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#1
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'87 Jetta GLI 16V - progress
OK guys, here's where I'm at now with this (formerly) dead VW:
After going through everything from air cleaner to intake, repairing what little I could find wrong, replacing all suspect vac hoses, and fixing one vacuum leak, I got it where I could drive it - barely. It's obviously running way lean, because once I get the throttle into the WOT enrichment, it wakes up immediately. I know the rice-rocket shop turned the fuel distributor adjustment screw a bunch, not knowing what they were doing. My question is, does that have an effect on the basic running mixture (as opposed to idle only)? Can I expect to crank the 3mm adjustment screw a little at a time and bring the mixture into a drivable range? I know the correct way to do this is with an ammeter reading the o2 sensor circuit, but the o2 sensor does not get hot enough to operate for this purpose. Remember this is a race car, and most people racing these effectively bypass the o2 sensor and treat it as a straight CIS system. -- - - Rex Burkheimer WM Automotive Fort Worth TX |
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#2
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Try turning the CO adjustment screw for best idle and see what that does.
Then turning that screw out (CCW) should lean the CO and the engine should become more responsive. Adjusting that screw should have an effect on off-idle response too AFAIK. Do you have a CO analyzer at your shop? Do you analyzer how rich the engine is running by examining the spark plugs at different times, like after a WOT run then turning the engine off to see what color the spark plug tips are, or after a cruise down the expressway, etc.? You can, or should be able to, hook your VOM in series up to the Fuel Pressure Regulator to read it's voltage. Good luck, dave (One out of many daves) "Rex B" > wrote in message ... > OK guys, here's where I'm at now with this (formerly) dead VW: > > After going through everything from air cleaner to intake, repairing what > little I could find wrong, replacing all suspect vac hoses, and fixing one > vacuum leak, I got it where I could drive it - barely. It's obviously > running way lean, because once I get the throttle into the WOT enrichment, > it wakes up immediately. > I know the rice-rocket shop turned the fuel distributor adjustment > screw a bunch, not knowing what they were doing. My question is, does that > have an effect on the basic running mixture (as opposed to idle only)? > Can I expect to crank the 3mm adjustment screw a little at a time and > bring the mixture into a drivable range? > I know the correct way to do this is with an ammeter reading the o2 > sensor circuit, but the o2 sensor does not get hot enough to operate for > this purpose. Remember this is a race car, and most people racing these > effectively bypass the o2 sensor and treat it as a straight CIS system. > -- > - - > Rex Burkheimer > WM Automotive > Fort Worth TX |
#3
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dave wrote:
> Try turning the CO adjustment screw for best idle and see what that does. > Then turning that screw out (CCW) should lean the CO and the engine should > become more responsive. > Adjusting that screw should have an effect on off-idle response too AFAIK. This is the 3mm screw below the hole by the fuel distributor, right? So screwing it in (CW) should richen the mixture? > Do you have a CO analyzer at your shop? No. > Do you analyzer how rich the engine is running by examining the spark plugs > at different times, like after a WOT run then turning the engine off to see > what color the spark plug tips are, or after a cruise down the expressway, > etc.? I do read the plugs occasionally, but it hasn't run well enough so far. I'm in the "rough" tuning stage now. > You can, or should be able to, hook your VOM in series up to the Fuel > Pressure Regulator to read it's voltage. I was told by a VW tech that the O2 sensor wasn't getting hot enough to do that, due to a convertor whose guts were gone. O2 sensor is in the cat convertor shell, shielded from direct exhaust flow. So I haven't done that. > > > "Rex B" > wrote in message > ... > >>OK guys, here's where I'm at now with this (formerly) dead VW: >> >>After going through everything from air cleaner to intake, repairing what >>little I could find wrong, replacing all suspect vac hoses, and fixing one >>vacuum leak, I got it where I could drive it - barely. It's obviously >>running way lean, because once I get the throttle into the WOT enrichment, >>it wakes up immediately. >> I know the rice-rocket shop turned the fuel distributor adjustment >>screw a bunch, not knowing what they were doing. My question is, does that >>have an effect on the basic running mixture (as opposed to idle only)? >>Can I expect to crank the 3mm adjustment screw a little at a time and >>bring the mixture into a drivable range? >> I know the correct way to do this is with an ammeter reading the o2 >>sensor circuit, but the o2 sensor does not get hot enough to operate for >>this purpose. Remember this is a race car, and most people racing these >>effectively bypass the o2 sensor and treat it as a straight CIS system. >>-- >>- - >>Rex Burkheimer >>WM Automotive >>Fort Worth TX > > > |
#4
