I'm having some nasty performance problems under boost. I can take it to redline with about 3/4 throttle and not miss a beat, but when I completely peg it, it sputters and hesitates as the boost rises, and I can hear the engine missing. The effect is as if a rev limiter kicked in...the foot is to the floor, but the engine is sputtering and RPMs either aren't increasing or are increasing VERY slowly.
Some data points:
1) I didn't notice this problem until I replaced my completely stock exhaust with a set of Kamikaze headers and a custom 2.5" cat and cat-back exhaust.
2) The spark plugs are the stock temperature range but don't seem to be damaged or otherwise malfunctioning (as far as I can tell from a visual inspection, at least).
3) I'm running the stock fuel pump with an AEM 1:1 FPR, with a static fuel pressure of 42 psi. I have a fuel pressure gauge between the fuel filter and the fuel rail, and the fuel pressure seems to rise appropriately under boost, though the gauge needle oscillates quite a bit. Presumably this oscillation is pulsation from the pump, since the gauge is installed before the FPR.
4) The problem is most prevalent when the engine is warmed up and heat soaked; on occasion I can take it out on a cool night after letting it warm up just enough to get the coolant up to operating temperature, open it up, and it will run strong with no misses.
5) I have five or six datalogging sessions during which the problem occurs, but I haven't seen anything obviously out of whack.
I'm looking for diagnostic and troubleshooting suggestions, rather than blind speculation on what could be wrong. (Intelligent speculation is welcome, however.)
-Andy
JRSC B16A misfiring under boost - suggestions?
JRSC B16A misfiring under boost - suggestions?
'99 EBP Si
S200 w/everything|12psi JRSC|Heatshield
AEM CAI|Kamikaze headers
Custom (quiet) 2.5" exhaust
Quaife LSD|JUN 9lb flywheel|ACT XTSS clutch
Eibach Pro-Kit/KYB AGX
Full polyurethane bushings/mounts
OZ 16x7 Superleggera + Sumi HTR Z II
S200 w/everything|12psi JRSC|Heatshield
AEM CAI|Kamikaze headers
Custom (quiet) 2.5" exhaust
Quaife LSD|JUN 9lb flywheel|ACT XTSS clutch
Eibach Pro-Kit/KYB AGX
Full polyurethane bushings/mounts
OZ 16x7 Superleggera + Sumi HTR Z II
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turbocivicex
- Posts: 19
- Joined: Sun Aug 18, 2002 4:00 pm
- Location: Ellicott City, MD
Problem solved
I discovered the source of the problem while swapping my stock spark plugs for a set of colder spark plugs: at least one of my plugs wasn't torqued tight enough. 
Wasn't loose enough to remove by hand, but it was definitely too loose, and I could see carbon all the way up around the spark plug threads where the combustion gasses had blown past. Bad.
Once I discovered this, all the symptoms began to make sense.
The problem was most prevalent under boost, because the cylinder pressures were much higher, causing the gasses to blow by the threads a bit more.
The problem got worse when the engine was hot, because the aluminum head expands more than the spark plug when hot, increasing the gap between the spark plug threads and the threads in the head. The hotter combustion temperatures under boost would have made the expansion problem even worse.
The problem didn't show up in a compression test, because the compression tester was seated in the spark plug hole properly.
And the problem started when I installed my new exhaust, because while I was working on my exhaust, I took the opportunity to pull my plugs and examine them (which I'd forgotten...doh!).
I've since determined the root cause of the problem--my click-type torque wrench, which is adjustable from nil to 150 ft-lbs of torque, isn't nearly accurate enough at low torque levels (the paltry 13-18 ft-lbs that the spark plugs require).
Apparently even Snap-On's torque wrenches specify that their accuracy is only guaranteed at more than 20% of full scale (and mine was a Craftsman, so it's definitely no better). So my next tool purchase will be a torque wrench that's better suited to low torque applications.
As an aside, if anyone has been looking for OEM quality plugs for the B16A in a colder heat range than stock (for boost applications), the OEM S2000 plugs fit the bill perfectly. They're platinum NGK R plugs, same size/shape/design, an
d just a slightly smaller gap (.044 vs .052) in a colder heat range.
Wasn't loose enough to remove by hand, but it was definitely too loose, and I could see carbon all the way up around the spark plug threads where the combustion gasses had blown past. Bad.
Once I discovered this, all the symptoms began to make sense.
The problem was most prevalent under boost, because the cylinder pressures were much higher, causing the gasses to blow by the threads a bit more.
The problem got worse when the engine was hot, because the aluminum head expands more than the spark plug when hot, increasing the gap between the spark plug threads and the threads in the head. The hotter combustion temperatures under boost would have made the expansion problem even worse.
The problem didn't show up in a compression test, because the compression tester was seated in the spark plug hole properly.
And the problem started when I installed my new exhaust, because while I was working on my exhaust, I took the opportunity to pull my plugs and examine them (which I'd forgotten...doh!).
I've since determined the root cause of the problem--my click-type torque wrench, which is adjustable from nil to 150 ft-lbs of torque, isn't nearly accurate enough at low torque levels (the paltry 13-18 ft-lbs that the spark plugs require).
Apparently even Snap-On's torque wrenches specify that their accuracy is only guaranteed at more than 20% of full scale (and mine was a Craftsman, so it's definitely no better). So my next tool purchase will be a torque wrench that's better suited to low torque applications.
