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post #1 of 29 (permalink) Old 10-09-2017, 06:59 PM Thread Starter
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Voltage issues and missing out

Hey guys, it's been a long time since I posted on here. I'm completely stumped with this car. I bought my son a fairly clean 94 4.6 T-bird. It has 2 issues, at 2,000 to 2,500 rpms, the car will miss out and the voltage gauge is all over the place. We have cleaned all grounds, tuned the car up, and even tried out a known good alternator with absolutely no luck. Has anyone experienced this before? There are also no codes stored.
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post #2 of 29 (permalink) Old 10-09-2017, 07:11 PM
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Explain "miss out"?

Do you mean the car will misfire? If so does it misfire continously? Does the car go past 2500rpms?

I think the voltage guage fluctuating might just be a quirk that is the result of a different issue.
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post #3 of 29 (permalink) Old 10-09-2017, 07:47 PM Thread Starter
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It misses as in the engine cuts out, like its losing spark. The voltage drops at the same time. It gets bad enough that you can't drive the car for long distances at all.
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post #4 of 29 (permalink) Old 10-09-2017, 07:53 PM Thread Starter
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The car will rev way past 2500. It seems to be getting progressively worse. When the voltage gauge fluctuates, all the lights dim, and flicker.
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post #5 of 29 (permalink) Old 10-09-2017, 11:38 PM
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Coil packs maybe,mafs maybe or could even be the pcm. Is it stock ? Odd no cel
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post #6 of 29 (permalink) Old 10-10-2017, 01:44 AM
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A bad battery can also cause quirkiness like this. But I do suspect the coil packs, they are often the cause of misfires and issues like that. I'm also thinking of any bad grounds that may cause this because it seems like a really weird set of symptoms.
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post #7 of 29 (permalink) Old 10-10-2017, 05:51 AM Thread Starter
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The car is completely stock. I had the same thought about the battery too, and changed it out with one out of my car. Still no change. I'm leaning towards a bad coil pack. It's just strange that there is no CEL lit up. I even scanned it to see if there were any codes stored and got nothing.
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post #8 of 29 (permalink) Old 10-10-2017, 07:52 AM
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How about the plug wires, were those changed too? Double check to make sure they were in the right order?

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post #9 of 29 (permalink) Old 10-10-2017, 12:14 PM Thread Starter
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Yeah, plug wires were changed and I've double checked the firing order.
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post #10 of 29 (permalink) Old 10-10-2017, 02:50 PM
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I had a similar problem; it was the alternator.

The brushes were bouncing at higher speeds, and the battery was already toast from poor charging.

I put in a new alternator, but rebuild kits are cheap; you will likely have to replace the brush ring, and that requires a soldering iron.

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post #11 of 29 (permalink) Old 10-10-2017, 05:15 PM
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Quote:
Originally Posted by Grog6 View Post
I had a similar problem; it was the alternator.

The brushes were bouncing at higher speeds, and the battery was already toast from poor charging.

I put in a new alternator, but rebuild kits are cheap; you will likely have to replace the brush ring, and that requires a soldering iron.

Ford 3G Alternator Repair Kit Regulator Brushes w/ Holder Set F- SERIES REBUILD | eBay
He says he already tried another working alternator which makes it more puzzling.
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post #12 of 29 (permalink) Old 10-13-2017, 10:06 AM Thread Starter
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Well I'm at a complete loss. I bought new coil packs for the car. That seemed to clear the problem up, but about 30 minutes into driving it, and it just shit all over itself again. I have no idea whats going on.
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post #13 of 29 (permalink) Old 10-13-2017, 11:09 AM Thread Starter
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Maybe the erratic voltage issue is from it missing out, Idk. How often does the ICM go bad in these cars?
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post #14 of 29 (permalink) Old 10-13-2017, 04:38 PM
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Quote:
Originally Posted by Grog6 View Post
I had a similar problem; it was the alternator.

The brushes were bouncing at higher speeds, and the battery was already toast from poor charging.

I put in a new alternator, but rebuild kits are cheap; you will likely have to replace the brush ring, and that requires a soldering iron.

Ford 3G Alternator Repair Kit Regulator Brushes w/ Holder Set F- SERIES REBUILD | eBay
I had this similar problem but it was the WIRING going to the alternator. It drove me crazy. If the alternator doesnt' get a signal (from the gauge cluster) to charge, and the battery doesn't have enough juice to make up for it, the car will do weird things like not rev beyond a few K RPM.

The funny thing for me was with a fresh battery, I ran on a track for 6 hours without any fuss. However, when I took it for an actual race a few months later, the car felt like it ran out of spark at 2.5K-3K RPM (when under load).

