ViribusUnits

OK, after replaceing my upper ball joint boots I attempted to give my car a full tune up.

I replaced the slightly cracked distributer. I replaced the old AFM to pendulim seal. I adjusted the idle switch to it's proper location. I proceaded to find the TDC mark on the orange harmonic ballancer, and set my timeing to 10 degrees before TDC, at about 650 rpm. I also set my idle to between 600 and 700.

Now, this is where I get into trouble.

I pull my O2 sensor wireing, and run my new digital volt meter between the ground and the large green wire, headed to the O2 sensor. It voltage read 0.94 volts I tryed adjusting the small screw on the AFM. It had no effect. I pulled the AFM, and pulled the idle adjuster screw all the way out. I ran carb cleaner down the idle adjustment by pass. I put the idle adjustment screw back into the thing. I set the screw to full open, this had no effect. I tryed it with the screw all the way in, this also had no effect.

What in the world am I doing wrong? I can't get the mixture to lean up any. The VU tailpipe nose test says the engine is running way rich, too.

This isn't makeing sence to me!

Help!

Question 1. To measure the CO in the exaust, you connect the positive side of the volt meter to the green wire coeming from the O2 sensor, and the negetive lead to a ground on the car?

Question 2. You set the idle with the O2 sensor pluged in, or not? (I did it with it in.)

Question 3. Does the venturary make a "woosh" sound? When I lean down twoard it, there is a "woosh" sound, and when I pull the outside hose off and seal the thing with my thumb, there is no sound.

Question 4. At any speed, my engine has a steady up and down movement to it's rpms. At idle it's about a 50 rpm cycle, at irregular times. I've just atributed it to the rich mixture so far.

Rufus Sanders

Don't ya just love these cars? We spend all summer loving them and all winter getting them to act right. (at least those of us who have winter...)

I'm not a guru, but I'd check the usual suspects when it comes to the L-Jet acting up. Go for those two sensors: Temp 2 sensor, and Thermo Time switch. From what I've heard, they both can mess up the mixture if they read the temperature wrong.

Also, check out this site:

<a href="http://www.conservatory.com/vw/manuals_nyx/L-Jetronic.html" target="_blank">http://www.conservatory.com/vw/manuals_nyx/L-Jetronic.html</a>

It has an L-Jet trouble shooting manual on it, althought it's for a VW, the basics should be helpful. - Ruf

User 4221

VU,
Question 1. To measure the CO in the exaust, you connect the positive side of the volt meter to the green wire coeming from the O2 sensor, and the negetive lead to a ground on the car?

--- Yes, you are correct

Question 2. You set the idle with the O2 sensor pluged in, or not? (I did it with it in.)

-- No, set the mixture with the sensor unplugged

Question 4: My '81 exhibits the same behavior.... Only when it has reached operating temp. Does your car do this when cold, warm or both?

I think Rufus is on to something.... Check your sensors. Temp Sensor 2 is a place to start. It's really easy to check. It is on the front of your block right above the fan pulley bracket.

HTH,
Scott

ViribusUnits

OK, so I did it right, so far.

My car does the fast slow cycle under all conditions.

The mixture is rich, still.

I checked the Temp II sensor, sorta.

OK, as I understand it, on most temp sensors the amount of resistance goes up with the tempeture. Now, is a higher Ohm number more resistance, or less?

When I tested the sensor, I had just gotten back from church. The engine was deffently more than the 105 degree test point for the engine. I measured .540 k Ohms.

I'm not sure how to interprete that. Are higher temps suppost to result in higher numbers for the Ohm?

PorKen

I did a search for L Jetronic on the web and found this tutorial which I found to be informative.
<a href="http://www.firstfives.org/faq/ljet/jetronic.pdf" target="_blank">Link: BMW L-Jet .pdf</a>

This and a few other sites say that over when the full throttle switch is closed (one said also over 3500rpm), the injectors are open all the time and the air flow sensor is ignored.

Also interesting: Temp I sensor is the air temp sensor in the AFM, Temp II is the water temp sensor.

Steve Cattaneo

Ground the DVOM to the battery ground terminal that will ensure you have a good grounding point for the sensor. The engine must be at operating temperature for the 02sensor to work properly.

A high voltage reading above 600mv is rich, lower than 300mv is lean. Since your car is running rich lets check the function of the 02 sensor; with the DVOM connected to the sensor induce a lean mixture by removing a vacuum hose ( brake boost hose) and rev the engine, the reading on the meter should good full lean 100mv. If you do not get this reading the 02 sensor is bad.
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User 4221

VU,
The temp sensor II is an NTC (Negative tempature coefficient) thermistor. Meaning, the hotter it gets, the lower the resistance.

Scott

ViribusUnits

Thanks.

So far, I've checked the Temp I sensor, the AFM, the thermo-time sensor, and the Temp II sensor. The AFM, and the Temp I check out.

If the TII is as you say, then mine is bad? I was at least 180`F or so when I measured the resistance to the TII. It read 500 Ohms. According to the mannual, it should read 250-400, right? So 460-500 means the computer thinks the engine's never warm? When I pull the plug to the sensor, nothing changes.

Steve, I know the sensor is doing something. When I pull it, the engine slows alought, and the exaust smells much more like gasoline. I'll do the test though, it's easy enough. I've always used the top frame of the fuse relay pannal for a ground. Well, the bolt to be precise.

Also, where do the two plugs for the thermo-time switch go? According to page 24-17 of the service mannual, they're labled G and W. For G to ground, above 40 degrees C, I get 74 ohms. For W to ground,I get 144, and for G to W, I get 70 ohms. That would mean the thermotime switch has something wrong with it. when I pull the plug to the thermo-time switch, the engine dies!?!?! Is it suppost to? I didn't think so, but thats what it does. Also, when I pull the connecter to the cold start fuel injector, but leave the thermo-time sensor hooked up, it has no effect.

