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    Thread: Weird idle after replacing Oxygen Sensor (?)

    1. Member Maggiolone's Avatar
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      04-16-2012 03:33 AM #1
      I replaced the CO2 sensor and relay in my MK1 1.7...car ran great for a few days after. No vibration, no loss of power, no weak launches into 1st gear. Car has new plugs, injectors, o-rings, etc.

      Yesterday, I started the car, and the engine ran sluggishly, producing a foul-smelling exhaust. I re-started the engine, and it again chugged at a low idle.

      I turned up the idle screw, and the engine came back to normal....now with more vibration.

      Is this more than just a matter of the idle screw needed adjustment? I have a feeling I have a bigger problem, but I doubt it since I have so many new vacuum lines and fuel line components.

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      04-16-2012 12:19 PM #2
      misfire? check ignition components. pull spark plugs and compare.
      I really suck at smog.

    3. Member Maggiolone's Avatar
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      04-16-2012 02:44 PM #3
      Quote Originally Posted by ziddey View Post
      misfire? check ignition components. pull spark plugs and compare.
      I immediately thought spark plugs, too. I had replaced them recently with new Bosch ones...maybe switch to NGK?

      I noticed the day before one plug was not screwed in all the way. I torqued it down when the engine was cool to Bentley specifications. I doubt that would cause any issues several drives later, though.

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      04-16-2012 02:46 PM #4
      Quote Originally Posted by Maggiolone View Post
      I immediately thought spark plugs, too. I had replaced them recently with new Bosch ones...maybe switch to NGK?

      I noticed the day before one plug was not screwed in all the way. I torqued it down when the engine was cool to Bentley specifications. I doubt that would cause any issues several drives later, though.
      ive had GREAT luck with NGK plugs..

    5. Member Maggiolone's Avatar
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      04-19-2012 05:43 PM #5
      Maybe it needs a new cat?

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      04-19-2012 05:55 PM #6
      nah, no emissions testing in illinois
      I really suck at smog.

    7. Member Maggiolone's Avatar
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      04-19-2012 06:17 PM #7
      Quote Originally Posted by ziddey View Post
      nah, no emissions testing in illinois
      That I know.

      But could the old cat be causing problems with the idle/off the line performance?

      If that's the case, I'd need to run a straight pipe and risk wrecking the valves.

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      04-19-2012 06:20 PM #8
      don't understand your logic here. saying it's clogged up? wrecking the valves?

      how is the flow out the tailpipe? if it's fine, cat is completely irrelevant.

      misfire or vacuum leak (improper fuel metering). figure out which it is. shoot starter fluid in the intake and see if it smooths your idle out. or perhaps you're running far too rich? unplug the o2 sensor and see what happens. cat is completely irrelevant.
      I really suck at smog.

    9. Member Maggiolone's Avatar
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      04-19-2012 07:02 PM #9
      There's an occasional sputter/burping from the tailpipe when the car idles.
      Do I need a new idle sensor? Or, is that found on Lambda MK2s?
      Last edited by Maggiolone; 04-19-2012 at 07:05 PM.

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      04-19-2012 07:08 PM #10
      misfire. due to ignition or mixture
      I really suck at smog.

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      04-19-2012 07:58 PM #11
      Quote Originally Posted by Maggiolone View Post
      That I know.

      But could the old cat be causing problems with the idle/off the line performance?

      If that's the case, I'd need to run a straight pipe and risk wrecking the valves.
      only way you wreck the valves, is if you run NO PIPE. like no manifold, or anything..

      you have to run just an open head, and you have to run the engine long enough to get the exhaust valves very hot, then you have to shut the engine down with the valves screamin hot, and both an intake, and exhaust valve need to be open on the same cylinder, so cold air can circulate, and bend the valve stem..

    12. Member Maggiolone's Avatar
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      04-21-2012 05:25 PM #12
      Replaced the cap, rotor and ran new plugs.

      Still got now a chugging misfire that results in stalling. I have replaced so many other things, except for the fuel pump.

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      04-21-2012 08:14 PM #13
      have you checked o2 sensor with voltmeter or duty cycle with dwell meter? if you've checked that you don't have ignition issues, move on to fueling. improper mixture misfire

      how does it run before it's warmed up? what if you unplug the o2 sensor?
      I really suck at smog.

    14. Member Maggiolone's Avatar
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      04-22-2012 04:52 PM #14
      Update:

      Fiddled with the idle screw to finally see if that could be the issue. It wasn't (now the idle is a little too high, and I'm worried the air/fuel mixture will be off).

      I think I might have isolated the problem. The EGR canister wasn't fully seated in that rubber boot in front of the throttle body. Pushed it back in; the car will run steady now.

      This may have been a misfire due to a vaccum leak....but could the aforementioned problem occur, disappear, and then re-occur like it just did? Could this misfire/stalling be caused by the timing being off?

      Everything was so new and reliable until now

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      04-22-2012 05:14 PM #15
      Quote Originally Posted by Maggiolone View Post
      Update:

      Fiddled with the idle screw to finally see if that could be the issue. It wasn't (now the idle is a little too high, and I'm worried the air/fuel mixture will be off).

      I think I might have isolated the problem. The EGR canister wasn't fully seated in that rubber boot in front of the throttle body. Pushed it back in; the car will run steady now.

      This may have been a misfire due to a vaccum leak....but could the aforementioned problem occur, disappear, and then re-occur like it just did? Could this misfire/stalling be caused by the timing being off?

