928 dies / won't start when hot
07-31-2011, 09:41 PM
#31
Basic Sponsor
Rennlist
Site Sponsor
Rennlist
Site Sponsor
Once the air filter box is removed you need a long screw driver to reach the screw on the lower clamp that holds the MAF to the elbow. Accesable from the passenger side through the fuel rail. I use a 15" phillips srew driver.
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
07-31-2011, 10:07 PM
#33
Rennlist Member
Bob,
The passengers side fuel rail cover will need to be removed - 2 metric allen head bolts. With a long screwdriver and a flashlight the band clamp on the MAF boot can be loosened and the maf removed .
I have also used a 1/4" ratchet with long extensons and flex joint . It may be a 7mm socket.
Pay attention to the MAF connector location, take a picture for reference berfore removing.
The maf connector can be pulled off, rock it up and down gently while pulling on it. Do not pull it by the wires, only on the connector body. Look at the boot on the connector and make sure there isn't any broken wires.
The maf has an arrow on the side to show airflow, when installed it should point down.
This will also allow you to get to two of the rear fuel lines, check the two fuel dampeners, clean the two grounds, inspect the CPS connector, inspect the vacuum 5 or 7 way splitter. There are other things to check while in there.
There maybe local 928'ers that can give you a hand.
People have garage parties all the time.
If you are going to take it to a shop they need to know 928's. This is not a car you want a mechanic to learn on at your expense.
Since you replaced the fuel pump the filter should also be done, fuel lines, replaced, grounds cleaned and many other basic items mentioned in previous posts as preventative maintenance.
The passengers side fuel rail cover will need to be removed - 2 metric allen head bolts. With a long screwdriver and a flashlight the band clamp on the MAF boot can be loosened and the maf removed .
I have also used a 1/4" ratchet with long extensons and flex joint . It may be a 7mm socket.
Pay attention to the MAF connector location, take a picture for reference berfore removing.
The maf connector can be pulled off, rock it up and down gently while pulling on it. Do not pull it by the wires, only on the connector body. Look at the boot on the connector and make sure there isn't any broken wires.
The maf has an arrow on the side to show airflow, when installed it should point down.
This will also allow you to get to two of the rear fuel lines, check the two fuel dampeners, clean the two grounds, inspect the CPS connector, inspect the vacuum 5 or 7 way splitter. There are other things to check while in there.
There maybe local 928'ers that can give you a hand.
People have garage parties all the time.
If you are going to take it to a shop they need to know 928's. This is not a car you want a mechanic to learn on at your expense.
Since you replaced the fuel pump the filter should also be done, fuel lines, replaced, grounds cleaned and many other basic items mentioned in previous posts as preventative maintenance.
07-31-2011, 10:51 PM
#34
Intermediate
Thread Starter
Join Date: Mar 2010
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
Glenn -
Thanks very much for your time and expertise. I just learned that the LH and EZK computers checked out fine. Do you believe that the CPS connector (corrosion) or the MAF connector or the ground connectors I will see could be the problem?
The car has been super reliable for the past 3-4 years and I have driven it every week. Heat is the only variable I can think of. What about a battery issue (I have a n optima red top - car always craks over in the winter just fine).
If the car dies again what would you siggest I do for diangosis? It will hve a fuel pressure gauge and I will have a spark tester with me. It is really hard for me to diagnose a problem when the car is running fine and when it dies I am stuck on the side of the road. If I had it towed to the Porsche dealer ($$$$$$$$) it wld be running fine when they checked it out the next day.
Thanks very much for your time and expertise. I just learned that the LH and EZK computers checked out fine. Do you believe that the CPS connector (corrosion) or the MAF connector or the ground connectors I will see could be the problem?
The car has been super reliable for the past 3-4 years and I have driven it every week. Heat is the only variable I can think of. What about a battery issue (I have a n optima red top - car always craks over in the winter just fine).