I'm going to give both sensors another round of testing tomarow, once they've had some time to cool down to cool temps.

I'm going to go do Steve's test to the O2 sensor right now.

//Edited// I just preformed Steve's O2 sensor test. My O2 sensor passes with flying collors. Thats cool. //

Steve Cattaneo

Your readings of the TT switch are not off, G to ground =100 /160ohm yours 74? W to ground 100/160 yours 144 G to W 50/ 80 yours 70 .

The G terminal wire brown/ yellow wire is wired into the cold start valve then back to terminal W of the TT switch, the yellow wire then goes to relay X1V.

Remove the temperature II sensor and the TT switch and clean the probe on both of them with scotch brite.


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ViribusUnits

I know the TT is suppost to be between 160, and 100 Ohms. I checked it 5 times. It's in the 70-80 range everytime, while the engine is warm. I'm guessing if it fails any one element, it is dead, right?

Do you know why the engine would die when I pull the plug to the TT, but not when I pull the plug to the cold start injector? From what I could tell, the engine shouldn't die when the TT is pulled, expecaly if it's already warm.

Steve Cattaneo

That is normal, on an L JET car if the temp. Time switch is bad or plug disconnected the car will not start. I do not know why.

If you feel that the switch is bad, change the cost is not much. On my 85euro if the tempII. Switch is disconnected the car will not start, LH.


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ViribusUnits

Well, sports fans, here is an itersting new development. I was crusieing down the freeway, and it occured to me, the thermo time connecter and the Temp II connecter looked awful alike.

The Temp II plug and the Thermo Time switch can be reversed!

Mine were. According to the mannual the brown plug goes to the Thermo time switch. I found that my brown plug was attached to my Temp II sensor. Uh oh. So, I switched them around about 5 minutes after this occrued to me at a gas station.

I switched them around, and guess what, the connecters are the same, except for the color. Now when I pull the thermo time sensor plug, the engine does not die. Neat uh?

It didn't cure any problems though, so thats frustrating. It's still running realy rich, and I've still got the same miss.

I've gotta redo my tests though, with unplugeing the cold start injector. With it wired up right now, maybe I'll have a chance of finding the problem!

This is just sorta a fyi.

dr bob

You may want to carefully check the temp sensor. The connection to the thermotime switch is power for the heater inside it IIRC. Putting full current across the sensor will kill it. The sensors (also IIRC) are reverse coefficient, so a burned out/open sensor might indicate a cold motor and call for a rich condition.

You can check the sensor easily with a multimeter. If it shows open, you know what the problem is and a new sensor is required.

A digital camera might be a reasonable substitute for labeling wires that are removed for a project task. With my feeble brain, I'm using both methods now. Masking tape used to be the weapon of choice, draw a diagram and add numbers to the wires. I've also used colored wire ties if there are fewer than six to keep track of. Six is my magic number only because I happen to have six differenr colors in my collection.

Let me know if the temp sensor II is the culprit, and satisfy my curiosity.

ViribusUnits

Well, here's what I know. I didn't switch the connecters around. I would have had to put each one one the other side of the fuel dampaner to do that, and I didn't. So apperently, I bought the car that way.

Usualy use masking tape and a marker too. I give the connecter a number, or letter combo, and I mark BOTH connecter. This away when I want to put it all back together, I match up the 1 with the 1, and the 2 with the 2, etc... Realy makes it easy. I don't do it when I'm only dealing with about 2 or 3 connecters. I've rarely had problems switching them around.

The thermo-time sensor is dead. From G-ground, it has a 70 ohm resistance, no matter what conditon it's in. Hot or cold. That says dead to me.

The temp II sensor might be alive, and well. I can never seem to get it hot enough to put the resistance in the test value for the book. The lowest I've ever had the resistance is 460 ohms. That was after a 1 hour 60 mph average cannonball run. More often it's higher than 500 ohms. It's suppost to be between 200 and 400 ohms. It could be I never get it hot enough, but I have trouble beliveing that.

However, I've got two more tests to do to it. One is I'm going to get a 200 ohm resister and wire it in. If the mannual is to be belived, that should mean computer thinks the engine is at least 105`F. That sounds pretty warm to me, and should turn off the warm up enrichment. IF the mixure goes down, I'll know that the Temp II is bad. The second one is I'm going to get a thermometer I can use to sepreatly measure the tempeture that the Temp II sensor is attached too. Maybe one of the fancy IR distance ones, or maybe a flexable probe I can plug into my new volt meter. (I've always wanted an excuse to buy eighter one, I think I might have just found it.) I tryed useing an alcohol thermometer, but I don't realy trusts it reading becuase I couldn't get to to get enough conntact with the right part. With the alcolhol thermo meter, I got quite a bit above 100`F. I'm kinda hopeing both of them arn't bad. Maybe a degraded Temp II sensor? Not quite dead, but not quite well?

Rufus Sanders

ViribusUnit, Wow, switching the sensor plugs.. gutsy, very gutsy. Acutally, you can tell if you have the correct sensor plugtged into the correct socket by checking the other end of the wire.

The L-Jet maunal I posted earlier has a diagram that shows which pins on the big L-Jet plug goes to which sensor. If your Temp II sensor is dead or bad, you can unplug it, stick any piece of wire in the plug to make a complete circuit between the two leads and measure for an open circ. or a zero resist. for those lines on the L-Jet plug. Pins 13 and 16 I think.

Then you'll know if the wires to your Temp II sensor are good, and you'll kknow if that plug really goes to the Temp II sensor.

In addition to the diagram, there's also a test chart for the Temp 2 sens. and the Thermo Time Switch that gives resist. values for various temps. Really useful- Ruf