Engine Stock 88 bucking at cruising speeds, my fist problem!

Rick88

Member
Mar 17, 2021
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My wife and I bought a 88 GT on Monday, today was the first time we have drove it most of the day. Drove it to my in-laws house about 15 miles away and took it on the interstate for the first time since we got it. It ran fine the entire way there. On the way home it started bucking at over 40 mph. I didn’t notice any change in the rpm or other issues with the gauges, but that’s not saying much as the gauges bounce a lot. Didn’t hear any change in the engine or backfiring either.

I’m asking for suggestions because everything I see people have modified engines and as far as I know this one is stock. I have only changed the air filter, plugs (gapped to .054, ones I took out looked ok), distributor cap and rotor, and pc valve. So normal tuneup stuff. It’s an automatic if that matters. Lol
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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Do this checklist, read through it then do the steps one at a time, it will show you how to find your problem, if you have any questions post them in this thread and the members will help you out.
 
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Rick88

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Mar 17, 2021
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Thanks everyone. We went out last night and got some stuff suggested, I will be working on her this week. We did notice that the RPM will fluctuate when it bogs/bucks/surges/whatever when we took it out again. I'll be sure to let yall know if anything pops up. Thanks again.
 

Rick88

Member
Mar 17, 2021
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Ok pulled koeo codes and got a 85. I need to replace the entire canister as this one is 1/2 hooked up and looks in pretty bad shape. There is no return nor purge valve. Should I ignore it for now? Also since there is no valve there is no wiring. I attached a picture of a connector, is this the connector for the valve? Disregard that the wires are missing shielding, I’m going to fix that also. F14FCA24-1C6F-451D-9A0C-4F365D8FDCBE.jpeg
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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No, that is for the ac limiter switch, the purge canister wiring is in the injector harness right by the coolant temp sensor.
 
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Rick88

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Mar 17, 2021
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Here are all the codes I got:
O= KOEO
R= KOER

85 - (O) Canister Purge Solenoid failure (Doesn't have one so nothing I can do at this time. Will it be ok without?)
14 - (R) Intermittent loss of PIP signal PIP or ignition module may be malfunctioning (I'll look into getting a new Ignition module)
28 - (R) VAT sensor, EDIS or DIS fault (Again will look at new Ignition module and check my sensors)
88 - (R) ??????????????????????????????????????????? Can't find anything about the code on KOER test
24 - (R) ACT, IAT, VAT sensor
16 - (R) RPM too low for HEGO (Will look up but guessing O2 sensors? May fix with ignition module?)
45 - (R) Thermactor air upstream (guessing an issue with VAT)

Let me know what y'all think. I'm going to do some more research on the ones I'm not sure on and wife isn't going to like the repair prices lol.
 

90sickfox

Wasn't a pretty sight...and I've got big hands
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You can ignore all the emissions codes. They aren't causing your issue. The missing PIP signal is the problem 9/10. The PIP is located below the rotor button under the distributor cap. You have to remove the distributor and take the gear off to replace it. When you look down there it should be clean plastic and not like baby powder. The plate the rotor button sits on has windows on the bottom that the PIP reads. That signal is sent through the most replaced part on a mustang....

......The TFi module.

That's the plastic box on the side of the distributor. Get a Ford motorsports one if you can find it. Make sure you put thermal paste on it also. Should be white paste...not kinda see through Vaseline looking stuff. That would be dielectric grease. Lately the parts stores have been selling them with the incorrect grease.
 

Rick88

Member
Mar 17, 2021
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Alabama
You can ignore all the emissions codes. They aren't causing your issue. The missing PIP signal is the problem 9/10. The PIP is located below the rotor button under the distributor cap. You have to remove the distributor and take the gear off to replace it. When you look down there it should be clean plastic and not like baby powder. The plate the rotor button sits on has windows on the bottom that the PIP reads. That signal is sent through the most replaced part on a mustang....

......The TFi module.

