WRD and cold idle

[FresnoBob]

I've read all the posts regarding WRD tuning and operation.  My WRD is not increasing cold idle.  As Stickandrudderman notes, the air does flow into the WRD via the air filter and removing or inserting the filter doesn't change idle speed when cold and there is little or no air detected when the car is warm.   Jumping my enrichment solenoid stalls the engine as well as jumping the CSV. 

However, the car idles at 600-700 rpm when cold, and then idles at 800 rpm when warm. 

I have 3 oval shims: .5 mm, .145 mm and .1 mm totaling 0.745 mm.  Removing all the shims didn't change the WRD function. 

I placed my WRD thermostat in boiling water and the plunger extended several mm and then returned once I cooled it. 

I note my WRD doesn't look like the others pictured.  Without removing the press fit pin, I can't remove the insert and I have no idea how to adjust the rotating pin which limits the insert travel.  I also assume adjusting the screw (with lock nut) on top of the insert will affect WRD function, but I can't loosen the lock nut as the insert spins.   In my understanding, as the thermostat becomes hot, it pushes down on the insert and reduces WRD function.  Therefore, more oval shims and/or further inserting the insert adjusting screw should increase WRD function.  Is this correct?  I note as I back off the WRD thermostat tower screws the car increases idle and runs better.  How do I increase my cold idle?  Any suggestions are most welcome. 

I don't have a way to measure CO.  Does anyone know where can I buy a reasonably priced CO meter? 

Thanks!

[ja17]

The rotating pin is for test purposes only. Normally it is left in the down position so as not to limit the travel of the piston. The WRD increases cold idle by allowing additional air through from the small air filter on the WRD. In addition the WRD also enrichens the fuel mixture when the heat feeler is cold and contracted. Try doing the split linkage test when the engine is cold running. With the linkage split, increasing the air by opening the venture should increase the idle.

[mrfatboy]

My friend has one of these that we use on my car for A/F mixture.  You would also need the bracket.

Innovate Motorsports (3837) LM-2 (BASIC) Digital Air/Fuel Ratio Wideband Meter incl. Bosch LSU 4.9 https://www.amazon.com/dp/B001S7W836/ref=cm_sw_r_cp_api_i_aOD4Cb7EV12D4

Innovate Motorsports 3728 Exhaust Clamp Cast-Stainless https://www.amazon.com/dp/B000CO9MF8/ref=cm_sw_r_cp_api_i_eQD4CbFQEZ9K7

Search for best price.



My other friend has this type that we use also.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F162003793729


I would suggest making sure the hot running CO and idle are correct before messing with the cold start/warm up idle.

[FresnoBob]

Hi Joe,

Just to ensure I understand the split linkage test in this instance, if I increase, through the injection pump linkage, greater fuel while the WRD is letting in air as observed, the engine should increase in rpm.  This would seem to indicate the that fuel to air ratio is wrong in the WRD during cold operation.  How is this adjusted?  Shims inside the insert?  I have no idea how to remove the insert or adjust the black bolt and lock nut on top of the insert; they just spin. 

[ja17]

Before the engine is warm, start and let idle. Split the linkage. Open the venturi a little and see if the idle increases. Next let the venturi close and move the lever going to the IP. Let me know which action increases the cold idle.

[FresnoBob]

I'm in Chicago this week, but will try this on Friday and report back.  Just for my understanding, how do you increase the fuel / air ratio as I clearly have lots of air coming through the WRD air filter? 

[ja17]

The WRD air passage should(shut-off (or nearly close) after the engine reaches 180 F. Check this first.

[FresnoBob]

Hi Joe,
I have checked that the WRD shuts off when warm and I can't detect any air coming through the air inlet. 

[Benz Dr.]

Assuming that the sliding valve is free to move up or down I'd say it sounds like you're too lean. If you can't move your idle mixture knob in much farther you could try adding a very thin shim under your barometric compensator. A half turn out could make all of the difference.

[wwheeler]

 I have been reading this and I think I understand what you are wanting. It sounds like the air flows into the WRD air filter when cold and shuts off when hot. That would mean to me that the air slide valve is moving and that the thermostat is also functioning.

Is what you are wanting to change is only at idle when cold? It sounds like it runs fine when warm? If so, the oval shims under the housing will do that. Add shims to make more rich and less to lean. But first as Joe mentioned, you need to know if it is rich or lean now. Do the linkage test when cold and at idle. Once you know that, hopefully changing oval shims to get you where you want to be. If the shims have no effect, there is something else wrong. Changing shims of .005” to .008” thick in the right direction, should have a noticeable effect.

Good luck

[ja17]

Yes, the oval shims change mixture during warm-up. But if your mixture is not correct when warm, the Dan is giving you the solution which changes mixture with a cold and/or hot engine. Until we understand if your engine is running rich or lean, hot or cold, we cannot prescribe which one of these or both fixes are needed.

[Benz Dr.]

Yes, the oval shims change mixture during warm-up. But if your mixture is not correct when warm, the Dan is giving you the solution which changes mixture with a cold and/or hot engine. Until we understand if your engine is running rich or lean, hot or cold, we cannot prescribe which one of these or both fixes are needed.

I agree. Not rocket science but not something that's simple to fix either. Check all of your ignition system first before you get too far into this job. Ignition affects everything.

