Strange Idle

[VDubbinIt]

I have a 1986 cabby that idles between 2000-2500 RPM's when first started cold. After about 5 minutes it will drop to a low idle and try to die (jumps from 500-100 falls again jumps..etc.) until it the oil has warmed to at least 80c. Once it warms up all the way it runs fine. It has been this way since I came into ownership (about 2 months ago). However recently (today) it will drop to 750ish once it idles after running at high RPM's for a length of time. I did change the air filter last night, could I have done something to cause it to consistently drop now?
Also, the camshaft oil seal is bad and is starting to come out, I plan on attempting to replace that tomorrow. There is also a buzzing noise by the fuel sending unit, could this buzzing be the cause? What would that be from?

[CalAltaDubber]

First, Welcome to TRF I hope you will enjoy our company.

Let's start with the easy one. The buzzing noise is normal, nothing to worry about there.

The valve cover gaskets are a weak point and do need replacing every now and again.

The big one is your idle when the car is cold. I have an '88 that idles rough until the Warm Up Relay (WUR) makes, then it runs great. But by your description, it seems a little more prolonged.

You might want to check the "Rusty Rabbit" http://www.therustyrabbit.com/. The site owner there has a great set of videos about how the CIS injection system works. This might help you diagnose your issue a little better.

Keep us informed how it works out for you.

[PDX Cabby]

I have a 1986 cabby that idles between 2000-2500 RPM's when first started cold. After about 5 minutes it will drop to a low idle and try to die (jumps from 500-100 falls again jumps..etc.) until it the oil has warmed to at least 80c. Once it warms up all the way it runs fine. It has been this way since I came into ownership (about 2 months ago). However recently (today) it will drop to 750ish once it idles after running at high RPM's for a length of time. I did change the air filter last night, could I have done something to cause it to consistently drop now?

First off check around for vacuum leaks. This *could* be a fuel delivery problem, but we're also talking about parts like gaskets, o-rings and vacuum lines that can easily be 25 years old. I'd recommend checking over all possible vacuum leaks first before even thinking about going on from there. See the Rusty Rabbit link above. I just discovered it the other day, and he's got some great advice about vacuum leaks.

Once that is done, then, yes, it's time to look at the two items that change as the car warms up. The Auxiliary Air Valve and the Warm Up Regulator

There is also a buzzing noise by the fuel sending unit, could this buzzing be the cause? What would that be from?

The buzzing is the Frequency Valve on your CIS-Lamda fuel distributor. If it's buzzing, then its working.

[VDubbinIt]

I did notice that one side of the clips for the air box weren't on. After making sure they were on good and tight, it runs normally.. except for now after replacing the valve cover gaskets, the idle was super high, the screw was backed out for some reason. After getting it back to normal idle, it dies randomly. It will almost definitely die when I turn right; not left, right. Odd??? What would cause this? I did notice a while ago that when turning right or left it would cause the idle to lower but now it just kills it. Any ideas?

[PDX Cabby]

Turning right kills the car, eh? That's a rotten gas tank, and a very, very well known issue. Pretty much the only repair is to replace the gas tank. If the tank is full, it shouldn't be a problem, just as the level goes down, the pickup tube gets exposed and sucks air, therefore killing the motor.

[gull]

Before you start thinking about replacing the gas tank, pull out the sender/pump unit and take a look at the hose inside the tank that connects to the in-tank pump. Sometimes the hose rots out and causes air to get in when the fuel sloshes around. While you have it out you'll have a good opportunity to get a look at the inside of the gas tank.

For what it's worth, symptoms when my in-tank pump was failing were:
- Random stalling in stop-and-go traffic. (I don't know why stop-and-go specifically; probably heat-related.)
- Hesitation after hard right turns, like when taking a freeway cloverleaf at speed, worst when the tank level was low.
- Eventually, the car just plain refused to start.

[kamzcab86]

Turning right kills the car, eh? That's a rotten gas tank, and a very, very well known issue. Pretty much the only repair is to replace the gas tank. If the tank is full, it shouldn't be a problem, just as the level goes down, the pickup tube gets exposed and sucks air, therefore killing the motor.

Gas tank isn't the problem in 1984.5 and up Cabriolets (unless it's rusted out and/or leaking). In-tank fuel transfer pump being faulty, however, is a great possibility.

Also, VDubbinIt, go to www.cabby-info.com/cis and do the procedures outlined there.

[VDubbinIt]

It only dies when turning right if it's in neutral and if the idle speed is at 1000 RPM's. Also, this was all of a sudden. Other than the idle speed screw, what else would cause the idle speed to be high?

I also noticed that my buzzing sound is gone Could this all be because of the frequency valve?

UPDATE:
I'm reading about timing and beginning to wonder if I may have thrown the time off? My friend tried to attempt taking the camshaft off and before I could stop him he tried doing so without something keeping the sprocket from turning. Would turning the cam in that way throw off my timing causing all of this ruckus?

Also, it now doesn't want to run very well when started warm... it's died most of the time except earlier it was fine, I pull off and while sitting at a stop light the oil light flashed at me.

[PDX Cabby]

oh... when sitting still... ignore the whole gas tank and fuel pump stuff...


Does your car have power steering?

There are a number of different things that control idle speed and its important to have a dwell meter, timing light, and, in an ideal world, a fuel pressure gauge. Idle speed is controlled by a combination of fuel, air and spark.

Do you have a bentley manual for the car? I have the whole thing online right now, but its a 300meg download and my server is slow. I broke it into chapters but haven't loaded them online yet (works great on my iphone though!)

I'd suggest taking a step back and starting over again. Clean the fuel injectors and replace the o-rings. Inspect and replace the vacuum lines. Clean the WUR. Clean up the grounds, and give it all a go again.

[VDubbinIt]

There is power steering.

I don't have a bentley but I have a chilton.

Also, I'm really beginning to think that my main problem is the ignition timing. I'm pretty sure what happened was when he attempted taking the sprocket off he turned it enough to throw it off. Unfortunately I don't have a timing light so I'm going to make an attempt at the method posted on the bad habbit rabbit page.



Once I do that I'll post an update. Fingers crossed I don't screw up my engine.

Btw here's a pic the car.

[gull]

Timing lights are cheap. You don't need one with an advance dial or anything for these cars. Just go get one, you'll need it again sooner or later.

[PDX Cabby]

I'd bet you're right with the timing. Turning the wheel will put an extra strain on the motor, and if the timing is off, or the vacuum leak significant, that strain can stall it

[VDubbinIt]

Code: Select all

While looking for the timing hole plug I discovered it's actually missing. I have no idea how long it's been gone either. Starting to think this car is doomed...

[Briano1234]

No, the previous owner may have destroyed it trying to get it out, it happens and I have been known to break a few myself. You can get replacements on www.germanautoparts.com .

Perseverance, determination, and monies will get your car back to OEM condition, it takes time.

[VDubbinIt]

Unfortunately I'm running out of the monies part

Is anyone in/around the seattle area?