Erratic Idle Problem Porsche 944 (Square Dash Model)

THE WHY

The words idle, problem, Porsche and 944 seem to appear more times together on any forum than any other niggle to do with the car. The reason they appear so frequently is that there are a number of situations and/or combination of situations that can cause the idle speed of your 944 to behave erratically as the following clip of my own car shows.




You will find a lot of posts talk about the cause being vacuum leaks or something known as the 'Idle Control Valve' or 'ICV' as it is often abbreviated (the Porsche parts catalogue calls it the 'Idle Speed Adjuster'). What is not often clear is that the ICV only appears on the Oval Dash models of the 944. The difference in configuration between the Square Dash and Oval Dash models can be seen in the two diagrams below.


Square Dash configuration

Part 9 - Auxiliary Air Regulator (944 606 103 00)
Part 16 - Electric Air Valve (944 606 215 00)

Oval Dash configuration

Part 18 - Idle Speed Adjuster (930 606 161 00) ... aka ICV

I have no idea why Porsche changed the design but if you are an oval dash owner you may want to check out this post if you want to test your ICV. If you're a square dash owner then read on.


THE HOW TO


(Amateur mechanic job time approx. 30 mins)


Fortunately the fix for my 1984 square dash model didn't require checking for vacuum leaks. The problem was actually dirty electrical contacts on the Auxiliary Air Regulator and Water Temperature sensor on the radiator. This occurs due to the constant heating and moisture that the engine bay is subjected to.


Auxiliary Air Regulator

Water Temperature Sensor (located top corner of radiator on the air box side) - Top view

Water Temperature Sensor (located top corner of radiator on the air box side) - Bottom view

To clean the contacts simply pull the connectors off their plugs, spray the contacts with some electrical switch cleaner and before reattaching apply some switch grease to the contacts to prevent moisture from corroding them in future.

How to remove and replace OPRV (Oil Pressure Relief Valve) on a Porsche 944

THE WHY

Since purchasing my 944 I'd always been aware of a slight fluid leak, but since none of the fluids (engine oil, power steering, water, brake fluid) seemed to be disappearing at any great rate and there were other more pressing issues I decided to put investigating it on the back burner.

Having now decided to tackle the problem I firstly discovered I actually had two fluid leaks, one from a power steering hose going from the reservoir to the pump which I dealt with right away by replacing the hose. The second however seemed to be coming from the engine but it was difficult to tell where from due to the oily grime all over the bottom of the engine and aluminium floor tray. So now the rest of the story follows how I went about identifying the cause of the oil leak and how the OPRV (Oil Pressure Relief Valve) fits into the story.

THE TASK

You'll need the following:

Karcher or other brand Water Pressure Washer
Gunk Spray Engine Degreaser
10mm socket
17mm socket (if you have the old style OPRV)
24mm socket (if you have the new style OPRV)
Ratchet socket wrench
Long socket wrench extension bar
2 x Axle Stands
Trolley Jack
Torque Wrench
Plenty of tissue or old rag

THE HOW TO

(Amateur mechanic job time: approx. 30mins - 1 hour)

Start by jacking up the front of the car and support on the first or ideally second stage of the axle stands.

Remove the seven 10mm bolts that secure the aluminium under-tray to the bottom of the car and remove the under-tray.

The picture above was taken after I'd degreased the underside of the car. I tried various methods of scrubbing, wiping and pressure steam cleaning but by far the best was pressure washing.

The best method I found was to let the engine run for 10 mins to warm it up, then spray Gunk Engine Degreaser over all the oily blackness you may have (Do not spray it near the belts or any bearings). Let the degreaser have 5-10 mins to take effect and then simply blast off with the water pressure washer (There's hardly any electrics on the bottom of the car but avoid them at all costs). Spraying the washer in quick bursts is the best method. Repeat as necessary and wipe down anything that looks oily, not forgetting to also clean all the oil of the under-tray too.

Now you have a clean canvas to identify your leak. Unless the leak is bad you probably won't be able to see it straight away, so this is where some patience comes in. Either leave it jacked up over night and see if you can identify a drip in the morning or re-attach the under-tray and do a few miles to put the engine under load which usually force the oil out of the place it is escaping. When you jack the car up again, you'll be able to see the area where the oil is dropping on the under-tray and then just trace it back up into the engine well.

The oil on mine was falling onto the left hand-side of the under-tray so I started to investigate in this area as shown my the orange arrow below.

This is where I found a drip coming off the end of the OPRV (Oil Pressure Relief Valve) nut.

Here's a couple of photos to show you what to look for (The nut has been removed but you can see the port it screws into)

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THE OPRV - here's where it gets complicated:

83-86 models will have a 17mm or 24mm nut
87 models onwards will and should always be 24mm.

Picture shows the difference between the 24mm on the left, 17mm on the right.

The 17mm nut may also look like this one below as well (photo taken from another Porsche source)

If you have the 17mm nut then you have the OLD discontinued OPRV, which can look like one of the two versions shown below (Difference is in the style of the nut and and piston). There are 4 pieces to each version, the nut, aluminium washer, spring and piston.

From the 87 model onwards a new OPRV was produced along with a retro-fit upgrade for people with the old style valve.

Here's the NEW retro-fit valve (944 107 035 11) for 83-86 models

And here's the one (944 107 035 02) for 87 models onwards

 And here they are side by side, 83-86 on left, 87 on right. (Main differences are in overall in length and the taper on the thread).

