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On my 96, the speedometer stopped this morning. Now the engine dies when I push the clutch in and come to a stop. I noticed the two issues at the same time. Are they both releated? Is there some sensor from the speedometer that the computer uses? I will check my gear when I get home. Any help would be appreciated.
 

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I have had this problem. I recently changed the gears in my rear end and put in a speed cal. the speed cal did not work properly and it made my speedo not work. My 99 has killed like yours once or twice before the gear swap,but since the speedo stoped working it is happening often. My friend has had the same problem with his car killing and he hasn't done anything to it. he would be driving and when he pushed in the clutch to come to a stop his car would kill. I bet alot of mustangs do this
 

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The two issues are indeed related.

On a 1999+ the car will stall constantly when coming to a stop. You can prevent this some by blipping the throttle as you slow down with the car in Neutral.

On a 1996-1998 this is most likely a problem with the speedometer cable. Check to make sure the gear is in properly, that the cable hasn't been melted through from a header or H-pipe, etc.

Either car will most likely stall if the EEC-V doesn't know how fast the car is going.
 

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Christopher Ihara said:
On a 1996-1998 this is most likely a problem with the speedometer cable. Check to make sure the gear is in properly, that the cable hasn't been melted through from a header or H-pipe, etc.
It's not a cable per se as the V.S.S. (vehicle speed sensor) sends a voltage to the computer rather than it being mechanivcal like itn the older cars. Check the connection to your V.S.S., I had the same problem and found that in pulling the computer to hav3e a chip burned, I had severed the ground for the V.S.S. that connect to the chassis where the computer is kept. It could be that ground, the wire having been severed, or even a bad V.S.S. Check your wiring before spending money on a new V.S.S. though (which can be found at most auto parts stores). The V.S.S. is located near the back of the tranny on the drivers side and the connector runs up over the tranny to the firewall and into the car.
 

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TIGGER said:
On my 96, the speedometer stopped this morning. Now the engine dies when I push the clutch in and come to a stop. I noticed the two issues at the same time. Are they both releated? Is there some sensor from the speedometer that the computer uses? I will check my gear when I get home. Any help would be appreciated.
Now, have you changed rear gear ratios? typically people compensate with a speedo gear- some speed shops will use one without telling you. Eventually it gets eaten up and you'll need a new one.

They are related. the computer kill the engine for some reason.

Blip the throttle and the engine won't kill itself. It's pretty frightening the first time you lose a speedo cable and your exiting the freeway and you have no steeing. remember it's hard to steer but you still can without power- you will have to pull on it like your trying to break it though.
 

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The IAC and speedo are on the same circuit apparently. If the speedo is providing no input, the IAC isn't giving any output. Therefore the car dies when coming to a stop..most notably, when you disengage the clutch. If you engine brake/gear down while slowing and then disengage the clutch, it's not near as apt to die on you.

This happened to me when my SpeedCal failed....twice.

Eric
 

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BlitzkriegMS_2 said:
The IAC and speedo are on the same circuit apparently. If the speedo is providing no input, the IAC isn't giving any output. Therefore the car dies when coming to a stop..most notably, when you disengage the clutch. If you engine brake/gear down while slowing and then disengage the clutch, it's not near as apt to die on you.

This happened to me when my SpeedCal failed....twice.

Eric
They aren't physically on the same circuit, but both are needed when coming to a stop. The cars computer uses the V.S.S. to know when the car is slowing down. It then signals the IAC to open up and hold the idle a hundred RPM or so above idle until the car comes to a complete stop to keep thje car from stalling, then a few seconds later it will idle down. If the V.S.S. isn't reading properly (i.e. a bad sensor, cut wire, stripped gear, bad SpeedCal, ungrounded) the computer will stay in closed loop won't know to open the IAC when coming to a stop and the car will die.
 

