CRC
-
Posts
154 -
Joined
-
Last visited
Content Type
Profiles
Forums
Events
Store
Posts posted by CRC
-
-
Have you checked the operation of the B pillar microswitch? It's pretty easy to get to and, from memory, just requires a small 8 mm spanner to undo one awkward nut, then the cover pulls off. The B pillar micro switch switches the control voltage from the double relay unit "to earth" (NPN system in the control world), so it's pretty easy to test. The earth point is under the passenger's seat.
You're at the same point as I was .... I wasn't TOTALLY sure that it was the double relay module that was at fault, a second hand one would be at least 20 years old, so prone to the the same issues, and I wasn't prepared to shell out over £200 to find that there was nothing wrong with the module and that it was something else that I hadn't investigated enough.
In the end, I chickened out and kept it all in "Fail safe" (aka manual) mode.
Looking at the wiring diagream, I would have thought the the "clamshell switch" on the back shelf might have come into the roof wiring, but it doesn't seem to.
I hope the new double relay solves your problem.
-
I've had those codes popping up randomly on mine for the last 5 years or so .... never in the winter, only in the summer, and mine are cylinders 1,2 &3.
The way the system calculates the misfires is by timing the time taken for the crankshaft to get to a certain point and then deciding that it's taking too long, so it logs it as a misfire. When the cumulative misfire count gets above a certain number, it turns on the codes.
On my last two MOTs, the car didn't have the codes when it went in , but it came out with them afterwards, so my assumption is that as it's stationary and ticking over, with revving for the emmissions test, it's engine / engine compartment temperature that causes the codes for some reason. It sailed through the emissions test, therefore it couldn't have been actually misfiring .....
The wiring diagram shows that the coil packs on one side have all their ground wires connected to a common ground point on the engine, so I'd like to clean it up and remake it ..... but I just can't find the darn thing.
It's never been a problem ... the car runs sweet as a nut ...... just annoying to have to keep turning the codes off about twice a year perhaps.
Oh ... and I did replace both O2 sensors when I changed the cats, but it made no difference.
-
Got it ..... you just have to remove the [img] at the start and the [\img] of the link . Cheers
-
I've pasted the image link as described in the "how to" but it still won't show .....
[img]https://i.imgur.com/Wq6s5S1.png[/img]
-
Thankyou .... ummm...... how did you do it
One thing to notice is that the switches on the windscreen switch and the B pillar switch all actually "switch to ground". From memory, the B pillar switch is connected to a ground point under the passenger's seat (near the convenience module) which may be rusty as that tends to be the area that puddles can accumulate.
-
I did attempt to fault find my double relay unit, but those ICs are daunting and there's a lot more in there than just two relays unfortunately.
My windows had stopped dipping as well ... or would occasionally dip when they fely like it.
At that point, I gave up.
Could someone advise on how to get Imgur images to actually display in the post, rather than just show the links. Thanks
-
Eventually, I concluded that I had a problem with the double relay unit and as I'd checked everything else out, I just gave up and left the roof as a manual operation .... it might not be cool, but it is guaranteed to work every time.
I just didn't have the arm reach or strength to get those clips off .... but a friendly, ex-mechanic, now turned scaffolder solved the problem.
You're probably better off trying to lever the top of the clip up and over the spigot end with a flat blade screwdriver rather than trying to hook it and pull it off, as they're pretty tight. You can get new ones ...
-
Once you get the clips off, the hinge lever as shown can be pulled off the "barcoded arm" and it will just open by hand. There is no lock to the clamshell other than the "barcoded arm" pressing it down on the back shelf.
-
-
I always think it's quite telling that Porsche actually included a tool in the original tool kit to enable you to pop off the arm joints and convert the roof to manual operation in the event of the roof mechanism failing with the roof in the open position.
This at least means that you won't get wet if it fails in the open position.
Unfortunately, they didn't include a tool to enable you to pop off the speed clips when the roof mechanism fails in the closed position (as mine did), but at least you wouldn't get wet if that happened.
