Chris Grayson's (of MC2Racing) Guide to a Reasonably Priced, Street Setup for Handling

Chris Grayson has been involved in Merkur XR4Ti performance for a very long time. He formed MC2Racing to provide quality performance parts t...

Wednesday, May 29, 2019

Repinning your harness to put an LA3 into a Merkur

There are more detailed, complete instructions at 

These are the pins that you have to move to put an LA3 into your Merkur:
1. Pull out pin 43 and move it to pin 27. This connects the VAF signal. 
2. Pull out pin 25 and move it to pin 43. This connects the VAT signal. 
3. Pull out pin 32 and move it to pin 31. This connects the boost controller. 
4. Pull out pin 35 and insert it into pin 33. This connects the EGR solenoid signal. 
5. Put a spare pin into number 24 and run it to Signal Ground which is pin 46 for permanent premium mode. Or install a switch so that you can switch between premium and regular modes.

You don't need to hook up an Air Charge Temperature (ACT) sensor. You don't need to hook up the Brake On/Off (BOO) switch. And you don't need to do anything to keep the cruise control working. The cruise is a completely separate system from the EEC-IV in a Merkur. No modifications necessary. 

Thursday, May 2, 2019

Throwback: MerkMeter User Guide

Since I have a gauge cluster with a MerkMeter and needed to understand what it was, how it worked and how to reinstall it, I had to go find information about it. I finally found information and had to pull this out of the WayBack Machine, I figured I'd post it here, so there's a live website for this content again.


MerkMeter User Guide

The exhaust gas oxygen (EGO) sensor is a crucial part of the engine management strategies of virtually all modern cars.  It basically enables the Engine Control Unit (ECU) to properly manage the fuel flow in response to changing engine operating conditions.  Responding to these changing conditions rapidly and accurately is a key component of the operating strategies employed by the software embedded in the ECU.  An improperly operating EGO can result in poor fuel economy, higher emissions, and poor drivability and performance.  Also, insight into the data a properly functioning oxygen sensor is sending to the ECU can be invaluable in monitoring the runtime health of the engine and diagnosing trouble when it occurs.  Just as a hot running engine, as indicated by the coolant temperature gauge in the instrument cluster, can be an indicator of serious problems, so too can an abnormal air/fuel ratio as indicated by the proper gauge.

Theory of Operation
The EGO sensors in our cars basically measure the difference in the oxygen content of the exhaust gas against that of the ambient air.  The air we breathe is about 21% oxygen.  The oxygen content of the exhaust gas of our cars is typically in the 0-2% range.  A small zirconium dioxide thimble in the oxygen sensor can generate a small voltage that reflects the difference in the oxygen in the exhaust (outside the thimble) vs. the oxygen in the ambient air (inside the thimble).  The greater this detected difference, i.e. the less oxygen in the exhaust gas, the higher the voltage produced by the sensor.  

For this type of EGO sensor to work, it must be heated above 600° F.  The exhaust gases passing over the sensor tip in the exhaust pipe accomplish this heating.  It generally takes about 2 minutes with the engine running above 2000 rpm for the EGO in an XR4Ti to be brought up to operating temperature. The Scorpio uses a Heated Exhaust Gas Oxygen (HEGO).  The HEGO, as the name implies, is brought up to operating temperature somewhat quicker due to an internal electrical heating element.  Output from both types of sensors is comparable. 

A new EGO sensor will output from zero to about one volt and can detect changes in the oxygen content of the exhaust very quickly.  These sensors are particularly sensitive around the ideal air/fuel mixture of about 14.7:1, which results in stoichiometric burn.  This is the ratio at which there is theoretically just enough oxygen to burn all the fuel.  (In practice the burn is never completely efficient and some residual oxygen will always be present in the exhaust).  The stock Bosch EGO sensors (or equivalents) generate approximately 0.45 volt at this mixture.  A voltage below 0.45 indicates a lean condition, while a voltage above 0.45 volt indicates rich. 

How does the EGO output voltage correspond to an air/fuel ratio value?  The answer to this question is dependent on many variables; the age and condition of the EGO, the fuel used, the operating temperature of the EGO among them.  Representative data from Bosch is shown below for a new zirconium dioxide EGO operating at 800-1200°F with an engine burning gasoline containing no alcohol:

Approx. Air/Fuel Ratio
12.0:1 or less

As a sensor gets older the maximum voltage it can generate and its sensitivity to changes may decrease.  Also if the sensor becomes contaminated with lead, silicone, or antifreeze residue it may become very inaccurate.  Bosch recommends that unheated oxygen sensors (XR4Ti) be replaced every 30,000-50,000 miles.  First generation heated sensors (Scorpio) should be replaced every 60,000 miles.

