Engine 1987 mustang GT, HO vs Non-HO questions

1970machwon

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I have a 1987 mustang GT with the AOD transmission, littered with issues. It's hard to describe but I'm under the impression that i have a non-HO motor despite the fact that my car should have an HO. it's running on the non-HO firing order on my distributor since i bought it, but I bought an ECM labelled "DC" which is stock in my car (for HO) if the mounting bracket label for the ECM is correct. It has the "5.0 HO" intake plaque as well. I believe my car has the E6TE heads (the junk ones they stopped using after 1 year of production) My car runs, but runs really rough, especially at idle. It idles high at around 1500-2000 RPM and i hear some slight engine noise. I used a laser temperature sensor on the exhaust headers to see which cylinders were working good. cylinders 3 and 4 hovered around 300-400 degrees while the rest stayed at and about 600-700 degrees, so they're either not firing, or firing intermittently since the injectors would be spraying before or after they should. My main question is, what should i do? i feel like i have three main options, but I'm not sure what would be better for performance or cost effectiveness or ease of the fix.
1) Buy a new ECM for my non-HO engine, although im not sure which one that might be
2) Buy a new cam to change the firing order to HO and get a little more performance in the process (is this possible? cam swapping the firing order sounds like it shouldn't work somehow)
3) Buy one of those fancy computer type deals that allows you to remap firing order and other things (I'm not too positive something exists like this that works, and it's likely expensive, and im a broke college kid)
I know you can't just rewire the injectors since the computer will sense rich/lean improperly, but I'm just lost on what my car has, and what i can do with it. Any help is greatly appreciated, even if it's just past experience or opinions.

To be honest, I'm not even sure this is the issue at hand. cylinders 3 and 4 could just be doing something unhealthy i dont know about. I bought an IAC and a TPS to try and solve the idle issue that I've yet to install that may help, but I imagine something greater is wrong here. by chance, is there any way to identify if the engine i have is the original in the car? kind of like a VIN match?
 
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General karthief

wonder how much it would cost to ship you a pair
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There is a stamp on the block behind the intake I think it's on the passenger side, it should be the last part of your vin#, it's kinda hard to see and is hand stamped so not pronounced. The heads will have a gt cast on one end below the valve cover by a headbolt, I would pull the upper intake, valve covers and note the valve opening sequences.
now before you tear it apart, have you tried the ho firing order?
Have you checked for codes?
In the technical/how to thread at the top of the tech page will show you how to do things like check for codes and cure that surging ldle/stalling problems, check it out.
 
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jrichker

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This doesn’t prove that the block is a HO block. Some trucks evidently use a HO firing order with a low lift cam (this will result in less than the desired HP output). However, it will definitely prove that a block can’t be HO because the firing order is wrong.

Remove the #1 & #3 spark plugs. Put your finger in #1 spark plug hole. Crank the engine over until you feel compression on #1 cylinder. Slowly turn the engine until the TDC mark and the timing pointer line up. Mark TDC on the balancer with chalk or paint. Put your finger in #3 spark plug hole and crank the engine 90 degrees. You should feel pressure trying to blow past your finger. If you do not feel pressure, repeat the process again. If you feel pressure, it is a HO engine.

No pressure the second time, remove spark plug #5. Put your finger in #1 spark plug hole. Crank the engine over until you feel compression on #1 cylinder. Put your finger in #5 spark plug hole and crank the engine 90 degrees. If you feel pressure now, the engine is not a HO model, no matter what it says on the engine.

Using a small carpenter or machinist square to mark the harmonic balancer off into 90 degree sections may be helpful here.

A 15/16 deep socket & breaker bar or ratchet may be used to turn the engine.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8


Do an end to the injector wring test to make sure that the injectors are properly sequenced for a HO engine and computer

Disconnect the main connector from the computer and pull it down so that you have good access to the computer side of the connector.
Place one voltmeter lead in pin 40 or 60 - they are both the main computer power ground. This lead does not change for any of the tests
Disconnect all the injector connectors from the injectors.
You will re-connect them one at a time to do the testing. Once you have checked an injector lead, disconnect it before testing the next injector. Fail to do this and you will get incorrect results

Turn the ignition switch to Run
Check pins 37 & 57; you should see 12 volts.

