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Still breaking up after 3,000rpm...what else to check?

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Old 04-28-2013, 05:22 PM   #1
StalkerGT
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Default Still breaking up after 3,000rpm...what else to check?

I have replaced my tfi module and ignition coil...when I hit 3,000-3,500rpm's it breaks up and the tach kinda bounces around. If I full throttle it it seems ok but if I hold it steady around 3,500 that's when starts to bounce around and break up....if the car is just sitting and I rev it up to that it doesn't do it. Seems to be only when driving. What else should I check? I'm stumped
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Old 04-28-2013, 08:36 PM   #2
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EGR related vacuum lines would be a good start.
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Old 04-29-2013, 06:10 AM   #3
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Ok I will check out the vacum lines today
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Old 04-29-2013, 08:13 AM   #4
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coil, the pick inside the distributor and the shaft in the distributor check it for wear from side to side I have seen a few wear out. Then you might want to start looking at valve springs
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Old 04-29-2013, 09:09 AM   #5
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to me it sounds like a fuel pump...have you checked the pressure?
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Old 04-29-2013, 09:55 AM   #6
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Good voltage?
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Old 04-29-2013, 11:07 AM   #7
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The tack jumping around kind of say electrical to me But I could be wrong that's for sure
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Old 04-29-2013, 01:24 PM   #8
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All vacum lines checked out ok...my fuel pressure is about 36-37psi with vacum on at idle. The regulator is new...fuel pump is Walbro 255 that was put in last summer. Now it's just doing it around 4,000 and when I let off the gas as the rpm's drop the tach still jumps around without hitting the gas pedal...but when the rpm's get under 3k it's fine and stops jumping. If the car is sitting and I rev it up to around 3,500 and hold it there it breaks up pretty bad...it doesn't really do it when the car is cold...just when it gets around 180 or higher. Sometimes cranks for a few seconds before it starts too. That's also when it is warmed up
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Old 04-29-2013, 02:42 PM   #9
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Fuel pressure is at 42 with vacum off...also realized today that when I slowly press the throttle the fuel pressure goes down a few psi. But if I hit it fast it goes up like it should. I stopped by a garage today and they suggested maybe the distributor but almost seems fuel related now? When the car is cold fuel pressure is around 37 at idle but when fully warmed up its at 34 at idle
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Old 04-29-2013, 04:26 PM   #10
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The tach is exclusively controlled by the negative wire of the coil, so if it's acting weird in any way it's either the wiring, the coil, or the tach. The breakup can be explained by anything else mentioned here, but it would be rare that they aren't connected.
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Old 04-29-2013, 06:13 PM   #11
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The tach only jumps around when it hits the point where it breaks up...doesn't jump any other time. What would cause it to not start right up when it's warmed up? That's when the breaking up is the worst also
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Old 04-29-2013, 06:50 PM   #12
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Did you mention in an earlier post that you replaced the tfi with a used one? That is a classic symptom of a failing tfi or coil. When its hot it is the worst.
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Old 04-29-2013, 07:03 PM   #13
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Yeah I replaced it with a used motorcraft one that I had laying around...wasn't sure if it was good or not
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Old 04-29-2013, 07:12 PM   #14
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They can test those tfi modules at autozone, but they need to run the test 3 times and its better if they run the test with the module heated up to operating temp with a hair dryer or heat gun. A new tfi is about 40 to 50 bucks at autozone and around half that off ebay

Also when you replace those you need to clean the mating surface up and apply some type of thermal paste or diametric grease .... The best way is to find a donor sn95 in the scrap yard and steel the mounting heat sinc from the passanger side fender then do the relocation
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Old 04-29-2013, 08:29 PM   #15
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Yeah that sounds like a good idea...I'm gonna get both modules tested. I hope that's all it is...such a pain!
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Old 04-29-2013, 08:41 PM   #16
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My ranger did that and they use the same dizzy mounted tfi, It would run so so when cold but about 10 min into a drive it would start to buck a little while holding a steady throttle. If I floored the gas it would clear up for a min or 2 then go right back to missing and hesitating. Hard to start especially when hot until finally it wouldn't start at all. Ive heard pple say they had such problems with the tfi module that they would carry a spare in the glove box just in case it went out on them again.

I think that the distributor is the absolute worse place to have an electronic ignition controller mounted just because it gets pretty hot there.
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Old 04-30-2013, 04:40 AM   #17
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I'm hoping that's all it is...I'm gonna go get the modules tested this week. I think I am gonna look into the relocation kit
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Old 04-30-2013, 04:58 AM   #18
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Yea hopefully that's all it is . Good luck to ya man, I know it sucks monkey marbles trying to pin down an ignition problem. Be it fuel or spark
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Old 04-30-2013, 07:07 AM   #19
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I will post back when I get them tested and will let you know what happens...thanks for the advice!
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Old 05-01-2013, 04:54 AM   #20
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Got both tfi modules tested...they were both good. Had them test them like 5 times so they got hot too. A few people have suggested that I change the distributor...I have one laying around so I might as well try it. Do I have to do anything special when I swap them? I know they have to be lined up the same way the old one comes out
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Old 05-01-2013, 04:54 AM
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