Please accept my in advance thanks for your time to read this long saga! As my Major Service was nearing completion, my Company asked me to do an overseas transfer. The Major was essentially completed, but the final tune was not done. Due to time (and tool) constraints, I brought the TR to an FCar dealer for the final tune. As you may recall, the engine did not seem to be firing on all the cylinders and was running very rough. The FCar dealer completed an emissions and compression test and made their preliminary conclusion they believe that the valve timing is off. Their preliminary conclusion is based on the bank to bank differential in compression and their inability to tune the HC and O2 into spec. ****The FCar dealer thinks that the engine needs to be pulled and the cams degreed.**** I believe that incorrect valve timing is a **highly unlikely** cause of these symptoms. The timing marks were aligned as before and dead on per the cam/ cam caps & crank. They were previously aligned so precisely and the car previously ran so well, that I did not degree the cams. When I bought the car in 1997, the belts were done by an independent FCar facility in Southern California. The tech explained that the drivers side (cyl 7-12) pre-cat was partially burned thru and that he had punched out the remaining catalyst. While doing the Major this last winter, remnants of the drivers side pre-cat was blown into and clogged the main cat. This prompted me to replace the system with Hyperflow cats and eliminate the pre-cats entirely. This week, the FCar dealer suggested that the currently high HC ppm on the drivers side would destroy the cat. I agree. I believe that the high HC & O2 on the drivers side is caused by something other than the valve timing. I believe that this issue was present before I even bought the car in 1997 and destroyed the pre-cat way back then. Presumably, the previous independent shop never even checked the emissions or FI tune during their version of a Major. :-( One last note: The drivers side air flow meter (the diaphragm) is sticky and very rough as it is slightly depressed (just off idle) by hand (engine off). The passenger side is smooth as silk. This was noted as I was bleeding the air from the new injectors that were installed. Surprisingly, the Fcar dealer does not think that this sticky diaphragm would effect the emissions HC or O2. I have not directly seen the results, but the FCar dealer tells me that they had confirmed that all cylinders are getting spark. To me, these emissions numbers indicate that a cylinder on the drivers side is not igniting the air/fuel. I am guessing . The car was in storage for 4 years prior to my belt replacement this last winter sticky rings or other storage related issues are potential culprits for the compression numbers. Regardless, to me they dont seem out of line the worst cylinder is only 3.3% off the average. Your thoughts? I am not an emissions or FI expert and ask your input: ~ Any suggestion on why the HC and O2 cannot be brought within spec? ~ Do the emissions or compression numbers cause you think that cam alignment is problematic? Any suggestions would be appreciated. I am convinced that the engine does not need to come out. Thanks again to all, Vince Image Unavailable, Please Login
Vince, High HC readings are almost always a sign of problems in the ignition system, resulting in a misfire. This is where I would start, without any doubt. Plugs/gaps, cap, rotors, wires...extenders; the same old stuff. Regards, David
I agree - especially given that both the O2 and HC are high. To me, it seems to indicate unburnt fuel and unused oxygen. A misfiring cylinder is presumably pumping unburnt fuel and oxygen into the exhaust. Any concerns around the compression numbers indicating bad valve timing? I just don't see it! Thanks! Vince
One thing I would inspect are the injectors. What I have learned about these European Fcars and Lcars...their injectors are junk and go bad, stuck open...and so on.
brand new injectors were installed. As I bled the air out, that is when I noticed the sticky air flow meter. Thanks, Vince
BTW one standard deviation on those compression numbers is 4.26 psi which yields a range off the median of: 178.0 to 186.5 psi These numbers are extremely close (within 1%) to the actual range of 176.4 to 188.2 psi To my eye, these actual compression values are just fine. If you disagree - please chime in. Rgds, Vince
Vince, I don't believe the numbers are off far enough to indicate bad valve timing. Mine was reading 210 on one bank and 180 on the other (bad valve timing). Once the cams were retimed everything fell into place. John
In this case, the issue of cam/valve timing (imbalance) makes perfect sense. Please realize that if the valve timing was the issue, all of your exhaust gas readings likely would be different; bank to bank. This is hardly the case here... David
The 4 and 5 valve engines breath quite well at very low lift so small valve timing inaccuracies can and often do cause big problems. It is a major cause of cat overheating problems. The shop has the ability to measure the gasses for individual cylinders and if all on one bank are reading similarly the symptoms do fit a cam timing diagnosis. Timing cams by the marks on the 4 and 5 valve motors just does not cut it. Here are some pictures of Ferrari cam timing marks that are correctly timed to within 1 degree by a degree wheel. Ferrari says to time with a degree wheel for a reason and it was not because they felt it would improve our opinion of them to admit the marks are sloppy. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
It also depends on where they are taking the exhaust samples from. If they are shoving the analyzer probes into the tail pipes and reading the results through the cats, that be an incorrect reading. If the O2 sensors are still connected during the reading and adjustment, that would also throw off everything off. As pointed out by Rifledriver, cam timing has a huge effect on emissions. Just look at and study the pics. The marks on the cams and caps are there for assembly reasons as a rough index mark for the cam position.