Computer wiring harness connector, wire side
71316.gif


Computer wiring harness connector, computer side
88243.gif


Here are the HO injector wires that are different; check to see that you have 12 volts on them one at a time.
Connect injector #3, look for 12 volts on pin 12 on the computer. Disconnect the injector connector from the injector before testing the next wire.
Connect injector #7, look for 12 volts on pin 42 on the computer. Disconnect the injector connector from the injector before testing the next wire.
Connect injector #5, look for 12 volts on pin 14 on the computer. Disconnect the injector connector from the injector before testing the next wire.
Connect injector #4. look for 12 volts on pin 13 on the computer. You are finished now and can reconnect all the injector connectors to the injectors.
 

02 281 GT

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There is a stamp on the block behind the intake I think it's on the passenger side, it should be the last part of your vin#, it's kinda hard to see and is hand stamped so not pronounced. The heads will have a gt cast on one end below the valve cover by a headbolt, I would pull the upper intake, valve covers and note the valve opening sequences.
now before you tear it apart, have you tried the ho firing order?
Have you checked for codes?
In the technical/how to thread at the top of the tech page will show you how to do things like check for codes and cure that surging ldle/stalling problems, check it out.
I'm fairly certain the "GT" cast into the cylinder head is a feature of the GT40 (non-P) cylinder heads only. There is no way to visually distinguish E5, E6, or E7 heads while they are installed on the engine.
 
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1970machwon

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Can confirm the whole e6te thing, i posted that on a thread a while back asking for some ID since it ran different spark plugs than what my engine should.
Does anyone happen to know what cars those heads were actually used on? Or if they might even be stock?
I changed out my TPS, IAC, and that didn’t fix any of my problems. I’ve yet to do much else because it’s too cold and i only get about 2 hours of daylight when I’m not busy, but i plan to update this thread as i go because this is a crappy issue. Could 2 dead cylinders cause the computer to idle my car high?
Also- i might add that i had to change out the cars harness and the fella on ebay said it’s for an ‘88 GT but most things were the same. My ECM is as follows
 

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Mustang5L5

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They stuck the e6 heads on pretty much every other 5.0 around the 87-93ish time period that wasn't a mustang or mark 7

Pre-91 birds and cougars, crown Vic's, town cars, etc.

You need to verify other parts on the car. What color are the injector? Orange or gray? Behind the distributor is a part number on the lower intake. What's the part number?

If it is running a non-ho firing order, it won't run properly with a HO ECU as those fire an injector at a specific time assuming the 351/Ho firing order
 
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General karthief

wonder how much it would cost to ship you a pair
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If you can beg, borrow or steal (not really but it fits) a 'camera on a stick' ( bore scope? ) and look for the eye brows on top of the pistons, I've found that non ho engines do not have them, can someone confirm this
 

1970machwon

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According to the pistons, I have a non-HO. They’re flat like the pictures 02 281 GT posted.
The injectors look like this, orange.
It’s difficult to to get to the intake behind the distributor, but after much struggling it appears to be
“RFE6SE
9K46LO”
The last two letters on the bottom row may be wrong, it was a struggle to even get my eyes at an angle to see it with cables and such in my way. If it’s like any other part, the key letters are the E6SE.
I’m thinking this engine has been kind of mashed together with a truck 5.0 (or some other car) internals and all the mustang looking bits like the intake are original.
I don’t know if it helps, but when i bought the car, the ECM had been clean cut right out of the car at the ECM pigtail. Maybe it was stolen, or the owner maliciously tried to sell me a zombie car with an intentional no-start. Either way I’m stuck with it lol
 

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02 281 GT

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The lower intake is the same on HO and non-HO engines that were equipped with the Mustang-style intake system. The only difference the engines would be in the upper intake. Non-HO engines have a much smaller throttle body than their HO counterparts.
 
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Mustang5L5

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To get right down to it, if the camshaft is not a HO cam, you won't be able to run the HO ECU as it fires each injector in sequence with its firing order which is determined by the cam. The non-ho engines used batch fire which fired each bank of injectors together.

You could rewire the injectors for the non-ho firing order...but honestly I'd start looking for a Explorer engine to use as a swap engine here.
 
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1970machwon

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To get right down to it, if the camshaft is not a HO cam, you won't be able to run the HO ECU as it fires each injector in sequence with its firing order which is determined by the cam. The non-ho engines used batch fire which fired each bank of injectors together.

You could rewire the injectors for the non-ho firing order...but honestly I'd start looking for a Explorer engine to use as a swap engine here.
Wouldn’t I be better off getting an ECM that would run the car first? I have performance plans but for now i just want a running car. What ECM would work?
 

Mustang5L5

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I don't know enough about the non-HO ECU to make a recommendation. They are all speed density, so grab a generic pre-91 cougar or t bird ECU and try it
 
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