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Old 07-29-2008, 03:22 PM   #1
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Unhappy Can somebody help!!

First I am not knowledgeable on inner workings of the mustang, so I need help. I have a 94 mustang GT convertible..it has been giving me problems since I purchased it 5 yrs. ago. It is obvious the previous owner did not take care of the vehicle what so ever.

I live in Las Vegas, where we are required an annual smog inspection..I've had to get work done so it could pass the test each year.

I've taken the vehicle to the Ford dealership and many other mechanics where i've spent alot of money to get this problem corrected, but all have been a waste of money and time. I've had almost everything under the hood replaced, yet no change. Now I am looking at replacing the catalytic converters in hopes that this will make a difference.

Problems:

1. Idles erractically
2. Runs lean
3. Lack of power
4. Pressing on the gas pedal in neutral..it shoots out some black substance from the exhaust pipes.

Any suggestions to a possible cure to this problem would be appreciated. Thanks.
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Old 07-29-2008, 08:12 PM   #2
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Re: Can somebody help!!

nearly impossible to diagnose a car over the internet. You can start by checking the basics like plugs,wires,cap,rotor,fuel pressure,tps,o2s and move on from there. You will need to plug it in to monitor your sensors and see what exactly is going on. If you dont have it fixed by the time of the sema show,Ill look at it while Im in vegas and hook it up to our computer and diagnose it for you.
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Old 07-29-2008, 08:39 PM   #3
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Re: Can somebody help!!

^^^ the man! TPS is going to be one of the best shops in the south.
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Old 07-30-2008, 02:58 PM   #4
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Re: Can somebody help!!

I appreciate the suggestions. I've checked and rechecked all the basics and like I said I've taken it to the dealership as well as other mechanics and as far as I know diagnostics were ran as well.

When is the sema show? If it is not fix by then..I would appreciate if you could take a look at it..is there a fee for you to take a look at it?
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Old 07-31-2008, 08:48 AM   #5
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Re: Can somebody help!!

Idling issues are fairly common on the '94-'95 cars but I haven't run across one I haven't been able to fix, either by finding a mechanical issue (IAC/dirty MAF etc) or adjusting the tune to accommodate the modifications.

One thing that most shops miss is cleaning the MAF. They will get dirty over time, especially if you run an oiled filter. If you are not getting any codes or a check engine light I would look at making sure the MAF is clean.

94-95 Mustangs Electrical MAF - Mustang-Tech

What sort of mods are done to your car?

How is the idle on a hot start, cold start and coming to a stop at a stop sign?

Wes
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Old 07-31-2008, 10:58 AM   #6
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Re: Can somebody help!!

I appreciate the info. I definitely will clean the MAF, and see if there are any changes. About a couple of years ago, I had the MAF replaced. The idling was steady temporarily. How often should it be cleaned?

There hasn't been any mods.

Idling during hot and cold starts, and at stop signs all pretty much the same..erratic. The check engine light periodically eluminates and then will go out.

Again, thanks for the info.
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Old 07-31-2008, 11:05 AM   #7
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Re: Can somebody help!!

Quote:
Originally Posted by Shelton View Post
About a couple of years ago, I had the MAF replaced. The idling was steady temporarily. How often should it be cleaned?
I like to clean them every six months or so, or about 200 miles after reoiling your filter (if it has a serviceable filter like K&N)

Quote:
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dling during hot and cold starts, and at stop signs all pretty much the same..erratic. The check engine light periodically eluminates and then will go out.
That check engine light may very well lead you somewhere. I'd try to get the codes read to see what comes up (the PCM will store active codes and also a code history).

Taking a stab here, have you noticed that check engine light comes only when you are cruising?

Wes
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Old 07-31-2008, 11:19 AM   #8
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Re: Can somebody help!!

Just a quick note, Mikey has the same check engine light behavior on his 94. Might be the same issue as far as the light coming on goes.
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Old 07-31-2008, 03:06 PM   #9
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Re: Can somebody help!!

The check engine lights normally does come on while I am cruising, and when I allow the vehicle to idle to for awhile.

I've had the codes read before each time I was told that one of the sensors had gone bad. And as I've said before every sensor has been replaced at one time or another.

Would you have any insite on if the MAF would also contribute to the car failing a smog inspection?
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Old 07-31-2008, 03:12 PM   #10
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Re: Can somebody help!!

