Another 328 stumble thread...

I came across tons of threads with lotsa good info/insight here...but figured it wouldn't hurt to start one of my own.

1986 328...Passed smog test in July...Recently started significantly misfiring...

Actually, noticed some time ago that at idle, every few seconds there would be a "puhhhh" sound from the exhaust, but at speed things seemed okay.

Over the past 5-600 miles, that has degraded to multiple misfiring, from idle through 5000 RPM.

=============================

Plugs are NGK Iridium with ~1000 miles.

Plug extenders on rear bank looked to be in pretty good shape connector-wise.

Connectors on the plug extenders on front bank were very corroded/oxidized.

Cleaned off the corrosion on all extenders and reinstalled to see if that would make any difference. Ran better...for awhile...then degraded to bad misfiring again.

On closer examination, turns out all extenders have carbon arc spots indicating shorting to the head (those weren't just grease/grime spots). Just for grins, ohmed out each as follows:

- rear bank 2185...2051...2808...2197
- front bank 2421...1918...2146...2083

So got a new set...supposedly for 328...but they have no resistance.

I'm a little confused by info in the threads: Are extenders with no resistance really compatible with the MicroPlex system? Or is there really a risk of blowing out the power transistor in the coil control module?

Next steps planned for this weekend are to ohm out all spark plug and coil wires and check/clean connections at coils and ECU.

Any other advice appreciated...

 

I just went through tracking down an intermittent miss fire. My car would run fine for about 1/2 to 1 hr, then the miss would happen. Is yours intermittent or does it happen right from startup?

 

My experience:

Misfire during normal driving. Sorted by replacing cables and extenders.

Only leftover is that now the car runs perfectly for 15 minuteswhen starting from cold, then has some misfire ONLY at idle.

Ideas?

Ciao

Eugenio

 

http://www.ferrarichat.com/ferrariads/showproduct.php?product=1079&cat=5

 

This is a confusing issue as "color" doesn't seem to be enough to identify which extenders have some resistance and which don't -- and IMO many cars have the wrong ones installed so even a testimonial/measurement from an Owner isn't without possible error. I believe 0 Ohm extenders are OK/correct for the Microplex systems, and other 328 owners have reported that they have used them and have not blown up the coil power module:

http://ferrarichat.com/forum/showpost.php?p=137803934&postcount=10

(and my TR Microplex has 0 Ohms extenders too -- although they are black and shorter than the 328 extenders).

Also, if your NGK Iridium plugs are the resistor type (an "R" in the NGK PN), you got some safety built in because they have ~5K Ohm resistance themselves (whereas the stock plug is a non-resistor type).

Can you please also give some other information about your old and new extenders just to add to the available data on the subject:

old extender resistance = ~2K Ohms
old extender color = ?

new extender resistance = ~0 Ohms
new extender color = ?
new extender F PN per supplier = ?

TIA

 

Steve,

I can shed some light on the extender issues, as I recently completed a major on a 1988 USA-spec. 328. As a point of reference, the last major service was done at the Dealer

Old extender resistance= ~5K Ohms (Most burned thru or cracked)
Old extender color = Shiny black (did not look "textured" like the 1000's of others I have seen)
Old PN = Unknown, but 100% installed by Ferrari dealer

New extender resistance= ~0 Ohms
New extender color = Dull slightly textured Red
New PN = 126699

Note: Original Champion A6G plug was replaced with NGK Iridium DR8EIX

Car runs 100%, with no issues.

Regards,
David

 

Thanks for posting the additional information David -- which just shows (again) how mixed up this issue seems to be

I wonder if the F Dealer was just trying to get rid of some old inventory or maybe substitued something? I do think this is sort of a one way issue. I.e., using a 5K Ohm extender on a Microplex is no big deal -- just like using a resistor style plug seems to work OK too. But using a 0 Ohm extender with a non-resistor plug on a Digiplex could be trouble -- just thinking out loud...

 

RK: Some miss @ startup; worse when warm.

RK: Mine misses regardless of RPM. Definite stumble/hesitation/disruption in power delivery under any load condition.

RK: Very nice looking wilre! I guess since there is a red sleeve over the wires anyway, color really doesn't matter, eh?

RK: Thanks
RK: Yes, they're resistor plugs.

old extender resistance = ~2K Ohms
old extender color = red

new extender resistance = ~0 Ohms
new extender color = red
new extender F PN per supplier = <<<RK: will check>>>

RK: Excellent! Thanks, David

 

Agree, this is a mess, with far too much mis-information out there.