The sensitivity and responsiveness of the EGO makes it possible for the ECU to dynamically adjust the air/fuel ratio. When the engine has warmed, as indicated by the Engine Coolant Temperature (ECT) sensor, the ECU will go into “Closed Loop Mode”.  This is a feedback mode in which the ECU will actively vary the fuel supplied via the injectors based upon the EGO signal.  When a lean condition is indicated by the EGO, the ECU will increase the amount of fuel supplied by the injectors.  If the EGO shows the mixture is rich, the ECU will reduce the fuel supplied.  The ECU will make the necessary calculations and dynamically adjust the mixture continuously while in Closed-Loop Mode as much as several times a second.

MerkMeter Behavior
The MerkMeter is essentially just a small voltmeter calibrated to a range of zero to one volt.  Each LED indicates an increment of 0.1 volt.  The leftmost red LED will light when the voltage from the EGO is about 0.1 volt.  The leftmost yellow LED lights at about 0.4 volt and the leftmost green LED lights at about 0.7 volt.  The rightmost red LED will light at or above 1.0 volt.  There is about 10 millivolts overlap between adjacent LEDs.  For example, a value of 0.69 volts will light both the rightmost yellow LED as well as the leftmost green LED.

What the MerkMeter displays depends upon the operating conditions of the engine:

Cold Engine
When the engine is cold, the MerkMeter will gradually display an increasing voltage as the EGO sensor warms to operating temperature.
Closed-Loop Mode
The MerkMeter will show this mode as a display that oscillates from about 0.1 volts to 0.8 volts and back again. When at idle the crossover time from lean to rich and back to lean might be about one second. At part throttle cruise, the crossovers might occur several times a second. The range and speed of these Closed-Loop oscillations can be an indicator of the health of the EGO. If the range of oscillations is considerably less than normal, or is skewed toward one end of the range or the other, oxygen sensor deterioration or contamination might be indicated. The same condition could cause the crossover rate to slow. A car that never goes into Closed Loop Mode might have some other faulty sensor or ignition circuit. The XR4Ti will operate in Closed-Loop Mode only below 2950 rpm.

Open-Loop Mode
In this mode, the ECU does not use the EGO signal to calculate how much fuel to supply. It instead supplies a fixed amount of fuel based upon other parameters. The MerkMeter will display a stable, slightly rich reading normally in the 0.7 to 0.9 volt range. This will most often occur when cruising above 2950 rpm (XR4Ti PF2/PF3 calibration).

Wide-Open Throttle
At Wide Open Throttle (WOT) the ECU will also go into Open-Loop Mode. The MerkMeter will normally display a steady rich reading in the 0.7 to 0.9 range for the duration of the WOT event. If the MerkMeter drops into the 0.1-0.3 volt range at WOT, it is a good indication that insufficient fuel is being supplied to meet the engine demands.

Display Driver:  National Semiconductor LM3914N
Fuse Protection:  0.5A fuse
Polarity Protection:  50V silicon rectifier diode
Voltage Requirements:  6-15V DC
Operating Current:
       No LEDs on -  ~5mA
                               One LED on -  ~15mA
                               All LEDs on -   ~95mA maximum
Signal Input Current:  Less than 100nA

The Complete Turbo 2.3L EEC-IV Handbook by Allan Slocum
Ford Fuel Injection & Electronic Engine Control by Charles O. Probst
Oxygen Sensor Technical Data Sheets by Bosch
Oxygen Sensor Diagnosis Olympic Imported Parts Corporation
Oxygen Sensor Information by Rick Kirchoff
Understanding Oxygen Sensors by Dave Cappert (broken link @
What is an oxygen sensor?” from Bosch REPORTER: Written by Technicians for TechniciansOctober 1998

Throwback: About the MerkMeter

Since I have a gauge cluster with a MerkMeter and needed to understand what it was, how it worked and how to reinstall it, I had to go find information about it. I finally found information and had to pull this out of the WayBack Machine, I figured I'd post it here, so there's a live website for this content again.


