WRD and cold idle

[mrfatboy]

Maybe your FIP air filter is clogged.  Remove it and do your cold tests.

When the engine is cold you will hear a loud air sucking sound. You can put your finger over the hole also and feel the suction.

As the car warms suction and noise is reduced due to the air slide valve closing.

When the car is fully warm there should be no suction at all.

[wwheeler]

I think I remember that your WRD had a lock out function? Meaning the screw on the side essentially disables the WRD and makes the pump run more lean as if it were at normal operating temperature. I believe the earlier versions have this as does my 220SE. My 280SE does not.

If it is running very rich at cold idle, engaging that screw will make it run leaner for sure. Might be good a test to confirm the rich running at cold.

[ja17]

Yes, two good suggestions!

[FresnoBob]

A very frustrating day experimenting with oval shims.  I even made my own shim out of a garden trowel, which at 1.8 mm thick, still didn't improve the cold idle.  There seems to be a variable I'm not controlling as sometimes the car will idle better if more air is added during a split linkage test, but at other times, adding more air immediately stalls the car. 

I double checked the linkage adjustment and the throttle and IP linkages hit the stop at exactly the same point. 

I wanted to try the recommended NGK BP6ES spark plugs, but the ends can't be removed and I am using the Karlyn STI copper core wires, and they use the screw on type ends (not the stainless steel snap on ends).  Which of these is incorrect?
http://www.karlynsti.com/Folders/Karlyn_STI_Ignition_Wire_Sets.htm

[mrfatboy]

I use the NGK BP6ES plugs. I was also able to remove the ends.

Did you remove the FIP air filter and check for blockages?  I would just remove while you do the tests to eliminate that variable for now.

What about the WRD Lockout feature that Wallace was talking about? Do you have it?  I have never heard of that before.

You said the throttle body and FIP linkages hit their stops at the same time but have you checked that the throttle body flap is fully closed when it is at its stop?

[mrfatboy]

Here is a long shot  .

Years ago a gentleman on this forum had a similar cold start problem.  It turned out that the vacuum pipe that is connected the FIP and runs behind the valve cover and connects to the intake manifold was crushed restricting air flow.

Fixing the pipe solved the problem.

[FresnoBob]

I've done the WRD air filter test and air flows unimpeded through the filter.  There is lots of sucking sound when the engine is cold and the air diminishes to undetectable when the engine is hot.  There is also no change in engine cold idle when you place the filter in the hole and remove it as described by BenzDr. 

I just received the new NGK spark plugs and the ends can't be removed.  I managed to crank one off in my vise, but core was then exposed.  From other posts on the forum, it seems screw on ends are correct and these plugs are different than received by others. 

I checked the air tube between the WRD and intake manifold and it is clear and not kinked. 

[mrfatboy]

I'm running out of ideas   I had a similar problem (also another member last year). Our problem turned out to be a small headgasket leak. While the car sat overnight  coolant would leak into the cylinder. Cold starts in the morning were rough and uneven until the cylinder cleared.

My friend was able to discover the leak by doing a pressure test on each cylinder.  The first one we tried we heard air bubbles 😳

[wwheeler]

A very frustrating day experimenting with oval shims.  I even made my own shim out of a garden trowel, which at 1.8 mm thick, still didn't improve the cold idle.  There seems to be a variable I'm not controlling as sometimes the car will idle better if more air is added during a split linkage test, but at other times, adding more air immediately stalls the car. 

For starters, adding shims to the WRD will make the mixture more rich when cold. For a mixture that is already rich, you need to remove shims. You say that the idle improves with more air sometimes and then other times, stalls the engine. Can you be more specific what the engine conditions are when it does or does not? Is this when the engine is cold and at idle? Those are the only two conditions that the WRD effects the mixture. 

Have you tried locking out the WRD function by the screw on the side?

[FresnoBob]

Hi Wallace - I've tried all shim conditions, including removing all shims.  I'm not sure where the lock out screw is located.  Can you give me a hint? 

[Benz Dr.]

That lock out screw often has a small roll pin in place and I've seen where the whole screw can snap off while trying to turn it, so I'm not a big fan on that idea.

