Idle running rough, help? (or "The Green Light Drag")

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skittishsynapses
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Idle running rough, help? (or "The Green Light Drag")

Post by skittishsynapses »

So my cabby has developed a new problem in the last couple weeks where her idle (for lack of a better word) stutters while she is running. It does not occur while running and parked, but while she is in drive. As soon as the hand brake is off and set to drive/reverse, the rpm goes from a little under 1000 to by my guess 500-700. One second she goes from steady and normal to the next where she's stuttering/sputtering. Almost like the car is struggling to maintain itself. It hasn't turned off on me while running While I'm accelerating there doesn't seem to be a problem (although I feel like the car is working harder based on the sound seems off from what I'm used to). But when i come to a stop, sometimes she pulls away no problem, but other times no matter how much gas I give the car, she gets "stuck" at a slow speed (caps at 20-ish mph), sputters like an old vw bug (sounds like one..loud pull away), and after a few seconds, accelerates normally.

I've also noticed the idle problem seems to arise more at night, than during the day. If it matters any, I'm based out of Los Angeles.

I'm not sure if I have a vacuum line leak, my transmission's off, or what!? Can anyone give me some insight as to what the heck is up with my '87 cabby?

ps. As an afterthought, my cabby didnt start to have these problems until after I tried to remove the oxygen sensor with the use of pb blaster. Before the o2 sensor change out attempts, her idle was fine. I still haven't managed to pop the o2 sensor out (it's stuck on there tight).
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by sixsracing »

May have done some further damage to the O2 sensor while trying to remove it. Inspect the plugs and see if one or more are black, you may be experiencing an injector hanging open. Any black smoke at startup or on hard acceleration?
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by Briano1234 »

unplug the o2 sensor, see if it don't start running a tad better.

If so change it out...

Have a mom and pop (not a chain) muffler shop weld a new o2 bung to the down pipe.
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by gull »

Yeah, probably the O2. PBlaster isn't good for them; they need to get exposure to ambient air (that's what the holes in the case are for) and the oil has probably gotten in and contaminated the sensor.
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by sixsracing »

Unplugging the O2 sensor may not get the results you are looking for. Most of the older vehicles ECM's are designed to go full rich without input from the sensor.

You can test the sensor with a multimeter. Postive probe to end of sensor wire (unplugged) and negative lead to battery. Read voltage, should fluctuate. Test the ECM in the same manner, should also fluctuate but less rapidly. Voltages should be in the .1 to .9 range give or take.

Keep in mind, none of this may be related to the sensor.
91 Cabriolet, red w/white
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by kamzcab86 »

sixsracing wrote:Unplugging the O2 sensor may not get the results you are looking for. Most of the older vehicles ECM's are designed to go full rich without input from the sensor.

You can test the sensor with a multimeter. Postive probe to end of sensor wire (unplugged) and negative lead to battery. Read voltage, should fluctuate. Test the ECM in the same manner, should also fluctuate but less rapidly. Voltages should be in the .1 to .9 range give or take.
Complete OXS and ECU tests: http://www.cabby-info.com/cis#Sensor .

It could very well just be coincidental that a whole new problem has popped up, but I agree with everyone else in that it sounds as if the PB Blaster has caused this one.

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Re: Idle running rough, help? (or "The Green Light Drag")

Post by gull »

If your car has a full-throttle switch, you can also try closing it by pressing it with your finger. It forces a predefined, slightly rich mixture, regardless of the O2 sensor's condition. If the car suddenly runs better when you press the switch, the O2 sensor is probably sending the wrong mixture information or the wiring to it is bad.
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skittishsynapses
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by skittishsynapses »

Okay, time answer and ask some questions.

No black smoke upon start up or acceleration.

Um, silly question, but what's an o2 bung? If I take my cabby into a mom and pop shop, what exactly should I be asking for? How much does this usually run? I'm a student with a part time job, so trying to keep any costs down would be good.

on an 87 cabby, where would I find the full throttle switch?

Thanks for the help so far everyone!

