Megaquirt my SN95, sanity check?

Alright, so, I have this stupid 95 Mustang with a 302 and it's all stock under the hood. I've had sensors slowly dying; first the TFI ignition module. Then the coolant sensor. Now something else is causing it to run overly rich (the coolant sensor replacement improved the situation, I think it's the intake air temp sensor this time) and I've got a check engine light. I go to pull codes (OBD-1 car, I've got a $25 code reader) last night to find out what else I should replace and lo, the car won't go into any test modes or throw codes to the reader. Assuming the code reader has gone bad for some reason, I go get a jumper wire to try convincing the computer to enter a KOEO test situation, and it's just not happening. Research says that the computers in these cars will often suffer from a burned trace or pin and I get to open the ECM up and try to rebuild the trace by hand or else find a replacement computer. Until then I can't pull codes and frankly I wonder about the longevity of this situation.

Here's where you come in; using a pre-assembled MS2 & PnP cable meant for my car, how much insanity am I looking at as far as getting this whole thing running again? Looking into it, I've got a tach wiring mod to do, an A/C mod so the compressor clutch is properly controlled (seems easy enough), and the costs related to such a swap. Does it make any sense to go that route vs. trying to find a new or similar condition ECM and try to fix whatever is causing all of this fun with dying sensors? My plan is to also add some heavy gauge grounds, one from the battery negative and one from the alternator bracket, and run both to a common stud mounted nearish the battery on the inner fender. Where else should I try to run one? I've wondered if a ground problem might have caused amperage to find a sneak path through the ECM or its sensors in the engine bay.

I'm trying to weigh my options. Eventually I would like to replace the engine in the car with an Explorer unit with EDIS and better heads, etc. So MS was always an option, I think if I went this route I could adapt fairly easily to later engine easier. Because of exhaust component age I've got leaks that seem easiest / smartest to fix by shot-gunning the center and back sections (the parts are stock, 17 year old, 150k mile bits with leaks at the junctions) so I'm looking at, say, $700 for the parts I want there... the MS is $600 plus at least one LC-1 (is there a better wide band out there for this for the money?) so $750 there, and I'd probably get a used netbook to do programming & logging with. What else should I consider?

I have another car and a motorcycle to use for getting around so I can park the car while a plan is formed. I'm also open to just dropping the car at a dealership, letting them use the troubleshooting break out boxes they have access to to ensure the wiring isn't a problem (harness has never been touched and looks good visually) but this car's tuning has always seemed off. Sorry this is so long.

How expensive can a used EEC-IV ECM be? I sold the LA3's for the Turbo Lima's for $35 5-10 years ago. Surely a 94-95 5.0 one would be less?

Man, I'm all about the Megasquirt but if it was me, I'd just fix it and leave it as-OEM.

TFI died? It's a Ford, they do that. I know some people who keep a spare module, module socket, distributor wrench, and timing light in the car. You can change it out in under five minutes if you're willing to spin the distributor around and then re-set the timing.

You could probably rebuild all of the electronics in the car cheaper than doing Megasquirt properly. Oddly enough, doing MS properly involves buying new sensors, so you're not really much better off.

Is the car "modified" in any way? Cold air intake, that sort of crap? It's amazing how cars with that kind of stuff on them are always the ones with weird drivability problems...

You mention exhaust leaks. Any of them upstream of an O2 sensor? Exhaust leaks can pull oxygen into the system, courtesy good old Bernoulli and his Effect, and drive the O2 sensor lean, causing the computer to dump fuel.

In reply to Javelin:

Would have to find one. The computer for my car isn't the same as the A9L (I believe it's called) that the Fox 5.0's used that people seem to like using a lot more. Haven't checked on car-part.com yet. If they're that cheap I'd take the gamble and just get one and try swapping it to see how it goes.

Edit: Looks like $100 should get me one off of car-part, so I guess that's baseline, can call around locally and see if a yard here sells for less.

In reply to Knurled:

The prob I have is watching random sensors die. Maybe they're all aged and me putting the car back into somewhat regular service is stirring the pot (I don't think the older couple that owned it before me drove it much). And even when I just got the car it never really ran that well after a full tune-up.

