr.Gas O/R X-pipe on for about 6 months and 5000 miles without MIL elims. and have never gotten a check engine light. I know the light works because it comes on when I turn the key on. No faults stored in the ECM. My guess is it's not going into closed loop but I don't know why. I've had it on a couple of long road trips and have never seen the C/E light. I recently replaced the T-stat because it took awhile to warm up. Still no light. Car has mods listed in sig.

The car runs great, my last dyno showed a 13.0 to 1 A/F ratio all across the RPM range. It does have poor throttle response for a few minutes when started cold, but it's always done that. The exhaust smells really rich, but I figure it's because it doesn't have any cats.

Anybody have any ideas?

Trace
 

·
Registered
Joined
·
978 Posts
Maybe the sensors? if it ain't broke though, don't fix it.
 

·
Registered
Joined
·
293 Posts
Discussion Starter · #3 ·
I take it you are talking about the O2 sensors? I guess it's a possibility but I would think a bad sensor would pop a code also.

I agree with the "if it aint broke, don't fix it" deal, but if it's not going into closed loop it's not monitoring the A/F ratio. If it's not monitoring the A/F ratio, fuel mileage will suck and It might be the cause of my poor throttle response issues.

There is something wrong with it though, most guys spend time trying to keep the C/E light out. I would like to see mine come on one time! :)
 

·
Registered
Joined
·
978 Posts
Point taken, If you want to make sure it is going into closed loop mode, The eaisest way I know of is to find someone with an NGK or similar highend diagnostic scanner and hook it up. Most good scanners will tell you when it goes to closed loop. Less exact would be to unplug the downstream o2 sensors and turn the car on to see if it pops a code.

Also as I recall the after-cat o2 sensors don't affect mixture. they are only ther to moniter the cats. So you could very well have a soft code in the computer memory if you were to scan it.
 

·
Registered
Joined
·
720 Posts
You know what, I have had my o/r h-pipe in for about a month and a half, and no light either.
 

·
Registered
Joined
·
293 Posts
Discussion Starter · #8 ·
hmmm....well maybe fords catalyst monitor really sucks. I'm a BMW tech and I know for sure that a OBD2 beemer will pop a catalyst fault after 2 drive cycles everytime. For about 2 months I drove my car just back and forth to work everyday so it didn't surprise me that there was no light. But I've had it on a couple of long trips lately and still no code. I've checked it with a Crap-On scanner many times.

You guys that have the same issue, do you drive your cars hard all the time? I guess if you drove it like you stole it (like I do) all the time it may never run the catalyst monitor.

More info from anybody would be great. I'm going to get to the bottom of this.

Trace
 

·
Registered
Joined
·
35 Posts
I am kinda in the same boat as you. No cats, 270rwhp, 13AFR across the board, smell fuel when not moving, no CE light. I do not drive my car hard all the time. I'm quite the opposite actually, I only get on it maybe once a day and even then it's only a short burst and not even WOT.

I also have abysmal gas milage, like 15mpg

apot
 

·
Registered
Joined
·
293 Posts
Discussion Starter · #10 ·
ttt
 

·
Registered
Joined
·
368 Posts
If the pcm finds a problem or somthing out of spec it will set the light after atleast one drive cycle. Usally a drie cycle is around 15-20 miles but can for whatever reason go up to 80 miles.

How many of you have or had a chip or custom program? or a car alarm that kills the ignition when set. Your pcm may have the memory turned off or a eec relay may be bad. My 99 use to have a stored code p0605 for a memory failure and eventually had no codes no matter what was unpluged, missing or damaged. But now with a fresh non chipped pcm I do get from time to time the light and code for cat monitors with my high flow cats installed.
 

·
Registered
Joined
·
293 Posts
Discussion Starter · #12 ·
Good to see a ford tech in here. There is no substitute for experience with this stuff everyday.

There is one other interesting thing going on here that may or may not be related. A month or so ago the battery light started coming on at high rpm high load situations. Would go off as soon as the rpm's came back down. within a week the battery light came on a stayed on, alternator not charging at all. Checked the battery and all cables between the alternator and battery for voltage drops etc. No problem found so I replaced the alternator. I still get a battery light to come on intermittently, will stay on for about 3 minutes then go back out. Doesn't seem to be any rhym or reason to it this time though. Is there a seperate relay that supplies field current to the alternator or does it come off of the main relay? I don't have access to any diagrams so this may be a pain to figure out. I would think if the main relay had problems the car wouldn't run or just cut off at times.

Gotta love electrical gremlins. :)

Trace
 

·
Registered
Joined
·
4,499 Posts
I thought drive cycles or trips could be as simple as ignition cycles provided ect up to temp, obviuosly rap(retained accessory power) would have to be deactivated by opening a door, probably counting to 10 and starting the car again, that should be trip #2, also provided you've gone at least a few miles to monitor wheel speed, 02 voltages etc.

my car gets 18mpg pounding on it w/4.10's, no change in gas milage or unfortunatley performance either from gears???

all thuway I'm sure I'd hit 20mpg

I just wish my car had some balls
 
1 - 13 of 13 Posts
Top