My feeling on this are pretty simple: On these Digiplex cars, I want to see some resistance, weather it be from the plug, or the extender. As I recall, the OE plugs, A6G's were non-resistor units, whereas the replacements DR8EIX clearly are...

So to play it safe,
Non-resistor plug-> Use resistor extender
Resistor plug-> Use either type of extender

I do agree with you 100% that the Digiplex's should "see" some sort of resistance from the plug/extender combination.

Even when I was running extenders on my 365BB, some were 2K, other were 5K ohm, all "Black" with the same part number.


Regards,
David

 

Came across these (not that I think I need them at this point; just research). Anyone use either or know if they're compatible?
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RK: This does seem logical/reasonable. Thanks, David...

 

Rick,

Beyond the plugs and obvious (at least to me) known issues with the extenders, I couldn't agree more with Dave Helms on the ignition wires. By far and away, this is the most common problem I find with all these cars when it comes to a "misfire" condition. I've had great successes with the Taylor Wires, although I run Magnecore wires on my BB.

Resistance testing the wires does not always reveal a problem, per se...as often as the wires warm up; due to engine heat, an open circuit...or worse, an intermittant connection occurs at one of the plug ends. I've had wire sets "PASS" on the bench, yet "FAIL" on the car.

Two test that cannot fail you...

With the engine, hot:
Connect your timing light to each wire->Spark flash should be consistent, else "BAD" wire
Repeat for each wire and coils

If you have an exhaust gas analyzer:
Look for excessive HC->Any sort of misfire will result in a HC count of over 1000ppm, typically even higher.

Also, pull those distributor caps off...and inspect very carefully for carbon tracking, as well as the "normal" burnt rotor and/or excessively worn carbon contact.

Simple problem...mildly annoying to find.

Regards,
David

 

Rick,
Those are a great find if they in fact do work as a direct replacement for the stock units. I paid something like double that price when i replaced mine. i replaced them thinking they were the problem.

My problem ended up being a frequency valve relay. It was intermittently working causing a severe miss when it did go out. It's the one in the trunk on the passengers side well. below the antenna. My relay had a big zip tie holding it together.

just a thought. hope it helps?

Will

 

new extender resistance = ~0 Ohms
new extender color = red
new extender F PN per supplier = mulsanneexpress.com, Spark Plug Extenders Part #4873, OEM extenders made in Italy, Fits the following Years/Models: Ferrari All V8 3.0 328 (4 Valve) Replacement for Factory OE Part #126699

Yup on all counts. Haven't used my fancy Sun induction timing light in years...maybe decades! Unfortunately, do not have and EGA...Thanks!

Had read through your thread on this as well, Will...and, yes, definitely helpful! Thanks!

 

Thanks for the additional information Rick -- seems it shows again that "color" means nothing.

 

It took a lot of problems with what is available on the market for me to justify spending many thousands of dollars on having custom Spark Plug Wire made. I will not shave down 8mm to fit the caps and at the price for new caps, I will run the risk and ream them out. I needed 7mm for the vintage cars that run through the loom tube regardless. I have enough problems justifing the expense of various supplies we use daily, imagine trying to explain to my wife that runs the office our need for a 5000' spool of plug wire! I found nothing on the market to be acceptable, not all plug wire is created equal. The correct resistance is 350 ohms per foot used with 0 resistance extenders as was found by the OP. I simply dissect the old wires and reuse the red silicone jacket and boots as they hold up fine.

 

Timely thread. My car hasn't run well in weeks, and I got out the timing light this morning. Of course the problem is on the FRONT bank, can't be on the rear where access is easy. 1 cylinder seems to be firing well, 1 is firing inconsistently, 2 aren't firing at all. I did find 1 plug extender that's cracked and broken, but when I pulled an extender from the rear bank and changed it out, it still didn't fire in that cylinder. This sucks.

 

Be careful when pulling the extenders out. The new style supplied now with the very small clip has a track record of leaving the clip in the plug valley when they crack. Inspect each extender as it is removed to be sure the clip is not missing. I have had to go in with the bore scope twice this summer to pick these clips out of the plug valleys and yes, it only happens on the front bank.

Dave

 

Is there any easy way to get them back IN? One of them took me about 15 minutes, I can't believe it was that hard. And my back hurts today from the contortion required to reach to the front bank.

 

The new ones are not very friendly! I now use an old plug and work them on and off a number of times until they fit and disconnet nicely and then fit to the car.

Dave

 

Crank sensors caused a the same sort of problem on my "80 308.

Larry