MerkMetertm     Merkur Air/Fuel Ratio Gauge

  • Graphically displays the output of the existing oxygen sensor
  • Patent pending design fits in the stock instrument cluster...No additional gauge pod is required!
  • One year warranty
  • Fits in all model year XR4Tis and Scorpios
  • All wires and connectors needed for installation are included in the kit:
  • Detailed and illustrated printed instructions included
  • Installs with simple hand tools in less than one hour
  • Three color display permits monitoring information in the driver's peripheral vision 
  • 10 segment display is calibrated for .1 volt per segment with a 1 volt range
  • Built-in fuse protection
  • Built-in battery reversal protection
  • Display can be configured in Dot or Bar Modes
  • High impedance precision circuitry will not effect oxygen sensor output to the ECU
Price was $74.99 (USD) for members of the International Merkur Owners Network, the Hardcore List, the XR4Ti List, the Merkur Club of America or any of the other Merkur clubs or organizations listed on the Merkur Desktop.

Price for others was $89.99.

Throwback: MerkMeter FAQ

Since I have a gauge cluster with a MerkMeter and needed to understand what it was, how it worked and how to reinstall it, I had to go find information about it. I finally found information and had to pull this out of the WayBack Machine, I figured I'd post it here, so there's a live website for this content again.


MerkMetertm Frequently Asked Questions

Q: Can I connect the MerkMeter directly to the EGO sensor wire in the engine compartment?
Absolutely no reason at all.  At the beginning of Step Four of the instructions this is mentioned as an alternate connection. It does involve taking a wire through the firewall and making a splice under the hood.  The wire provided with the MerkMeter installation kit may not be long enough to reach.  If you splice near the EGO sensor, make sure the splice is well insulated and away from the turbo heat.  The wire insulation on the OE Ford EGO is Teflon and can stand up to the high heat in that part of the engine compartment.  Make sure any wire you use will be as durable.  The connection at the computer is much easier, IMHO. The ECU can be pulled down pretty easily and does not normally need to be disconnected from the wiring harness. This also has the advantage of putting the splice in the cockpit where it is less susceptible to adverse environmental effects.  However, the call is yours.

Q: I don't want the MerkMeter on all the time.  Is there a way I can install an On/Off switch?
Yes.  The easiest way to do this is to splice into the black ground wire attached to MerkMeter and insert the switch of your choice.  The splice should be made in the wire between the MerkMeter and where it is attached to the back of the instrument cluster.  Some people have put a spare fog light switch into the empty spot where the cruise control switch fits.  If this is not desired, it is possible to just mount the switch under the dash where it is accessible.

Q: I don't like the standard LED arrangement.  Can I rearrange them?
An adhesive is used to secure the LEDs in place and it is not recommended that you try to remove them. For a nominal charge, we can customize your MerkMeter with any LED scheme you prefer. 

Q: Why is Dot Mode recommended over Bar Mode?
It really just comes down to personal preference.  Many people I have talked to about this find that one color is easier to distinguish in their peripheral vision.  Also, some find the "Christmas Tree" effect of Bar Mode to be distracting.  Others like the pizzazz of all those lights flashing in Bar Mode.  The MerkMeter will draw more current in Bar Mode to illuminate the LEDs.  However, it  will never draw more than ~95mA.  In the final analysis, it just comes down to what you like.

Q: Does the MerkMeter give average readings of the air/fuel ratio over time?
In Instant Mode, which is the default operating mode, it gives precise and immediate readings of the voltage generated by the EGO.  It can be set into Dampened Mode prior to installation.  Dampened Mode will slow the rate of change of the display so that it reflects a rough moving average. There is no computation taking place to calculate this "average", but the time constant chosen for the damping circuit works pretty well in practice.  When the ECU runs in Closed-Loop mode at about 2500 rpm, the typical EGO output varies from about 0.1 volt to 0.7 volt and back again about three times per second.  The MerkMeter in Dampened Mode will show a steady illumination of 0.4 to 0.5 volt.  This is right around the 0.45 volt indication of the stoichiometric air/fuel mix of 14.7:1 that the ECU is attempting to average.  In practice I think it is generally more useful to keep it configured in Instant Mode since the transient events are usually what you are going to want to see.  When you stomp on the accelerator you want to see if there are periods where the mixture leans out briefly.  Dampened Mode will mask these fast, short duration events that might be important.  I put the Dampened Mode into the circuitry because it was relatively easy to do and some people might prefer to see an average.

