Hits wall at 4000 rpm/limited performance - ref sensors?

j.c · **Posted:** Fri Aug 03, 2018 2:38 am

Could the AFM have been changed for the wrong type, according to Clarkes, there were 2 types, pre 85.5 and post 85.5, not sure which type you should have, I suppose you could measure the supply voltage
http://www.clarks-garage.com/shop-manual/elect-22.htm

mikseymono · **Posted:** Fri Aug 03, 2018 6:43 am

j.c wrote:

mikseymono wrote:

Have just found out the speed sensor female plug is intermittent. This is the plug that goes back to the DME (ECU) It is the wires just behind the plug....certain bending produces no tach bounce/start and another way starts straight away......probable my fault as I have pulled these apart 20 times or more in setting various sensor gap combos....

So, finally, a problem that I can solve....HOORAY.

So, what are the options please to repair this lead.....not much room or length in the lead to splice much.

Would this have an impact on my rev issue or am I being over optimistic?!

M

Yes, it definitely could have a bearing on your symptoms,
pull each individual wire until one or more stretch, pull on the ones that stretch until the insulation breaks, if it breaks right at the plug (most likely) the plug should be able to be dismantled unless it is molded (I'm on holiday and no Porkas in Crete that I can see) the best 2 options are, if you can dismantle the plug to each individual pin, do so, bend the tabs which crimps the bit of insulation left on the pin open, snip off the remains of wire, strip back 3mm of insulation off the wire going into the loom, place wire back in the pin, bend tabs back over wire leaving the exposed 3mm of wire resting on top of the original undisturbed crimp, solder the wire on to the connector, try to keep the amount of solder to a minimum as too much will not allow the re-assembly of the connector, re-assemble connector.
One potential problem is that the copper wire might be oxidised, if this is the case, if you have "Bakers" flux or similar, use it, if you don't you can scrap the copper wire thoroughly with a stanley blade or sandpaper.
The second way is to get a complete connector with wires attached and solder the connector (with wires) to the loom, try and used heatshrink to insulate solder joints, there is also liquid vinyl tape if space is tight

Thanks for this...was thinking of just exposing wires and cripping to the male plug then taping up.

Before I investigate are there three separate wires and therefore three connections to be made?

With my rev issue it mostly started before but couldn't get above 4000 rpm really....would a fraid wire have this impact even though it started and ran to an extent?!

Cheers,

M

j.c · **Posted:** Fri Aug 03, 2018 8:12 am

mikseymono wrote:

j.c wrote:

mikseymono wrote:

Have just found out the speed sensor female plug is intermittent. This is the plug that goes back to the DME (ECU) It is the wires just behind the plug....certain bending produces no tach bounce/start and another way starts straight away......probable my fault as I have pulled these apart 20 times or more in setting various sensor gap combos....

So, finally, a problem that I can solve....HOORAY.

So, what are the options please to repair this lead.....not much room or length in the lead to splice much.

Would this have an impact on my rev issue or am I being over optimistic?!

M

Yes, it definitely could have a bearing on your symptoms,
pull each individual wire until one or more stretch, pull on the ones that stretch until the insulation breaks, if it breaks right at the plug (most likely) the plug should be able to be dismantled unless it is molded (I'm on holiday and no Porkas in Crete that I can see) the best 2 options are, if you can dismantle the plug to each individual pin, do so, bend the tabs which crimps the bit of insulation left on the pin open, snip off the remains of wire, strip back 3mm of insulation off the wire going into the loom, place wire back in the pin, bend tabs back over wire leaving the exposed 3mm of wire resting on top of the original undisturbed crimp, solder the wire on to the connector, try to keep the amount of solder to a minimum as too much will not allow the re-assembly of the connector, re-assemble connector.
One potential problem is that the copper wire might be oxidised, if this is the case, if you have "Bakers" flux or similar, use it, if you don't you can scrap the copper wire thoroughly with a stanley blade or sandpaper.
The second way is to get a complete connector with wires attached and solder the connector (with wires) to the loom, try and used heatshrink to insulate solder joints, there is also liquid vinyl tape if space is tight

Thanks for this...was thinking of just exposing wires and cripping to the male plug then taping up.

Before I investigate are there three separate wires and therefore three connections to be made?

With my rev issue it mostly started before but couldn't get above 4000 rpm really....would a fraid wire have this impact even though it started and ran to an extent?!

Cheers,

M

According to this wiring diagram, (https://www.manualslib.com/manual/39253 ... 155#manual ) each sensor has 2 wires connected and shielding connected at the plug but not actually connected to the sensor,
As you have ruled out a lot of potential issues then you are left with possible causes and although it does seen strange that it would run fine the at 4k stop, you never know what a broken wire might do as in the transmission of high freq. pulses, interference induced due to broken shielding etc,
Did you check to make sure you've got the correct AFM for your DME (ECU)?

broady_6 · **Posted:** Fri Aug 03, 2018 9:20 am

Cam timing, cough cam timing

Waylander · **Posted:** Fri Aug 03, 2018 1:16 pm

the plugs are called Junior Timer Plugs or sometimes EV1 plugs

they are available for not much money from Brandshatch Performance

https://shopbhp.com/

I have replaced the Hall sensor plugs, Injector Plugs, Temp sensor Plug on my 968 with parts from here,

https://shopbhp.com/products/tyco-amp-3 ... -and-seals
https://shopbhp.com/products/amp-3-way- ... h-ev1-type

mikseymono · **Posted:** Fri Aug 03, 2018 2:17 pm

broady_6 wrote:

Cam timing, cough cam timing

as in check Cam timing?!

