Hello everyone! Hope all is well. Here's a real head scratcher, related to my earlier post with the title something like "Do fuel distributors just stop working?". So, my '87 US TR has a very noticeable misfire on the driver's side. Especially noticeable during idle (so much so that you can feel the on again / off again differences in the Driver's side exhaust gas airflow, whereas the passenger's side's exhaust airflow is smooth). Under load though, you can still feel the misfire stutter on the Driver's side. The exhaust air temperature is at least 20 degrees F cooler on the Driver's vs Pass side too. I was doing the following maintenance anyway, so I was hoping this stuff would fix it, but it hasn't: 1. Brand new Bosch fuel pumps (the previous ones were cheapie Chinese ones) 2. New Bosch Fuel Pressure Regulator on Driver's side 3. New distributor cap, coil, coil voltage regulator, rotor on Driver's side 4. New Iridium spark plugs The misfire goes away when I spray just a little bit of carb cleaner down the air metering unit. So, to me that could be: 1. Vacuum leak 2. Clogged injector (or something else clogged leading up to the injectors) To examine these possibilities, I: Vacuum Leak: I sealed off all vacuum inlets in the intake manifold Clogged injector: My fuel pressure is 5 bar at the top of the Fuel Distributor. I also took out each fuel injector and ran them under load for 90 seconds. They all put out the same amount of fuel, in spec. I have previously disconnected the supplementary US air pump which injects air into the exhaust. According to the CIS bible (Bosch Fuel Injection and Engine Management by Charles Probst), there are three areas that control mixture: 1. The metering unit's mixture screw, which I have not touched and is not accessible because t's below some kind of cover 2. An Air bypass valve / screw on the throttle body, and 3. The Pressure Actuator electromagnet Just wondering your thoughts on my experience so far and what you think my next steps should be. Does anyone have experience with the Pressure Actuator (the black box on the side of the fuel distributor)? THanks as always!
Can you explain this more? You ran all of the injectors in the same bank into individual containers for the same time at the same airflow plate opening? The TR WSM specifies doing this check for equal fuel delivery at three different fuel flow rates (i.e., three different airflow metering plate openings) -- are you saying that you did all three? Are you relying on the cutoff valves to be closed (and the rest of the air injection system to be well-sealed) to prevent air from entering the exhaust stream during warm-running, or have you done something more permanent? Do you notice any difference in this problem for cold-running (open loop) vs warm-running (closed loop)? Or alternatively, if you unplug the O2 sensor on the trouble side (and force open-loop operation), does the behavior change during warm-running? You're probably going to have to eventually get the "anti-tamper" plug out to get access to the mixture screw cover screw and the mixture screw. The usual strategy is to drill a small hole into it, drive a sheet metal screw into that hole, and then use the head of the sheet metal screw to pull out the (tapered) anti-tamper plug. The voltage output of the O2 sensor single wire (relative to ground) during warm idle with the single wire unplugged from the harness can tell you a lot: less than 0.5V DC = lean; greater than 0.5V DC = rich. This won't be super-constant voltage, but it shouldn't be changing much. The voltage output of the O2 sensor single wire (relative to ground) during warm idle with the single wire plugged into the harness can also tell you a lot: it should be "wandering" around every few seconds from ~0.2 VDC to ~0.8 VDC -- this would tell you that the EHA is working and the system is trying to run closed-loop. Have you made any of these measurements? Of course, when you get really desperate, it might make sense to do a compression and leakdown test The EHA (aka Pressure Actuator) is a device that changes the lower chamber pressure. By unplugging the O2 sensor, the current supplied to the EHA is set to a fixed default value (open-loop). There's almost no reason to worry about the EHA operation if you can't get open-loop to work well.
Hey again Steve! Yes, I took all the injectors out of their ports, put them in glass jars and did the 90 second test with the fuel pump jumped 30 and 87. I didn't do the measurements of the fuel output until the end of the process, and throughout I was depressing the air plunger on the mcu at various rates. I was primarily looking for any cylinders whose volume were significantly less than the others and I didn't find any. I'll do the o2 sensor voltage tomorrow, but it seems to run its worst when cold (closed loop, right?). Once it warms up, it runs better but you can still hear the missing. And were you being facetious about the compression test? I was thinking that if there was a cylinder problem, the extra carb cleaner down in the mcu wouldn't make a difference? But it definitely does. Maybe I should make a video? Thanks as always.
No, when cold, it runs open-loop (where the EHA current defaults to a more middle-range, fixed value and the mixture screw is mostly in control of the A/F ratio). When it warms up it runs closed-loop, and the EHA can add a little richness if the open-loop mixture screw adjustment is just too lean. If the open-loop mixture adjustment is too lean, you would see this in the unplugged open-loop O2 sensor measurement at warm idle (i.e., it would be a low value below 0.5V DC). You are probably right that your experiment adding richness, and getting an improved result, is a good sign that it is not some horrible mechanical condition issue. However, if you get to the point where you can't identify any other issue not much else you can do.
