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Discussion Starter · #1 ·
I left this morning a little late (saw the grass-frost, knew it'd be some time to kill the icees on the car). Started up (got a little more than the little hiccups); kicked the defroster on, oh man, that just set it off. Decided to drive to the bank (deposit a check), hoping it'd improve (usually does when warmed up a bit).. but no, it drove like ****.

It's a 99 GT Auto (recently turned 151k miles old). Recently installed a K&N CAI, had the fuel filter changed (thought it'd make the hesitation hiccups go away... it did, for a bit), IAC could probably use a jet or two for cleaning (but last time, it wasn't too dirty, but I'll do that shortly anyways).

I saw that SES came on when I returned home from the bank (pay-work isn't happening today now, but car-work is the only entry the menu).

Sucks, because I JUST got an apartment and I'm moving this weekend (bank account is virtually empty now, just a couple hundred, but doubt that'll last much longer now..).

I've been doing a bit of research this morning and what I've read kinda frightens meh. But I need my wheels to do anything, so I need to work on it today.

I read in some threads here to check the COPs, and the test is to either unplug (see if the engine runs better) or switch (to see if the problem follows the COP).

I'd rather try the unplug test first, but I am wondering: is it ok to just unplug it (preferably before you start the car), and see what happens, or do I need to worry about the injector for the cylinder (the code indicates #6 is misfiring).

I've had #5 misfire about 4ish months back, and I replaced the COP with an Accel COP, which seemed to improve the vehicle, but now I'm thinking that the #5 COP is 'eating' too much juice from the wire (I don't know if this is true or not, I'm not an electrician/mechanic.. yet) and thus starving the #6 COP, or if #6 is going bad, etc.

Is it OK to just unplug the COP and then start the car?

I've only an Actron CP9125 reader, so I don't have any data-logging capabilities (I've been wanting to upgrade, but other things just keep getting in mah way.. Suggestions on a tuner?).
 

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I've had #5 misfire about 4ish months back, and I replaced the COP with an Accel COP, which seemed to improve the vehicle, but now I'm thinking that the #5 COP is 'eating' too much juice from the wire (I don't know if this is true or not, I'm not an electrician/mechanic.. yet) and thus starving the #6 COP, or if #6 is going bad, etc.
That isn't it.

Just try swapping the #6 COP with one from another cylinder, and see if the misfire moves with the COP. If it does, you've found the problem. If not, you can try new plugs, swapping the #6 fuel injector with one from another cylinder, etc.
 

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My mustang doesn't have COP's but when I had issues with my F150 I just unplugged the wire harness connector to the COP while the truck was running. There's no reason to pull to whole COP.

If you find out it's bad ei. no change in motor, make sure the COP wire/boot isn't burnt out before you replace the whole COP. You can get new boots for under $10. COP's are not cheap.
 

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If the cylinder is misfiring at idle, that'll work. If it only does so under load, you'll need to swap COPs around.
 

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unplug the injector to #6, if no idle change the injector is bad.
Next swap the COP with another COP and see if the misfire follows the COP.
Also check the rubber boot for the COP, they're known to deteriorate and cause misfires.
 

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Discussion Starter · #6 ·
So I unplugged #6, no change in the engine running.

For shits and giggles, I unplugged #5, definite change in engine running.
 

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Sounds like #6 COP or boot/wire.

Like stated above, make sure it isn't just the boot/wire burnt out before replacing the whole COP.
 

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I was chasing a misfire for the longest time after my x pipe install. Best thing to do is try new spark plugs and buy new wire sets. Fixed my problem right away.

Wire sets are $5 or so each at autozone and new plugs are like $15 I think

Only took me $300 and a month to figure that out -_-
 

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Discussion Starter · #9 ·
Just got back from the mechanic.

Apparently, vacuum leaks are no bueno.

They also switched #5 and #6 COPs, and she is running much smoother now.

Not bad for $122. Labor was ~90 + parts (hoses + clamps).

However, I still feel the slightest (and I mean.. slightest) hesitation. I'll drive it around some more this and next week, see if the computer adjusts itself because vacuum is correct (or close to it, and thus not so much unmetered air).

In the next few months, however, I think I'll just put down for 8 new COPs and plugs. (Motorcraft, of course).

Also ran my 'defroster test' - surges, but it sure as hell doesn't idle horribly.

We'll see what tomorrow morning brings (what effect coldness has on startup+idle).
 
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