Advice needed on what was a "No start"
02-06-2012, 08:46 PM
#46
Team Owner
The MAF hot wire test is,
turn the key to the run position wait for 30 seconds,
then turn the key off,
look at the MAF you should see the wire glow for about 3 seconds ,
you can remove the MAF from the boot and leave it connected so it will be easier to see if the wire is glowing.
as previously mentioned you should replace the temp 2 harness connector now.
the 2 dampers and the one FPR should not lose any vacuum while you have the vacuum tester on it.
the easier test is to remove the vacuum line for each one and smell them after the engine has reached running temperature, any of these leaking would result in a hard start and thus holding the pedal to the floor. while cranking.
While you doing these tests get a battery jumper cable hooked up to the negative terminal and connect it to one of the shock tower nuts leave this connected this will eliminate the ground strap as an issue.
My guess is your MAF is ready for a rebuild and it might be a good idea to swap out the O2 sensor.
replacement and refurbishment of these parts should be done now as well.
NOTE the MAF and O2 sensor are probably causing the running issues your now having concentrate on them first.
turn the key to the run position wait for 30 seconds,
then turn the key off,
look at the MAF you should see the wire glow for about 3 seconds ,
you can remove the MAF from the boot and leave it connected so it will be easier to see if the wire is glowing.
as previously mentioned you should replace the temp 2 harness connector now.
the 2 dampers and the one FPR should not lose any vacuum while you have the vacuum tester on it.
the easier test is to remove the vacuum line for each one and smell them after the engine has reached running temperature, any of these leaking would result in a hard start and thus holding the pedal to the floor. while cranking.
While you doing these tests get a battery jumper cable hooked up to the negative terminal and connect it to one of the shock tower nuts leave this connected this will eliminate the ground strap as an issue.
My guess is your MAF is ready for a rebuild and it might be a good idea to swap out the O2 sensor.
replacement and refurbishment of these parts should be done now as well.
NOTE the MAF and O2 sensor are probably causing the running issues your now having concentrate on them first.
02-06-2012, 09:11 PM
#47
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Thanks, Mrmerlin. No glowing wire after repeating the test three times. Does that mean the MAF is no longer functioning????
I've not smelled any trace fuel on any of the vacuum connectors. I no longer consider the ground strap to be any part of this as I've replaced the ground at the battery and the one from the engine to the frame/car body.
O2 has been replaced as well.
I'm leaning towards a MAF or MAF + LH rebuild. Hoping to find a MAF & LH to borrow locally.
Thanks for your thoughts. Hopefully others have ideas to share, too.
I've not smelled any trace fuel on any of the vacuum connectors. I no longer consider the ground strap to be any part of this as I've replaced the ground at the battery and the one from the engine to the frame/car body.
O2 has been replaced as well.
I'm leaning towards a MAF or MAF + LH rebuild. Hoping to find a MAF & LH to borrow locally.
Thanks for your thoughts. Hopefully others have ideas to share, too.
02-07-2012, 12:02 AM
#48
Team Owner
send the MAF off for a rebuild also replace the Temp 2 sensor connector ,
and while your at it toss in a temp 2 sensor.
Dont worry about the LH for now,
get a good MAF and then go from there
and while your at it toss in a temp 2 sensor.
Dont worry about the LH for now,
get a good MAF and then go from there
02-07-2012, 06:25 AM
#50
Rennlist Member
OK, no leaks from dampers or FPR, apparently. The readings you get from the MAF show it is basically working, but it would have to tested on a calibrated flow jig to check fully. The MAF only has to be a few % out of spec and the engine will run badly.
John - no hot wire after turning on ignition.
I did as you prescribed and I capped the vacuum lines to the dampers and FPR, no trace of fuel from running on any of the open ports. I further tested by restoring the vacuum connections and then using my mightvac to pull a vacuum on each of the FPR and dampers individually. No trace of fuel and no smell of fuel.
More testing....
I decided to do the following tests from the WSM:
Test Point 5 - Air Mass Sensor
a) Power Supply - I connected volt meter to the plug terminals 2 and 4 at the MAF - voltage was 11.65v
I then connected volt meter to the plug terminals 17 and 21 on the LH Control Unit plug - voltage was 11.65v
b) Checking Resistance of hotwire circuit at the MAF
I measured a resistance between terminals 3 and 5 with the ohmmeter and read a value of 5.1 (normal is 3.6 - 4.1) Is this an issue???
c) Checking the hot wire signal
Connected plug to the MAF, Took out the LH Relay (XXV) and bridged terminals 87 and 30. Connected terminals 6 and 7 and read correct voltage of 1.6v
Couldn't blow on hot wire to read difference in voltage reading but a couple of times when wind blew, voltage went from 1.6 to about 1.7 or 1.9.
