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The engine is still intermittently running roughly. After a cold start, I ran it for about 30 seconds, stopped the engine, the quickly measured the temperature of the three left bank manifold pipes right where they bend about two inches from the engine. I put a thermocouple, held with a forceps, directly against the pipe and waited until the temperature was near its final value (the thermocouple will asymptotically approach a final temperature, which takes minutes). Measured temperatures:
Cylinder 1: 74 deg C
Cylinder 2: 90 deg C
Cylinder 3: 98 deg C
I waited about ten minutes and restarted the engine. This time it ran smoothly. All three temperatures were about 90 deg C.
I waited about ten minutes again and ran the engine again. This time it ran roughly. Measured temperatures:
Cylinder 1: 80 deg C
Cylinder 2: 97 deg C
Cylinder 3: 91 deg C.
When the engine is running roughly, cylinder 1's pipe is definitely cooler than the other two. I wonder if it's not getting enough fuel or air, or not burning the air-fuel mixture completely. Remember that I replaced all of the plug and coils, and the cylinder 1 fuel injector.
Sounds like cylinder 1 has a mechanical issue. Before I swap the simple stuff I always quantify mechanical integrity.
The FRA and RKAT look normal. RKAT is in % so 1.x % is excellent.
FRA should be 1.0 +/- 0.15 or so (don't quote me on this one. It's just typical tolerance). Your FRAs are around 1.05 so they are normal. Slight difference between the 2 banks is normal too.
We need to see the same plots (+ O2 voltage) when the engine is runnng rough.
Question, when the engine runs smoothly, does it pull strong and feel normal?
Originally Posted by DrMEMS
Here is a 2000-second run with RPM, rough running, misfires (only 2 counted) and finally FRA and RKAT for cylinder banks 1 and 2 plotted on the bottom graph. One thing that stands out is that RKAT for the two banks is different, but I don't know what this means. Also, when there was roughness, bank 2's FRA changed a little bit. On this run the all of the idling was smooth.
Sounds like cylinder 1 has a mechanical issue. Before I swap the simple stuff I always quantify mechanical integrity.
So if you're such a "specialist" how do you figure it's a mechanical problem with cylinder 1? In your opinion what kind of mechanical problem would this be that comes and goes? You can keep your theories to yourself, you always make simple things complicated. In effect a lot of your potential customers have gone to me or other shops and you loose their business. Just mind your own business because every time you get into mine you loose customers. You should've learned this by now
The engine is still intermittently running roughly. After a cold start, I ran it for about 30 seconds, stopped the engine, the quickly measured the temperature of the three left bank manifold pipes right where they bend about two inches from the engine. I put a thermocouple, held with a forceps, directly against the pipe and waited until the temperature was near its final value (the thermocouple will asymptotically approach a final temperature, which takes minutes). Measured temperatures:
Cylinder 1: 74 deg C
Cylinder 2: 90 deg C
Cylinder 3: 98 deg C
I waited about ten minutes and restarted the engine. This time it ran smoothly. All three temperatures were about 90 deg C.
I waited about ten minutes again and ran the engine again. This time it ran roughly. Measured temperatures:
Cylinder 1: 80 deg C
Cylinder 2: 97 deg C
Cylinder 3: 91 deg C.
When the engine is running roughly, cylinder 1's pipe is definitely cooler than the other two. I wonder if it's not getting enough fuel or air, or not burning the air-fuel mixture completely. Remember that I replaced all of the plug and coils, and the cylinder 1 fuel injector.
This simple test confirms it is indeed a cylinder #1 problem. I've seen many cases where mechanics misdiagnose which cylinder # it is in reality. Sometimes diagnostic computers will show you wrong cyl#, this test just confirms which cylinder we are dealing with.
As other people suggested if this was indeed mechanical problem with valve lifters, in this case one of the valves wouldn't close all the way. In example: if it was exhaust valve you would have rich mix of fuel in exhaust and O2 sensor would show you this problem.
In case it would be intake valve problem you would have misfires on all cylinders because of the pressure created in the intake and it would backfire, especially with higher rpms you would hear explosions in the intake.
I think it's an electrical problem with fuel supply to the #1 injector. My other bet is ignition coil is not getting power all the time.
I had two local mechanics look at the engine. Both listened with a stethoscope and heard excessive noise on the rear end of bank 1 (at cylinder 1).
The engine builder offered a complimentary engine repair, but I'd have to ship the car from California to Illinois for about $3000 round trip.
Locally removing and reinstalling the engine would cost about $2500. Adding in shipping gets the cost to over $3000 as well.
In the end I had the local mechanic who had installed the rebuilt engine do the work. He had to remove the exhaust and drop the engine a little, which didn't quite give him suitable access. After removing the scavenging pump, he was able to get the cam cover off. He said he'll never try doing this job again without first removing the engine (which is what the manuals say to do)!
One of the cylinder 1 intake valve lifters (aka cam followers) was stuck so badly that he couldn't budge it by hand. I had him install all 6 new lifters. In the end it cost me $3300 and a 10-day wait. After one drive, (a) it idles smoothly, (b) it doesn't tick-tick-tick when hot, and (c) the sewing-machine-like whine I was hearing is gone (we were concerned that this was the chain, but the chain looked fine).
I believe the misfires and rough running are finally fixed@. Now it's time for autocross!
I thought the engine builder was in FLA? Not Illinois. My experience was the builder foot the bill for transport when something went wrong.
We are in Florida, if your builder messed something up he should have paid for shipping. In our case it was a mechanical part which got stuck (valve lifter on cylinder #1), it happened 1 year after purchase. Our warranty is for 6 months and during that time repair and shipping cost is fully covered by MB Motorsports. Again, it was a mechanical part which failed and we did not make, not our work which led to the problem. All parts we use in our rebuilds are produced by someone else, by giving 6 months warranty we take a risk. We can warranty our work for much longer than 6 months but not the parts, they can break even when they're new.
We have offered a free repair because he is our customer but he would have to ship his car to us. He chose to do it locally.
03-06-2016 | 11:21 PM
Now it's time for autocross!