[jeffc280sl]

Don't want to complicate the rich and lean running condition discussions but I had a failed barometric compensator on my FIP.  The compensator varies fuel mixture as altitude is changed.  As Joe and Dan suggested there are many things to check and adjust. 

I would leave the barometric compensator for last.  I got pretty deep into this subject years ago and wrote about it here.  You can read about this device in the tech manual, fip, altitude compensator.

I also wrote about very fine and difficult tuning of the fuel injection pump. This is very challenging and probably beyond most owners patience.

Once everything else is near perfect one can take tuning to the next level.

[FresnoBob]

The split linkage test was exceptionally clear - I need more air.  Increasing throttle opening dramatically increased rpm, while adding more fuel didn't increase idle at all.  I obviously need to lean my cold start fuel mixture.  There is lots of air flowing through the WRD filter, so how do I change the mixture?  The car idles well when warm. 

On a separate, but related note, I received my A/F ratio meter today and can begin testing.  Any suggestions as to what I should test first?  Per Mrfatboy's suggestion, I purchased:
 https://www.amazon.com/dp/B001S7W836/ref=cm_sw_r_cp_api_i_aOD4Cb7EV12D4

[jeffc280sl]

Have you read this section of the tech manual?  Its a good start.

https://www.sl113.org/wiki/Fuel/Injection#Pump

The A/F ratio tester you purchased is very capable.  I used one to interface with the car and report measurements to my laptop.  There is a ratio test you can run at idle which is straight forward.  With your device you can measure A/F ratio at multiple rpms under load to see how your FIP compares the on road dyno tests established in the BBB.

[FresnoBob]

Thanks Jeff,

The A/F at warm idle hovers between 12.5 and 13.0.  Mrfatboy suggested a target of 12.5, but I haven't found that number on the forum.  Do you agree? 

[mrfatboy]

Bob,

My memory did not serve me well. But close   Take a look at this chart.

https://www.mgexp.com/article/co-afr.html

Here are the specs from the BBB

Idle       
750-800   RPM CO  3.5 - 4.5  =  AFR 12.80 - 13.20

Lower partial   
1500      RPM CO  1.5 - 3.0  =  AFR  13.40 - 13.95
3000+  RPM CO  0.2 - 1.5  =  AFR  13.95 - 14.50

Full load   
3000+  RPM CO  2.0 - 4.0  =  AFR  12.85 - 13.20

[FresnoBob]

Thanks Mrfatboy,

I am now hovering between 12.5 and 13.0 at warm idle, so I'm satisfied with that.  I need the proper clamp to test above idle as I don't want to damage the O2 sensor tip. 

I know I need to lean out my cold start mixture, but I'm waiting for Joe A to give me some advice regarding the thickness of my oval shims, which now total 0.745 mm. 

[mrfatboy]

I would think shim thickness will be different for every car.  Mine is. 3mm now. 

You will just have to experiment.  The problem is you have to wait for the car to cool for each test. 😀

[jeffc280sl]

I think your idle measurements are close to ideal.  Mrfatboy gives you most of the dyno test specs you want to meet if you go that far.  Its far easier and maybe cheaper given your labor rate to send your FIP out for calibration on a flow bench.  For those with unlimited time and frustration levels you can try and do a similar calibration test on the road.  The BBB gives us the specs to meet.   Like I said do everything else you can think of first.  Your LM-2 is capable of collecting and storing on road test data like rpm, MAP sensor data (need to install a sensor on the SL intake manifold, like a modern car) and A/F ratio.  Basically at specified RPM and load levels you should have desired A/F ratio.  To achieve the correct A/F ratio the FIP can be adjusted.  Please don't try this without giving the entire process serious consideration.  You have to be a little nuts to play with the FIP.  See my write up and pictures in the tech manual

[wwheeler]

Since your cold idle is rich and your warm idle is fine, you obviously don't want to mess with the mixture for all of the ranges. Just focus on the mixture at idle when cold. Removing oval shims could do the trick. But, .745 mm isn't a lot to work with. I have .711 mm now and my mixture is good. So you can remove those and hopefully that will be enough. Not sure what combination of shim thicknesses you have, but removing a .20 mm shim should produce a difference.   

Looking at your picture on the first post, it would appear that your thermostat has an adjustment on the tip? I know that exists, but I do not have one and not sure how to adjust it. If the shims are not enough and you have an adjustment on the thermostat tip, you can extend the tip and that will be the same as removing shims.

[ja17]

Yes start by removing an oval shim.  When the barometric unit fails, the mixture usually becomes much more lean.

[FresnoBob]

Thanks Joe - is the target then a split linkage test where increasing throttle or IP both increase rpm in a balanced way? 

[ja17]

Doing the "split linkage test" when the engine is warm and cold will give you a good overview of the fuel mixture. Opening the venturi with linkage split should increase idle 100 to 200 rpms. In this way the air adjustment screw on the intake will have some range of adjustment after the engine has warmed.

[FresnoBob]

I've tried every combination of shim, from no shims and adding the 0.1 mm or 0.145 mm and the 0.5 mm, but the car still won't idle when cold.  As the car runs so well when warm, I'm thinking I've missed something in my WRD function. 

As the car sputters along at cold idle, I tried increasing both the throttle and IP, and either one would stall the car. 

[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.