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Discussion Starter · #1 ·
Hey all,

I just got my cobra about a month ago and absolutely love it. Great car and very different from my integra. I'm having a light problem and was looking for some help. My situation seems similar to another thread below. Here it goes, I'll do my best to describe the problem:

With light throttle (about 20-40%), the car seems to stumble or shudder, or kinda jerk when accelerating. This seems to happen between about 1800-3200rpms. Seems most noticable when giving more gas in higher gear to speed up (like when going from 30 to 40mph in fourth gear). Can't notice it in first gear, but it's most apparent in third and fourth, but then again I'm usually cruising in one of those gears.

I usually shift at about 2500rpm's or so when cruising around, so I'm in a high gear for the most part. Feels like someone who hasn't driven a stick is taking off or something, but not to that extent. If I really get on it say at wot above 4k or so, very little seems different. The engine "hesistates a bit toward the upper end (5k onwards) but nothing like the jerking above.

Don't have much a clue myself. Maybe bad spark plugs, wires, fuel pump, fuel filter? I put 91 in the car as the manual states, so I don't think it's anything to do with bad gas. The clutch is worn, but I don't that is the cause. It doesn't seem like it's slipping, but then again I'm not used to anything with this amount of power. I hope it's nothing too serious. Maybe a small tune up (plugs, wires, filters, and what not) can take of this.

I know about cleaning imrc's and what not, could this be the problem? This might be besides the point but the car still runs very strong, only a car behind my friends 2002 bolt-on ss (m6) at 85mph and still getting 16mpg in the city and about 21mpg on the highway.

Any help would be greatly appreciated, thanks and take care.

Vik
 

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hmmm....i had a problem kind of like that with my 96 last summer.. when i was at the track, it would hesitate high end.. i just bought new plugs for it, and it went away. I dont really know what year of cobra you have, but im sure it might have some mileage on it? if so it isnt going to hurt you to go ahead and change plugs, wires, cap and rotor, fuel filter....i think those should help, if not keep posting, some1 will figure it out for ya

chris
 

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Discussion Starter · #4 ·
Thanks for the responses guys. Sorry I didn't post it, thought my sig would come up. Yeah, it's a 1996 cobra with 96k on her, so I'm sure replacing all of the those little things will help it run smoother...

I haven't looked too much into the imrc cleaning and what not, but what all is exactly needed to do this? Anyone with some experience want to chime in? I'll probably start looking into links and how to do this.

Just wanting to make sure everything is good to go before auto-x season, and I plan on visiting the track a few times. Thanks and keep the responses coming.

Vik
 

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I have sometimes had the same problem at low rpm's from idle to 3000. What are the imrc's? Any other info would help. I have the plasma booster ignition but I unhooked it and still ran into the problem. The problem seems to occur mostly when the car is cold.
Im also running no cats, i thought that maybe the sims were the problem because my check engine light comes on sometimes but the only code it throws is O2 sensors. They are fine also.

Appreciate any help.
 

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Do a search on here for "cleaning IMRC's" sound like they may be sticking open if the car is only stumbling from 1800-3200...The IMRC's are secondary intake port butterflies that are supposed to open at 3250rpms and if yours are stuck open that would most definately cause drivability issues...It involves taking the intake off the engine and cleaning these plates with some carb cleaner...pretty easy job really, just some bolts to take out and it would only take about a day or weekend at most to get it all cleaned up...
 

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I appreciate the advice, I will definitely try this. I never thought of that, they could be getting stuck open every once and awhile.

Thanks Jim
 

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Interspy, if the Idle Air Control hasn't been replaced, that's where I'd start..
 

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If 99 cobra's do not have imrc's, what would the problem be? I am positive that the motor stumbels up to 3000 rpm, even at idle but it only happens only once a week.

Please help
 

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RKKCOBRA, MY 99 COBRA WITH 35K DOES SOMETHING SIMILAR. If I accelerate in 3rd or 4th at 2500rpm it feels like it stumbles a bit. It makes a very very mild backfire noise. I'm guessing it's possibly a coil pack or maybe a spark plug in the back passenger side area. The spark plgs in the back by the firewall get wet sometimes when washing the motor. The spark plug cover shield doesn't seal very good, and water may drip down into the plug, eventually fouling it. I think it's the fuel filter, change it every 10k. Try the fuel filter first, if that works done deal, if not most likely a loose spark plug wire, or fouled plug in the back passenger side by the firewall.

I'm gonna get my fuel filter changed next time I get an oil change. Probably inspect the spark plugs were I told you. If that doesn't work then it's most likely a coil pack.

Regarding your question about how the 99-01's work w/o IMRC'S, haven't the slightest. Call 1-800-ford svt and ask them, and then let me know.

Late
 
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