My lazy azz finally got around to replacing the cap, rotor, coil, and wires a couple of weeks back. (The plugs were replaced in 2006). The car is an 89 M6 with 55k miles.

This seemed to cure a shaky idle that was becoming progressively worse. (But, it was yet to feel like a hard miss).

When I replaced the wires, I found an old one had worn thru the insulation as it rounded the valve cover. When I put the new ones on, I tried different routing. Because most of the old looms broke, I used zip ties to group the driver's side together. This held them up off the valve cover. The pass side was replaced in orig routing -- including the extra plastic tubing that encased that side.

For about a week, I enjoyed the smoothest ride since I bought the car in 1999. It's a stick and low RPMs had never been this smooth. Whooo hooooo!

But, after a week, the roughness started to return. I looked and found the #7 wire touching the valve cover with a tiny bit of oil where it meets the block. The #5 wire (next to it) had a tiny singe where it touched the air tube. I reajusted an went on.

The problem has continued to erode. Now I DO have a hard miss at idle -- especially when warm. I suppose it could be #3/#5 injector since they measured 12 ohms cold. (Haven't checked them hot yet). But, the marked improvement and slow decline after new wires/cap makes me wonder.....

A work buddy said I couldn't strap wires together like I did. He said the looms were installed for a reason. He thinks I might be bleeding voltage across wires.

Just curious what the experts think....

gp

 

Advanced Auto sells a product that looks like the black drain pipe extentions you would put on your downspouts around your house. It is just slighly bigger that the diameter of the plug wires, you can put this on and it will help protect the wires some. It's not the best looking but if it helps, it may solve your problem!

Enjoy the ride!

 

These HEI ignition engines are very sensitive to plug wires, holders, and separators, too.

I couldn't believe the difference ordering a new, complete, set of wire holders and seperators made in solving my light miss at idle problem after I changed the wires.

I got mine from Mid-America Motorworks (MAM).

 

I have done testing on mine with wires all over the place and not had an issue. Some people have a mess of wires and leave them that way and there car runs fine to. So IMO having your wires tied or routed odd is not the problem. You could run the car in the dark and look for sparks. Slowly lift up the wires and watch. Also spray them with water. It's possible those wires are damaged but I doubt it. If it is missing really bad, unplug each wire and see witch one it is. You can also do this with the fuel injector clips as it is easier. This can tell you witch cylinder is having an issue.

 

My wires go everywhere but I have yet to get a good set of wire looms for them.

 

He is right. Some people seem to get away with it, but electrical pulses in high tension wires, close together and running parallel with another, can induce (similar to how your coil works) voltage from one wire, into an adjacent wire. That can cause misfires and and any other number of problems. Imagine if the spark for a certain cylinder was to come at 60° BTDC instead of the proper 10°. Talk about your preignition!

At this point I would double check each of the wires by ohm checking them. Then, assuming no problems, I would invest in a wire separating system, factory or otherwise, to keep the wires out of harms way and apart. Then, if you still have an idle problem, you will have eliminated one possible cause and can look elsewhere, confident of what ISN'T the problem.

RACE ON!!!

 

Similar situation in my engine bay - after lots-o-mods I've scrapped the looms and just have the wires routed in out of the way locations. But in some cases, they're ty-wrapped to each other and against the frame.....my reasoning is that when you look at where the wires run behind / below the pwr. steering pump (right against the block) it can't be all that bad to have them against other pieces of the frame.....eh?

 

Try to keep wires as far apart as is practical. If they do have be close, try to have them at ninety degrees to each other, not parallel.
Less inductance (I think that's the correct term) that way.

Larry
code5coupe

__________
not easily impressed....

 

I should have revived my thread from three weeks ago with this and updated.

Saturday I put the Mid America Wire looms on the Vette.

Yes, it is very smooth and not missing at all.

Not to mention without good looms they can easily fall down onto the exhaust manifold and now your in a world of hurt.

CC and I were confused however, since I drive an '84 do I have to change the name from Cross-Fire??

I mean, really, I put the looms on and now the wires are not performing any cross firing like the General advertised in the side of the car

"Cross Fire" maybe "Back Fire" or "Car Fire"

 

Anyone who doesn't believe a shetload of current passes through those wires, just hold your hand near the glowing corona area of the plug boot while your engine's running.

Proper holding/seperation of those wires is essential to stable electrical delivery, I'm convinced of that.

 

Sure having your wires all in order is good but I doubt it is the cause of your hard miss. Checking it out should be quick and easy. This is what I would do, unplug each wire at the cap, the one that you unplug and the idle still has the same miss, is the one misfiring. Throw one of the old wires back on to test it, you did save the old wires for testing right?

 

You just grab a wire and pull it out?

 

Using ty-wraps is an acceptable alternative to wire looms.

The trick is to pull the wrap snug not tight. If the wrap is distorting the the wires insulation then it is too tight.

The reason being that by pulling the ty-wrap too tight, this will pinch the insulation and defeat its ability to isolate the adjoining wires. Thus cross firing can occur.

 

Yes, at the cap. Or you can disconnect the fuel injector clip it will be pretty much the same thing.

 

While it is running, you just grab a wire at the distributor and yank?

And you've never been bitten while doing this?

 

My (two ties) are loose enough the wires can be slid up/down. Really they are VERY loose.

Though replacing the wires DID cure a problem where it appeared the insulation was cracked (creating the possibility of arcing) I think I have another issue....

I note the problem increases as the car gets hot. More importantly, I can "cure" it for a minute if I stop/restart the motor! According to Vader's website, the ECM does not go closed loop for 66 seconds when the car is hot (5 minutes cold). Because open loop CLEARLY runs smoother than closed loop, it's obvious the computer is trying to compensate for a problem AND MAKING IT WORSE!

Because it's not throwing codes and because 2 of my injectors read 12 ohms (vs 16), I'm coming to the conclusion that the injectors are at fault. I'm guessing they degrade further as they get hotter (but I haven't checked hot resistance yet). Additionally, they are on the driver's side where the O2 sensor would "see" the problem injectors and "report their condition" to the ECM.

I've read the injectors fire in banks (though this sounds stupid). Regardless, I would assume the O2 sensor is seeing the lean condition created by the failing injectors. In open loop, the engine's idle is not horrible because everything else is O.K. In closed loop, the ECM sees the fault and makes the mixture richer.

Well, 6 of the 8 injectors were O.K. but now they're instructed to run rich. This mean the majority of the cylinders are now out-of-whack -- just to compensate for the 2 marginal ones. As a result, I'm smelling rich fumes (especially with my sidepipes) in addition to feeling a crappy idle.

When I shut the car off, I get 66 seconds of "uncorrected" running which brings the specs temporarily back nearer to the norm. When it goes closed loop, it IMMEDIATELY worsens again.

What do you think of this theory? Can you think of any other condition where stopping and restarting the engine could create temporary improvement. Also, remember the condition worses as the car gets hotter......

gp