Quite an admission from Porsche really ....... we know that it's going to fail at some time, so don't blame us when it does .....
-
I agree with others. I'm pretty sure it was fitted for the American market and was designed to pump air into the exhaust when the engine was cold and running a very rich mixture to keep it going ..... "on full choke" as you might have said back in the day.
The theory was that the pumped air would combine with the unburnt hydrocarbons at this point to ensure that they were completely combusted and no "black smoke" would come out of the exhaust.
All our MOT emission tests are performed with the engine fully warm, so even if fitted, it wouldn't be operating.
A mate of mine had that system fitted to an old 1.8 turbo Passat and it drove him mad as the engine light would keep coming on, warning him of a fault on something that wasn't needed and would cost a small fortune to replace the pump on no doubt.
-
Another thing to take into account is that fact that the cross sectional area of a tube is a function of the SQUARE of the radius and hence the diameter( A = D x D x 3.142 / 4)
If you apply that equation to the 68 mm tube ( 6.8 cm) then A = 36.32 square centimetres, and for the 74 mm tube A will be 43.01 square centimetres.
Say the engine is sucking 1 litre of air per second (1,000 cc per second), then the velocity in the 68 mm tube will be 1,000 / 36.32 = 27.5 cm/sec.
In the 74 mm tube it will be 1000 / 43.01 = 23.25 cm/sec.
As the MAF sensor calculates the VELOCITY of the air going past it, if it measures 23.25 cm/sec and the 74 mm tube is fitted, it will calculate that only 844.4 ccs has entered the engine and won't get the fueling right.
To keep the fueling right with 74 mm tube, the engine map would have to be told that it now had a bigger throttle body so that it could calculate correctly ..... imho
-
I forgot to say that the ECU will also be smart enough to take into account the inlet air temperature and possibly the air pressure, because the temperature of the air affects the DENSITY of the air and the density multiplied by the volume flow will give the MASS FLOW of the air .... which is the value needed to work out the mass flow of the fuel to inject .... the density of which won't change much with temperature rise.
I have an old 1985 BMW K75 bike that is also fuel injected, and it uses a "swinging vane" in the air inlet which then rubs on a potentiometer to tell the ECU the air flow rate ..... obviously that's a very old system and the new MAF sensors that just measure the amount of cooling of the MAF heater element are very clever and a big improvement.
Strangely, I was watching an old Wheeler Dealers episode last night and Ant was working on a Carrera that someone had fitted a "go faster" high flow air filter which was pulling air from the engine compartment rather than outside the car. He correctly pointed out that air at 100 degrees from the engine compartment is a lot less dense than air at, say, 20 degrees from outside the car, meaning that less oxygen molecules are being sucked in for a given volume.
He said that that was the equivalent of running at an altitude of 6,000 ft ..... or 20% less power!!
Possibly the induction roar made it sound more powerful though .....
-
Sorry .... should have realised there were more pages on this thread ....
-
Maybe I'm missing something, but here goes ....
The MAF sensor works like this (internet)
Put simply, a MAF has two sensing wires. One is heated by an electrical current, the other is not. As air flows across the heated wire, it cools down. When the temperature difference between the two sensing wires changes, the MAF sensor automatically increases or decreases the current to the heated wire to compensate.
So, the amount of cooling of the MAF determines the VELOCITY of the air passing the MAF sensor.
But the ECU needs to calculate the VOLUME of air which is entering the engine so that it can increase or decrease the amount of the fuel that needs to be injected to try and attain the the perfect stoichiometric air fuel ratio.
The standard ECU will use the diameter (and hence the cross sectional area) of the throttle body multiplied by the air velocity (that it has calculated from the MAF cooling method) to calculate the VOLUME of air entering the engine and will adjust fuel amounts accordingly.
If the diameter of the new throttle body is now larger, the velocity of air passing the MAF will now be smaller for a given air volume flow, so the standard ECU (which thinks that the standard throttle body is still there) will calculate a lower air flow than before and will adjust the fuel accordingly.