Both these newer style valves are serviceable to a degree in that you can replace the external and internal O-rings using this procedure below which was posted by a kind chap on the PelicanParts forums. Note valve type A requires two different size O-rings for the internal and external, whereas type B uses the same size O-ring for the internal and external.

The photo below shows what one of the newer OPRV's looks like when you take it apart. Note the aluminium sealing ring far left, damaged black internal O-ring in the middle and what should be a thicker green O-ring at the end (also damaged). If you need to replace the entire valve they aren't cheap either, £250 from Porsche.

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OPRV removal

Take a 17mm or 24 mm and socket extension bar that should be long enough to enable you to ratchet it from inside the wheel arch.

Once I had it removed I ended up with this

Notice the small nut that was inside the piston that some previous enterprising owner/mechanic had used as a space packer. I also found the spring to be 3-4 coils shorter than it should be, so who even knows what vehicle it was from. So not only did I have a leak from ORPV, I now had to replace the OPRV and at £250 that's quite a hit.

So here we are the OLD alongside the NEW

Installing the new OPRV is the reverse of removal, making sure you use a new aluminium sealing ring and lightly oil the o-ring and length of the valve to aid it's insertion. You should then use a Torque wrench to tighten to 45Nm.

Finally re-install the under-tray, run the car making sure the oil pressure gauge doesn't exhibit any strange behaviour and you're done...........well almost.

After doing all this I still found I had more oil leak coming from the same area, it now looks likely it's the gaskets for the Oil Cooler that the OPRV screws into. This looks a bit of an ugly job and not having the time to do it I'm going to get a mechanic to sort it out. For anyone that wants a go here's the procedure and here's another.

Finally here's the Porsche bulletin that goes into a few pages of detail on the OPRV. (Click the pictures for larger versions)

How to repair heater control valve on a Porsche 944 (Square Dash Model)

THE WHY?

One of the good things about the 944 is that it doesn't take long for the engine to warm up, which is great in the winter when you need to de-mist the inside of the windscreen and heat the passenger compartment. However it's not so good in the summer if like mine your heater is always giving out hot air even when the heater slider is set as far over to the left handside (the cold setting) as possible. This is caused by usually one of two possible problems. Either the hot/cold slider has a broken cable or the heater control valve (HCV) is faulty. It is usually the heater control valve (HCV).

THE TASK

It is important to note here that the HCV and heater mechanism are completely different on the square dash 944 model to the oval dash 944 model. Oval dash owners should look here and here as this guide is only for square dash owners.

This job is relatively simple (if a little fiddly) and should only take an hour or two.

You will need the following:

Long & small flat bladed screwdrivers
Long-nose pliers
Heater Control Valve (approx £20 from Porsche main dealer)

THE HOW TO

(Amateur mechanic Job Time approx: 1-2 hours)

Firstly it's important to know what the HCV actually does. The HCV is basically a tap that allows hot water from the engine to enter the heater matrix. When you set your heater to hot the tap opens and lets hot water into the matrix and when you set it to cold the tap closes stops the hot water entering the heater matrix.

It's also important to understand how the heater controls work on a square dash 944 as I've seen alot of confusion over this on some forums. There are 4 controls for the heater. This is what they do:

Upper left slider controls the direction of heat (footwell & centre)
Upper right slider controls the direction of heat (centre & windscreen)
Lower slider controls the hot or cold setting
Dial to the left of the sliders controls the fan speed (Off & speeds 1,2,3)


To begin with it's important to make sure the cable that goes from the hot/cold slider to the HCV is not the fault. Start with the lower hot/cold slider all the way over to the cold setting as shown below.


Now open the bonnet and locate the heater control valve which sits tucked down at the back of the engine smack bang in the centre. Below is a picture of the heater control valve.


Because the heater slider is set to cold the heater control valve should have its white arm all the way over to the left hand side (as shown below). You can even see the cable extended.


Now go back inside the car and move the hot/cold slider all the way towards the hot setting. Go back and look at the HCV and you will now see the white arm has moved all the way over to the right (as shown below).


If the white arm of the HCV is not moving then your problem is with the cable. Either the cable has become disconnected at the HCV end or at the hot/cold slider end. Or the cable has broken in the middle somewhere. If the arm is moving you now know that it is very likely that the HCV is the fault.

To remove the HCV you will first need to remove a small metal clip that locks the black outer of cable to the HCV. Do this with your fingers or a pair of long nose pliers. DO NOT LOSE THE CLIP otherwise the cable will not be able to work the HCV. Now unhook the inner cable from the small hole at the end of the white arm on the HCV. Next you will need to undo the 2 hose clips that help secure the 2 hoses to either side of the HCV. Once this is done twist and wriggle the HCV loose from the hoses. Do not be alarmed if water comes out of either hose whilst doing this, just make sure you don't allow the lower of the two hoses to hang down once you have removed the HCV as water will go all over your clutch, just wedge it so that it's upright.

Below is an image of my new HCV (left) against the old HCV (right). Note the washer in the middle that appears to have come loose inside in the old HCV.


You are now ready to install your new HCV. Installation is the reverse of removal. By far the hardest and most important part is re-attaching the metal clip around the black outer of the cable, it took me several attempts and you might be advised to familiarise yourself with how the clip works with the HCV before you attach the hoses to the new one.

One last important thing is that you may or may not have to top up your coolant level as some will be lost when you removed the HCV.