I have the money to do the MS and I dread dealing with the stock computer after a head, cam, and exhaust swap.

There's a drop-in K&N filter. I have wondered if oil from the filter has caused problems with the MAF & IAT. That's it. Everything else is stock. The leaks are before and after the O2's, the H-pipe was pulled last fall when I swapped the throwout bearing for a new unit. I have both lean and rich out of limit errors last I pulled codes. I'm eying a Magnaflow X-pipe with cats and then a Dynomax back section.

You better believe that Fords and K&Ns don't mix. Fords are bad to get dirty MAFs with paper filters, let alone oily ones. Dirty MAFs generally run you lean, not rich, though.

I see where you're getting at if you have upgrades planned down the road. It will be good practice to learn how to tune MS on a fairly mundane engine, because when you get things into the nasty/fun zone, tuning gets a little weird sometimes, and it helps if you already have the "feel".

You're not going to like what I'm going to suggest, though: IMO, you should make the car run well now, and only after it's running cleanly, switch to MS. If you have any faulty sensors, wiring issues, or mechanical problems, switching to MS won't take them away, and you'll have the additional headache of trying to tune while dealing with those problems.

You really do need to fix those exhaust leaks if they are before or close to the O2s. They will cause problems. It's a shame you only have a codereader and not a scantool, Ford codes are next to worthless.

I concur with others get the sensors sorted out first. Simple quality time with a multimeter. If you don't have one and are thinking MS in the future go get one. Once you know the sensors are good to go then MS

Take the MAF out and clean it with electrical contact cleaner (in a spray can) This should help things.

Also if you go ms you don't have to junk the sensors. You just have to give the MS unit the proper calibrations / settings for the sensors. There is a DIY P&P unit for your car Here >>> http://www.diyautotune.com/catalog/diypnp-ford-60-pin-eeciv-unassembled-kit-p-421.html This tels me that they must also have the settings / calibrations for the MS to use the ford stock sensors

It does not look like they have an assembled one yet. You could ask them if they would assemble it for you if you want to go that rout. I don't know if DIY will do that but hay it never hurts to ask.

In reply to dean1484:

Well, there's this thing; http://www.diyautotune.com/catalog/megasquirtii-v357-plug-and-play-for-19861993-50-mustang-p-418.html

I like the unit you linked me to thou, I'm not afraid to build the thing (time for a better solder gun!) and it would save me a noticeable amount of money and no jumper harness between factory wiring and the MS box. I've already got both a DVOM and analog VOM so the bases are covered as far as meters. I've cleaned the MAF once upon a time, didn't really focus on the IAT. Will need to bust out the Haynes manual and start reading output voltages / resistances I guess.

So maybe Phase 1 = good exhaust without leaks and a second hand ECU swap. Phase 2 could be building the MS P&P and swapping in once the car is happy (or as happy as it can be) with a factory ECU and all sensors are working well.

Knurled: Is there a scan tool to read actual sensor data through the ECU on these things that a mere mortal can acquire or do I have to pay a ninja to swipe one from a dealership? I didn't think there was anything like that out there for the home hobbyist without going to a Tweecer setup (which I have no interest in doing).

Dealerships probably don't have the necessary equipment for these older cars anymore. ;)

You might find a shop selling an older scantool like the infamous Snap-On Big Red Brick, or a Mastertech, or similar for a couple hundred bucks. Still probably beyond what's reasonable, of course.

In reply to Knurled:

I'd like to use one of the big red Snap-On's to maintain this thing, I actually got some seat time with them back about a dozen years ago while working on my B.S. in Auto Tech so that'd be just fine. What I'd really love is for someone to sell, cheap, a cable to attach one to a computer via USB. While I'm dreaming maybe it could be delivered via unicorn?

This thread is relevant to my interests... been thinking about doing an MS controlled EFI swap into my '70.

In reply to darkbuddha:

This is probably of greater use; http://www.diyautotune.com/tech_articles/megasquirt-carb-to-efi-part1-nova.htm

There was also an article in The Magazine about this on a Volvo 122 that, while somewhat different, spells out what you're looking at dealing with.