      Everything was so new and reliable until now
      First off, your car doesnt have an EGR valve.. thats the aux air valve.. basically the high idle valve.

      im surprised your car even ran with that un hooked..

      and it came out because you never put it back in the intake boot, or else the clamp is REALLY LOOSE..

      i dont see the timing being an issue, unless its GROSSLY RETARDED..

      as long as you tighten the clamp that holds the tube in, it should not ever come back out..

      and i would say that your back fire was from the vacuum leak.

      and dont worry about your idle air fuel mix, you CANT adjust it, so dont worry about it being off.. that screw you played with, thats an IDLE SPEED setting, not IDLE MIXTURE setting.. this is a throttle body, not a carburator..

      the idle speed mixture is set with the main mixture screw on the fuel dizzy, and unless you messed with it, then you should not need to mess with it ever..

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      04-22-2012 06:24 PM #16
      Timing does not just go "off" out of no where, unless the distributor hold-down bolt wasn't tightened, in which case, you'd have noticed the timing off a long, long time ago.

      Adjusting the idle screw only alters the amount of air that bypasses the closed throttle body. It is metered air, and would not affect your mixture. If anything, it'd just do a lousy job of masking whatever underlying issue.

      You car does not have an EGR. It's not clear what you're talking about, but I'm assuming you're referring to the hose that connects from the charcoal canister to the intake boot on top of the fuel distributor? If that was unplugged, then yes, you would be having an issue with unmetered air. Again, check for vacuum leaks all around.

      I'd suggest hooking up a voltmeter to the o2 sensor and a ground to see what your mixture is, both in closed loop (o2 connected), and open loop (o2 disconnected). Watching the voltage with the sensor disconnected would allow you to play with all your vacuum parts / spray starting fluid and see changes in mixture. Fix accordingly. When all is said and done, you should be seeing roughly around 0.7v with the o2 sensor disconnected. Better get, use a dwell meter to diagnose cis+l.
      I really suck at smog.

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      04-23-2012 09:35 AM #17
      Quote Originally Posted by ziddey View Post
      nah, no emissions testing in illinois
      There is in northern IL-- Chicago metro area.

    18. Member Maggiolone's Avatar
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      04-23-2012 01:17 PM #18
      Quote Originally Posted by dkfackler View Post
      There is in northern IL-- Chicago metro area.
      Car is exempt due to age.

      So I have been at work since I adjusted it and haven't driven it since the last time.

    19. Member Maggiolone's Avatar
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      04-26-2012 02:55 PM #19
      Quote Originally Posted by ziddey View Post

      You car does not have an EGR. It's not clear what you're talking about, but I'm assuming you're referring to the hose that connects from the charcoal canister to the intake boot on top of the fuel distributor? If that was unplugged, then yes, you would be having an issue with unmetered air. Again, check for vacuum leaks all around.
      Well, that idle air valve either has a leaky seal or it needs replacement altogether. The car will run fine now once warmed up. However, for the first 30 seconds after I start it, it'll get a rough, shaky idle

      http://www.theautopartsshop.com/fuel...280140107.html - Only place I can find a new replacement

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      04-26-2012 03:04 PM #20
      Is it just a low idle or is it actually rough?

      Have you verified your mixture yet?
      I really suck at smog.

    21. Member Maggiolone's Avatar
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      04-26-2012 03:20 PM #21
      Quote Originally Posted by ziddey View Post
      Is it just a low idle or is it actually rough?

      Have you verified your mixture yet?
      It appears to be slightly lower, and rougher for the first 30 seconds of operation

    22. Member Maggiolone's Avatar
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      05-02-2012 02:07 PM #22
      I gave up, and and took it to a shop that does old Euro cars.

      They found out it had jumped timing by two teeth. I'm having the belt replaced. They said even after adjusting timing, it ran great.

      My fear is that the valves are ruined.....or could they? Are the old 1.7's interference?
      I've been seeing yes and no on that.
      Last edited by Maggiolone; 05-02-2012 at 02:24 PM.

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      05-02-2012 02:46 PM #23
      nah you're fine
      I really suck at smog.

    24. Member Maggiolone's Avatar
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      05-02-2012 03:03 PM #24
      Quote Originally Posted by ziddey View Post
      nah you're fine
      That's what I was hoping. I turned up the idle slightly to get it to the shop 3 blocks away from my house without stalling (they do Alfa Romeos and ancient Mercedes' so I figured they'd know CIS).

      The old 8V saves the day.

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      05-02-2012 03:14 PM #25
      Quote Originally Posted by ziddey View Post
      nah you're fine
      any more than 2 teeth and i might worry. did they say if it was the cam or IM shaft that was 2 teeth off?

      you could be 100 teeth off on the IM shaft, and never bend a valve.. the cam is what needs to be mis-timed to wreck your valves.. but being an old, low compression 1.7L, i DOUBT you even came close to touching your valve..

    26. Member Maggiolone's Avatar
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      05-08-2012 07:03 PM #26
      Car seems to run fine, but the idle has dropped again now....after the timing, new plugs, new wires, etc.

      Maybe it's the WUR?

    27. Member Maggiolone's Avatar
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      05-12-2012 12:40 PM #27
      Update: I had the WUR taken out. Clenaed it, and found some black gunk in the screen. Car seems to idle find for now....

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