You can check this by measuring the voltage at the alternator output and at the battery.
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post #15 of 29 (permalink) Old 10-13-2017, 07:31 PM
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OMG I decided to start posting today and this is the first thing that pops up? I made a few upgrades recently and started having problems. I went to a 70mm maf, underdrive pulley's , ignition modulator (from SC Performance) and 160amp alt w/4gu wire. I know the computer needs to re-learn due to the battery being disconnected . I cant do 70mph because the feels like the rev limiter is not allowing me to go over 2000rpm. 65 and it runs nice and smooth with lots of power. That is if you don't step on it . The needle will fluctuate and it starts to buck. It ran well before any upgrades.
Totally unrelated but just a short while before all this my volt gauge decided to take a dump.

I was thinking to change the plugs. Easy, cheap, fast fix. Who knows . Because my cats got clogged and it wouldn't run even 10mph until they were cut off. I'll pull a battery out of my Jeep too just to see. Another symptom is it slow cranks sometimes. Maybe it is an Alt problem?

Thanks for starting this thread and sorry you had to.


Even in park if you rev to 2k it acts like the rev limiter is preventing it from going 2 grand or over.

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Last edited by purplexj; 10-13-2017 at 08:14 PM.
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post #16 of 29 (permalink) Old 10-13-2017, 08:19 PM
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Quote:
Originally Posted by purplexj View Post
Even in park if you rev to 2k it acts like the rev limiter is preventing it from going 2 grand or over.
It will to keep you from overrevving in neutral. Well, it will at some low point, anyway; not sure of the exact point.

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post #17 of 29 (permalink) Old 10-14-2017, 01:41 AM
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Quote:
Originally Posted by purplexj View Post
OMG I decided to start posting today and this is the first thing that pops up? I made a few upgrades recently and started having problems. I went to a 70mm maf, underdrive pulley's , ignition modulator (from SC Performance) and 160amp alt w/4gu wire. I know the computer needs to re-learn due to the battery being disconnected . I cant do 70mph because the feels like the rev limiter is not allowing me to go over 2000rpm. 65 and it runs nice and smooth with lots of power. That is if you don't step on it . The needle will fluctuate and it starts to buck. It ran well before any upgrades.
Totally unrelated but just a short while before all this my volt gauge decided to take a dump.

I was thinking to change the plugs. Easy, cheap, fast fix. Who knows . Because my cats got clogged and it wouldn't run even 10mph until they were cut off. I'll pull a battery out of my Jeep too just to see. Another symptom is it slow cranks sometimes. Maybe it is an Alt problem?

Thanks for starting this thread and sorry you had to.

Even in park if you rev to 2k it acts like the rev limiter is preventing it from going 2 grand or over.
On the 70mm MAF: have you had your ECU tune modified to account for the difference in airflow over stock? If not, why do you think this helps your car if you haven't adjusted the programming?
The MAF tells the ECU how much air is coming in by reporting a certain voltage. The ECU tune has a transfer function (basically a table that it extrapolates from). If, for example, a stock 60mm MAF reports 2.5V for 200CFM of airflow, a larger 70MAF will actually flow say 250CFM but report the same voltage. If the ECU isn't reprogrammed, it's not going to know what the hell just happened.

This will cause all sorts of weird bucking/surging or bogging down issues -- just like if you had a failing or dirty MAF.

I don't see how any of the other stuff (underdrive pulleys, ignition control module -- which I guess you meant by ignition modulator, and amp.

One more thing: on the underdrive pulleys. I get the value of an underdrive WP pulley but did you also use an alt pulley? If so, why if you decided to upgrade the alternator to a bigger one to make more current? Why do an upgrade on the alt (increasing the load on you engine) and then turnaround to derate its effectiveness with the oversized pulley?

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post #18 of 29 (permalink) Old 10-14-2017, 06:30 AM
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I didn't get it tuned, but that's why i'm asking on here. I come from the time of points and carbs. So I ask people who know. I've had a lot of older Jeeps which didn't need tunes for 90% of their upgrades. My older Oldsmobile learned the much more minor changes itself.

The other stuff I mentioned just to mention. I don't see how they could have caused a problem either.

I didn't do the 3G upgrade. It's the stock alt that was rewound. It was rewound at a rebuilder for free. The stock alternator was in place with it's stock pulley and the lights were dim. So i figured, for free why not. I should have just gone with bigger battery cables and additional grounds like i usually do. Still have the underdrive pulley which is slightly bigger than stock. Also the stock original alt. In hindsight the dimming could have been caused by the idle being so low.

