86 Mystery Mods Progress!

[5.0Droptop]

I did a quick google

Autolite 764 seems to be the plug of choice for gt40 iron heads
Here is a cross reference chart for that plug if your plugs are different. http://www.sparkplug-crossreference.com/convert/AUTOLITE/764

 

[Slobin3d]

So heres my suggestion updated


You must check and set base timing that is imparitive. Id Set the timing to 12* base——>That is with the spout plug removed.
Ohm coil to ensure its within range.
Check that plugs are correct ones and gap plugs to .052
Check that the plug wires firing order is correct.
Check cap n rotor.
inspect plug wires.

I replaced the cap/rotor, they were looking to be due. The plugs are good, and coil tested good. The timing is correct. I also checked the tps, it also checks out. As well the fuel pressure regulator, it holds vacuum and no fuel smell out of it.

After changing the cap it improved a bit, the idle is lower and steady, but it still cuts out under hard acceleration. I videoed the tach as I drove. To show what I'm having going on. Waiting for it to upload


I'm wondering if I'm having a fuel pressure problem, or need larger injectors??

 

[5.0Droptop]

I replaced the cap/rotor, they were looking to be due. The plugs are good, and coil tested good. The timing is correct. I also checked the tps, it also checks out. As well the fuel pressure regulator, it holds vacuum and no fuel smell out of it.

After changing the cap it improved a bit, the idle is lower and steady, but it still cuts out under hard acceleration. I videoed the tach as I drove. To show what I'm having going on. Waiting for it to upload


I'm wondering if I'm having a fuel pressure problem, or need larger injectors??

I would get a fuel rail guage. You can buy the kits that are permanent mount pretty cheap. Then you can check the fuel press. It could be running a bit lean i suppose. I think the 93 cobras had 24# injectors with the gt40 heads and intake.

You might be able to get away with an adjustable fuel press regulator if it just needs a little more fuel.

Try unplugging the vac line from the regulator and cap off the line. With no vac to regulator your fuel press will rise about 5psi. Then start and run it. See if things change.

 

[5.0Droptop]

I would clean the maf meter as well with sensor safe cleaner if you have not already done so.

 

[Slobin3d]

I would clean the maf meter as well with sensor safe cleaner if you have not already done so.

That I did do too

 

[Slobin3d]

View: https://youtu.be/uWMLoajle2g


Video of the car, it will accelerate fine if I roll in smooth and slow, stumbles when you push it

 

[5.0Droptop]

View: https://youtu.be/uWMLoajle2g


Video of the car, it will accelerate fine if I roll in smooth and slow, stumbles when you push it

If its running lean it “should” throw a code.

It could be running out of fuel under hard acceleration. Try the unpluged vac line like i mentioned and drive again. If it improves then id say it needs more fuel. Your injectors are orange so i would assume they are 19# injs and it appears to be a stock fuel regulator. You are well beyond stock with heads intake and headers exh etc. i dont know if its cammed or not. Id say you likely are lean.

 

[Slobin3d]

If its running lean it “should” throw a code.

It could be running out of fuel under hard acceleration. Try the unpluged vac line like i mentioned and drive again. If it improves then id say it needs more fuel. Your injectors are orange so i would assume they are 19# injs and it appears to be a stock fuel regulator. You are well beyond stock with heads intake and headers exh etc. i dont know if its cammed or not. Id say you likely are lean.

Yeah, they are Accel #19 injectors. I'll try it with the regulator bypassed. I was thinking of running my fuel pump at 18v and see if that helps any too

 

[90sickfox]

I had a problem similar to that. The pick up was bad and loose inside the distributor. With the cap off you can look down inside the distributor. The part the rotor sits on has square windows cut out of it. There's a pickup that reads those windows. Take a small screw driver and check to see if its loose or disintegrating. Mine actually turned into a dusty white chalky mess. The car still started and idled but I couldn't get on the gas hard.

I believe the pickup is what the computer uses to keep the spark plug fire and timing correct. If I revved moderately it was OK.

Usually, fuel can make it loose power but it doesn't feel like a misfire....or rev limiter. It kind of just won't go when you need it but its not as violent. It'll bog as one event...not multiple cuts at one time.

 

[5.0Droptop]

Yeah, they are Accel #19 injectors. I'll try it with the regulator bypassed. I was thinking of running my fuel pump at 18v and see if that helps any too

Im not sure if 18v will help. The regulator will only allow x amount of pressure.

 

[Slobin3d]

I had a problem similar to that. The pick up was bad and loose inside the distributor. With the cap off you can look down inside the distributor. The part the rotor sits on has square windows cut out of it. There's a pickup that reads those windows. Take a small screw driver and check to see if its loose or disintegrating. Mine actually turned into a dusty white chalky mess. The car still started and idled but I couldn't get on the gas hard.

I believe the pickup is what the computer uses to keep the spark plug fire and timing correct. If I revved moderately it was OK.

I will look at that too

 

[General karthief]

This is a project.
Sometimes you have to go back to basics, check the distributor like was mentioned and go back over everything, also check to see how much slop you have in your timing chain, and check for codes again.

 

[Slobin3d]

Pulled the vacuum line and plugged it, from the fuel pressure regulator, no change. I'll look into the pickup on the dizzy, and finding an efi fuel pressure guage

 

[5.0Droptop]

Research the tfi module too

 

[Noobz347]

This is the prefect time to run @jrichker 's Surging Idle Checklist:

https://www.stangnet.com/mustang-forums/threads/help-me-create-the-surging-idle-checklist.698148/


You have a running vehicle that is not yet stable. Run it through step-by-step.

It looks daunting at first but when you break it down, it's really not tough at all and will save you a ton of time and money.

 

[5.0Droptop]

Any progress?

 

[Slobin3d]

Any progress?

I picked up a fuel pressure gauge, and filter, also new tfi and pickup, but with the holidays I haven't had a chance to do anything

 

[5.0Droptop]

Just thought about it. Figured Id check and see.

 

[Slobin3d]

Update. Not much, been to cold to work, but I picked up a used stock MAF sensor and housing to replace the "custom" sensor I fixed. I didn't realize but the car has what I'm sure us a explorer MAF housing, which is much larger the the mustangs, but still has the stock 86 throttle body.

What if any issue would having the larger diameter MAF cause? If I read correctly it's still tuned for 19# injectors, but is 65mm instead of 55mm like the fox mad and TB.

 

[Mustang5L5]

Explorer MAF will not work on a Mustang. The MAF transfer function is not correct.