steel_3d
15+ Year Contributor
- 494
- 14
- Jul 3, 2003
-
LA,
California
I have a problem with my engine running rough, and I'm not even sure which forum to put this in so this will do.
The engine started running rough gradually over two or three days where I wasn't changing anything, just driving my 80 mile a day commute.
At this point it runs on about 3.5 cylinders.
-unplug #2 injector:
1) idle doesn't change appreciably
2) o2 voltage does go lean, sometimes the ecu can actually compensate and start cycling again. When I plug the injector back in, the o2 goes rich till the ecu compensates again. My idle fuel adjustment is +25% to get the o2's to cylce. This has always been pretty high even before, like +15, I chalked it up to crappy deadtime of PTE 680 injectors. But the plugs were roughly the same color before.
3) the medium-loud ticking/tapping/clacking noise that the engine has made since day one goes away and all I can hear is a more quiet, regular ticking (not as quiet as injectors, sounds like mild lifter tick). The louder clacking is irregular, like tap tap tap... tap tap... tap tap tap... tap... etc. This goes away when the injector or spark plug wire is unplgged.
4) if I try to drive the car the engine vibration is way worse than if the injector is plugged in.
This is why I say it runs on 3.5 cylinders. Even though the idle doesn't change when I unplug #2 which would tell me it's not firing, it drives better and the o2's are richer if it's plugged in, so it must be kinda firing. Very weird. The idle does get a lot worse if I unplug any of the other cylinders. #2 is definitely getting spark, and the plug gap is correct.
I've replaced injectors and spark plugs.
I've also swapped the injector and spark plug wires between #3 and #2. The engine ran the same as before. If I unplug #2 the idle doesn't change, but if I unplug #3 the engine wants to die. So this tells me there's no difference electrically between the #2 and #3 wiring. I still checked a bunch of stuff just to be sure. Swapped the ecu, plugged in a spare injector and made sure it pulsed, measured the voltage, resistance, duty cycle, etc at all the injector plugs, there was nothing special about #2. I changed the order of my original injectors, again no change. #2 is only half firing.
So this leaves me with a mechanical problem. So I did compression and leakdown tests. The compression numbers measured in the order 2 4 3 2 1 1 2 3 4 are
#1
------152-----------
158 159 158 156
158 162 159 156
Looks pretty even, eh? It's weird though how the numbers for #2 went up after more cranks.
The last test I did on april 28 was
162 156 162 162
Weird how #2 was the lowest.
In the first compression test I ever did after 10 minutes of idle on the new engine was
167 177 170 172
Here again apparently #2 had the highest compression. Numbers are higher since this test was done with the cam gears set straight up, while now I'm running 6 deg retard on the intake and 6 deg advance on the exhaust cam for a smooth idle. This gives lower compression numbers.
So in terms of compression numbers, the trends are slightly weird, but the numbers don't jump out saying #2 is ####ed.
So I just did an improvised leakdown test. #2 was definitely holding pressure on the compression stroke at TDC, and in my rough guesstimate without a gauge it held pressure the same as all the other cylinders. I went though the roation of the crank several times, and it made sense where the cylinder was sealing (compression stroke), and where it was leaking (everywhere else). Same as all the other cylinders.
An interesting thing I noticed is that if I let #2 and #3 rest at TDC for a few minutes, the lifters eventually collapse and BOTH cylinders will seal, even the one that's on the exhaust stroke. I'm assuming this is normal, since #3 does it the same as #2.
Took a bore scope to look inside the cylinders, no sign of valve nicks, but #2 is dark and wet, as well as the spark plug, which makes sense for a cylinder that isn't firing right. There's no standing fluid in there. I've bore scoped the cylinders several times during the life of the engine and #2 didn't show any difference until now. All cylinders have slightly wet patches, mostly at the top between the intake valves. The aluminum is actually still clean and shiny near there, slightly wet looking (this hasn't changed in the past several months and they all look alike). I'm guessing the incoming gas washes them off in that area.
Even stuck the bore scope down the injector holes, again can't see anything visually special about the intake and valves on #2.
The valve cover's been off a couple of times, everything seems in order, lifters feel solid.
The engine doesn't show signs of a blown headgasket.
The tapping noise at idle has been there since day one. But it's loud enough that it's always worried me, however it's never worsened or got better. If the idle is low enough and the engine is warm enough it goes away, but I can hear it again if I raise the revs a bit. It seems like piston slap, though I can't say I know exactly what that sounds like. I installed the wisecos at 4 thou cylinder to wall clearance measured at the specified spot, I measured this several times. Of course the pistons were installed with marks facing the right way. So I don't see how I could be getting piston slap. Don't think it's a bearing issue, since it never got worse, and my oil's always been completely free of metal. I measured all the bearing clearances myself with bore gauges, there was nothing crazy going on there.
I doubt it's physical contact like piston to valve or piston to head, as that would have caused much more racket or damage on my high rpm excursions if it was already touching at idle. I never noticed any change in noise through my cam timing adjustments. Stroker clearance issues could also be applicable, though I clearanced all the potential problem areas by grinding away good amounts of metal.
What I regret is that I never checked piston to valve and piston to head clearance, and didn't degree the cams, so of course those are the things that are always in the back of my mind. Though the symptoms don't seem to indicate that those are the issues.
So I am officially stumped. None of this makes sense to me. At this point I'm desperate and hoping someone has the miracle answer, because I sure don't. Now more than ever I can wholeheartedly say that ANY help would be greatly appreicated
Thanks guys. Sorry for the novel, but there was no point posting this and having you guys ask all these questions one by one.