Too bad you don't have OBD-II.

All the cool USB stuff is OBD-II only.

There's something to be said for industry standards, even if it's because the government mandated it. With ONE connector and a very small handful of communications protocols, it's easier for small third-party vendors to come up with useful products, instead of having to have one of two flavors of Ford, one of four flavors of GM, Chrysler, one of three flavors of Nissan, etc.

pres589 wrote: In reply to dean1484: Well, there's this thing; http://www.diyautotune.com/catalog/megasquirtii-v357-plug-and-play-for-19861993-50-mustang-p-418.html

That is for up to 93 I don't think it will work with your car as a P&P. The one I pointed you to looks to be specific for your car.

I think you have a plan re getting it up and going. There is a 5.0 sn95 in the local P&P I could see what they want for the ECU. I am betting $30-$50. I can swing by and ask them tomorrow. I have a wanting for some turbo parts.

Any special tools needed to remove it form the car.. . . . Where is it in those cars?

For what it's worth, Ford has some of the most easily tuneable ECM programming out there--even the OBDI stuff. I'd leave the stock electronics and get a good tuner program like Moates Quarter Horse.

In reply to dean1484:

I don't know what size but the fasteners holding the ECM in are, I believe, normal hex head bolts. Small ones. It lives behind the passenger side kick panel. If the car in the yard you've seen is a Cobra it doesn't help me. I don't know if AT vs MT matters, mine is a manual trans.

Will: I have no seat time with any tunable ECM so it's all hearsay to me but it seems like the MS would be one of the easier to deal with ECM setups out there in regards to being able to tune on the road and integrate the brains with a wide-band O2 sensor. I've heard of the Quarter Horse but not sure what it's like to live with without a dyno. Can you expand on that?

You can absolutely do road tuning with the QH setup and a wideband. I know several guys who have tuned their cars that way, and done pretty well with it, until they could get to a dyno for final tuning.

In reply to dean1484:

How'd it go pulling that ECU, did you snag that?

In reply to pres589:

Call me 339-222-two zero zero three. I am going to the yard this am and I need yo know your price limit. Or text to the same number.

Solid.

Well I was at the yard and learned that there are 6 possible ECU's for your car. I will need the numbers off your unit. They are interchangeable with several cars and years. Unforchantly if it is a unit that they have to get it will cost you. If you can get me the ECU numbers I can then see what they have.

Just pulled back the kick panel (and watched the plastic around the heater blower fan disintegrate when I touched it during the process...) and the ECU has the following markings; T4M0 and F4ZF-12A6540-EA. T4M0 is apparently one of two possible GT 5-speed computers that could have been installed in the car.

It's kinda funny, fiance has a 95GT and the first time it through a check engine light i tried everything to get my reader to pull codes but after a little research i found out that the 94-95 are odd balls. They have a OBD1 port under the dash but IT ISN'T HOOKED UP FROM THE FACTORY. You have to approach it just like a pre-obd ford and use the jumper box under the hook and count the blinks of the check engine light.

Also if you really need to replace the ECU get one out of a 86-93 5.0 mustang, they bolt right in,have a better factory tune and take better to upgrades like cam changes

The ADLD under the dash in this car is an OBD-II part but like you've noticed, it doesn't really do anything in a normal fashion (I believe a couple pins are connected to something, but it isn't useable for trouble shooting and should be ignored). Pre-OBD would be something without a check engine light like we're used to, like something with points and a carb. OBD-I is up to 1995 and not a standard data stream like OBD-II.

Grounding the diagnostic pin under the hood does nothing currently, it used to work, it is now dead and from research most likely caused by a burned or otherwise open trace inside the ECU. Which is why I wrote this thread, trying to find a way to remedy the situation, and I'll try to find a drop in replacement Ford ECU for the time being. And from everything I've read, the 86-93 computers are similar but not pin/plug compliant and would require surgery on the factory harness to make work. Which doesn't interest me at all.

Hay there is a 93 mustag with a 5.0 and a standard in the P&P. I was looking at the interior the other day. Intrested? I can get a price.