I have a SN95 Cobra upper/lower intake and the Ford Racing Cobra 1.7 rockers i am going to put on but did not get a 65mm TB yet. I was going to get a tune after everything was done if it could wait. But i need to ask questions. Because i don't know. I was going to get a chip when everything was done from Super Coupe Performance. Stock gears on it now but picking up 3.27 track lock pumpkin from a SC, i like to do a lot of hywy driving.

You sound like a smart person so i appreciate any advice or passing on of knowledge. I'm not however trying to piss anyone off, if that's how my questions came off.
Don't read any sarcasm or anger into anything i say. I try my best to see things other people way lately. Now i'm ranting.

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post #19 of 29 (permalink) Old 10-14-2017, 09:50 AM
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I'd get with Dave Dalke or decipha first; the QuarterHorse seems to be the preferred tuning add on (you can later burn to a chip and use a F3 adapter, but I'd just leave the QuarterHorse installed myself!) and they both have tunes and tuning capacity to use the QH on your machine; add a wide band O2 (confer with Dalke and/or decipha or whoever does your tuning first for optimum brand!) and you're ready to datalog and have them tune remotely, all set to swap the MAF and anything else you do.

Consider this the equivalent of someone with a well trained eye reading your spark plugs from the old carb days.

And the tuning ... well, what changes would you make without touching the jetting on a carb? Some changes the ECU can make on its own, but swapping the MAF is like swapping the intake but using the same carb; you'd need to check jetting on the carb, you need to tell the ECU about the new MAF. It's the same basic thing, just is it mechanical (swapping jets) or electronic (loading a new transfer)?

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post #20 of 29 (permalink) Old 10-14-2017, 04:47 PM
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First off, apologies to v8nick for jacking his thread. Thanks to RalphP for his imput.
I shouldn't have jacked this thread, i'll start one of my own later on. I'm going to switch the maf back tomorrow until i have everything ready to go in at one time and can use all the good information i've gotten on this thread. S4gunn thanks as well. I've read quite a few of your replies in other threads and obviously you have a lot of knowledge.

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post #21 of 29 (permalink) Old 10-15-2017, 12:05 AM
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First off, apologies to v8nick for jacking his thread. Thanks to RalphP for his imput.
I shouldn't have jacked this thread, i'll start one of my own later on. I'm going to switch the maf back tomorrow until i have everything ready to go in at one time and can use all the good information i've gotten on this thread. S4gunn thanks as well. I've read quite a few of your replies in other threads and obviously you have a lot of knowledge.
PurpleXJ
I just realized that you were not the OP and hijacked this thread. Start your own and we can continue this discussion.

V8Nick:
Did you measure the voltage of your car at idle yet? If you are not seeing >14V, I suspect the alternator isn't generating the power needed to keep the car running >2.5K RPM under load. This could be an issue with the alternator OR as I mentioned the wiring.

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post #22 of 29 (permalink) Old 10-15-2017, 12:52 PM Thread Starter
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13.46 volts at idle. I just changed the ICM, and have another set of plug wires coming tomorrow. Hopefully that cures it.
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post #23 of 29 (permalink) Old 10-16-2017, 12:14 PM
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13.46 volts at idle. I just changed the ICM, and have another set of plug wires coming tomorrow. Hopefully that cures it.
Did you measure this at the alternator output or at the battery?
IMO, that's at the low end of acceptable.
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post #24 of 29 (permalink) Old 10-16-2017, 12:24 PM Thread Starter
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That was at the battery.
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post #25 of 29 (permalink) Old 10-18-2017, 02:10 PM Thread Starter
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Ok, so I changed the icm, and threw on another set of plug wires. The car runs great until its good and warmed up. After about 30 minutes of run time, it just shits all over itself. I'm completely out of ideas.
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post #26 of 29 (permalink) Old 10-18-2017, 06:12 PM Thread Starter
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I just drove the car around some more. Or really seems to crap out at lower rpms now, but once you get on it, it clears up. Idk if its possibly fuel related. Maybe a dirty fuel filter. It obviously won't hurt to change it. Looks like this weekend I'll dig out my fuel pressure tester and see what I find on that.
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post #27 of 29 (permalink) Old 10-25-2017, 07:48 PM
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Have you looked at upstream o2 sensor voltages when the hesitation happens? How was fuel pressure.

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post #28 of 29 (permalink) Old 10-26-2017, 09:46 PM Thread Starter
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I haven't even had time to mess with it. We've been working 7 days a week. I might get this Sunday off. Once I get a day to mess with it, I'll post an update
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post #29 of 29 (permalink) Old 11-16-2017, 09:12 PM Thread Starter
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Well, we have gotten no where with this car. Fuel pressure is fine. I've been told a few times the engine could have a cracked cylinder. So I did pick up a PI motor a few months ago, so looks like I will possibly be swapping it in.
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