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Discussion Starter #8
Thanks for the input, I will have to jack up my car over the weekend and check the gear. By what I understand, those white replacement speedo gears for 3.73's do not last long. Mine has approx 20k miles. If my speedo gear is indeed my problem, where is a good place to get another? The local shop I bought mine from is out of business. Ford did not seem to carry it.

Refresh my memory, what tooth gear is needed for 3.73's?
 

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Ussually they are color coded, so if you know the color of what you're currently using your ok.

Otherwise, vendors like steeda know what tooth to use with what gears and cars....

This is cool, I knew that the two things were related but I never knew WHY.
 

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Interesting info, playahata. FWIW... I had the SpeedCal on my car. Then, I got a Fordchip.com dyno-tune. He compensated for my 4.10 gears directly thru the EEC. So, since I had the SpeedCal, and that, I had no speedo, and my odometer, etc. didn't work. Anyways, the car died 3 times withing 15-20 minutes of eachother, and wanted to die other times. Finally getting the SpeedCal out of the car caused the car to hold idle when depressing the clutch/slowing down in neutral. Weird phenomenon... :D
 

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I remember the gear I bought was white.
 

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So the VSS does have something to do with idle when you are slowing down?? If so, I need to be fuggin Ford tech, b/c the guy that tried working on my car obviously sucks.

My car has been having an idling problem, not that it idles too low, it idles too high. Ford tested all they could and couldn't figure it out. I asked the tech about the VSS, and he said that it had nothing to do with idle, or when slowing down, BS.
 

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I fixed the speed cal from dallas mustang and my car hasn't killed once today. Yesterday it killed twice. SO i hope that is the end of it
 

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Calvert2812V said:
Interesting info, playahata. FWIW... I had the SpeedCal on my car. Then, I got a Fordchip.com dyno-tune. He compensated for my 4.10 gears directly thru the EEC. So, since I had the SpeedCal, and that, I had no speedo, and my odometer, etc. didn't work. Anyways, the car died 3 times withing 15-20 minutes of eachother, and wanted to die other times. Finally getting the SpeedCal out of the car caused the car to hold idle when depressing the clutch/slowing down in neutral. Weird phenomenon... :D
Sounds like the SpeedCal was giving incorrect (if any) info to your PCM. From the sounds of Blitzkrieg's post, it's a common occurence.
 

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playahata said:
Sounds like the SpeedCal was giving incorrect (if any) info to your PCM. From the sounds of Blitzkrieg's post, it's a common occurence.
Well, I believe the flash to the EEC cancelled out anything that the SpeedCal was trying to tell the EEC, and vice versa. I mean, I had no speedo, no odometer, and no tripodometer, but I had a tach. That made the drive home from Detroit pretty fun. :D And yes, I would agree that this is a common occurence.
 

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Calvert2812V said:
Well, I believe the flash to the EEC cancelled out anything that the SpeedCal was trying to tell the EEC, and vice versa. I mean, I had no speedo, no odometer, and no tripodometer, but I had a tach. That made the drive home from Detroit pretty fun. :D And yes, I would agree that this is a common occurence.
I know what you mean, drove my car for three months without the speedo before I got my issues sorted out. I just learned to trust the traffic around me and made sure to err on the slow side.
 

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Calvert2812V said:
Interesting info, playahata. FWIW... I had the SpeedCal on my car. Then, I got a Fordchip.com dyno-tune. He compensated for my 4.10 gears directly thru the EEC. So, since I had the SpeedCal, and that, I had no speedo, and my odometer, etc. didn't work. Anyways, the car died 3 times withing 15-20 minutes of eachother, and wanted to die other times. Finally getting the SpeedCal out of the car caused the car to hold idle when depressing the clutch/slowing down in neutral. Weird phenomenon... :D
Brandon,

I had to read this a couple of times to understand exactly what you meant but finally my dim light bulb came on and yes, I'll bet that is exactly what was happening. Your tuner blasted the info to the EEC that included 4.10 compensation while probably unaware of the presence of the SpeedCal or at least with the knowledge that it was gonna be removed from the equation. With the new program loaded, the EEC was trying to calculate using the modified info from the SpeedCal instead of the native information it was expecting and thus couldn't process the weird values.

