Wiring diagram

[David S]

Has anyone got a copy of the wiring diagram that I might be able to a copy.
   
   Having replaced the exhaust the car still runs like the cats are blocked, Neil Fisher reckons it is a wiring problem. So looks like a winter period trying to understand the wiring, unless anyone has had a similar problem and resolved.
   
   Let me know, thanks

[David S]

To provide more detail on the faults I am chasing or wiring errors:
   
   1. I have a loss of power, the car was put on a rolling road prior to replacing the exhaust. As a supercharged Ace it should be showing 320-340 bhp, the rolling road showed a maximum of 201 bhp and would not rev past 4000 rpm. The check of the cats showed the first two badly burnt with the inners boith twisted and collapsed. Having replaced the exhaust, the car still runs as if the cats are blocked. Discussing this with Neil Fisher his view is that this is wiring related.
   2. Whilst on a steady throttle the engine will fluctuate, no idea on this one
   3. Rev counter after 2000rpm starts showing increased revs upto and holds at 4000, until the accelerator is released for a few seconds and then it drops back to 2000 - I think this is an earthing issue although changing the distributor cap has marginally improved the problem.
   4. The Coil pack has been replaced and appears to have 2 wires (excluding the high voltage lead to the distributor)the white wire I lose into wiring loom and a newly installed black wire that goes into the fuse box. My understanding of older coils is that 1 wire goes to the ignition and 1 wire to the distributor. Looking at some of the diagrams on Google that there may be 1 or 2 wires which are earth. Question is how many wires come from the Coil pack and where do they go.
   
   Any advise welcome
   
   thanks David

[DGoose]

Hi David,
   
   It was good to meet up at the NEC, look forward to seeing the car when you get the niggles sorted.
   
   This applies to the standard 302EFI (US version) but I guess in principle would apply to your car also.
   
   One of the common causes of cats overheating is an incorrect TPS (throttle position sensor) setting, I had this issue on my 1994 car when I bought it and the cats actually glowed red.
   
   Loads of the mustang forums discuss this in detail but from memory you should have an output voltage at idle of around 0.9 from the TPS, any higher than this at closed throttle and you will simply dump unburnt fuel in to the exhaust system as the fuel air mix is way to rich, hence knackered cats.
   
   If TPS is really out of kilter this will also prevent performance at WOT (wide open throttle)as the ECU doesn't ask for enough fuel.
   
   TPS voltage is very easy to check with a multimeter and a couple of small safety pins through the wires but do set your base idle first.
   
   I'll try to find the article I found as this went in to much greater detail than above.

[DGoose]

http://www.allfordmustangs.com/forums/5-0l-tech/177382-proper-tps-idle-settings-5-0-fix-idle-surge.html
   
   
   http://www.muscularmustangs.com/tps.php

[Max Allan]

http://forums.corral.net/forums/ is another good site for Mustang 94/95 engine probs.
   
   I had a CD with wiring diagram for all variants of Ace, but lent it to someone who never returned it. However, I found it pretty useless. For a start it required AutoCAD to open and none of the circuits were colour coded making it difficult to track path of a circuit when scrolling around the page.
   
   I agree with DGoose - sounds more like a fueling or ignition problem than wiring problem. Is ignition advancing with increased revs? Is fuel filter OK?

[AcemanToo]

Neil Fisher of Redline has a set of wiring diagrams for the Brooklands Ace. I asked him for a copy some years ago but he couldn't find them. Might be worth trying him to see if he's found them in the meantime. I once spoke to the man who designed all of the Ace wiring - I think his surname began with a K - not much help I know, but I've got his contact details somewhere. If I find them, I'll post them here.

[Nev]

I have some diagrams, will have a look early next week for you, incase they can be of any help.

[Max Allan]

Hi David
   
   Any further forward unearthing the cause of your engine malfunction?

[David S]

So far have replaced the distributor cap and rotor, the rotor had been broken and glued together this was not operating correctly and had scorched the inside of the distributor cap, this has made a small improvement.
   
   Looking at DGoose information I need to remove the IAC to be able to loosen and adjust the TPS. The bottom bolt for the IAC does not seem to allow for a small socket and do not see enough space for a spanner. Need to have another try before going to the local garage

[DGoose]

Hi David,
   
   Easiest way to get the IAC off for cleaning is remove the entire throttle body.
   
   You can test the TPS voltage without having to remove it simply by sticking a couple of pins through the wires and attaching your voltmeter to the pins.

[David S]

Finally received some new fuses for the multi meter this morning.
   
   Battery test measures at 13.3v seems a light high for a 12v battery.
   
   Checked the TPS, it has three wires as per the website page DGOOSE sent me, of course being AC each of the coloured wires does something different than shown, however it states the middle wire and this correct ignore the colour (in my case the wire is all Grey). The measurement shown was 0.96 rather than 0.98-0.99. Is this a big enough difference to cause a lack of power[?]
   
   If warm enough over the winter break will strip down the throttle body in order to remove the IAC then re-fit to adjust the TPS

[DGoose]

Hi David,
   
   If the reading is low rather than high the ECU would call for less fuel than required, the difference between the reading you have and optimum is pretty slight but could still under fuel the engine  I guess.
   
   Did you check the reading with the throttle wide open ?
   
   Engine doesn't need to be running for this, provided the ignition is switched on the TPS will be live, just hold the throttle fully open and see what voltage you get -
   
   Maybe clean the air flow sensor next, nice easy job but be careful as the filament is quite delicate.
   Use electrical contact cleaner and a cotton bud as described on the mustang forums.
   
   Good luck,

[David S]

Just tested with throttle wide open and measures 4.63v.
   
   MAF looks like it needs a special tool to unscrew, was going to check a spark plug but these are not standard size socket to remove looks like 16mm.

[DGoose]

In the process of elimination I think you can safely say the TPS is not the cause of your lack of top end revs, seems as though it is doing what it should.
   
   The four screws holding the MAF in place have anti tamper Torx heads (standard torx with a pin in the middle) sets of bits are readily available on ebay etc.
   
   If, like me, you're too impatient to wait for proper tools and if the the screws are not overly tight you may be able to shift them with nose pliers, side cutters or similar. If the filament has gunge and muck on the forward facing surface clean very carefully with electrical contact spray.
   
   I had an issue on my car after cleaning & re-conditioning the piper cross filter, seems that I was a tad liberal with the conditioning spray (oil ?) and the excess was sucked through the filter, up the intake and coated the MAF sensor - result was hesitation at full throttle and noticeable lack of power at higher rpm although the engine would still rev to 5k if asked to.
   
   Cleaned the filament and back to normal.

[SB7019]

If you are in a hurry both Screwfix and Halfords sell box sets of bits that include the Torx security ones.   If you have a branch of either close by you can check online to see if they have any in stock.  I bought a set years ago and also find them very useful for fixing ( or al least trying to fix) domestic electrical items as well.