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Old 06-23-2003, 08:54   #1 (permalink)
DukeU
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Question PCM computer unit malfunctioning? ('95 5.0 HO)

Hi Ford-guys,

It seems that the input of the speed sensor in the Powertrain Control Unit is gone. A dumbo in the workshop mixed up wires for the reverse lights with the speed sensor, putting 12 volts on the input and instantly blowing the fuse. So at least 10 amps must have passed thu.

Now the car stalls at every stop after the clutch is depressed. Any way to go around the speed sensor? Any sources for a new PCM unit that ship to Europe (I live in Holland)?

Thanks, Duke.
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Old 06-23-2003, 16:46   #2 (permalink)
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Re: PCM computer unit malfunctioning? ('95 5.0 HO)

Try www.corral.net But Ithink you can get away with a resister in there. I'd take it back to the workshop. Or are you worried about them making it worse ???
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Old 06-24-2003, 06:09   #3 (permalink)
XR9UTE
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Dukeu,
What is the catch code on the EEC? Should be something like T4M0,U4P0,W4H0. Are you sure the VSS was shorted?
It wasn't your clutch/NDS switch that was shorted.
Can you open up the EEC and see if there is any burnt tracks?
I may be able to find an EEC for you if it is terminal. Or I could supply you a Tweecer and you could turn off the strategy relating to VSS/Idle not to mention tune for any mods you care to do in the future.

Regards,
Pete.
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Old 07-01-2003, 03:06   #4 (permalink)
DukeU
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Re: PCM computer unit malfunctioning? ('95 5.0 HO)

Sorry guys for not responding sooner, but my boss sent me to the corners of Europe for an emergency case and I just returned this morning.

Quote:
Originally Posted by ebxr8240
Try www.corral.net But Ithink you can get away with a resister in there. I'd take it back to the workshop. Or are you worried about them making it worse ???
I'll check this link. Going back to the workshop is not an option, this is the UK manufacturer of the body/chassis and they are not a Ford workshop. And they have proven that they are not good with electronics! After having worked on the chassis someone mixed up one of the wires coming from the reverse switch and the VSS sensor on the tranny. This has put 12V that normally goes to the switch on the VSS input of the EEC, blowing the fuse in the reverse lights circuit. I will check again that this is switching plus 12V, not switch to ground.

Quote:
Originally Posted by XR9UTE
What is the catch code on the EEC? Should be something like T4M0,U4P0,W4H0. Are you sure the VSS was shorted?
It wasn't your clutch/NDS switch that was shorted.
Can you open up the EEC and see if there is any burnt tracks?
The funny thing is that none of these codes are generated (I will try again this weekend). Mind you, I have no tester, I must do with manually switching the trigger and watching the malfunction light giving the flash codes.

I am sure the wires were mixed up and the fuse went because of this. After myself having disconnected the two wires the fuse lived.

At the time I had no clutch switch connected. I have now, but no change. I did open the EEC to see for any burnt tracks, but non of that, it looks in good shape (new in fact).

Quote:
Originally Posted by XR9UTE
I may be able to find an EEC for you if it is terminal. Or I could supply you a Tweecer and you could turn off the strategy relating to VSS/Idle not to mention tune for any mods you care to do in the future.
Pete, can you tell me the costs for that tweecer, and is there a manual with that? I am afraid that replacing the EEC is in the cards for me. I will check it all again (10th or so time) to make sure I did not oversee anything. The car is a Cobra replica (see www.gdcars.com), so going to the Ford dealer is not an obvious thing to do.

Meantime the car is no fun to drive, stalls at every junction, so I am determined to solve it one way or the other. Before this it ran fine.

Thanks guys, I will come back on this after some more checks.
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Old 07-01-2003, 05:00   #5 (permalink)
XR9UTE
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Dukeu,

Let me know the catch code of the EEC you have?
You will not see fault codes for a blown NDS.
Tweecer is about $800-$900 aussie or $1300-$1400 for the RT.
The Caledit software has a help manual and there is a great mailing list where you can get help.
I may be able to repair your EEC. I can source another one too.
You should be able to get a stable idle without a VSS though. Have you tried adjusting your TPS/Idle speed settings?

Regards,
Pete.
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Old 07-03-2003, 08:45   #6 (permalink)
DukeU
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Pete,

Let me describe what happens: when approaching a junction, I let go of the throttle: the car brakes on the engine compression and the fuel supply is killed. So far it works as it supposed to.

However, once coming to a stop, depressing the clutch will cause the engine to stall. It is as if the fuel supply is not turned on in time. In a few cases the EEC picks up just in time to get it going again, but you can see a dip in the revs downto almost 300 rpm. Most of the time it just stalls at that point. It will start at the first throw again and idles fine.

I added a clutch switch hoping that this would cure it but it almost feels like it made it worse. I added a powerchip but that did not change anything, only it sure added power&torque as it should.

Early '95 at the first test drives after the build I had the same thing but then I did not have the VSS sensor connected, because I used the hole for a mechanical speedo. Once the VSS was placed back in and wired up it behaved as supposed. So I am pretty sure it has to do with the VSS.

Sometime in the next days I will check the wiring upto the EEC unit again and run the tests and let you all know what came out. First I am sent off to an oil rig for work for a day or two, so a new post will take some time.

Question: This engine is from an US Mustang Convertible; are the Ozzy Ford units the same? Any clue about costs for a new EEC unit?

Thanks & regards, Duke.
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Old 07-05-2003, 08:23   #7 (permalink)
XR9UTE
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Re: PCM computer unit malfunctioning? ('95 5.0 HO)

Email me direct at pie@icenet.com.au
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