That's the plastic box on the side of the distributor. Get a Ford motorsports one if you can find it. Make sure you put thermal paste on it also. Should be white paste...not kinda see through Vaseline looking stuff. That would be dielectric grease. Lately the parts stores have been selling them with the incorrect grease.
Thanks! So let me clear this up... take of distributor cap and rotor, look in and if the bottom of the distributor looks like baby powder the pip is bad. Either way replace the TFI?

Sounds a lot better than getting to that ACT sensor... if the pip is bad I’ll just have to replace the distributor, I don’t have a press to get that gear off.
 

90sickfox

Wasn't a pretty sight...and I've got big hands
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Replacing the distributor should come with a new PIP and TFI.

The PIP sits down in there like a white Lego block with an area for the windows of the plate to pass through. The white plastic will dissentagrate and turn into powder. If your is good you could do just the TFI. If its powdery replace the distributor.

Disclaimer ; this is ( if ) the wiring to and from the distributor is in good condition. Meaning no bare wires and securely connected to the TFI. These cars are getting old.

Take a few pictures from different angles all around the engine bay. People here have hawk eyes ( me not included ) and can help see things you may not notice.
 

Rick88

Member
Mar 17, 2021
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Alabama
Here are some picture of the distributor. Upon further inspection I think I’m just going to replace it, it looks old if not original lol. Sucks that I just replaced the cap and rotor. Didn’t even think to look at the tfi or anything else. The wires do look good tho. Let me know if y’all see something I don’t.

And thanks for the help! This is my first restoration and have never really gone deeper than a standard tune up on a car so I’m still learning. E7DA09DE-F249-4E2D-878A-BE711CC61A77.jpeg 3EF35401-9B77-453C-BDB5-3303D8EFBFE3.jpeg 85172689-32BB-43ED-99AC-C8CF47452C33.jpeg 077A65C6-06BC-4206-A6BF-8EFFA15A265E.jpeg DD34C861-B1B3-4025-A690-89F06AE7832F.jpeg 9B204162-2D2A-4856-9408-6FF01A834F71.jpeg
 

Steel1

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I've always had the best luck replacing ignition parts with genuine Motorcraft parts, especially TFIs.
If it were me I would pull that factory distributor , replace the guts with Motorcraft parts and reinstall.
You could have a local shop press off / on the gear for you , there is a roll pin that needs to be removed
and reinstalled as well.
I've gotten all the parts in the past from rock auto.

These cars tend to not like aftermarket ignition parts in my experience.
 
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Potomus Pete

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Thats what i did....75 bucks. Brought it to the garage with the parts. Too many problems with other distributors.
 
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Steel1

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Just to add , that rusty disc in your pictures with the tabs hanging off it is you're shutter wheel.
When I built my 393w I had to run a non-oem distributor, I replaced all the internals with Motorcraft parts
except the shutter wheel.
I chased a intermittent miss for months only to find out it was being caused by the aftermarket shutter wheel.
Turns out the aftermarket shutter had tabs and spacing slightly different from factory , enough to create an issue.
 
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Rick88

Member
Mar 17, 2021
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Alabama
Just to add , that rusty disc in your pictures with the tabs hanging off it is you're shutter wheel.
When I built my 393w I had to run a non-oem distributor, I replaced all the internals with Motorcraft parts
except the shutter wheel.
I chased a intermittent miss for months only to find out it was being caused by the aftermarket shutter wheel.
Turns out the aftermarket shutter had tabs and spacing slightly different from factory , enough to create an issue.
So you got me thinking tonight. I switched back to the stock distributor cap and rotor just to test it. I researched issues with the 5.0 and MSD and found a ton of problems. I'll take her for a spin tomorrow. If it works, it works; if not, what do you think is the best route? I can't find a full Motorcraft replacement but can find a Duralast, Accel, Spectra, or a Cardone rebuilt. I've never heard of the last 2. The Cardone says they are rebuilt using OEM specs, but I would still have to get a TFI separate. I've already called all of the salvage yards within 50 miles and they don't have any Foxbodys so there goes that idea.