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"Rex B" > wrote in message ... > dave wrote: > > Try turning the CO adjustment screw for best idle and see what that does. > > Then turning that screw out (CCW) should lean the CO and the engine should > > become more responsive. > > Adjusting that screw should have an effect on off-idle response too AFAIK. > > This is the 3mm screw below the hole by the fuel distributor, right? > So screwing it in (CW) should richen the mixture? It should. > > You can, or should be able to, hook your VOM in series up to the Fuel > > Pressure Regulator to read it's voltage. > > I was told by a VW tech that the O2 sensor wasn't getting hot enough to > do that, due to a convertor whose guts were gone. O2 sensor is in the > cat convertor shell, shielded from direct exhaust flow. So I haven't > done that. Your 02 sensor should be a heated one and come online within a few minutes of the engine running. Also I like to check the FPR voltage to make sure that there is some and also that it changes. |
#5
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> Your 02 sensor should be a heated one and come online within a few minutes
> of the engine running. So the internal heater should be able to get the sensor into the working range, without benefit of a blast of exhaust heat? > Also I like to check the FPR voltage to make sure that there is some and > also that it changes. Is that a standard test? That's the rectangular box on the side of the FD, correct? Rex |
#6
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"Rex B" > wrote in message ... >> Your 02 sensor should be a heated one and come online within a few >> minutes >> of the engine running. > > So the internal heater should be able to get the sensor into the working > range, without benefit of a blast of exhaust heat? yes at least initially, but exhaust should be hitting even with a gutted cat. I am not totally sure on this since I only deal with 'working' & complete cats. <g> > >> Also I like to check the FPR voltage to make sure that there is some and >> also that it changes. > > Is that a standard test? That's the rectangular box on the side of the > FD, correct? Should be in the Bentley. |
#7
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dave AKA vwdoc1 wrote:
> "Rex B" > wrote in message > ... > >>>Your 02 sensor should be a heated one and come online within a few >>>minutes >>>of the engine running. >> >>So the internal heater should be able to get the sensor into the working >>range, without benefit of a blast of exhaust heat? > > > yes at least initially, but exhaust should be hitting even with a gutted > cat. > I am not totally sure on this since I only deal with 'working' & complete > cats. <g> How dull Actually, the O2 sensor on this car (and I assume other Mk2s) is placed in the shell of the convertor. The bung is in the angled taper (the lower \ in the ascii art below) section such that it sits outside of the main flow, angled back toward the catalyst core. In that position I expect it would get a good portion of the heat as radiant from the hot core. That core is gone, the exhaust flow alone is not optimal from a heat standpoint. ____ ----/ \------ ----\____/------ |
#8
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I have seen some cats that have lost their guts through the exhaust but the
engines were still running fine with the 02 sensor online. I have also seen many 02 sensors installed in exhaust pipes, so they are not in the exhaust manifold nor cat. Just try yours and see. ;-) "Rex B" > wrote in message ... > dave AKA vwdoc1 wrote: >> "Rex B" > wrote in message >> ... >> >>>>Your 02 sensor should be a heated one and come online within a few >>>>minutes >>>>of the engine running. >>> >>>So the internal heater should be able to get the sensor into the working >>>range, without benefit of a blast of exhaust heat? >> >> >> yes at least initially, but exhaust should be hitting even with a gutted >> cat. >> I am not totally sure on this since I only deal with 'working' & complete >> cats. <g> > > How dull > Actually, the O2 sensor on this car (and I assume other Mk2s) is placed in > the shell of the convertor. The bung is in the angled taper (the lower \ > in the ascii art below) section such that it sits outside of the main > flow, angled back toward the catalyst core. In that position I expect it > would get a good portion of the heat as radiant from the hot core. That > core is gone, the exhaust flow alone is not optimal from a heat > standpoint. > ____ > ----/ \------ > ----\____/------ |
#9
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dave AKA vwdoc1 wrote: > I have seen some cats that have lost their guts through the exhaust but the > engines were still running fine with the 02 sensor online. > I have also seen many 02 sensors installed in exhaust pipes, so they are not > in the exhaust manifold nor cat. > > Just try yours and see. ;-) The tech told me his milliammeter would not come up into the working range because the O2 sensor was not getting hot enough, so it needed a new cat before he could tune it. But honestly I did not try it myself, nor did I verify that the heater circuit was working. I will do that, thanks Rex |
#10
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"Rex B" > wrote in message ... > > dave AKA vwdoc1 wrote: >> I have seen some cats that have lost their guts through the exhaust but >> the engines were still running fine with the 02 sensor online. >> I have also seen many 02 sensors installed in exhaust pipes, so they are >> not in the exhaust manifold nor cat. >> >> Just try yours and see. ;-) > > The tech told me his milliammeter would not come up into the working range > because the O2 sensor was not getting hot enough, so it needed a new cat > before he could tune it. But honestly I did not try it myself, nor did I > verify that the heater circuit was working. I will do that, thanks > > Rex Well that is a possibility, but I would have to see that myself. You can plug into the FPR, jump the fuel pump relay, turn the ign. on and read the current without the engine being on. At least that is what I remember and I usually do this to vehicles that don't start. :-) Remember that I am NOT plugging into the 02 sensor but the Fuel Pressure Regulator wiring. good luck, dave |
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