To me, this is the more important issue to note/understand before deciding what to do next. The cam timing(s) may well be off spec, but, IMO, that (by itself) would not produce a symptom that a layman would describe as "rough" or "irregular" running due to the alternate-bank-firing pattern of a TR engine. I.e., even if the cam timing on one bank was far enough off to significantly reduce the power produced by each cylinder in that bank, the reduced power pulses would be all quasi-equal, all evenly spaced relative to each other, and still perfectly interlaced with the power pulses coming from the cylinders in the other bank. However, if the engine runs quasi-smoothly/well, but overheats the cats when pushed, or can't be adjusted to meet the emission targets upstream of the cats, then I'd be more inclined to agree that there's not much else to fix/check other than the cam timing (assuming the compression/leakdown numbers are OKish -- which yours seem to be). JMO. So is the shop reporting that 1) it can be adjusted to run smoothly (with the O2 sensors unplugged), but the emission numbers can't be met, or 2) it runs roughly, regardless of adjustments (with the O2 sensors unplugged), and the emission numbers can't be met? 4 years of storage is killer for a K/KE-Jet.
No way to get 14% CO2 with ignition problems. If the tester is in a good state of calibration (they really need it every year) those numbers suggest no ignition trouble. CO2 is the single best combustion efficiency indicator of all the gasses tested. The only way to get 14% is to have a good burn. 4 degress too much overlap is enough to get 400 PPM HC at idle and that will never show on a compression test. The O2 should be disconnected and the mixture should be set for best running. If there are no cylinder misses, the ignition is working properly and we already know the compression is good. What is left at that point is to adjust CO to 1.25% and if HC is still mid triple digits and is even (more or less) across all 6 cylinders you probably have a cam timing problem. At least that is what Ferrari says and has been my experience. That car tested before the cats should be able to produce 1.25% CO, less than 140PPM HC (100 is best), over 14% CO2 and less than 2% O2 at 1000 rpm. They will come very close to passing California smog without cats. There is still the possibility of an injection system problem but on a motor that had the cams set by eye I would not even be diagnosing that until the cams were known to be correct.
Which is also an explanation to those who wonder why they get different gas analysis bank to bank on 3x8s, the fuel system is same for all assuming good injectors.
Brian (Rifledriver) as always ...thank you for your input. You are a great asset to this board!!! Thanks, UZY
timing marks being off is common. When I did my majors on my Ferrari 512TR I had two marks on my cams. LOL!
Dear Ferraristi, I stand in awe of the technical expertise on this site....I'm so jealous. Vince, lets try something simple. Since you say nothing was moved when you did your major (whether the timing was correct or not ), it may be in something you moved. If a likely consensus also points to ignition or missing spark..... When you pulled your caps and wires off for your major, perhaps one of the wires is not connected in the cap. As you know, the wire at the cap is held by a pin piercing the plug wire. If the wire has been in place for awhile and then moved, I find the pin burns the wire around it. Once moved, contact is broken as the brittle filaments lose contact with the pin. Even if you take your ohm meter, you might have connectivity by the act of moving the cap. I would remove each pin, snip a small piece of wire, reinsert and re pierce. I know, not in the league of great advice given here...but I've seen this a few times. Shamile Freeze...Miami Vice !
Just a question: If cam timing were off, wouldn't the compression test for that bank indicate it? During the major, were the ignition wires replaced? I've replaced wires before, and the car ran so poorly, I thought I hooked the wires up in reverse order. It turned out the new plug wires were no good. Jim
4 degrees or so of increase in overlap is all that it takes. That will not show up in a compression test.
Cam timing must be degreed in on a 4 valve motor when changing the belts, FNA pounded this into the tech's during the 80's...and with good reason. More than one motor has been pulled immediately after a major service because some tech took a short cut and tried to save an hour of so. I've seen these exact symtoms when belts have been changed, but not degreed in. 3 degrees can make a huge difference.