I went through nine kinds of hell with my speedo / SpeedCal for over a year while chasing down an intermittent problem which turned out to be a faulty wiring harness. It appears that Willie (TriBlkCobra) and Dallas Mustang have worked out all the bugs in the SpeedCal and the units work right every time now... as long as they're installed correctly.
 

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BlueStangGT said:
Brandon,
I had to read this a couple of times to understand exactly what you meant but finally my dim light bulb came on and yes, I'll bet that is exactly what was happening. Your tuner blasted the info to the EEC that included 4.10 compensation while probably unaware of the presence of the SpeedCal or at least with the knowledge that it was gonna be removed from the equation. With the new program loaded, the EEC was trying to calculate using the modified info from the SpeedCal instead of the native information it was expecting and thus couldn't process the weird values.
Well, he did know that I had the SpeedCal, and he also knew that it was going to be removed. What made me mad, was that the shop was supposed to remove the SpeedCal for me, at the time I was getting the car tuned. Well, that didn't happen, so I had to deal with poor driveability problems (dying). Anyways, I just find it interesting to see that when the EEC isn't able to process weird info, such as that, that when no speedo is detected, that the IAC remains closed. Its really pretty neat that the two work together, but unfortunate for us, in some occasions. Glad to hear that a new harness fixed your problems, and that all of the SpeedCal issues are resolved. Willie should be commended for going the extra mile.
 

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OK, time to clear some stuff up here....

1. All cars from 94 and up use an electronic speedo, there are no mechanical speedo cables on this car.

2. All of these cars use the VSS to control the IAC valve and prevent stalling during braking.

3. If your car stalls during decelleration/braking for whatever reason, you run the risk of losing braking due to the hydroboost brakes on our cars.

4. The PCM on the car has ABSOLUTELY no way of knowing that a SpeedCal, Abbott, or differernt driven gear (if applicable as on 94-98 cars) is present on the car. They will merely BOTH correct the VSS signal and get the wrong answer. Brandon, I read your post and can only think that something was wrong with the SpeedCal. I'm guessing thats why you we're removing it anyway.

5. The white 23 tooth speedo gear is NOT a Ford gear, it is a Mopar gear and the mesh isnt exact. Thats why it shreds. GT's with 8 tooth drive gears seem to have more problems than Cobra's with 7 tooth drive gears.

Most of you guys posting here look familiar and with the exception of Eric I thought I'd resolved all of them. And most of you guys we're running the old design I believe also.

Eric I know both of your's were the old one. And I thought when we talked I speculated that you were having some power distribution issue as if I remember right the 2nd one died when you disconnected the battery (I think that was you) and that the new one incorporated a blocking diode to protect against reversed power. Did you ever mail the 2nd one back to DMP (or did I get it?). The reason I'm asking is that they've got an old one which had a fried cap on it that could have been yours. And yes indeed you fried two of the old ones and as I stated when we talked several times, I would have loved to get ahold of your car to find out why. But there wasnt any way for that to happen and understandably you were tired of dealing with it. At which point I believe I passed on the info to DMP on all the heacaches you'd had with it and all the work we'd done to try and figure it out. In fact, I believe you contacted me over a speeding ticket and lack of operational speedo at the time and we were talking of trying to get a letter to you about the inop speedo. However, last I heard from you you'd taken care of it on your own.

nickcam79, how did you "fix" the SpeedCal?

I do believe its time to do that SpeedCal FAQ page I've been putting off.....
 

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Re: OK, time to clear some stuff up here....

TriBlkCobra said:
I had the same stalling problem after my Speed Cal died. Killing my speedo, AND causing my car to stall intermittantly when stopping.

The speedcal shorted due to my poor wiring of the power lead, rubbed on the body, blew the fuse.

I replaced the fuse, and rewired the power cable. All is fine now.
 
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