You did check to make sure that your CSV isn't leaking?  Are you driving your car to get your engine fully warmed up or just letting it idle until warmed up? I've seen where the slide valve wouldn't fully close unless the engine was really warmed up from a drive.

On the surface, this looks like a really serious issue but in reality it's not so much. As long as your engine starts when cold you can always get in your car and drive it until it's warmed up. At that point, your engine runs normally and that's when you need a proper mixture ratio. By driving your car until it warms, your warm up period is greatly reduced and so is your chance of fouled spark plugs. Now if your engine is running rich at road speed when warmed up, that is a serious issue.

[FresnoBob]

OK, I know that eccentric screw that compresses the insert.  It does smoothly rotate and I'll try that as an experiment. 

Once the car is warm, I measure 12.5 to 13 as an air / fuel ratio at idle.  I haven't received the proper clamp for the sensor, so I can't test the A/F under load or higher idle. 

My CSV seems to function well and if I jump 12V to it, the car immediately stalls.  This is also the case with jumping the enrichment solenoid. 

This has just been incredibly frustrating and I'm sure I'm missing something stupid...

[wwheeler]

That does seem to indicate it being too rich when cold. In addition to the WRD lock out screw, I did also notice that your thermo bulb rod has an adjustment nut. That would go along with you having the WRD lock out screw as that is on earlier cars I believe.

I do not have this adjustment on mine, but have read here where it can be adjusted. I wonder if it has been adjusted in so far that it runs rich regardless of the elimination of shims. People like Joe and Dr. Benz may have more experience with this than I do. At this point, no idea is too crazy.

I suppose in the worst case scenario if the bulb has been that badly adjusted in the past, once you correct it, it may effect the warm running idle mixture.   

[FresnoBob]

Hi Wallace,

I used the eccentric screw to isolate the WRD function and the car would barely run when cold. 

I have tried to adjust the WRD insert screw and lock nut combination, but this seems impossible without removing the insert, thus requiring removal of the small roll pin, and I'm not up to trying that.  After my unsuccessful experiment with the isolated WRD, I restored WRD function and again confirmed that rpm dramatically increases by adding more throttle in a split linkage test when the engine is cold, and there are currently no oval shims installed. 

Perhaps someone has some experience with adjusting the insert screw and lock nut.

[mrfatboy]

I have an extra FIP that I play around with. It came with the old thermostat bulb that has the adjustment nut on it.

I just checked my notes and a couple of years ago I compared the old style and new style thermostats.  They both measured the same.  The rod was 18mm when cold and 22mm when fully extended.

I think I posted pics here and there was a discussion.  If I find it I will post it.

[mrfatboy]

  After my unsuccessful experiment with the isolated WRD, I restored WRD function and again confirmed that rpm dramatically increases by adding more throttle in a split linkage test when the engine is cold, and there are currently no oval shims installed. 

No oval shims and adding fuel via split linkage test resulting in increased rpms suggest it is now lean. Add your smallest shim and test again.

[Benz Dr.]

The old style IP thermostat only moves 1.1 mm or about .050 '' when fully warmed. It will move more than that but that's all you need to shut the slide valve off. The later IP thermostat is something like 7 - 8 mm IIRC.

[FresnoBob]

I have shims of 0.1 mm, 0.145 mm and 0.5 mm.  I've tried all combinations, including no shim at all.  In each case, the car runs better with more air in the split linkage test. 

Given the Benz Dr.'s advice that the old style WRD only moves 1.1 mm before shutting off the WRD function, this is clearly a very sensitive device.  I tested my WRD thermostat in boiling water and it extends at least 1.5 mm

Does anyone know how to adjust the screw and lock nut on the WRD insert?  I tried with two pairs of needle nose pliers and was unable to adjust them.  It seems to me that oval shims would perform the same function though. 

[wwheeler]

You said you added throttle and the engine increased. Not sure if you added the IP (more fuel) or the throttle plate-butterfly (more air) with the linkage split. I am going to assume you added more air based on previous posts which means the mixture is too rich with the WRD working. Please correct me if I assumed wrong.

