[cobrabro]

Hey SVT bro's,
My 98 Cobra has developed a stutter while cruising in any gear with just a little throttle. One of MY IMRC cables recently broke and it started after I zip tied them open. I also got a new tune for them being open all the time but it still stutters while cruising. It revs out fine during normal or WOT. It still idles with a little shimmy like it always has and I can't figure that one out either.
(Plugs are about 1 year old and wires are about 6months old (Motorcraft))
Any thoughts?

[jessemachone]

plug wire leaking voltage to ground. the ford racing wires ar known for leaking.

bad coil pack - you could check for a bad coil module by intermittently shorting a coil to ground and listen for the one that doesn't make a difference when you short it.

bad injector.

[cobrabro]

Originally Posted by jessemachone plug wire leaking voltage to ground. the ford racing wires ar known for leaking. bad coil pack - you could check for a bad coil module by intermittently shorting a coil to ground and listen for the one that doesn't make a difference when you short it. bad injector.

Thanks, but what makes me curious about that is that it runs fine except and cruising speed and I even posted a 13.93 at 101.5 recently at over 1000 feet with just a tune and ram air (ram air not the cause because it started before ram air was installed).

[cobrabro]

I have a new symptom to add to this. Since my IRMC's were broken, it took them out and removed the valves and bars and JB welded the holes and put it all back together. (Also tried to clean the B/dry ports/Valves as they were nasty at 70k miles while the wet ports were clean as a whistle.) It runs fine and strong now except for the continued weak stutter while cruising and now a pronounced momentary power loss that seems to happen on the same road only on my way home and just for a few seconds. I will be in 4 gear after coasting down a hill and then cruising back up the other side in 4th at around 2,000 rpm. I hear a clunk (like the drivetrain just took a jolt) and I have no power and the engine sounds like it is struggling. I give it a lot of gas and the car doesn't accelerate at all and the rpms stay where they are. So I let off and put it in 3rd and it is normal again going up the hill and for the rest of the way home.
Anybody experienced anything similar or have any ideas?

[ccm302]

Not sure about the up and down hill thing, but I've had the stutter issue before with a dirty EGR valve. Other than that, I don't know.

[Cricket]

What kind of buildings are around your car on that hill? Antennas or anything of that nature?

[mayosailor27]

Coil packs. When they get hot, the electronics inside even though they are made not to do it, "open circuit" (cant think of the exact word) When cooled, now the circuit is back closed, since heat makes things expand and vice versa, being cool, thye work fine again.

[ccm302]

^ +1...i forgot about that. I had a lightning that had that problem too.

[cobrabro]

The hill it happens on is a residential area. It has happened some other places now. This issue may be totally isolated to the stutter only while cruising. I will try to look at the egr when I have a chance. CCM 302 were you able to clean yours or did you just get a new one?
So on the coil packs - wouldn't it stutter all of the time - during acceleration also if it was the coils?
Thanks guys, apperciate you helping me think through this.

[ReefBlue1994]

Mine was a vacuum leak on my foxbody, like if you dont keep on the gas it lugs?

[ccm302]

Originally Posted by cobrabro The hill it happens on is a residential area. It has happened some other places now. This issue may be totally isolated to the stutter only while cruising. I will try to look at the egr when I have a chance. CCM 302 were you able to clean yours or did you just get a new one? So on the coil packs - wouldn't it stutter all of the time - during acceleration also if it was the coils? Thanks guys, apperciate you helping me think through this.

I was able to clean mine.

With the coils, mine would stutter going up hills under any load really. It seemed like the higher the load and lower the rpm, the worse it got. After it downshifted, it would go away. It usually did not do it under acceleration. It ended up being that I had water in the back two spark plug jackets on the passenger side. Pulled the coils and plugs out, dried them off, and it was fine after that. My SVT mechanic said it's the way that Ford designed the plastic grate where the water drains. Apparently when it gets full, it spills right over into these two cylinders. He also said that everytime it rained, within about a day or so, he'd have F-150's out the wazoo that were misfiring.

[cobrabro]

Well it doesn't stutter under heavy load which is also kinda odd to me , it just pulls on through. It's only on light cruising, say a flat road where I have to give it just a little gas to maintain speed in 3rd -5th. I checked the plug holes tonight and they were all nice and clean and dry. I inspected the wires also and didn't see any signs of them arcing (plus they aren't pretty new.) Gonna take the EGR off Saturday and see about cleaning it. I'm thinking it is either that (EGR), a vacum leak or maybe something wrong with the tune. Thanks again-

[Cricket]

If It's happening else where then my idea was shot out. When you said it was earlier I thought it was isolated, and an antenna was around that could have been messing with your ECU. Heard of it happening to a few people before.

[mayosailor27]

Check the coils, or switch the coils from passenger to driver and vice versa.

[ccm302]

Originally Posted by cobrabro It's only on light cruising, say a flat road where I have to give it just a little gas to maintain speed in 3rd -5th.

That's what makes me think it's the EGR. Because that's exactly when and where mine would stutter. But then again, I'm also not a mechanic.

[cobrabro]

I hope that will cure it (EGR) - going to clean it tonight or tomorrow. So how did you clean your EGR or what did you (or anyone else) use to clean it since it sounds like you did it successfully? Read a lot of threads out there about different cleaners and possibly damaging the thin membrane of the diaphragm.

[ccm302]

I just used a carb cleaner. The idea is just to break loose all of the caked on carbon build-up so that diaphragm can move freely again. I think anyway. How many miles are on it?

[cobrabro]

Originally Posted by ccm302 I just used a carb cleaner. The idea is just to break loose all of the caked on carbon build-up so that diaphragm can move freely again. I think anyway. How many miles are on it?

Ok, that's what I did. The EGR wasn't terribly dirty (at 70k miles) but I used carb cleaner and filled the top chamber and it closes completly because no fluid went into the lower portion. I then opened the valve with suction to the nozzle on top and it let the fluid into the lower portion. I screped the walls of each section also. Anyway, it didn't help any so it is somthing else.
I'm sure it was a good thing to do though anyway.
Going to investigate the tune with BAMA tunes next. Maybe they missed somthing else in my IRMC delete tune. I also have a new fuel filter to put in it.

[ccm302]

I'm sure the fuel filter won't hurt. Sorry to hear that didn't work bro.

[cobrabro]

Well ccm302 you were at least partly right about the EGR. After reading another stutter thread, I unplugged the EGR from the top vacum tube. The stutter seems to be gone now. It sounds like the EGR lets exhaust gas in during the rpm range I was having trouble with and so it seems like with the IRMC delete, maybe it was running too lean during those rpms because having both ports open probably sucks more air in (although with not as much velocity/swirl). Question now is, do I have to run no EGR now? or is something else like the DPFE sensor or O2 sensors not working properly to notice the extra air that the EGR is letting that the MAF doesn't know about?