Ok I just got a 88GT and noticed the intake didnt say "HO" instead it just says "5.0 EFI" which I didnt know if speed density cars said "HO" or not like my 95 does...So I did more looking and it has wierd firing order "15426378", it has orange top fuel injectors and I noticed on of the engine hoise hooks on diver side it had "E6SE" stamped on it. Whats confusing me is it appears to run fine and has as much power as a stock 5.0 would have. The car also has the factory tube headers. It appears all stock...but how if it's running the speed density computer is it ok? What comp/ecu should it have? Is it probably a 86 GT engine?
I got a "new" 88GT and has funny engine and I have ?s
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ID89GT
10 Year Member
It's probably a non-HO engine...same as 1986 gt.
The firing order and computer need to match. Using a mustang speed density computer, with a non-HO firing order camshaft will still run, but not as well as it should.
You really need to do a little more digging and see what parts are on there. What computer part number, heads are probably e6 heads, e6 upper intake, etc.
If the cam is a non-HP firing order, you'll want to change that. But confirm first.
The firing order and computer need to match. Using a mustang speed density computer, with a non-HO firing order camshaft will still run, but not as well as it should.
You really need to do a little more digging and see what parts are on there. What computer part number, heads are probably e6 heads, e6 upper intake, etc.
If the cam is a non-HP firing order, you'll want to change that. But confirm first.
ID89GT
10 Year Member
If it is running with non ho firing order then it has a std 302 cam. Could be roller could not. I had an 87 gt with an 85 Lincoln engine running 302 firing order and using the speed density comp. Never has a prob with it. But the car won't run if you change the firing order without changing the cam to either a 351 cam it an ho cam.
tims 86
Member
ok im a little confused, if it is a speed density computer it wont have the maf sensor, and vice versa correct? simple way to tell 
ok im a little confused, if it is a speed density computer it wont have the maf sensor, and vice versa correct? simple way to tell
That's not the question.
Question is non-HO firing order with potentially a HO computer.
The non-HO cars use batch fire where the HO cares use sequential firing of the injectors where the fuel injector is timed to fire when the cylinders spark plug fires too.
There are non-HO computers that will work.
All I'm recommending the op do at this point is identify what he has. I wouldnt change anything yet
tims 86
Member
88 mustangs were speed density to exept for california cars.
srry, all the vice-versa talk got me aliltwisted around.
Ok so I pulled off the plate on the intake that said "5.0 EFI" the plate doesn't say "HO" but "HO" is cast on the intake manifold under the plate...so I have a HO intake manifold? this engine is kinda confusing me cause it runs with the non HO firing order... but has the orange "HO" injectors, says "HO" cast on intake manifold. tube factory headers, the installation looks clean untouched on the engine which makes me wonder why a mechanic or shop would reccomend non HO replacement? Judging by some of previous owners fog light wiring and stereo wiring I'd say there weren't mechanicaly inclined enough to do a engine lol....should I try the HO firing order and see how it runs?
First, pull pass kick panel and look at computer. Get any and all part numbers and post here. Let's see what EEC it's running before changing anything
This doesn’t prove that the block is a HO block. Some trucks evidently use a HO firing order
with a low lift cam. 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
with a low lift cam. 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
I had a similar problem. Got my 91 from a young guy that didn't know much about cars. I have a non HO firing order, orange injectors, solid motor mounts, cast e6 heads. I stopped guessing and took it out for my 306 I just built. Now I know what I have done to the motor!
Boy am I glad this thread was started----this site rocks!---I too have an 88 GT vert but the engine looks "flukey"...my firing order is 1 5 4 2 6 3 7 8...and the computer says EEC-1V SFI-SD1 E7SF-12A650-C1A ... I changed the firing order to the HO 1 3 7 2 6 5 4 8 and it started but ran like total crap. SOMEBODY HELP! ... My upper does say 5.0 HO..also the harmonic balancer is so crusty I can't even see the markings on it for timing so I know I will need to do the crank compression trick to find when cylinder 1 is at its firing order in case I need to time it.
The camshaft controls the firing order. Switching the computer will not change the order that the ignition fires. The plate on top of the intake manifold is held on by 4 screws and you can bolt it onto many different 5.0 manifolds, so its presence is meaningless. Go back and re-read my post for help identifying what you have.
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