A question when you disabled the WRD - Is it possible that the mixture was better but the engine barely ran because of low idle speed and not because of incorrect mixture? In order for an engine to run well cold, it needs more of BOTH air and fuel which increases the idle speed. So the WRD not only allows more fuel, via the I. pump, but also more air through the air filter and to the intake manifold.

Just wondering if you could manually increase the throttle (both air and fuel) slightly while the engine is running cold and the WRD disabled? Grasping at straws at this point.

[FresnoBob]

Thanks Wallace,

I meant the rpm increased by addition of more air through the throttle plate. 

When I disabled the WRD, the engine ran really poorly and trying to increase fuel and air through the linkage (which was not split at the time) wouldn't get past the sputtering.  I think the WRD A/F ratio should be more rich than required for a warm engine, which it seems to do, but just to a far greater extent than necessary.  When warm, my A/F ratio at idle is between 12.5 and 13.  There is a bunch of air going through the WRD during cold running so with the air filter removed, a strong sucking sound and actual air is observed by hand. 

I keep coming back to the screw and lock net on the WRD insert.  Does this change A/F ratio, or just how much the WRD functions?  At 1.1 mm of travel, this is quite a precise adjustment and I can see why later IP models used the 7-8 mm of travel. 

[wwheeler]

You bring up a good point about screw and nut on the WRD. Since that rod acts directly on the air valve, it would change both the air and fuel. When you change the length of the rod, it alters the timing of the WRD, or in other words, when it shuts off at a certain engine temperature. Later thermo bulbs that do not have this adjustment, use small round shims on top of the piston. That is what I have.

The only mixture adjustment available on the WRD that I know of, is the oval shims. I just can't think of anything else that would make the mixture more rich only during the engine warm up phase. All the other mixture altering devices are primarily when the engine is cranking or they affect at all temps. You state that when you changed the number of oval shims, there is no effect on the mixture. I guess that sounds like we are fishing in the wrong pond. Maybe ignition is at fault? I am afraid this is beyond my knowledge level and the big guns need to step in. 

[Benz Dr.]

Please note: the 7 - 8 mm I stated in an earlier post is just a guess on my part and it could be more or less than that amount. 1.1 mm on the earlier IP is an accurate amount and everyone should be safe following that.

Keep in mind that your ignition system will be challenged during warm up. If something is amiss you will likely see more problems during that phase of the warm up cycle.

If you remove a spark plug and carefully inspect it you should look at the ground electrode and the center tip. If the very end of either, or both, have a small clean area it's a sign of low voltage going to the spark plug. In an over rich environment the spark will only ignite some of the fuel and a lot will exit as black smoke. Low voltage only makes this condition worse.

Inspect all of your high tension wires and replace anything that has carbon core. I also remove all resistors from the system leaving only 1 K ohm spark plug terminals.  Your ignition system has to be in perfect working condition before you look at fuel systems.     

[FresnoBob]

I'm sorry if I gave the impression that the oval shims had no effect.  The car clearly ran worse the more shims were installed.  What seems a bit strange is the large amount of air going through the WRD air filter.  With the filter removed, there is clearly a lot of air sucking through the 20 mm opening. 

I have new copper spark plug wires and I've tried various sets of spark plugs.  My wires are:
http://www.karlynsti.com/Folders/Karlyn_STI_Ignition_Wire_Sets.htm

I agree that ignition issues could be causing a weak system to not operate well when cold.  My points are less than a year old and I haven't changed any ignition adjustments since the car ran well (but never cold). 

I'm going to adjust the valves as I haven't done this yet and have no idea as to their gaps. 

[Cees Klumper]

The number/combined thickness of the shims only affect the length of time that the WRD enrichens the mixture, but not the degree of richness, I believe. If that's correct, then adding or taking out shims does not affect how rich or lean the engine runs during warm-up.

[wwheeler]

Cees, I think you are referring to the small round shims that are stacked on the air valve in the WRD. Those in effect change the length of the thermo bulb rod by moving both the air valve piston and the rod below the piston that changes the fuel in the IP. That does change the timing when it shuts off.

The larger oval shims we are referring to are for the WRD housing and only moves the rod that changes the fuel in the IP. So those oval shims should alter the cold mixture.