86 Gt Running Rough

Jaystang73 · Feb 26, 2017

Hey all proud owner of an 86 gt convertible has the 302 HO, i would like some advice if anyone can kindly help me, ok the issue im having is bought the car with the top end fully disassembled, valve covers, lower and upper intakes throttle body egr ect ect. Ok i put everything back together and i put a new msd coil, distributor and rotor, i had to manually set the timing which wasnt to bad, the exhaust was shot so i removed the old cats and mufflers, at the moment i got it running but its lacking power when i put in drive or any driven gear, otherwise when not in park or nuetral, i put new plugs and wires checked timing again and all is correct, but its still running really rough ,the other day i had actual flaming exhaust shooting out of the driver side exhaust, i went over everything and everything seems to be correct am i missing something? I just dont know what direction to go, im a decent wrench turner just at a stand still.

General karthief · Feb 26, 2017

First question is are you running open headers?
Check all your vacuum lines, make sure you have all the ground wires connected to good clean metal, there is a ground that connects to the inner fender panel by the battery that has two wires, one from battery ground to a small self tapping bolt and from the harness below the solenoid to that same bolt.
Another ground wire from the back of the drivers side head to the firewall, these are important.

Jaystang73 · Feb 26, 2017

Im not going to run open headers. I just have not redone the exhaust yet, i havent checked those ground wires you are referring too yet and also the smog pump has been deleted and there is a vacum line that had broke off on the upper passenger fender well which im not sure where it went to i have the lines from the upper intake installed one to the tree one to the egr and one to the fuel pressure regulator oh and the pcv valve line so ill check those ground lines tomorrow, another question with all the exhaust system off for the exception of the headers and tubes down to where the cats were which i removed will this make a difference in the timing or the way the car is running

General karthief · Feb 26, 2017

No effect on timing but it may run different, will be hard to work on it with no exhaust, it can effect your hearing too.
Get a pic of that vac line but I suspect it connects to your heat/air defrost stuff, cap it untill you can hook it up to the correct place,

Jaystang73 · Feb 27, 2017

Ok when i get home from work ill take a pic of it for you, i appreciate your help, ive always loved stangs finally got one, so im not that familiar with the 302 setup so from time to time i need a little guidance so thanks again

jrichker · Feb 27, 2017

The following are diagrams courtesy of Tmoss & Stang&2birds

Vacuum diagram 89-93 Mustangs -the 86 should be similar...

Jaystang73 · Feb 27, 2017

karthief said:
No effect on timing but it may run different, will be hard to work on it with no exhaust, it can effect your hearing too.
Get a pic of that vac line but I suspect it connects to your heat/air defrost stuff, cap it untill you can hook it up to the correct place,

Jaystang73 · Feb 27, 2017

Here is a pic of the engine, left side fender well is where the vacum line is broken i included a close up and a little further away pic to have a better idea

Jaystang73 · Feb 27, 2017

jrichker said:
The following are diagrams courtesy of Tmoss & Stang&2birds

Vacuum diagram 89-93 Mustangs -the 86 should be similar...

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring; http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

TFI module wiring for 94-95 Mustang GT
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-IgnitionControlModule.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Mustang 5.0 Lights and Radio schematic, by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxLights-Radio_diag.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

T5 Cutaway showing T5 internal parts
http://www.veryuseful.com/mustang/tech/engine/images/5_Speed_Cutaway_Illustrated.jpg

Visual comparison of the Ford Fuel Injectors, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/Ford_Injector_Guide.jpg

Convertible top motor wiring http://www.veryuseful.com/mustang/tech/engine/images/mustang88VertTopMotorCkt.gif

Engine mounted fuel injector harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangEngineHarness.gif

Location of the TPS, IAB, and the 10-pin connectors on a 5.0, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/TPS_IAB_Pic.jpg

Starter circuit
http://forums.stangnet.com/attachment.php?attachmentid=21328&d=1080916057

Alternator diagram for 94-95 Mustangs.
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-Alt.gif

Thank you

General karthief · Feb 27, 2017

Looks like it should go to your bypass valve by the air pump

Jaystang73 · Feb 27, 2017

So i have the air pump delete would that make a difference

90sickfox · Feb 27, 2017

If you're shooting flames the spark plug wires are crossed. There are 2 firing orders for ford 5.0 engines. 13726548 HO and 15426378 non HO. The rotor turns counter clockwise in the distributor cap. There's no way to tell whether the engine is ho or non ho externally. Try both of them. For flames to shoot the engine has to fire on the exhaust stroke instead of the compression stroke.

I've been there with a motor I thought was HO but wasn't. That thing ran rough as hell until I switch the firing order.

General karthief · Feb 27, 2017

Plug it, if it's attaches to a small solenoid on the back side of the passenger shock tower or into a three way connector. I'm thinking it is for the air pump solenoid.
I'd have to see a better pic of the connected end of that vac line to be sure where it's supposed to go, it looks like some non stock type vac lines.

Jaystang73 · Feb 27, 2017

I guess just because the top plate says ho doesnt mean its an ho right now the firing order is ho so tomorrow ill change it to non ho and see what happens there, i may have some more questions for you gentlemen again if its no bother

Jaystang73 · Feb 27, 2017

It is on the shock tower attached to a solenoid with a filter of sort on top

Jaystang73 · Feb 27, 2017

It is on the shock tower attached to a solenoid with a filter of sort on top

Mstng93SSP · Feb 27, 2017

Check your firing order, even if you already have. 5 and 6 are easy to cross, it happens a lot. Make sure the wire from the cap that is supposed to go to #5 goes to the first plug in the front on the driver's side.

Jaystang73 · Feb 27, 2017

Yes ill double check it tomorrow and go over the entire firing order again, i appreciate all the help i can get

General karthief · Feb 27, 2017

Asking questions are not a problem, thats part of what this site is for. There is a lot of info in the how to section of 5.0 tech forums, the people here have been there done that and will help you get up and running, I'm just kind of a traffic cop, I try to either point you in the right direction or find someone who can.

jrichker · Feb 28, 2017

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

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86 Gt Running Rough

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Wasn't a pretty sight...and I've got big hands

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You have a nice rear end there Dave.

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