Q: Is the MerkMeter reliable enough to use for performance tuning?
The gauge shows the voltage generated by the oxygen sensor in response to the air/fuel ratio in the exhaust gas.  It is very accurate as far as this goes.
Perhaps the real question being asked here is "Can you correlate the meter display with a precisely defined air/fuel ratio?".  The answer here is only going to be as good as your EGO.  An old EGO is not as accurate as a new one.  The operating temperature of the EGO has a great deal to do with its accuracy.  Bosch has published some numbers that correlate voltage generated with air/fuel for given operating parameters.  The standard EGO is designed to have maximum accuracy around 14.7:1 and does this job very well.  It is much less accurate at the top and bottom of its operating range.  If you want to tweak the fuel delivery to get from a 12.6:1 to a 12.5:1 air/fuel ratio at WOT, then a standard EGO and the MerkMeter are not the first choice.  But neither is any other measuring instrument I have seen costing under $1000.  For this kind of accuracy you need a calibrated, wide-range sensor with precisely known operating characteristics.  These kinds of sensors are intended to be used in conjunction with dynos in test/tuning setups and are not normally used in everyday operation.  
When I talk about the MerkMeter I try to equate it to a coolant temperature gauge.  The temperature gauge is there partly to inform you as to current status of the engine temperature, but also to let you see if there are changes over time. If the engine seems to be running hotter now that it was a few months ago with the same operating conditions, then that could indicated a problem developing.  It is the same with a runtime air/fuel meter.  If a vacuum leak develops or injectors are not firing, you will see the mixture lean out immediately.  If the EGO is getting old and lazy you will see Closed-Loop crossovers slow down from where they were months or weeks before.

Q: Why does the reading on my meter change when I turn on my headlights?
(Many thanks to Allan Slocum and his Idea Factory for finding the answer to this particular problem and to Brad Anesi for pointing out a simpler fix than what I had in mind. -JRW)

This is a common problem on many cars, but particularly so it seems with Merkurs.  This is undoubtedly due to poor electrical grounds.  In tracking down this problem, I have seen as much as 160 millivolts between a given ground and the battery negative terminal.  For lights and such, this does not usually cause any problems.  In the case of an air/fuel meter however, this can be significant.  If you realize that the meter is comparing the voltage from the EGO sensor to what it thinks is a good ground (ideally 0 volts), you can see that a 100 millivolt error will cause the meter to read one LED lower than it should.  I have had reports from MerkMeter users that they have seen this same problem with other makes of A/F meters if the ground is bad.  Also, a bad EGO ground to the EEC-IV can cause the ECU to get bad data from the EGO sensor. 
The ground on the XR4Ti instrument cluster is particularly bad.  Although it made for an easier installation, my choice to take the ground off the stud on the back of the cluster was a really bad idea.  If this ground is bad on your car, you will see the MerkMeter reading drop at least one LED when you turn on the panel lights full "on" using the dimmer.  On all kits shipped after February 1, 2001, I have included new instructions and a short jumper wire for connecting the meter ground.  For installations made before this time, the problem can be easily corrected by grounding the instrument cluster to the chassis ground screw directly behind the cluster.  (See figure at right).  Adding a simple jumper (18 AWG or larger) from the ground stud on the cluster to the chassis ground is all that is needed.  If you need more detailed instructions and/or the jumper wire please contact me.  This fix has the added benefit of improving the overall ground to your instrument cluster.
Another notorious spot is the ground screw right under the battery tray on the XR4Ti.  This is baked by the turbo heat and is especially susceptible to corrosion.  
Also check your "EGO Ground" wire.  This is an orange wire that connects Pin 49 on the ECU to a screw on the turbo compressor housing.  If this wire is missing, disconnected, broken, or corroded, the EGO may not be properly grounded.  Our cars really could use a four-wire EGO that would provide a direct ground as well as a heater element.