OK, and the results are in! When cold, voltage from the O2 sensor gradually decreases over 2 minutes from .929 V to .300 V, stays around .29 to .27 for a minute, then 'tink' the thermoswitch hits, and then the voltages start varying wildly from .3 to .9 every couple seconds. From .9 to .3 over the span of 2-3 seconds, then back up again over 2-3 seconds, lather, rinse repeat. When spraying carb cleaner into MCU, it goes from 1.0 - 1.1 and stays there while being sprayed, but once that wears off, the volts plummet to .2 (and the engine runs rough) for 30 seconds, when it seems to correct itself and begin the .9 - .3 thing (I have all this on video btw ) The Passenger's side stays consistent at between .8 and .9 Something I also noticed is that I DO appear to have vacuum leaks around a couple of my injectors. Basically, I took the vacuum host off the front of the fuel distributor, hooked it up to my air compressor, pumped 20 PSI in to the intake manifold and sprayed the whole thing with dishwashing liquid and water. Bubbles came out of a couple injector housings, as well as the side of the FD? Note the red areas in the pic. Sure, they're small vacuum leaks but do you think they're the root of the problem? Image Unavailable, Please Login
Oh and forcing open loop by disconnecting the O2 sensor didn't have much, if any, effect. If anything, it ran a little better when the O2 sensor IS connected.
First, the O2 sensor output during the start of cold-running is meaningless -- it only has meaning when the O2 sensor is warm. Since you report the idle O2 sensor output just before the "tink" was .27~.29 V = your mixture adjustment is too lean. You should measure this again at warm idle with the O2 sensor unplugged -- this is the condition in which the mixture adjustment is made. It should be ~0.7V. Also, if the basic mixture adjustment is too lean, connecting the O2 sensor improving things makes sense as the EHA can add some richness in closed-loop mode. Your passenger side staying consistent at between .8 and .9 V (at warm idle with the O2 sensor plugged in) indicates it is set somewhat rich and the EHA can't lean it out enough. Again, the important measurement is at warm idle (i.e., after the "tink") with the O2 sensor unplugged. I'm guess that you don't have cats as being that rich, and having cats, usually overheats the cat. With regard to your pressure test, 20 psi is too high to be reasonable. The pressure difference the various seals need to hold is more like 8~10 psi. I'd retest at that pressure before deciding if something needs to be fixed (also doing that type of test might require rotating the crankshaft to different positions as some intake valves of some cylinders would be open and you could have leakage going out the rings and/or out the exhaust valve, if open).
Thanks for the info as always, Steve. What are your thoughts on the air-bypass screw on the front of the throttle body? Would that be a good way to enrich / lean the mixture enough without cracking open the actual mixture screw? Thanks!
No, the air bypass screws (and throttle plate stops) are used to set how much air enters the engine (i.e., the idle RPM). When you allow more (or less) air to enter the engine, the changed deflection of the airflow metering plate changes the amount of fuel added (or subtracted) in a corresponding way = the A/F ratio does not change (just the RPM). If it was running well before, and this trouble just appeared, you could try running a bottle, or two, of the Chevron Techron Concentrate before making adjustments (I use the "treats up to 20 gallons"-sized bottle in about 15 gallons of fuel). Or has it always had this issue? (However, removing the anti-tamper plugs is no sin IMO.) Are you catless?
I think the misfire has always been there, although it has gotten worse lately. Maybe the maintenance stuff I did exacerbated the problem? I am catless.
Thought that you were catless, otherwise, your rear coachwork would be on fire . Not the best for minimizing emissions, but richening up your Driver's bank to the same level as your Passenger bank (i.e., so rich that it stays rich even when running closed-loop) it would probably run well (ICE run very well a little rich). You could certainly bring the Driver's side richness up to have the unplugged O2 sensor at warm idle be 0.7~0.8V and then see how it runs closed-loop (O2 sensor plugged in). If no joy, bring it up to where the Passenger side is with the unplugged O2 sensor at warm idle (although setting the Passenger side also to be 0.7~0.8V with O2 sensor unplugged at warm idle would be the more correct action).
Lol, thanks for the continued info. Just for my edification, my fd has the anti tamper thing in place, right? I'd hate to go drilling and end up messing up the unit. Image Unavailable, Please Login
If the top of the thing in the center hole is just a smooth Aluminum surface = it's the anti-tamper plug. Your picture is a little too bright to tell, but if you can see a slotted screw head down in the hole, the anti-tamper plug is gone: Image Unavailable, Please Login This thread: https://www.ferrarichat.com/forum/threads/cis-mixture-plugs.319669/#post-140438757 shows a removed anti-tamper plug that Shamile took out -- it fills up the whole center hole of the boss.
As if you need to be reminded, Steve, you are a GOD! I adjusted the drivers side mixture screw and tada, no more misfire! It runs so smooth now! One thing I noticed though is that, no matter how much I adjusted the passenger side mixture (within a quarter turn), the voltage output from the o2 sensor never oscillated, it just stayed around .8 volts. What are your thoughts on that? Thanks again for all your help!
those around 0,8 V you always have or only when the sensor is warm ( operating temperature )? if always then the sensor have to be replaced
Glad that you got the misfire sorted -- we can't have TR out there running poorly Are you saying: at warm idle with the O2 sensor unplugged (open-loop mode), no matter how lean (CCW) you adjusted the mixture screw, even to the point of obvious bad running, the O2 sensor output just stayed ~0.8V DC? If so, I'd agree with romano that that justifies investigating/replacing the O2 sensor. For closed-loop mode to work properly, you must be able to manually "swing" the O2 sensor output from lean (less than 0.5V) to rich (more than 0.5V) in open-loop mode with the mixture screw at warm idle.