Will do over the weekend. Hoping for one tooth out at least.................

mikseymono · **Posted:** Fri Aug 03, 2018 2:21 pm

Waylander wrote:

the plugs are called Junior Timer Plugs or sometimes EV1 plugs

they are available for not much money from Brandshatch Performance

https://shopbhp.com/

I have replaced the Hall sensor plugs, Injector Plugs, Temp sensor Plug on my 968 with parts from here,

https://shopbhp.com/products/tyco-amp-3 ... -and-seals
https://shopbhp.com/products/amp-3-way- ... h-ev1-type

Thanks...these look good!

M

mikseymono · **Posted:** Sun Aug 05, 2018 1:00 pm

OK...

so checked timing. TDC marks were perfectly lined up on the cylinder and then checked under the bell housing and this was spot on to. Rotor arm is pointing to No.1 Cylinder.....looks all good to me. Have picture of top cylinder, see below.

Can we rule out the timing now?

broady_6 · **Posted:** Sun Aug 05, 2018 7:46 pm

TDC on the cylinder, is that something on the 924? My 944 has a small window in the top of the bell housing with a pointer and I then line up OT on the flywheel with that.

Bit of a sod if that is the answer though. Im a bit out of ideas other than what other folk have said, change your DME.

Come to think of it, the photo I showed you of the older style DME needs to have the older style AFM installed. (I have got both old and new)

If you have the sealed type DME and newer AFM then the engine does run a little smoother and with more power. But if you mix old DME and new AFM you will get running issues as the AFM gives a different signal. I cant remember the exact details, but there was a thread on here 4 or 5 years ago, which is why I bought a newer style DME and AFM to do some back to back tests.

So to sum up, the photo of the DME you showed was of a newer style, it could be you need the older type. Must be someone who can do you a loan if they have a spare?

Gryphon · **Posted:** Mon Aug 06, 2018 7:51 am

AFM wise, the older ones are designed for a 12V input and the output voltage is proportional to airflow, 0-12V. The newer ones are designed for a 5V input, and their output is proportional to the angle of the 'barn door'.

I think that a newer AFM on an old dme would report a lot less air than is actually passing until it's wide open - probably makes things run very lean. An older AFM on a new DME would report more air than actual. To graph it out, if the amount the door opened was along X, the output would be something like these two lines - curved for the old, linear for the new.

Found on another forum...
Old DME 944.618.111.01 goes with AFM 0.280.202.064
New DME 944.618.121.04 goes with AFM 0.280.202.028

http://www.clarks-garage.com/shop-manual/elect-22.htm

The high RPMs where you have problems are normally where the AFM is pretty much wide open so has little effect on the engine management... Both AFM's should give the same maximum voltage output at wide open so to I suspect this isn't the issue - but worth checking that your DME and AFM match!

mikseymono · **Posted:** Mon Aug 06, 2018 10:34 am

Now..I checked the balance belts as well...the top one was spot on but the bottom one was about 120 degrees off....it was spot on a couple of weeks ago......how has this moved?!

M

Waylander · **Posted:** Mon Aug 06, 2018 1:02 pm

mikseymono wrote:

Now..I checked the balance belts as well...the top one was spot on but the bottom one was about 120 degrees off....it was spot on a couple of weeks ago......how has this moved?!

M

belt too loose, idle wheels in wrong position

just guessing

broady_6 · **Posted:** Mon Aug 06, 2018 4:59 pm

I was just about to say the idles in the wrong place. ie too high up

mikseymono · **Posted:** Mon Aug 06, 2018 5:03 pm

yes...sounds about right...and maybe I was too loose with the belt...or its missing a tooth............currently got electrical gremlims at the moment having shortened the battery slightly whiclst trying to attach a ground to the back of the alternator..............deep joys....
M

broady_6 · **Posted:** Mon Aug 06, 2018 8:47 pm

A tip Jon Mitchell once gave me was, be very careful, belt covers off and slightly loosen the balance belt tensioner lock nut, just so its easy to undo with out slipping. now start the engine and hold the tesioner and undo the lock nut. tension the belt until it sounds like a washing machine on the fast spin, then back the tension off till the noise just goes away. Tighten the lock nut, turn the car off and torque up properly. Ive done this a dozen or more times now and it has never failed. you'll be surprised how slack the belt is, but with the idler set correctly ive never had bother.

Its easier done with the car jacked up and work from underneath, helps keep your sausages clear of the whizzy belts.

But for the love of science please be careful if you do try it.

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Hits wall at 4000 rpm/limited performance - ref sensors?

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