Q: Is there a better way to secure the meter in an XR4Ti than using the double-stick tape?
This issue only applies to the XR4Ti installation since the tape is not used in the Scorpio.  Over time the heat under the dash might cause the double-sided tape to lose its adhesive properties.  The solution is to install the meter in a manner similar to that used for the Scorpio.  This method is a little trickier for an XR4Ti since there is less room to fit the wire tie.  However, with a little care it can be done and will hold the meter very securely.
The white wire tie with the eyelet on one end can be used to hold the meter in position.  Thread the end of the tie through the empty hole at the back-right of the meter.  You want to orient the tie so that the end can be pulled up through its locking slot with the eyelet above the meter.  Remember that the component side of the meter faces down.  Place the tie end slightly into its locking slot.  At this time only feed the end far enough into the locking slot to hold it in place.  Place a screw through the eyelet and thread it a couple turns into the hole in the cluster case just above where the meter is installed.  You want to leave as much slack as possible so the meter can be pivoted up and into the slot.  (One of the screws holding the front cluster lens in place can be used if no other is available).  Carefully slide the meter into its slot with the component side down.  Now carefully tighten the tie by pulling the end through the locking slot.  You may have to adjust the tie as you tighten and feed the excess through the hole in the meter.  Slowly tighten the screw and remove the slack in the wire tie in stages until the meter is secure in its slot.  Be careful not to over-tighten the screw or tie as the meter board could crack or break if too much force is used.

Common Merkur issues and recommended fixes

Found this elsewhere on the Internet (on that classic DIY website hosting company angelfire of all places) but thought it was worth reposting since my custom domain name isn't going away any time soon, Blogger isn't going to go away any time soon, and neither am I. Well, I guess that's what we all think. Ha ha.

So, here it is, the common issues and common first things to try to resolve them on your Merkur XR4Ti.

Driveshaft torsional dampener or guibo
  • It is not a U-joint. It must be in perfect shape with no cracks. The driveshaft must have zero degrees runout when checked at the guibo or it will deteriorate quickly. 
Rear brake lights
  • The ground wire which is brown in the connectors will corrode and short out the adjacent connectors. Remove the bad ground wire in the light panel and solder a wire onto the light bulb holder that is directly connected to this ground wire. 
Valve cover gasket
  • Recommended: The Ranger gasket works well and is reinforced with steel so that if the top end is getting pressurized it will help to stop the oil from leaking out. 
  • Also works: Use the blue silicone rubber Fel Pro gasket to eliminate oil leaks onto the exhaust manifold.  
Leaking sunroof
  • Blow out the drain lines that connect to the pan in the roof. If this doesn't help then you need to fix either the drain hoses or the drain pan. 
Bad window switches
  • Take apart the switches and clean them or buy good used ones. 
No rear view mirror
  • Buy the correct Ford rear-view mirror attachment kit. 
Poor performance
  • Usually ignition parts. 
Yellowed headlights
  • Normal polish and refurbish. Polish the plastic lenses with a plastic polish. 
Broken hazard flasher
  • Only real option is to find a used one in good shape. 
Broken hatch lock
  • Find a good used one in good shape. 
Wetness in the car after it rains
  • Either fix the sunroof drain tubes or the tail light gaskets. 
Inconsistent idle
  • Clean the ENTIRE intake tract until all carbon is gone. Replace all the gaskets. Set the base timing, base idle, then the TPS. 
Heated seats don't work
  • Fix the small wire in the back of the seat. Both heaters are hooked together, If one doesn't work then the other won't work. 
Hard leather seats
  • Use a good saddle soap multiple times to restore the moisture into the leather. Maintain the leather regularly. Window tint will help stop the sun damage to the seats. 
Gauges don't work
  • Usually a cold solder on the daughterboard. This is located on the back of the instrument cluster. 
Oil blowing out of the engine
  • The Ford PCV valve is not adequate to hold the boost from entering the crankcase. Add a good one way valve in line with the stock valve to stop the boost from entering the crankcase. A brass brake booster valve will work well for this. Also the dipstick is not calibrated correctly. Put in a new filter and five quarts of oil. Run the engine for one minute and shut it off. Let the car sit for 30 minutes and check the oil level. Mark the correct level line on the dipstick with a file mark. 
The buzzer in the dash goes off whenever you step on the gas
  • This probably means that the Wastegate Actuator is bad. Cost: between $50-90 dollars. 
Front end shimmys at different speeds
  • Replace all the front end bushings and balance the wheels and tires as a start. 
Door rattles when it's closed
  • The track may be broken. Very common on the drivers side door. Weld the track back together or find a good used one. 
Bad radio reception
  • The wire that runs to the antenna in the rear decklid glass frequently breaks. Replace it. 
Automatic Transmission leaks
  • The factory cooler is way too small. Replace it with the biggest one you can afford and bypass the one in the radiator. Also the dipstick tube leaks where it goes into the trans. You can fix this by removing it and wrapping it with Teflon tape and reinstalling it.