If the MAF is reading airflow incorrectly the computer will make the wrong assumption about how much air is making it into the motor and ultimately inject an incorrect amount of fuel. In my experience this usually results in a lean condition which will be picked up on a smog inspection. If you have the inspection sheet you can give me the observed and passing numbers from it and that will help in figuring out what is wrong.

I wonder if the check engine light thrown involves the EGR. The EGR will come on during cruising. If one of the vacuum lines to it is broken you could be getting an EGR code.

I'd be curious to have the codes read again, sometimes a "new" sensor can be faulty out of the box.

Regardless, I would take a stab at cleaning the MAF as my first step.

Are the O2s in the list of items replaced?

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Old 07-31-2008, 03:14 PM   #11
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Re: Can somebody help!!

the maf will cause it to do funny things with the fuel like run lean, the light should store in the computer and then be accessable with a diagnistic scanner then it can be traced from there.i agree with wes, its cheap to clean and sounds like it could very well be an issue, 2 years is a long time to go without cleaning the maf.

mikeys problem is probably more to the fact of the FMU doing funny thigs with the fuel, we are going to trace that problem when we pull it off and do his tune.
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Old 07-31-2008, 03:18 PM   #12
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Re: Can somebody help!!

they say the number 1 item replaced on mustangs is the MAF, they tend to gunk up and go bad.
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Old 07-31-2008, 03:32 PM   #13
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Re: Can somebody help!!

I believe I do have the last inspection sheet, which was only from a month ago..I was told the numbers were off the charts. Meaning not even close to passing the inspection. I can get those numbers to you once I locate where I put the sheet.

What exactly is the EGR..I've heard that word being thrown around during one of my visits to the mechanic.

Yes, the o2 sensors were the first in the line of sensors that were replaced.

From what you guys are telling me, it seems to point to the maf..I definitely will start with that first, its cheap and sounds easy enough to do. Hopefully the fix, is just as simple as that.
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Old 07-31-2008, 04:50 PM   #14
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Re: Can somebody help!!

The EGR (Exhaust Gas Recirculation) lowers emissions by activating at cruising speeds, recirculating exhaust gasses back into the intake stream to be reburned.

The EGR is not active when idling or at wide open throttle so it is not a drain on performance. It actually improves gas mileage as well.

You will see people delete the EGR system, this is because a) it is broken and they don't want to fix it, b) they think it is ugly c) it will not fit on their aftermarket intake/exhaust or d) they are misinformed about what it does.

Let me know how cleaning the MAF affects your problem, troubleshooting over the Internet is tough some times but for a free item you can check in the driveway I think it is an excellent start. While you are in there, trace the vacuum lines and look for any breaks in the lines.

Wes
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Old 08-01-2008, 12:32 PM   #15
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Re: Can somebody help!!

I was able to clean the MAF, unfortunately there was no change. Though I noticed a positive difference in power, even though it seemed as if the engine was racing..meaning I would press the gas pedal and the rpm would raise but the engine would have a delayed response.

Initially after the cleaning of the MAF, idling during the cold start was better, but when I took the car out for a drive..the check engine light came on (as it normally does) and once I returned and let the vehicle idle.. once again it was very erratic..almost to the point to where it would be close to shutting off.

It definitely seems as if the air flow is restricted, that is why it was suggested that I replace the converters. Any suggestions?
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Old 08-01-2008, 12:36 PM   #16
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Re: Can somebody help!!

My next step would be to figure out what is throwing the Check Engine light and to also verify there are no vacuum leaks.

Is the idle air control motor in the list of things that were changed out?

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Old 08-01-2008, 12:41 PM   #17
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Re: Can somebody help!!

I don't recall that being changed out.
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Old 08-01-2008, 12:54 PM   #18
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Re: Can somebody help!!

Quote:
Originally Posted by stanger007 View Post
...either by finding a mechanical issue (IAC/dirty MAF etc)
The IAC (Idle Air Control, aka ISC Idle Speed Control, aka IAB Idle Air Bypass) is a valve that is mounted on the throttlebody. When the throttle plate is closed (your foot is off the pedal) the PCM regulates idle speed by opening and closing the valve to allow air in. There is also a secondary method of idle control where the spark advance/****** is used but that is outside of this discussion.

Over time the valve can get sticky, the motor to move the IAC will get sluggish and the car can't react quickly enough to changing conditions.

The hanging idle you have (on your mostly stock car from what I gather) can be contributed to this valve being dirty or just worn out or also a vacuum leak as said above. If you can find someone close that has one you can swap IACs with, I would try that to stop the cycle of just buying new parts to throw at it. I keep a spare IAC in my box of tuning supplies for just such a reason.

