Ok guys, I'm new here so if this post is in the wrong place I apologize. Anyways here is my situation. I have a 1998 GT, that after 170K on the odometer the head gaskets went. I came across a 4.6 DOHC out of a local wrecked 1996 Cobra that only had around 38K on it so I bought it. Got it with the wiring harness and trans. I did the swap and it fired right up, BUT it has an odd 'miss' or stutter in it. If you listen to the exhaust note it almost sounds like a mild cam but it isn't. I have already installed new plugs, plug wires, IAC, PCV, air filter, and fuel filter. I'm not sure where else to look. I'm contemplating pulling the intake to clean the IMRC plates to see if that helps. The engine only has about 41K on it now, but it sat up for several years after the car it was in was totaled which is why I'm thinking about doing the IMRC cleaning. Thanks in advance for any advice!
96 Cobra Rough Idle
- Thread starter mustanglyf
- Start date
only thing i can think of would be to check tps voltage.. idk or the coil packs
High lift does not make for a rough idle. BTW, 800 foot lift cams must be huge!
As for the OPs problem, it could be anything. What computer did you use? Has it been tuned? Have you checked for vacuum leaks?
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You shut your whore mouth, my attempt to be funny has failed, I do not need to remind me of my incapabilities.
I used the original computer that I received with the engine. Since apparently the engine was a early 1996 build, I had to have a chip burned to turn off the Alarm system since apparently 96 was different enough from 98 to not be able to be programmed. While correcting that issue with the chip I also had the tuner turn off the check engine lights for the air bypass system (it was removed during install) as well as bumped the timing to run 93 octane instead of 87. That's all the tuning that has been done to it.
As for vacuum leaks I have tried the carb cleaner while listening to idle method and haven't found any.
As for vacuum leaks I have tried the carb cleaner while listening to idle method and haven't found any.
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not to hi jack your thread but i have the same problem with my 98 cobra that has the shutter/miss like you described, but couldn't find out what it could be, and i searched all over the forums :shrug:
The only thing that I haven't replaced is the EGR valve and EGR solenoid, I've heard that this can cause rough idle issues, but I wanted to hear other opinions first.
Make sure you have no vacuum leaks, and all your hose clamps are tight, also make sure your egr valve is clean, make sure your maf isnt caked with shit , curios, what did you gap the spark plugs at?
I would have to ask is it really a problem. I have looked at more than one Cobra that you hear what sounds like a small miss but they run like a bat out of hell. Plugs look good, idle is with in spec, no Cel, A/F right where it should be and all data logged specs good. I have to ask...normal? That depends on if it is a miss or just a spit sound. I do not know the answer but mine seems to have a slight bit of a miss but runs so good I just have to fig....Normal. BTW put a beer on the Cobra on the intake and very little wiggle.....lol
Check the compression to all your cylinders. If the motor set for a few years, one or some of the lash adjusters could be bad.
My car does the same thing. And when I had my sct tuner plugged in, i was checking the spark, and it looked to be a little bit bouncy. I replaced everything except the coil packs. I am thinking that might be what the problem is.
My 96 Cobra has the same rough spitting idle at first start up and it seems to disipate as the motor gets warmer.
I used Bosch Iridiums...no gap to set
that might be your problem right there... get rid of those and pick up a set of ngk tr5's and gap em at .054, that cleaned my idle up dramatically, i had a small miss with the original platinums. should be able to get all 8 plugs for under 20 bucks....
I might try that this coming weekend to see if it helps.
Sorry for it taking so long for me to post back to this thread. So far I have replaced the Bosch iridiums with some new platinums and set the gap to .054. I also took the EGR off and found it to be caked with crap inside so I replaced it as well as the solenoid. My idle has cleaned up alot and I can feeel some power improvement but it still feels weak. I'm wondering if, after seeing the inside of the EGR, my IMRC plates may need cleaned as well as installing an oil catch to help prevent the build-up. Does this sound like a good idea or no?
Thanks again for the help and input guys.
Thanks again for the help and input guys.
Mine does also, I'm going to try the NGK's
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