If the car dies again what would you siggest I do for diangosis? It will hve a fuel pressure gauge and I will have a spark tester with me. It is really hard for me to diagnose a problem when the car is running fine and when it dies I am stuck on the side of the road. If I had it towed to the Porsche dealer ($$$$$$$$) it wld be running fine when they checked it out the next day.
12-11-2011, 12:47 AM
#35
Rennlist Member
Join Date: Sep 2007
Location: Ridgecrest, California
Posts: 1,363
Likes: 0
Received 143 Likes
on
28 Posts
Was there any resolution to RBA84's hot start issue?
I'm having the same issues now with Oregon ('87). It starts fine cold. Idle starts at about 1200 (like the other 2 S4s) but instead of the idle coming down as it gets warm, it goes up. It goes all the way up to about 2000. Car can be driven but idle stays high. I learned that I can't shut it off anywhere but home because if I do, it won't start again until it is cold. Symptom is that it just cranks and cranks with no start. Have fuel pressure, recent intake refresh with no vacuum leaks. I swapped out computers (LH and EZK) and no change. Before I start troubleshooting, thought I'd check here to see if someone else had a similar problem and found the solution. THANKS!
I'm having the same issues now with Oregon ('87). It starts fine cold. Idle starts at about 1200 (like the other 2 S4s) but instead of the idle coming down as it gets warm, it goes up. It goes all the way up to about 2000. Car can be driven but idle stays high. I learned that I can't shut it off anywhere but home because if I do, it won't start again until it is cold. Symptom is that it just cranks and cranks with no start. Have fuel pressure, recent intake refresh with no vacuum leaks. I swapped out computers (LH and EZK) and no change. Before I start troubleshooting, thought I'd check here to see if someone else had a similar problem and found the solution. THANKS!
12-11-2011, 02:20 AM
#37
Racer
Join Date: Mar 2011
Location: Beaverton, OR
Posts: 388
Likes: 0
Received 0 Likes
on
0 Posts
Similar issue for me dwayne, was the o2 sensor in my case due to wiring wear fault. open the wire loop to see if it helps maybe? different variables in my case, there were still vacuum leaks at the time of replacement, but it definitely helped.
Best of luck,
Jonathan.
Best of luck,
Jonathan.
12-12-2011, 12:42 AM
#40
Team Owner
swap in a different MAF ,
while your doing that inspect the 2 plastic junctions that plug into either side of the MAF boot they have a habit of cracking and disintegrating,
also consider that the short curved hose to the IAC may have split.
Inspoect the dampers and the FPR for fuel in the vacuum lines
while your doing that inspect the 2 plastic junctions that plug into either side of the MAF boot they have a habit of cracking and disintegrating,
also consider that the short curved hose to the IAC may have split.
Inspoect the dampers and the FPR for fuel in the vacuum lines
05-01-2012, 11:55 AM
#41
Team Owner
for the OP you should do a crank clearance/ flexplate inspection
Dwayne you have an airleak or a sticking throttle cable
Dwayne you have an airleak or a sticking throttle cable
05-02-2012, 12:01 AM
#42
Rennlist Member
Join Date: Sep 2007
Location: Ridgecrest, California
Posts: 1,363
Likes: 0
Received 143 Likes
on
28 Posts
Thanks for bringing this post back, Stan. I forgot about posting to it and posting the final resolution. Turns out I tracked the problem down to a grounding issue with the Temp II sensor.
When I put the intake back together after the refresh, I decided to install the paper gaskets under the water bridge because I had a leaking issue with the '88 and a Tech Bulletin suggested using the paper gaskets to remedy a leaking water bridge. Since this cured the problem on Idaho '88, I decided to take the proactive approach and install paper on Oregon '87. The paper gaskets actually insulate the water bridge from the heads and the ground that is needed for the Temp Sensor II to function correctly. Normally not a problem because the 4 bolts that secure the water bridge to the heads also provide ground contact.
