i've been experiencing a mystery motor hesitation at idle. it feels like the motor will idle normal and every 3 seconds the idle pattern will have a rough beat sending a slight vibration through the car. the tach doesn't register anything and motor sounds normal.

i decided to check the plug gap and condition because i haven't looked at them since i bought the car brandy new. i found cylinders 1 & 2 to be improperly gapped at 1.25mm and cylinder 4 at 1.2. here is what these plugs looked like:




cylinder 3 had a problem! obviously the spark plug has broken. what could have caused this? do i have any possible damage? where did the broken metal tip go???

 

also, being a spark plug noob, i'm going to the local autoparts store to get a replacement plug. i'll just get stock ngk pfr6g-11, but i don't know if one of these numbers identifies the stock heat range.

what is the stock heat range?

 

6 is the heat range, 11 is the gap 1.1 mm

 

Looks like it got too hot/detonation. White specs aren't usually too good, usually means the motor is detonating. Do a compression check on the motor to see if it that cylinder is still holding up well. A broken electrode can cause some havok inside a cylinder.

 

how's your timing?

 

the timing is advanced to 18deg (done almost 2 year ago) and i have a toda header; the motor is completely stock otherwise. i did a valve adjustment a few months ago and the motor sounds great.

i had planned to pick up a compression gauge and now i will certainly do so.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by magic hat #9 &raquo;</TD></TR><TR><TD CLASS="quote">the timing is advanced to 18deg (done almost 2 year ago) </TD></TR></TABLE>

I'd check it be sure...

 

do pep boys, advance, etc carry the ngk pfr6g-11 under a different sku? i've called all over the place and no one has heard of this plug. i'm going to be stuck driving it as is tonight and going to acura for the plug in the morning.

 

Try the NGK coppers. BKR6E-11.

 

In our area I couldn't find NGK. I had to order them. I went to Autozone and purchased the Bosch Plat ( regular not the 4-prong thing). I have in my car now with no problems. But, I will be replacing the Bosch with NGK's in a week or so.

 

do spark plugs need to be replaced all at once as a matched set, or can i just replace the one plug with the same model as the other used ones?

 

Do a leakdown test. I guarantee you have burnt exhaust valves.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mac8008 &raquo;</TD></TR><TR><TD CLASS="quote">Do a leakdown test. I guarantee you have burnt exhaust valves.</TD></TR></TABLE>

No he dosen't, that's absurd.

Get new plugs, check timing.

 

looks like lots of oil burning to me...........

 

how many miles on the car, now? just try changing the plugs now and see if that helps with your original hesitation problem.

plug color looks about normal, however the buildup on the broken plug could be due to the tip breaking off for some reason. Hopefully the tip went out the exhaust before it did any damage.

If it were me, I'd replace all the plugs with the copper equiv. for now to see if you get rid of the original problem. Then order the correct plugs when the car is running right or after a few thousand miles with the copper plugs.

like was suggested, recheck the timing, too.

good luck

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by magic hat #9 &raquo;</TD></TR><TR><TD CLASS="quote">do spark plugs need to be replaced all at once as a matched set, or can i just replace the one plug with the same model as the other used ones?</TD></TR></TABLE>

YES YES YES

I am nearly sure the hesitation is being caused by the Plugs/Ignition.... I'd chage the Wires if those haven't been changed yet either. Check your Distributor Cap and Rotor.... All this is normal Maintenance and are simple things to check before you go off tearing into the engine.

Replace the easy stuff and then if that doesn't change anything Loo deeper.

 

was teh car tuned for toda header.. i could see that header causing the car to run leaner.. but how much of a difference i dn't know.. ever had the car dynoed with your setup? what was a/f ratio

or.. it could be due to spark 1.2xmm gap.. as long as that exceeds service limit according to helms manual

 

i got the plugs, i'm sure replacing all 4 will fix my hesitation problems.

my timing is advanced to 18deg btdc, but i'm sure the mechanic did not do it incorrectly. i watched him do the job; we checked the a/f ratio on the dyno and it was fine.

 

if you want advice than learn to take it, check your timing!

those plugs look fricken horrible... something is not right, and chances are whatever it is is prolly worse now.

-Bryan-

 

I had a major hesitation problem with my over the weekend. I found the problem to be a
faulty distributor (I replaced plugs, rotor, cap earlier in the month). Borrowed one from a
firends car, slaped it on mine and it ran fine. The screw from the rotor came out and killed
my distributor=(

 

my local mechanic and i came up with a theory. cylinder 3 (with the broken spark plug) will not be fully igniting its fuel mixture. subsequently the o2 sensor will dial back the fuel input when it sees the increased amount of unburnt fuel in the exhaust. thus, the motor will run lean and turn all the plugs white.

anyway, the car is at the garage getting the timing dialed back to stock 16 degrees and i will replace all 4 plugs tonight and do a compression test. i'm going to recheck the plugs in a month to make sure they are ok and aren't white. then i'll get the timing readvanced to 18 deg (more power) and recheck the plugs shortly after that to make sure it doesn't go lean again.