Not sure where to go from here.
I did as you prescribed and I capped the vacuum lines to the dampers and FPR, no trace of fuel from running on any of the open ports. I further tested by restoring the vacuum connections and then using my mightvac to pull a vacuum on each of the FPR and dampers individually. No trace of fuel and no smell of fuel.
More testing....
I decided to do the following tests from the WSM:
Test Point 5 - Air Mass Sensor
a) Power Supply - I connected volt meter to the plug terminals 2 and 4 at the MAF - voltage was 11.65v
I then connected volt meter to the plug terminals 17 and 21 on the LH Control Unit plug - voltage was 11.65v
b) Checking Resistance of hotwire circuit at the MAF
I measured a resistance between terminals 3 and 5 with the ohmmeter and read a value of 5.1 (normal is 3.6 - 4.1) Is this an issue???
c) Checking the hot wire signal
Connected plug to the MAF, Took out the LH Relay (XXV) and bridged terminals 87 and 30. Connected terminals 6 and 7 and read correct voltage of 1.6v
Couldn't blow on hot wire to read difference in voltage reading but a couple of times when wind blew, voltage went from 1.6 to about 1.7 or 1.9.
Not sure where to go from here.
02-07-2012, 11:03 AM
#51
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This is enlightening and confusing. I also noticed the adjustment screw does not have a plug/cap covering it, don't know if it should.
I've had the recommendation of getting a rebuilt unit but if you're saying the unit is basically working, John, what should I do?
I've had the recommendation of getting a rebuilt unit but if you're saying the unit is basically working, John, what should I do?
02-07-2012, 11:20 AM
#52
Rennlist Member
It's basically working, but that doesn't mean it is actually in calibration.
You can splash the cash on a rebuilt unit (the shotgun approach) or send it to Louie Ott my agent who will measure it on his calibrated flow jig. He also has my rebuilt units in stock, if you need one.
You can splash the cash on a rebuilt unit (the shotgun approach) or send it to Louie Ott my agent who will measure it on his calibrated flow jig. He also has my rebuilt units in stock, if you need one.
02-07-2012, 11:28 AM
#53
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Okay. Thanks, John. I'll contact Louie and another recommended source for a MAF rebuild. In looking at Louie's site, I'm not sure what a SuperMAF is, I'm sure he'll tell me 
02-07-2012, 12:21 PM
#55
Rennlist Member
Hi Stan,
The test I described is to check whether the MAF has the thermal runaway problem that afflicted the earlier MAFs....
If they have this problem, the output volts are higher than they should be, resulting in rich running. In the worst cases you can see the wire glowing orange after a fw seconds when igntion is switched on.
The test I described is to check whether the MAF has the thermal runaway problem that afflicted the earlier MAFs....
If they have this problem, the output volts are higher than they should be, resulting in rich running. In the worst cases you can see the wire glowing orange after a fw seconds when igntion is switched on.
The MAF hot wire test is,
turn the key to the run position wait for 30 seconds,
then turn the key off,
look at the MAF you should see the wire glow for about 3 seconds ,
you can remove the MAF from the boot and leave it connected so it will be easier to see if the wire is glowing.
.
turn the key to the run position wait for 30 seconds,
then turn the key off,
look at the MAF you should see the wire glow for about 3 seconds ,
you can remove the MAF from the boot and leave it connected so it will be easier to see if the wire is glowing.
.
02-07-2012, 12:43 PM
#56
Team Owner
Thanks for the info John , I didnt know about a burn cycle with the engine running. and a thermal runaway.
Should there also be a MAF burn off cycle once the ignition is switched off,
it does indeed glow on my 88 when the ignition switch is turned off.
At this point the OP needs a fresh MAF as his symptoms are indicating a worn MAF unit,
this is easy to rule out if you have a good MAF to plug into
Should there also be a MAF burn off cycle once the ignition is switched off,
it does indeed glow on my 88 when the ignition switch is turned off.
At this point the OP needs a fresh MAF as his symptoms are indicating a worn MAF unit,
this is easy to rule out if you have a good MAF to plug into
02-07-2012, 02:22 PM
#57
Rennlist Member
The "thermal runaway" test is done with igntion on but engine stopped, because the incoming air would cool the wire so you wouldn't be able to see it glow.
If you run the engine with a MAF with this fault, then the plugs will look black like the pictures in this thread.
You're quite right about the normal burn off, of course.
My idea was that if jej3 had the MAF tested, and it came up OK, then he could save himself some money.