( Yes, I did an intake leak test, and there are no leaks
)
The engine started running rough gradually over two or three days where I wasn't changing anything, just driving my 80 mile a day commute.
At this point it runs on about 3.5 cylinders.
-unplug #2 injector:
1) idle doesn't change appreciably
2) o2 voltage does go lean, sometimes the ecu can actually compensate and start cycling again. When I plug the injector back in, the o2 goes rich till the ecu compensates again. My idle fuel adjustment is +25% to get the o2's to cylce. This has always been pretty high even before, like +15, I chalked it up to crappy deadtime of PTE 680 injectors. But the plugs were roughly the same color before.
3) the medium-loud ticking/tapping/clacking noise that the engine has made since day one goes away and all I can hear is a more quiet, regular ticking (not as quiet as injectors, sounds like mild lifter tick). The louder clacking is irregular, like tap tap tap... tap tap... tap tap tap... tap... etc. This goes away when the injector or spark plug wire is unplgged.
4) if I try to drive the car the engine vibration is way worse than if the injector is plugged in.
This is why I say it runs on 3.5 cylinders. Even though the idle doesn't change when I unplug #2 which would tell me it's not firing, it drives better and the o2's are richer if it's plugged in, so it must be kinda firing. Very weird. The idle does get a lot worse if I unplug any of the other cylinders. #2 is definitely getting spark, and the plug gap is correct.
I've replaced injectors and spark plugs.
I've also swapped the injector and spark plug wires between #3 and #2. The engine ran the same as before. If I unplug #2 the idle doesn't change, but if I unplug #3 the engine wants to die. So this tells me there's no difference electrically between the #2 and #3 wiring. I still checked a bunch of stuff just to be sure. Swapped the ecu, plugged in a spare injector and made sure it pulsed, measured the voltage, resistance, duty cycle, etc at all the injector plugs, there was nothing special about #2. I changed the order of my original injectors, again no change. #2 is only half firing.
So this leaves me with a mechanical problem. So I did compression and leakdown tests. The compression numbers measured in the order 2 4 3 2 1 1 2 3 4 are
#1
------152-----------
158 159 158 156
158 162 159 156
Looks pretty even, eh? It's weird though how the numbers for #2 went up after more cranks.
The last test I did on april 28 was
162 156 162 162
Weird how #2 was the lowest.
In the first compression test I ever did after 10 minutes of idle on the new engine was
167 177 170 172
Here again apparently #2 had the highest compression. Numbers are higher since this test was done with the cam gears set straight up, while now I'm running 6 deg retard on the intake and 6 deg advance on the exhaust cam for a smooth idle. This gives lower compression numbers.
So in terms of compression numbers, the trends are slightly weird, but the numbers don't jump out saying #2 is ####ed.
So I just did an improvised leakdown test. #2 was definitely holding pressure on the compression stroke at TDC, and in my rough guesstimate without a gauge it held pressure the same as all the other cylinders. I went though the roation of the crank several times, and it made sense where the cylinder was sealing (compression stroke), and where it was leaking (everywhere else). Same as all the other cylinders.
An interesting thing I noticed is that if I let #2 and #3 rest at TDC for a few minutes, the lifters eventually collapse and BOTH cylinders will seal, even the one that's on the exhaust stroke. I'm assuming this is normal, since #3 does it the same as #2.
Took a bore scope to look inside the cylinders, no sign of valve nicks, but #2 is dark and wet, as well as the spark plug, which makes sense for a cylinder that isn't firing right. There's no standing fluid in there. I've bore scoped the cylinders several times during the life of the engine and #2 didn't show any difference until now. All cylinders have slightly wet patches, mostly at the top between the intake valves. The aluminum is actually still clean and shiny near there, slightly wet looking (this hasn't changed in the past several months and they all look alike). I'm guessing the incoming gas washes them off in that area.
Even stuck the bore scope down the injector holes, again can't see anything visually special about the intake and valves on #2.
The valve cover's been off a couple of times, everything seems in order, lifters feel solid.
The engine doesn't show signs of a blown headgasket.
The tapping noise at idle has been there since day one. But it's loud enough that it's always worried me, however it's never worsened or got better. If the idle is low enough and the engine is warm enough it goes away, but I can hear it again if I raise the revs a bit. It seems like piston slap, though I can't say I know exactly what that sounds like. I installed the wisecos at 4 thou cylinder to wall clearance measured at the specified spot, I measured this several times. Of course the pistons were installed with marks facing the right way. So I don't see how I could be getting piston slap. Don't think it's a bearing issue, since it never got worse, and my oil's always been completely free of metal. I measured all the bearing clearances myself with bore gauges, there was nothing crazy going on there.
I doubt it's physical contact like piston to valve or piston to head, as that would have caused much more racket or damage on my high rpm excursions if it was already touching at idle. I never noticed any change in noise through my cam timing adjustments. Stroker clearance issues could also be applicable, though I clearanced all the potential problem areas by grinding away good amounts of metal.
What I regret is that I never checked piston to valve and piston to head clearance, and didn't degree the cams, so of course those are the things that are always in the back of my mind. Though the symptoms don't seem to indicate that those are the issues.
So I am officially stumped. None of this makes sense to me. At this point I'm desperate and hoping someone has the miracle answer, because I sure don't. Now more than ever I can wholeheartedly say that ANY help would be greatly appreicated
Thanks guys. Sorry for the novel, but there was no point posting this and having you guys ask all these questions one by one.
( Yes, I did an intake leak test, and there are no leaks
)
