John Speake

1.8v is fine. Look elsewhere

derporsche928

John, yep, my other known good MAF checked 1.8v also, but thanks for affirmation to move on....
David, I'll probably swap LH Brain tomorrow after I check a few more things.
Garth, the 12.4v was with the motor off,.... haven't checked running, but will.... Also, LH test point 21 makes reference to the alternator as a source of the type of problems I'm experiencing, and only gives diagnosis procedure of removing belt. I'm checking other things first, but that's another on my list. Your reference to the hall sensor is something I was considering tonight at work, and I need to check it out also..... Should get a lot more checked-out Friday when I have a full day....
Sometimes it's hard to jump quickly and clearly in and out of troubleshooting, because it takes my pea brain a little bit to re-orient itself to the task at hand....
To recap, I don't think it's false air,... This problem started before intake removal, and had good vacuum before and it passed the inner-tube on MAF air-leak test, I'll check again though to be sure.....
MAF, and Temp Sensor 2 have been eliminated as causes.
Ignition wiring, dist. caps, rotors, coils have spec'd out okay.
Ignition Modules have been ruled out.
Almost through with LH diagnostics test points, other than what requires an oscilloscope, and there are a couple of those items which are potential causes....... One being the Hall Sender, which is on the hit list........ Then I'm moving on the the EZK Test Points........
Ernest, Yes, I am hoping for restoration of bwaaah and vrooom post soon.....
Thanks again fellas,
Greg

John Speake

Have you confirmed that all injectors are firing and all plugs have spark ?

Hall sensor/knock sensor problems should not affect idle, that you report....

Shorts on injector connectors are very common.

derporsche928

Well, some progress, but the car is running worse than ever......
While I was replacing plug wires and fitting new plugs, I decided to go ahead and re-tension the timing belt, and bleed the tensioner, so I lost a little time yesterday, but found a pretty poor connection with the hall sensor and corrected it, and buttoned everything back up. I went to start it today, and, as I said, now the car won't hardly start without gas and a little prodding..... It feels like it's running on only 4 cylinders, and this was confirmed by finally kicking out a fault 31 indicating injection circuit shut down, along with the corresponding red LED light. In troubleshooting the cause, I found no ground at the ignition circuit control relay pin-out AL.
Looking at the wiring diagram, AL goes to pin 6 of the cooling element, which I am assuming is the finned box on the right front in front of the radiator. It looks like it's also tied in with the LH pin 28, and the manual calls for a continuity check from AL to LH 28, and I do have continuity between them.
Looking further at the cooling element, it looks like pin 1 should go to ground, but it does not.
(I also hooked up a spare cooling element, and it does not give me path to ground from AL either....
So, to sum up, I have no path from AL to ground, but do have it from AL to LH 28.
I checked the wire from from AL to pin 6 of the the cooling element and have nothing, as if the wire is broken. Is there a fuse or another connection point I'm missing between AL and pin 6 ?
I'm stuck again, and now am wondering if the fans failure to shut down is related. (Frame 1 concern)
The troubleshooting continues...... Trying to trace this wire down with the wiring diagrams, but I'm certainly no genius when it comes to the inner workings of each of the separate components, so I may be missing something here......
Best,
Greg

Bill Ball

The ignition montoring relay is supposed to have delay before it trips. Is the car running poorly right on start-up? I only ask because I want to make sure it's not just a problem with the monitoring system throwing a false alarm and shutting off half the injectors. If the car runs poorly immediately on start-up, then that's not it and jumpering the relay plug won't help. From you AL readings it sounds like another issue (however, note: AL only grounds with the ignition on), but I need to study the wiring diagrams, and even then I'd be guessing. John should be checking in tonight.

worf928

Give us a little more detail here. What did you find with regard to the HS connection? Your symptoms track those of one of Doc Mohr's cars. It turned out to be the Hall sensor.

EDIT: did you swap brains yet?

Herman K

Changing out the control unit part # 928 618 421 00
Pet Main group 1 Sub group 05 Illustration 105-06 item # 7
solved all the problem - Search my past post and you'll find the relevant experience.