As an aside, if anyone has been looking for OEM quality plugs for the B16A in a colder heat range than stock (for boost applications), the OEM S2000 plugs fit the bill perfectly. They're platinum NGK R plugs, same size/shape/design, an
d just a slightly smaller gap (.044 vs .052) in a colder heat range.
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turbocivicex
- Posts: 19
- Joined: Sun Aug 18, 2002 4:00 pm
- Location: Ellicott City, MD
same EXACT problem
Its almost uncanny. I posted a message at Hostboard with the same title even.
I have a 99si, B16. JRSC, stepper pulley, that is experiencing the EXACT same symptoms. However, I know exactly when my problem started. I had the car tuned back in spring by Tom Payn. It turns out, I think the blower belt may have been slipping while on the dyno (I have a 3" thermal, so its impossible to hear things like this at WOT). Last month, I replace the belt with the proper size and my indicated boost went from 8psi to over 10psi.
Immediately after I replaced the belt, and thus increased the boost, the misfiring thing started. Ill go home and check my plugs tonight, and see if thats it, but i kinda doubt it. I'll also check boost cut and let you know what i see.
I have a 99si, B16. JRSC, stepper pulley, that is experiencing the EXACT same symptoms. However, I know exactly when my problem started. I had the car tuned back in spring by Tom Payn. It turns out, I think the blower belt may have been slipping while on the dyno (I have a 3" thermal, so its impossible to hear things like this at WOT). Last month, I replace the belt with the proper size and my indicated boost went from 8psi to over 10psi.
Immediately after I replaced the belt, and thus increased the boost, the misfiring thing started. Ill go home and check my plugs tonight, and see if thats it, but i kinda doubt it. I'll also check boost cut and let you know what i see.
Unfortunately, I have very little time lately to work on the car.. so sorry for the delay, and I dont have much to share.
But here is what I do know. I took a look at the plugs today. They dont look good. They are black, except for a pure white on the center electrode. The top electrode is worn away slightly, but not bad. Either way, the gap has increased.
Here was the big surprise though. When I went to remove the plugs with my spark plug socket, I was surprised to find that the rubber grommet in the socket (meant to grab the plug) was gone! It didnt take long for me to find it on the plug in CYL 2! I shoved the wire right over it.
I havent taken the car for a spin yet, and im not sure this is the problem.. but it couldnt help.
Also, I took a look at my dist. cap based on the suggestion from hostboard. The MSD cap has a little post that juts out from the cap, and is open to the air. I wonder what this thing does. Is it a vent of some sort? I'm sure it allows moisture in. I dont recall the stock one having a vent of that type. At first I thought it was there to run external wires in, but its way to narrow. Thoughts? Anyway. I plugged it with some hondabond to keep moisture out.
Next step is to drive the car and see if the misfire is still there (i bet it is). Then check boost cut.
But here is what I do know. I took a look at the plugs today. They dont look good. They are black, except for a pure white on the center electrode. The top electrode is worn away slightly, but not bad. Either way, the gap has increased.
Here was the big surprise though. When I went to remove the plugs with my spark plug socket, I was surprised to find that the rubber grommet in the socket (meant to grab the plug) was gone! It didnt take long for me to find it on the plug in CYL 2! I shoved the wire right over it.
I havent taken the car for a spin yet, and im not sure this is the problem.. but it couldnt help.
Also, I took a look at my dist. cap based on the suggestion from hostboard. The MSD cap has a little post that juts out from the cap, and is open to the air. I wonder what this thing does. Is it a vent of some sort? I'm sure it allows moisture in. I dont recall the stock one having a vent of that type. At first I thought it was there to run external wires in, but its way to narrow. Thoughts? Anyway. I plugged it with some hondabond to keep moisture out.
Next step is to drive the car and see if the misfire is still there (i bet it is). Then check boost cut.
Another thought...what fuel pump and fuel pressure are you running? I'm beginning to wonder if the stock fuel pump is up to the task. I'm running the stock pump with 42 psi of static fuel pressure, with an AEM FPR...so under boost this would climb to around 52 psi. This might be too much for 85-90% duty cycle on 440cc injectors...
Guys, I'm almost 99% positive of what your prob is. 1st you NEED to to use a colder range plug go ask the part guys for a NGK part# ZFR7F11 normal copper plug. The prelude ones are a 6 (ZFR6F11) heat range and will do for low boost levels but you really need the 7 heat range. Also your plug gap needs to be more like .030 or .035 I had mine gapped at .044 and I had the same problems, then I koncked the plug gap down and viola!!! Hope this helps guys I would be willing to bet this will solve most if not all of your problems...
Later,
Sean C.
Later,
Sean C.
B18C1 with a "slug" on the exhaust... 
Good ideas, but I'm already running a colder plug with a smaller gap.
The S2000 OEM plugs are identical to the OEM Si plugs, they're just one heat range colder (7) and have a smaller gap (.044 vs. .052 on the stock plugs).
Not to mention that the MSD ignition that Kannon has would let you run a bigger gap without problems...
Keep the ideas coming, though...we'll get it eventually.
The S2000 OEM plugs are identical to the OEM Si plugs, they're just one heat range colder (7) and have a smaller gap (.044 vs. .052 on the stock plugs).
Not to mention that the MSD ignition that Kannon has would let you run a bigger gap without problems...
Keep the ideas coming, though...we'll get it eventually.