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Annoying stumble

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Old 06-07-2015, 11:54 AM   #1
SWGSSSlacker
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Default Annoying stumble

So the car is up and running again with the 3rd purchased ICM. Third time's the charm! I now have a issue at constant cruising speed, say 5th gear, 70 mph at 1750/1800 rpms. The motor will be running smooth and then it'll stumble and then run smooth again but this is an annoying rinse and repeat issue. It happens in any gear honestly as long as the rpms are constant but I'd rather it not happen in 5th gear. I plan on driving the car to Florida several times! I can live with the issue in 1st -4th gear, it is still annoying but in 5th it sucks.

Any suggestions? I researched here and found one related topic about this issue but it kind of went off on a tangent towards the end.

Last edited by SWGSSSlacker; 06-07-2015 at 12:59 PM.
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Old 06-08-2015, 07:45 AM   #2
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Sounds like the pip sensor is going bad. Mine did that a while back and it felt like I hit a large pothole when it first did it. I thought my fuel pump took a crap it hit so hard.
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Old 06-10-2015, 10:38 PM   #3
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Anyone here that can verify what the voltage from the PiP sensor (hall effect) is supposed to be running at during normal idle? I've researched and found it's supposed to be between 3-6 volts but mine is running/flashing between 6.5-6.7 volts.

The stumble only happens at cruising speed, any other time accelerating or decelerating the engine runs perfectly fine. The distributor is new and it came with all new internal components, the ICM it had was bad but the PiP sensor appears to be working as intended.

Could the TPS voltage need to be adjusted higher or lower ? It was set at .95 volts during KOEO testing.
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Old 06-12-2015, 09:45 AM   #4
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TPS voltage doesnt matter. The PCM will automatically reset itself to see what ever that voltage is at idle to be 0% throttle. The PIP reading 6.5-6.7 is probably normal. Mine did it once the car was good and hot while it was cruising in 5th gear. Even though the dizzy is new with new parts doesnt mean they are good. Ive read of guys buying new dizzys and having to get OEM Ford parts to put in them just do the car would run correctly.
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Old 06-12-2015, 07:24 PM   #5
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Ok, installed new PiP sensor, checked and reset timing and still have the same issue.

Annoyed in Texas!
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Old 06-15-2015, 06:29 AM   #6
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Try doing a KOER/KOEO test and see what you get. Might give you a direction to go in.
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Old 06-18-2015, 06:43 PM   #7
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Ok....ran KOEO and KOER tests.

KOEO: 34
KOEO: (stored) 18, 34

KOER: 34, 44, 94, 18

Cylinder balance test: 9 and 9 (pass)

TPS is set at .95.

PiP sensor: flashing (dist. to pos. battery term.) 8.05-8.1 VDC
flashing (dist. to neg. battery term.) 6.2-6.3 VDC

I'm ready to give up! The car still runs fine at idle and above 2000 rpms.
The annoying stumble is still there between 1000-2000 rpms worst at 1850
rpms which is 70mph in 5th gear.
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Old 06-18-2015, 06:54 PM   #8
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The Smog pump and all of it's piping has been removed, vacuum lines plugged.
The cylinder heads have plugs in them where the emissions piping once connected.
The EGR valve and sensor have been taken off, inspected and cleaned (if needed).
The EGR and sensor was replaced about 6 months ago.
The EGR valve is hooked up electrically and still under vacuum while running.

Just some info. due to the codes on my previous post.

As for the code 18 (loss of tach signal) I'm still not sure what's going on there.
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Old 06-22-2015, 07:25 AM   #9
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Not sure where that would be but that can cause your stumble issue. The tach signal goes to the coil, tfi module, dash, and pcm. If you loose that signal then the pcm doesnt know when to fire the plugs. Id start checking that wire for any damage. I know itll be a pain but for the most part it runs in the engine bay. There shouldnt be any connecters between any of those components other than one that goes to the dash. The wire is a tan/yellow wire. You should see if on one side of the coil and then trace it back from there. One thing you can try is flexing that wire while the engine is running and see if it stumbles.

There is also a red/green power wire that goes to the coil. It has a fuse link in it that is in between some splices and the ignition switch. Might not hurt to check the ignition switch also as well as that wire and fuse link.
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Old 06-22-2015, 07:25 AM
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