Good luck

1994 GTS 5 spd

AO

I'd double check your wires and coil connection to make sure you didn't do something stupid when you did the belt re-tentension. I think if the coil were disconnected it would trip the ignition monitoring relay.

daveo90s4

Following on from Andrew's post, the Porsche service bulletin that discusses the ignition monitoring circuit specifically draws attention to the LH coil high tension lead, and provides a superseded part number. It also says how to test the ignition monitoring system. I have a copy of that bulletinn courtesy of Dave Roberts & Wally Plumley. If you think that could be the problem and you haven't got a copy of that bulletin then I can easily post here if required. Let me know.

Regards

derporsche928

Hello,
Bill, regarding your question, (frame 20) It started poorly and ran horribly right on start -up, as if it was down some cylinders, but the red LED didn't light up until after 15 or 20 seconds, so you may be on to something.....
FWIW, from what I see, the AL is supposed to be grounded with the ignition in the off position....
David, yep regarding your question, (frame 21) I'm wondering the same thing about the Hall Sensor, as before, it started right-up and idled (albiet, with issues)..... Regarding the HS repair, I went to unplug it to check out the connection, and the HS plastic around the pins came out with the female wiring harness connector, so I used some industrial glue and put it back over the HS pins..... What a PITA to get to this thing...... I did have one concern, as I couldn't really tell which way the broken piece went back over the pins, and depending on how it was put back, it could affect how it was hooked back-up, as it has the key for proper connector orientation on it. I looked at the wiring diagrams to confirm this by looking at the wire colors of each connector, (red wire HS to red/white connector wire --- I even confirmed it the EZK pin 5 connector) but now I'm wondering if, in spite of my efforts to ensure correct connection, I got it wrong, or perhaps finished-off a flaky HS.....
No, I haven't swapped brains yet...... Guess I'm a little skeptical (or wishful thinking) that it's the problem, when I'm not getting correct signals elsewhere....
I believe I'm going to re-investigate the HS tomorrow.
Herman, thanks for your input, (frame 22) I was thinking this was the Cooling Element, (see my post on frame 19) but this is called Output Final Stage in the parts catalog.
Was I looking at the right thing? I tried hooking up a spare when I was troubleshooting to compare readings, but did not think to try starting it with it hooked up. I'll look up your past post, and I'll try this tomorrow.....
Andrew, yep, (in reference to frame 23) this is the first thing (along with the HS) I though of, and I double checked the coils and plug wiring, and it's all correct. I had bought a spark jump tester, and was going to check each of them, along with pulling each injector one at a time today to confirm them per Johns advice, (frame 18) but then I had this nearly no-start condition and obvious 4cyl. run issue, so I never got that far...... Tomorrow's a new day, and I feel like I'm on the verge of a discovery....... One things for sure, I'm going to invest in an oscilloscope, as there are too many things that can't be checked properly without one......
Thanks again fellas,
Best,
Greg

Bill Ball

I'm with the other guys. Since the ignition monitoring system started to trip right after your plug/wire change and the car is running much worse, you need to look at the coil and plug wires. In other words, this could be giving you a legitimate signal because as little as one of the plugs near one of the exhaust temp sensors is not firing. Bad plug wire, bad plug, bad coil wire. It's just that with all your sophisticated testing, I thought you had already ruled that out before you got out the ohm meter.

So, pull each plug one at a time and ground the tip against the block/head and see if you get spark at each one. Even after the monitoring system trips, the plugs still should be getting spark, as the system kills the injectors.

derporsche928

Dave,
Thanks for the help....
Are you referring to the coil to dist cap wire?
Yes, if you could post this bulletin, I'd appreciate it.....
Or, if it's easier you can send it to schickelg@bellsouth.net
BTW, if any one would care to discuss this problem further, my number is 502-863-5144
Best,
Greg

Bill Ball

Test the plugs first. If they are all firing, then pursue testing the ignition monitoring system or simply bypass it temporarily by connecting the relay's plug leads 1 to 3 to 5. That will temporarily eliminate it as an issue and allow you to see where you are.

derporsche928

Thanks Bill, I'll try that tomorrow.....
I definitely have spark at each plug.....Checked it yesterday and today again....
If this works, then I may need further guidance on monitoring system itself....
Best, Greg
PS.... Those are some bad-*** burn-out's

derporsche928

Bill,
I don't recall the monitoring system relay having any spade connectors labeled 1, 3, 5.....
Is this how they're marked on the plug itself, and if so, are you saying to connect all three of these together?
Thanks,
Greg