- Jonathan
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by sixsracing »

It's a round threaded hole about the size of a quarter or a little larger in diameter and about 1/2' tall. You weld it to a surface and then thread the new O2 sensor into it.

Chances are, if you were to go to a muffler shop they would remove the offending O2 sensor and replace it. I'm sure with a proper torch and up on a lift with some leverage it would come out.
91 Cabriolet, red w/white
86 Cabriolet white/white (oldest daughter)
97 Golf, black (youngest daughter)
98 Beetle, red
94 Cabrio, dark green (oldest son)
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skittishsynapses
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by skittishsynapses »

hurrah! bittersweet success!

Who knows what I did right this time, but the o2 sensor came off! I'm running on a new sensor. I still need to reset the o2 sensor light. The car does run much better, sounds a bit better. But, the acceleration problem still persists.

My girlfriend pressed on the full throttle switch and according to her, that calmed down that rough idle. The connection to it has been broken, being held together by tape (see image). Where can I find this part and what's the average price?

The other problem I've read this could be would be the fuel filter. Problem is, I can't replace the fuel filter because the lines are old and cracked. I have no idea where to find the lines for these either. I've included a photo below with arrows to the lines I am trying to replace. Can anyone tell me where I can purchase these hoses? Or rather, what the names of these lines are?

Or...it could be the vacuum lines. No clue. Anyone care to lend their expertise?
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Briano1234
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by Briano1234 »

The switch is the WOT (wide open throttle), the hoses and lines are probably best gotten at a "yard" of your choosing along with the switch. Although a good hardware store or radio shack may have that switch..
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sixsracing
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by sixsracing »

If the idle changed while working the switch then the switch is good.

The hoses have rubber protective coating on them but are reinforced and if they are not leaking then they are fine.

I would check for vacuum leaks first. Using a can of carb. cleaner with a straw spray along the intake manifold slowly. One area at a time. You do this to momentarily fill the gap/crack that may be leaking air. If the idle goes up or smooths out you have found a leak. Don't stop when you find one. Fix it and then move on, check the repair and see if there are more.
91 Cabriolet, red w/white
86 Cabriolet white/white (oldest daughter)
97 Golf, black (youngest daughter)
98 Beetle, red
94 Cabrio, dark green (oldest son)
Cogito Ergo Zoom
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skittishsynapses
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by skittishsynapses »

okay so I posted this in my oxy sensor post:

unfortunately for me that [replacing my o2 sensor) didn't seem to fix the rough idle I've been experiencing. Upon driving my car last night, the idle seemed the same, if not worse. She even had trouble going uphill, getting stuck at 25 mph, reving very high 3500-4000 (which I have never seen my car do), and still sputtering upon acceleration. Ugh. I have no idea what the heck is wrong with my car!

***

I pulled off to the side of the road and let my car sit for a 20 minutes. I promptly drove home and parked on flat ground. I don't know if my 02 sensor is bad or what happened. The idle was sputtering/chugging. All I know is I am extremely frustrated and very close to giving up the ghost on my cabby if these problems can't be fixed. Sigh. anyone. help?!
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by gull »

First step is to check for vacuum leaks. If that doesn't solve it, and you're sure the ignition system is OK, I suggest getting a fuel pressure gauge set and finding out if your system and control pressures are correct. You need a gauge with a valve and a few fittings. J.C. Whitney sells a kit that works fine.
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sixsracing
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Re: Idle running rough, help? (or "The Green Light Drag")

Post by sixsracing »

Try to eliminate the possibilities cheaply first.

Checking for vacuum leaks (although leaks should not affect drivability to this point)

Exhaust blockages (such as converter failure)

Fuel pressure (gauges can be relatively inexpensive)

Still need to "read" the spark plugs for color

Spray pattern on the injectors (may have to walk you through that one)

Many of these things can be performed with no parts repaced and little to no expense.
91 Cabriolet, red w/white
86 Cabriolet white/white (oldest daughter)
97 Golf, black (youngest daughter)
98 Beetle, red
94 Cabrio, dark green (oldest son)
Cogito Ergo Zoom
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