Andre Hedrick

I had a random miss on my '81 and after it was traced to a loose connection to the #1 injector, I replaced all connectors and cleaned the contacts on each one. This yielded 20+ feet in first and 4+ feet in second w/ LSD on a 185K miles on my little 4.5L. The meats on the back on 245x50x16 w/ AA traction.

Before you make things go fast, make sure you can stop please.

Brett928S2

Hi

Well ...when I hit the Nitrous switch...my hp is approaching 500 and my kickdown switch is normally ON..........my autobox has done 126,000 miles...

I am constantly amazed at how well Porsche built our cars and particularly the Autoboxes...if I had to guess....I think they were planning much more hp to go through that box...600 possibly ....

All the best Brett

PORSCHE 928 S2 AUTO V8 4.7 LTR 1986 IRIS METALLIC BLUE WITH X-PIPES ,RMB ,PROMAX CHIPS, KICKDOWN SWITCH.K&N.NITROUS KIT 150 HP.
PCGB UK 928 FORUM MODERATOR - Email managingdirector@pchealthcare.co.uk

blown 87

On the mass air flow sensors (not AFC) has any one had any luck cleaning the wire?
It is rather high $$ to replace this part if you do not have to.
We had a 850 Volvo in the shop a few months back, it ran fine, no codes, no misfire, good compression, etc, it just felt low on power compared to the rest of them I have driven.
After checking every thing relating to fuel I took a chance on a new mass meter, the owner said that it had more power than it did when it was new.
That truly is one item that can not be tested with normal shop stuff to find out if it is right.
I guess that means that is one more thing I need to change when i do the manifold and cam covers.

Brett928S2

[QUOTE=blown 87]On the mass air flow sensors (not AFC) has any one had any luck cleaning the wire?
QUOTE]

Hi

Isnt it self cleaning ?? I think John Speake told me it cleans itself if you have been over 2000 revs and come back to tickover....I think.....

Having said that....the difference between one I "THOUGHT" was working fine and Johns new one was fairly amazing lol

All the best Brett

PORSCHE 928 S2 AUTO V8 4.7 LTR 1986 IRIS METALLIC BLUE WITH X-PIPES ,RMB ,PROMAX CHIPS, KICKDOWN SWITCH.K&N.NITROUS KIT 150 HP.
PCGB UK 928 FORUM MODERATOR - Email managingdirector@pchealthcare.co.uk

worf928

Yup.

There is a 'burn-off' cycle that occurs when you shut off the motor after the motor has run at certain conditions (I don't remember what they are off hand, but it's something like over a certain RPM after engine warm, etc.) The burn-off cycle heats the wire to IIRC 1000+ degrees F.

AFAIK It is this heat cycling that eventually kills the wire. After being heated to 1000 degrees and cooled to 50 degrees a couple of times per week for a few years, that teensy wire gets tired and its properties get non-linear. I hear that newer Mass-Air sensors use a film rather than a wire and that the film's degradation properties are worse than the wire. (I dunno about that but I know that I'm putting a new MAS in my Audis every 50k miles. )

worf928

Maybe the better question is "has anyone had the ***** to try?"

Normy

Heinrich- this thread is wisdom that all owners here ought to read. Listen, I have been from one end of my engine to the other trying to figure out why I had a high-throttle miss, and eventually I found not one, but several small problems that added up to a serious performance deficit.

I discovered one recently: The engine wiring loom is on its last legs, most specifically the MAF connector. 21 years of heat are taking their toll. I can just imagine the hassle that would have resulted from someone buying this car before me and trying to supercharge it when it wasn't running right to begin with!

It's all in the details, IMHO.

N!

Normy

One thing I learned on here regarding the MAF is to NOT use a K&N filter. Apparently, the oil from the filter eventually gets on the wire and coats it, causing erroneous readings. My wire was black with this crap, and the adjustment pot would just spin in circles, essentially doing nothing. New MAF from Speake = big improvement.

N!

heinrich

Normy yes, very true. That MAF connector is often showing open wires. I hadn't thought about the wiring harness.

heinrich

Did it. Wasted one. Guess my big brass ones cost me some $$

worf928

I guess I should've asked: "Has anyone other than Heinrich had the ***** to clean one"

What happened when you tried? Busted wire?

the flyin' scotsman

So if all the routine maintenance (plugs, wires, filters, oils, rotors,caps) has been done what we're talking about is taking it to the next level.

Without a 'spanner' is there another method of testing the hall and knock sensors?

ew928

Twang.
At least Heinrich didn't try and solder the busted thinner than hair wire back together.

Mine's got a nice K&N protective coating.
Be doing the MAF refurb real real soon.

Ernest (NYC)
K&N made a satisfying clang when it hit the dumpster.

worf928

I 'fixed' a warm start problem a week ago by disconnecting, cleaning and reconnecting the Temp II sensor. (In between I tested the resistances of course - and they were in-spec.) Now maybe I didn't really 'fix' the problem - but prior the problem occurred all the time and since it has not (so I'm told.)

All those connectors - especially the older nearly-naked spade connectors - can add up to hard-to-pin-down intermittent phase-of-the-moon glitches. A little oxidation here and a little corrosion there and pretty soon the computer doesn't know what the hell the sensor is trying to say to it...

Shredded impulse, knock sensor, and hall sensor connectors. Connector boots pulled back to reveal the pins and not pulled back over. Connectors not put back into their retention brackets. Front main harness cut in effing half and butt-spliced back together during a t-belt job because the lazy fookin' mOEron of a technician couldn't be bothered to unroute the harness. I've got a pet peeve harness list that goes on and on and on...

worf928

Theoretically there is an adaptor for those three-pin connectors so that you can hook an o-scope to them while the lump is turning. On a practical level if those sensors are more than about 10 years old when you disconnect them the sensor-side of the connector crumbles. All four have a bracket. Tech's seem to love to leave the connectors out of the bracket. When those connectors are not put back into their brackets they are subject to harsher vibration and impacts and degrade faster.

I always know that a no-start diagnosis has been performed on a 928 when I see that the impulse sensor connector is not in its bracket.

Here's my three-pin sensor methodology:

1) You will have to replace breather hoses under the intake. When you do , replace the knock sensors. (Chances are you will find that they are baked well-done in a coolant and oil gravy anyway from a leaky cross-over o-ring and/or filler neck gasket.)

2) When the passenger side cam cover comes off for powder coating or gasket replacement replace the hall sensor.

3) If the impulse sender is in its bracket don't mess with it. (Unless the supercharger kit you are installing requires that it be relocated or otherwise touched in which case you'd better have a new sensor handy. (Ask Olsen about that... ) )

The sensors are short money in the general scope of things. They'll add 10% to the parts bill for an intake refurb or an under/over cam cover refurb. That's when they are easy to get to. (Impulse sender is easy to get to in any case.) After 15+ years and 100k miles I think those sensors deserve to be retired.

AND since they are difficult to diagnose without a Hammer (or Spanner) or almost impossible to diagnose (on pre-89s) you will drive yourself nutso when they fail. I did - find my thread from a few years ago on "Powerless GT"

EDIT: The knock sensor and hall sensor failure modes are the hair-pullers unless you have a Hammer and your car has the diag connector. The impluse sender failure mode is pretty simple: no spark, no fuel, and no start.