Barely Rough Idle

[SHOCRUZR]

As the subject states, I've been having this problem for a week now and after cleaning the IAC Valve, disconnecting the negative battery for 5 minutes, I drove around and went to the highway about 20 or so miles and a 3-5 miles of stop and go driving. It has improved but not totally gone. It is best described as "barely rough idle".

Now, I did search our V8SHO website and came across Dan Carman's Electrical Gremlins Odyssey. Would this be the best route to fix this? Remember, I never had my "Service Engine Soon Light" on.

Am I right to assume that if the TPS sensor or EGR valve or CKPS or CMPS goes bad, they will throw a code?
How about a coil pack?

I presented this problem to the V8SHO email list, and got only a single reply stating that "It might be a coil pack". That was 2 weeks ago. I decided since then to replace the IAC valve with a new one and the problem remains the same. I did check the old IAC valve and gave me with 23 ohms of resistance. The new one gave me 11 ohms.

 

[Mr Anonymous]

99.9999% of the time, it's a coil. The fronts are easy enough to test, just disconnect each coil one at a time, and the one that causes no change in idle quality is the culprit. If they all cause the same change, then it's probably a rear.

A bad coil won't usually throw a light until it is completely dead. It makes pinpointing the failing one a frustrating endeavour. I've been recommending to people to just go to their local Ford dealer, pay an hours labor to have them put the car on the WDS and run a cylinder balance test. That will pinpoint which cylinder isn't contributing its fair share, and then requires replacing only one coil (especially if a rear), instead of 4 or even 8 as some people will.

 

[Mr. SHO]

^What he said. Before I ran into all those TPS/CMPS/CPS/wiring issues, I had a coil go bad on me. I had that barely noticable missing at idle thing for a few months before it worsened to the point that it would occasionally just die in the middle of a WOT run, triggering the CEL, which would go out a few minutes later. When I got the cams welded, I had Kirk put in 4 new coils in the back row, and I haven't had the problem since (about 18K miles later). I never did get a steady CEL that would stay on for more than a minute or two, even though there was obviously something very wrong with the way the car was running.

 

[SHOCRUZR]

At this point, especially with the cold weather, I will try to wing it until it is warmer. Crossing my fingers that it won't die before then. I am hoping it will last until April and I will work on this. Thanks for the info.

I will test the front coils sooner, weather permitting.

PEACE!

 

[SHOCRUZR]

Last weekend was warm enough to work on this. 4 new coils and spark plugs on the back. Guess where the bad coil is??? Coil #8!!!
I guess I can be happy with the fact that the back bank have new stuff and it will be a while before it fails. If it does I can change it quick the second time around.

Mr. Anonymous and Mr. SHO, thanks for the info and assistance with this.

Although, I did test the fronts by disconnecting it and I could not detect any difference with the idle from the coil # 5, 6, & 7. Although my way of knowing that COP #8 is the culprit, I just shook it just like a light bulb, hoping I can hear a slight rattle, which I did. Visual inspection showed the the spring is moving too much compared to the others.

 

[woody32]

just a quick input here,my cheapo-deluxe $30 (ish) code reader from wal-mart reads my codes(koeo,koer,and memory)does the cylinder balance stuff,as well as the relay test,and the timing checking function. to be fair and honest here,i still haven't made it away from getting my koeo stuff all straightened out,but i am gettin there quickly.(never did it yet,but it says the puter will self test itself), and give out indivual readings,(i.e. cylinder # and percent of output,etc)..........doesn't just buying the code reader sound like it might be a good option here for some of us ?......not trying to knock mr.anonymous or mr.sho but if the person is on a really tight budget this might work out ok,as well as the benefit of being able to check the cars codes and general running condition at all times.

 

[Mr Anonymous]

just a quick input here,my cheapo-deluxe $30 (ish) code reader from wal-mart reads my codes(koeo,koer,and memory)does the cylinder balance stuff,as well as the relay test,and the timing checking function. to be fair and honest here,i still haven't made it away from getting my koeo stuff all straightened out,but i am gettin there quickly.(never did it yet,but it says the puter will self test itself), and give out indivual readings,(i.e. cylinder # and percent of output,etc)..........doesn't just buying the code reader sound like it might be a good option here for some of us ?......not trying to knock mr.anonymous or mr.sho but if the person is on a really tight budget this might work out ok,as well as the benefit of being able to check the cars codes and general running condition at all times.

The problem is that your code reader is for EEC-IV cars, and the V8 Gen III SHO is an EEC-V (nee OBD-II) car. On the EEC-IV cars, the cylinder balance test firmware is integrated into the PCM. On the OBD-II cars, it's only available on the WDS computer (NGS doesn't even have it, and that's a $2000 piece of equipment).

It would be swell if we could simply put a scan tool on the V8 SHO to run the cylinder balance test. It would be even more swell if the PCM could detect a failing coil a lot earlier and flip a light to save people a ton of troubleshooting time and effort.

 

[cellar]

i think I am having the same problem right now as you were. I had a bad coil on the rear bank of em and had them all replaced on the back. The only difference I can tell between whats happening now and what happened then is that I could feel the misfire while i was driving, with this situation now I cant. Also, i didnt notice it before with the other bad coil, but i only get the little shudder in idle when i have the car in drive. Sigh, if its the coil this time again i hope its in the front.

 

[claypool72]

I'm having the same problem described here but I just finished putting brand new Visteon coils (the real deal) and plugs. I'm almost positive it's not a vacuum leak. And the miss is different levels of barely. Sometimes 0 with a mini blip, then sometimes a little more. Thanks. I know the threads old. But I was searching at least.

 

[gdubya]

I just replaced my back 4 plugs and packs, noticed water in the bottom, is this from the throttlebody gasket? any help is appreiciated

 

[claypool72]

Bottom of what

 

[gdubya]

bottom of the plentium

 

[claypool72]

I think this is normal. I had the same thing. Search for catch-can. That's one way to eliminate this problem. And yes it can become a problem with sticking secondaries ringers and build up on top of pistons.