Check this out for some pictures of what we're talking about: Ford Mustang IAC IAB - Solving your idle problems

You can attempt to clean it but oftentimes if this works it is only temporarily and replacement is the best option. Pepboys carries the correct part if it comes down to this.

Wes
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Old 08-01-2008, 06:08 PM   #19
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Re: Can somebody help!!

Thanks for the info. once again Wes. I will take a look at today.
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Old 08-09-2008, 07:13 PM   #20
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Re: Can somebody help!!

Went out of town. Just got back and now finally getting to working on the car. I've ran into a problem. The bottom screw on the IAC..i'm having a tough time getting to it. Will I have to remove the throttle body just to get to it. Or is there some other way..that is less painful. Don't want to remove the throttle body and mistakenly mess something else up.
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Old 08-10-2008, 02:40 AM   #21
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Re: Can somebody help!!

Quote:
Went out of town. Just got back and now finally getting to working on the car. I've ran into a problem. The bottom screw on the IAC..i'm having a tough time getting to it. Will I have to remove the throttle body just to get to it. Or is there some other way..that is less painful. Don't want to remove the throttle body and mistakenly mess something else up.
you don't need to remove the throttle body.....try using a 1/4 drive ratchet to get at it....thats what I did, and if I remember correctly i had to use a swivel as well
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Old 08-19-2008, 09:40 PM   #22
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Re: Can somebody help!!

ok someone please help i go to turn on the air and when i turn it on to max a/c or nomal or vent it just stays up on defrost and puts out hot hot air... the only think that really works would be the low and hi switch but the other ones are just stuckk

???????
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Old 08-19-2008, 09:53 PM   #23
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Re: Can somebody help!!

The vacuum line on the firewall is broke - look for a thin black hard plastic tube to be broken.

The line runs from the driver's side tee by the brake booster to the passenger side where it goes in the firewall by the heater core.

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Old 08-21-2008, 10:04 PM   #24
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Re: Can somebody help!!

ok. Took some work, but I finally was able to get to the IAC. Noticed a slight difference but the engine continues to "race". As you said I think it might be time for a new IAC. Now are there any other suggestions you might have as to the car not passing the smog. Any other areas that might be the cause of the failure.
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Old 08-21-2008, 10:16 PM   #25
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Re: Can somebody help!!

Post up your failing smog numbers so I can see what tests they were dinging you on.

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Old 08-22-2008, 12:01 AM   #26
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Re: Can somebody help!!

Attachment 19649

Attached is the smog test from this past May. Wasn't able to locate the most recent, which was about a month or so ago, but I'm sure I have it.
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Old 08-22-2008, 09:21 AM   #27
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Re: Can somebody help!!

You are running rich, which also will tend to make the car surge.

The HC is indicative of a rich burn, a VERY lean burn, or a cam that's got too much overlap and is letting raw fuel slip out the exhaust.

CO is indicative of a rich burn...where there just wasn't enough O2 to turn the combustion into CO2.

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Old 08-22-2008, 04:50 PM   #28
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Re: Can somebody help!!

Ok thanks. Now is there something I might be able to do to fix to this or would you suggest I take it back to the repair shop to have it diagnosed and then have them attempt to fix it.
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Old 08-22-2008, 04:55 PM   #29
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Re: Can somebody help!!

I'd take it back to a reputable shop so they can diagnose the problem rather than just replace sensors and spend your money. This is one of those times it's easier to have the car in hand to troubleshoot.

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Old 08-22-2008, 05:01 PM   #30
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Re: Can somebody help!!

Yeah, i can understand that. Unfortunately I figured it would come down to taking it back to a shop. Well, I definitely appreciate all the assistance you and everyone else has given.


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Old 08-22-2008, 05:26 PM   #31
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Re: Can somebody help!!

If you were a little closer I'd get you to come by the shop so that I could plug into the computer and see all the sensor data and identify what the computer was trying to do. Sure saves a lot of parts swapping and potentially swapping a good part for a "new" but bad one and causing more problems.

Wes

P.S. Did you ever clear then computer (disconnect neg battery cable and hold brake) then get the latest codes read again after driving a while?
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Old 08-25-2008, 09:05 PM   #32
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Re: Can somebody help!!

Yeah. If only. Now, back to the shop I go. I'm sure they will do exactly what you said..start part swapping. Replacing parts that have already been replaced once before.

No, I did not know you could clear the computer. I will be sure to do that. Thanks again.
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