Resolved 1989 GT Slight Stutter Under Load

[Tim83]

Hi folks,

I just recently resolved a code 14 issue from a previous thread (linked below) but I'm having a new issue. The car starts, idles, and drives beautifully until I stomp on the gas pedal and rev it out. It gets above 4k or so and you can hear a distinct break up in the sound the engine makes along with a very slight hesitation or loss of power. It's minor but plainly noticeable. It doesn't sound like a misfire or detonation, no backfire, no other sounds coming from the engine. I pulled and inspected each plug and wire and they all appear to indicate normal operation. KOEO give me the neutral pressure switch, KOER gives me code 91, Multiple cylinder balance tests passed with code 90. I believe the 91 is related to a leak in the driver's side collector where it may be sucking in air, the car is definitely running a bit rich. I'm hoping to check the leak this week. Any thoughts on what else I can check for? The only part of the ignition system that hasn't been replaced is the coil. I believe it's also an MSD unit but I'm not sure. Could this even be a coil issue? Could the collector leak but the problem? Thank you in advance!

Recently done:
Ford Performance 9mm wires
Motorcraft Plugs AGSP32CK with .054 gap
TPS
EGR
MSD Pro Billet Distributor
Checked plugs and wires
Checked for arcing
Cleaned Mass Air
Replaced fuel filter
Base timing set to 16-17 degrees
Smoke test with no vacuum leaks
Noid light indicates good injector pulse

Mods:
Trickflow HCI
BBK CAI
70mm throttle body
75MM mass air
BBK shorty headers with matching exhaust all the way back

Previous issue:

1989 GT Possible air/fuel issue

Hi folks, I hope everyone is enjoying the summer. I've been having an intermittent issue with my car and I'm hoping someone can help me figure it out. Under normal driving conditions the car behaves as it should but after some spirited driving, mainly winding it out in the first 3 gears, it...

stangnet.com

 

[AeroCoupe]

Fix the exhaust leak as it can screw with the O2’s
Would definitely try another coil
Have you tried less initial timing?
What brand TFI coil is on the MSD distributor?

I had a high rpm breakup years ago and it was my distributor just being worn out. Bought a reman one and put the PIP and TFI from the old distributor on it and that solved the problem. The bushings in the body of the original distributor were worn out. With the new MSD in yours that is probably not the issue but wanted you to know I feel your pain.

 

[Tim83]

Fix the exhaust leak as it can screw with the O2’s
Would definitely try another coil
Have you tried less initial timing?
What brand TFI coil is on the MSD distributor?

I had a high rpm breakup years ago and it was my distributor just being worn out. Bought a reman one and put the PIP and TFI from the old distributor on it and that solved the problem. The bushings in the body of the original distributor were worn out. With the new MSD in yours that is probably not the issue but wanted you to know I feel your pain.

I went back and looked at my log book and noticed that I never double checked the voltage when I installed the new TPS. I checked it now and found it was sitting at 1.10v KOEO. I adjusted down to .98-.99 but that didn't resolve my issue. Should have another coil by tomorrow and will try that.

The TFI is MSD and came with the distributor. I've got a new motorcraft one laying around as well.

I'll back off the timing a bit and see if that helps.

 

[Tim83]

Looks like it was the coil causing my issue. I installed the new one this evening and the problem was gone. Thanks for the help and take care!

 

[Mindseye007]

Hi folks,

I just recently resolved a code 14 issue from a previous thread (linked below) but I'm having a new issue. The car starts, idles, and drives beautifully until I stomp on the gas pedal and rev it out. It gets above 4k or so and you can hear a distinct break up in the sound the engine makes along with a very slight hesitation or loss of power. It's minor but plainly noticeable. It doesn't sound like a misfire or detonation, no backfire, no other sounds coming from the engine. I pulled and inspected each plug and wire and they all appear to indicate normal operation. KOEO give me the neutral pressure switch, KOER gives me code 91, Multiple cylinder balance tests passed with code 90. I believe the 91 is related to a leak in the driver's side collector where it may be sucking in air, the car is definitely running a bit rich. I'm hoping to check the leak this week. Any thoughts on what else I can check for? The only part of the ignition system that hasn't been replaced is the coil. I believe it's also an MSD unit but I'm not sure. Could this even be a coil issue? Could the collector leak but the problem? Thank you in advance!

Recently done:
Ford Performance 9mm wires
Motorcraft Plugs AGSP32CK with .054 gap
TPS
EGR
MSD Pro Billet Distributor
Checked plugs and wires
Checked for arcing
Cleaned Mass Air
Replaced fuel filter
Base timing set to 16-17 degrees
Smoke test with no vacuum leaks
Noid light indicates good injector pulse

Mods:
Trickflow HCI
BBK CAI
70mm throttle body
75MM mass air
BBK shorty headers with matching exhaust all the way back

Previous issue:

1989 GT Possible air/fuel issue

Hi folks, I hope everyone is enjoying the summer. I've been having an intermittent issue with my car and I'm hoping someone can help me figure it out. Under normal driving conditions the car behaves as it should but after some spirited driving, mainly winding it out in the first 3 gears, it...

stangnet.com

that is what mine at 4k until I changed the TFI module then it went away...