Holy Shuddering Cefiro

[MafiaRide]

Hi guys, wondering if any of you have experienced this before. Last Saturday I replaced my old spark plugs with new ones. Specifically the Iridium IK-20 as suggested by one of the forum members.

Bear in mind that previously my car idles steadily and does not shudder. Of late when I stop at traffic lights, I usually let it remain in "D" and step on the brakes. After a few seconds, the car will shudder and the rpm dips very very slightly then back to normal. Then ok for a few seconds and shudder. Pretty random but will only happen after the car has been running for some time, ie: 30 mins [that's how far from house to work].

Something which I also tested was that this only happens when the aircon is on. When it is off, the car is fine whether it is on "D" or "P".

Question is, is it the Iridium plugs or something else? Appreciate if anyone can shed some light on this. Thanks.

 

[defcon1]

Hi guys, wondering if any of you have experienced this before. Last Saturday I replaced my old spark plugs with new ones. Specifically the Iridium IK-20 as suggested by one of the forum members.

Bear in mind that previously my car idles steadily and does not shudder. Of late when I stop at traffic lights, I usually let it remain in "D" and step on the brakes. After a few seconds, the car will shudder and the rpm dips very very slightly then back to normal. Then ok for a few seconds and shudder. Pretty random but will only happen after the car has been running for some time, ie: 30 mins [that's how far from house to work].

Something which I also tested was that this only happens when the aircon is on. When it is off, the car is fine whether it is on "D" or "P".

Question is, is it the Iridium plugs or something else? Appreciate if anyone can shed some light on this. Thanks.

One of your ignition coil packs is weak and misfiring. This is a common problem with the cefiro, and I have had the same problem...in fact, still having the problem now, but have no time to look into it.

IK plugs have slightly higher resistance than the original platinum versions. With the original platinum plugs, even with a coil pack in a slightly weakened condition, the spark produced could still have been adequate. However, once you put the IK's in, the weakened coil was not discharging hard enough to overcome the increased resistance...hence, the misfiring especially when you stop at traffic lights and press on the brakes.

The effect is visible if your car ignition system is monitored with a oscilloscope. You will see a graph with 6 peaks, but one peak is lower than the others. My mechanic in Sg is so sensitive to this (drove the feilo for the past 5 years, but had to scrap it just last week) that he can detect the slightly weaker ignition even before the car begins misfiring just by holding the steering wheel.

The only option is to locate the failing coil pack and replacing it. But I have managed to reduce the effect of this, and consequently extend the useful lifespan of my coilpacks by installing an ignition spark stabilizer...basically an ignition voltage stabilizer.

Coil packs generally last about 6 years before they actually start giving problems (under normal usage). They cost about RM 175 per piece, so changing a set of six is not really expensive. Still, it's a waste to change what is not failing, so I tend to change them one at a time. Just takes a bit more time to locate the failing one.

 

[MafiaRide]

Thanks defcon. I was suspecting the coilpacks as well but Lee suspected it was the plugs that were not gapped properly. The plug gap was at 1.1mm and should have been 0.9mm. After he regapped it, the car is fine, in fact slightly better ;-)

Interesting that you brough the igniyion spark stabilizer up. Is the Ignition spark stabilizer something like pivot volt stabilizer? Thx

 

[defcon1]

Thanks defcon. I was suspecting the coilpacks as well but Lee suspected it was the plugs that were not gapped properly. The plug gap was at 1.1mm and should have been 0.9mm. After he regapped it, the car is fine, in fact slightly better ;-)

Interesting that you brough the igniyion spark stabilizer up. Is the Ignition spark stabilizer something like pivot volt stabilizer? Thx

Very similar. But a little more difficult to install cos it involves cutting into the wire harness (-ve wire, I believe) that comes from the coil packs. Works in basically the same way i.e. provides a reservoir of charge that stabilizes the coil packs' consumption.

Good to know about the irridiums. I suspected that the resistance was higher than platinums, and/or that our ignition coils were a little weak. You might want to post the fix more prominently on the main forums as a "What to do if..." topic. I would like to include it in our FAQ later on and don't want the credit tagged to my name...

 

[ongteckweng]

went to service my car @ my dad's trusty TC mech...he works from home during weekend. its been a year since i sent my car to him...

had my rotors changed, engine oil n filter....asked him about the plugs n he said its not recommended to use iridium plugs as cases like mafia often happen. best still to use the original platinum version...

but wonder why nlexis ride has no prob? he is using Denso Iridium as well...

 

[defcon1]

...plug gaps...

 

[MafiaRide]

Lee swapped my old plugs back in and it was confirmed that my coilpacks were still good as my old stock plugs didn't have the shuddering. Swapped back in the Iridiums last Saturday with the idle adjusted slightly higher [8++rpm].

What I found was it shudders when idling is at 6++rpm which our cars should idle. So far, no shuddering. After the coilpack suspicion was confirmed, I did some tests and my conclusion is that if you want to use iridiums, our cars can handle the plugs when in motion but not too good during idle cause of plug resistance [defcon pointed out] and the coilpacks couldn't supply enough electricity for the spark to jump the gap. Also found that at around 800+rpm, this is not an issue anymore.

I would recommend changing to iridiums. The difference I felt between stock and iridiums are significant, at least according to butt dyno especially if you like to floor the accelerator alot. Smoother and slightly quicker rev to the redline.

Yes, and plug gaps. Must be 0.9mm.

 

[ongteckweng]

ok..understood...thanks for the info...
basically the gap must be 0.9mm n if there is slight misfiring on 600++rpm during idling, increase the rpm n its done...noted...

 

[Doink]

ur iridium spark plug not good...or too hot...maybe will have some knocking...
yesterday i tried using hks spark plug also...mine misfire and knocking...
so changed back to ori...

 

[MafiaRide]

Mine has no knocking. In fact power delivery is good all the way through. It doesn't "misfire" anymore either.

 

[ongteckweng]

i just installed the Denso Iridium IK-20 with 0.4mm gap. it was suggested by my friend, a performance dealer in Tmn Paramount. nlexis is using the same plug.

mine didnt have any prob. in fact, the performance is much more better. earlier before changing the plugs, my engine had a minor misfire whenever the car is standstill with the gear engaged at D....

now, its gone! the engine is so much smoother! pickup performance has increase n it take less time to reach top speed.

mafia, whats the previous gap on ur iridium?

 

[MafiaRide]

1.1mm. Bad setting.

 

[ongteckweng]

1.1mm. Bad setting.

ic...so u got it regap to 0.9mm n its better now...

 

[MafiaRide]

Yup. No misfiring anymore. Put in pivot volt stabilizer and even better. Idling is much more stable and smoother.

 

[ongteckweng]

the pivot VS is good but u need to be careful with water coz its not water proof. another thing, there is a lot of fakie. but im sure u got the original stuff from a reputable seller.

u guys know, those local VS is also working wonder n its cheaper. most r in water proof body (aluminium) which provide alternative to Pivot.

 

[MafiaRide]

Thanks for the concern Ong. Got it from my old trusted friend in N1. Located the thing by the side of the battery. Water shouldn't reach it if I don't use the car as a submarine ...hehehee

 

[ongteckweng]

Thanks for the concern Ong. Got it from my old trusted friend in N1. Located the thing by the side of the battery. Water shouldn't reach it if I don't use the car as a submarine ...hehehee

ah...should be fine then....