If you run the engine with a MAF with this fault, then the plugs will look black like the pictures in this thread.
You're quite right about the normal burn off, of course.
My idea was that if jej3 had the MAF tested, and it came up OK, then he could save himself some money.
Thanks for the info John , I didnt know about a burn cycle with the engine running. and a thermal runaway.
Should there also be a MAF burn off cycle once the ignition is switched off,
it does indeed glow on my 88 when the ignition switch is turned off.
At this point the OP needs a fresh MAF as his symptoms are indicating a worn MAF unit,
this is easy to rule out if you have a good MAF to plug into
Should there also be a MAF burn off cycle once the ignition is switched off,
it does indeed glow on my 88 when the ignition switch is turned off.
At this point the OP needs a fresh MAF as his symptoms are indicating a worn MAF unit,
this is easy to rule out if you have a good MAF to plug into
02-07-2012, 02:29 PM
#58
Three Wheelin'
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Thank you, John. At this point, i think it is very much about choosing where to put the money in the car.
I genuinely believe if I am running the original LH and original MAF, after 156K miles, so it would stand to reason that both need to be rebuilt. I just don't like peeling off $1,000 bills and putting them on the car if I can help it
My fear in all of this is I could simply just do the MAF and LH swap and then I'll figure out I'm not quite there.
If I'm not then a new list starts:
CPS
Injectors
Top end Refresh (including CPS, Knock Sensors, etc..)
Psycho Therapy bills
I now think I understand why people own multiple of the 928, saves on the therapy bills to have one running at all times
I genuinely believe if I am running the original LH and original MAF, after 156K miles, so it would stand to reason that both need to be rebuilt. I just don't like peeling off $1,000 bills and putting them on the car if I can help it
My fear in all of this is I could simply just do the MAF and LH swap and then I'll figure out I'm not quite there.
If I'm not then a new list starts:
CPS
Injectors
Top end Refresh (including CPS, Knock Sensors, etc..)
Psycho Therapy bills
I now think I understand why people own multiple of the 928, saves on the therapy bills to have one running at all times
02-07-2012, 04:48 PM
#59
Rennlist Member
Thank you, John. At this point, i think it is very much about choosing where to put the money in the car. We all are in this vice, tho it's easier when it is cosmetic rather than about reliability.
I genuinely believe if I am running the original LH and original MAF, after 156K miles, so it would stand to reason that both need to be rebuilt. Maybe not both Stan: post 48: Always check the cheaper item first, move up the scale; OR the simpler one if it involves removing stuff. .
I genuinely believe if I am running the original LH and original MAF, after 156K miles, so it would stand to reason that both need to be rebuilt. Maybe not both
Stan: post 48: Always check the cheaper item first, move up the scale; OR the simpler one if it involves removing stuff. .
04-26-2012, 05:00 PM
#60
Three Wheelin'
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FINALLY!!!!
Well, I had to walk away from the 928 for a while but wanted to get it running again before SITM. This Monday (yes, 3 days ago) I decided I was over trying to figure it out and pulled the MAF and LH to send overnight to Louie Ott.
Let me tell you, I got the BEST service in the whole world. I overnighted at 6PM on Monday and 3 hours ago received the replacement MAF and LH.
Put them in, charged the battery and car started right up. I did all of this on my "Lunch Break" so I'll be putting everything back together tonight and tomorrow but I can get back to my regularly scheduled maintenance work and the month of May could become the "Drive your Shark Everyday" month.
I want to sincerely thank the helpful advice of many on the board here. All told, I spent about $1700ish or so on parts but have a much better car. Here is the parts list for anyone interested....
Let me tell you, I got the BEST service in the whole world. I overnighted at 6PM on Monday and 3 hours ago received the replacement MAF and LH.
Put them in, charged the battery and car started right up. I did all of this on my "Lunch Break" so I'll be putting everything back together tonight and tomorrow but I can get back to my regularly scheduled maintenance work and the month of May could become the "Drive your Shark Everyday" month.
I want to sincerely thank the helpful advice of many on the board here. All told, I spent about $1700ish or so on parts but have a much better car. Here is the parts list for anyone interested....
- New Plugs
- New Caps
- New Rotors
- New Plug Wires
- New Temp II Sender
- New Temp II Sender Harness
- New 02 Sensor
- Replaced internal Fuel Pump with Strainer and changed Fuel Filter
- CEP Refresh - All new fuses, many new relays, deoxit on every terminal
- Ground Refresh
- New Rear and Engine Ground Straps
- Coronas
- Rebuilt JDSPorsche MAF and LH that were BOTH bad!!!!!