98 cobra breaking down on acceleration - Mustang Evolution

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Old 12-12-2015, 09:19 AM   #1
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98 cobra breaking down on acceleration

my 98 cobra runs like a scalded ape when it is stone cold, but after it starts to warm up it misses under hard acceleration above 2500 rpm. I have changed plugs, installed new screaming demon coil packs and gapped the new autolite platinum plugs to .065 gap as stated in the directions. the wires are new looking msd 9.5 mm. has anyone ran into this same problem?
bhk308

next payday I am going to buy new ford racing 9 mm wires but I don't think it will change anything.

HELP
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Old 12-12-2015, 11:18 AM   #2
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Have you scanned for any trouble codes?
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Old 12-12-2015, 01:34 PM   #3
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Have you scanned for any trouble codes?
yes it has a 02 sensor temp code, took the cats off.
and it says lean right bank

but when it is first started up completely cold she will run like new

problem only comes in with warmed up engine
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Old 12-12-2015, 01:59 PM   #4
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Do you know the number of the code?

From your description of the code, it could be caused by anything from a 02 sensor that isnt connected, to a vacuum leak...
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Old 12-13-2015, 03:41 PM   #5
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While I can't believe your MSD wires are carbon core I have seen this same misfire with bad OEM carbon core wires. Typically it misses going uphill with 1/2 open throttle but is fine cold or easy driving at low speeds. Surprised you don't have the check engine light on with misfire codes.
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Old 12-13-2015, 09:27 PM   #6
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Similar, and my issue was plug wires. There are no "cheap" wire sets for our cars, but I went with Duralast as a temporary fix.
I will never buy MSD wires or Ford Racing wire sets again because they failed prematurely. Probably just bad luck on my part, but I refuse to pay twice for crappy wire sets.
I will be getting a new set of OEM wires.
------------------------------------------------
Part Name: Spark Plug Wire Set
Brand: Motorcraft
1996 Ford Mustang Spark Plug Wire Set | FordParts.com

Part Number: 12259(WR-5875)

Please update, so i can learn me sumin' too.
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Old 12-14-2015, 11:49 AM   #7
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Start with the basics ..

Check fuel pressure
Clean MAF / IAC / Check TPS voltage
Clean and check TB
Check fuel filter

Always do motorcarft parts , especially coil packs .. aftermarket are junk and offer no more spark than oe parts.


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---------- Post added at 12:49 PM ---------- Previous post was at 12:48 PM ----------

O2 codes .. does it say sensor 1 or 2 ..
Upstream can cause drivability issues.

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Old 12-15-2015, 03:59 AM   #8
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ok when I put the bbk h pipe on it I put in the 02 deletes don't know how old anything is as I just bought the car 3 months ago and can't contact previous owner as I bought it at a lot.
I put the plug wires on it yesterday afternoon and no change. the tps is at .996-4.8 volts and smooth through out the full range of throttle plates. the plugs that came out were ngk platinums and looked almost new. I will try cleaning the mass airflow this weekend. fuel filter is new. after that I am lost
bhk308
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Old 12-15-2015, 08:30 PM   #9
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Beleive the ecm, replace the bad o2 sensor. When in closed loop o2 sensor controls mixture,when cold in open loop the ecm uses pre-programmed values so car runs as it should. Your code is telling your ft o2 right side has a heater circuit out.


When the rear with cats are taken off the code will say poor cat efficency


change that rs ft 02 sensor then enjoy her running right
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Old 12-16-2015, 08:35 AM   #10
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Plug gap is .052 dude, no idea where you got .065 from.


The coil packs, you just wasted how ever much money that was. For the wires, only ever buy OEM. You can get OEM (Motorcraft) from Rockauto for $50 and they are the best wires you can put on the car.


My bet is there is a sensor issue somewhere.


NEVER just start throwing parts at a car without pulling codes first or this sort of thing is what happens.
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Old 12-16-2015, 10:01 AM   #11
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Plug gap is .052 dude, no idea where you got .065 from.


The coil packs, you just wasted how ever much money that was. For the wires, only ever buy OEM. You can get OEM (Motorcraft) from Rockauto for $50 and they are the best wires you can put on the car.


My bet is there is a sensor issue somewhere.


NEVER just start throwing parts at a car without pulling codes first or this sort of thing is what happens.
I did code it to start with
I had a coil pack breaking down because when I changed them most of the problem went away the coil manufacturer says to gap plugs at .065 because of the voltage increase of the new coils.
I have been a mechanic for over 40 years just not familiar with the mustang electronics
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Old 12-16-2015, 10:17 AM   #12
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The coils you got are no stronger than a new OEM unit. Gap is .052 regardless of what they say.
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Old 12-16-2015, 10:44 AM   #13
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Yeah I'd gap them to .52-54

And you can always swap the O2 sensors and see if the dtc changes banks..

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