Not sure how increasing the throttle body size can improve things without other adjustments ..... though I may be completely wrong.
-
I bought Febi discs and pads for the front a few years back and they were / are very good at around £60 all up as I recall.
Strangely, I couldn't find any Febi rear discs or pads and was browsing through the Autodoc website and noticed they were selling Stark rear discs at £9.16 each !!
I checked out Stark and found them to be a large German automotive parts manufacturer, so ordered up rear discs and Stark pads for around £30 as I recall, expecting them to be very poor, but they were "engineering works of art" when the arrived. Fitted fine and work well.
I accept that spending more money on brakes is probably an option if you plan spirited driving or track days etc., but for normal motoring there are some good deals out there.
Since that time, Stark components have increased quite dramtically in price, so maybe I just got lucky ....
-
FWIW, I leave mine unlocked (or the alarm has a mind of it's own) and then just open the drivers door, put the key in the ignition, start the car and drive away.
Because my roof has been converted to manual, I drop both windows a bit before stopping, close the roof manually and then hold down the lock button on the remote function (which now has woken up) to raise the windows fully up. I then unlock the car using the remote and open and then close the drivers door to make sure the car stays unlocked.
Life can be very complicated owning a Boxster ... simplicity is good.
-
I feel your frustration regarding the roof and the whole double relay issue.
Min was also stuck in the "roof up" position and eventually got it open by reaching through and removing the two spring clips on the clam shell ...... really not easy, but just about doable.
Shown below are some graphics of my attempt to solve the issue by taking out the double relay ( it's way more than just two relays in there as you can see.)
The wiring diagram was my attempt to fault find (98 2.5 Boxster), but in the end I gave up and became an advocate of the manual system .... which works perfectly every time, in all weather ..........
Why can I never seem to get Imgur image links to actually show as graphics in the post?
-
-
Surprised at that ..... I have a 98 2.5 and I've never had to depress the clutch to start it .....
-
Thanks, I'll take that on board and have a look with my Foxwell code reader to see. Certainly no engine management light on at the moment.
-
It would make sense for the ECU to have software that protects the engine in the event of an oil pressure failure, and I can't really explain the cars behaviour any other way. I think it would definitely have taken time and revolutions to get to a point where the pump had picked up oil and filled the filter housing and generated pressure.
Quite a good feature if that is the case.
-
The other day, I decided to replace the coil pack plastic tubes and O rings as they were leaking down onto the exhaust and causing an unpleasant hot oil smell after a run.
I hadn't started the car for a couple of weeks, and though I would normally take the car for a run before an oil change, the MOT had run out, so I figured that after a couple of weeks without starting, the oil would have drained down as much as it ever would, so after jacking the back end up, I decided to drain the oil at the same time, allowing it to fully drain while the coil pack tubes were being replaced.
All went well, refilled oil to correct levels and tried to start the car.
Normally, the car always starts on the first turn of the key, regardless of how long its been idle, but in this case there was no attempt to fire at all. After reasoning that it wasn't possible to get the wiring wrong on the coil packs, I carried on trying it but without success. Eventually, the car fired up on about the seventh attempt and ran fine and has been good ever since .... and also passed the MOT with no issues.
It did occur to me at the time that it was actually quite a good thing that it didn't fire immediately as cranking the starter those five or six times ensured that the oil light had gone off by the time it fired and that oil was present where it needed to be ...... which made me wonder if the ECU is smart enough to hold off the injection until it's seen oil pressure.
I've never heard of this and just wondered if anyone knew .....
-
On 9/30/2022 at 11:34 AM, Alan36 said:
Stripped the door down to fit new window and the lock barrel rod wasnt engaged with the locking mechanism (I might have changed the locking mechanism and not fitted correctly).
I did exactly the same when I repaired the door lock once, but luckily realised before the 5 days expired and went back in and fixed it.
Need a new roof relay Dagnab it!
in 986
Posted
Good stuff. Well done.
I know well that feeling of apprehension when you press the switch for the first time on what you know was a quite expensive gamble .....