But, in my case, I had the water bridge powder coated and i did not remove the powder coating from the contact points under the washers of the four mounting bolts. Therefore the water bridge was effectively isolated from ground and my Temp II sensor was not getting ground. I verified this by attaching a ground lead to the Temp II sensor and the idle settled right down to normal. The semi-permanent fix was to remove one or two bolts from the water bridge and remove the powder coating material under the washers so they would make contact with the water bridge metal. The 928 has been running normal ever since. I think the permanent solution will be to remove the paper gaskets when I have occasion to have the intake off again and just stick with the red silicone gaskets.
Another mystery solved.
When I put the intake back together after the refresh, I decided to install the paper gaskets under the water bridge because I had a leaking issue with the '88 and a Tech Bulletin suggested using the paper gaskets to remedy a leaking water bridge. Since this cured the problem on Idaho '88, I decided to take the proactive approach and install paper on Oregon '87. The paper gaskets actually insulate the water bridge from the heads and the ground that is needed for the Temp Sensor II to function correctly. Normally not a problem because the 4 bolts that secure the water bridge to the heads also provide ground contact.
But, in my case, I had the water bridge powder coated and i did not remove the powder coating from the contact points under the washers of the four mounting bolts. Therefore the water bridge was effectively isolated from ground and my Temp II sensor was not getting ground. I verified this by attaching a ground lead to the Temp II sensor and the idle settled right down to normal. The semi-permanent fix was to remove one or two bolts from the water bridge and remove the powder coating material under the washers so they would make contact with the water bridge metal. The 928 has been running normal ever since. I think the permanent solution will be to remove the paper gaskets when I have occasion to have the intake off again and just stick with the red silicone gaskets.
Another mystery solved.
05-02-2012, 03:50 AM
#44
Three Wheelin'
Join Date: Feb 2009
Location: Washington "Dc"
Posts: 1,810
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for bringing this post back, Stan. I forgot about posting to it and posting the final resolution. Turns out I tracked the problem down to a grounding issue with the Temp II sensor.
When I put the intake back together after the refresh, I decided to install the paper gaskets under the water bridge because I had a leaking issue with the '88 and a Tech Bulletin suggested using the paper gaskets to remedy a leaking water bridge. Since this cured the problem on Idaho '88, I decided to take the proactive approach and install paper on Oregon '87. The paper gaskets actually insulate the water bridge from the heads and the ground that is needed for the Temp Sensor II to function correctly. Normally not a problem because the 4 bolts that secure the water bridge to the heads also provide ground contact.
But, in my case, I had the water bridge powder coated and i did not remove the powder coating from the contact points under the washers of the four mounting bolts. Therefore the water bridge was effectively isolated from ground and my Temp II sensor was not getting ground. I verified this by attaching a ground lead to the Temp II sensor and the idle settled right down to normal. The semi-permanent fix was to remove one or two bolts from the water bridge and remove the powder coating material under the washers so they would make contact with the water bridge metal. The 928 has been running normal ever since. I think the permanent solution will be to remove the paper gaskets when I have occasion to have the intake off again and just stick with the red silicone gaskets.
Another mystery solved.
When I put the intake back together after the refresh, I decided to install the paper gaskets under the water bridge because I had a leaking issue with the '88 and a Tech Bulletin suggested using the paper gaskets to remedy a leaking water bridge. Since this cured the problem on Idaho '88, I decided to take the proactive approach and install paper on Oregon '87. The paper gaskets actually insulate the water bridge from the heads and the ground that is needed for the Temp Sensor II to function correctly. Normally not a problem because the 4 bolts that secure the water bridge to the heads also provide ground contact.
But, in my case, I had the water bridge powder coated and i did not remove the powder coating from the contact points under the washers of the four mounting bolts. Therefore the water bridge was effectively isolated from ground and my Temp II sensor was not getting ground. I verified this by attaching a ground lead to the Temp II sensor and the idle settled right down to normal. The semi-permanent fix was to remove one or two bolts from the water bridge and remove the powder coating material under the washers so they would make contact with the water bridge metal. The 928 has been running normal ever since. I think the permanent solution will be to remove the paper gaskets when I have occasion to have the intake off again and just stick with the red silicone gaskets.
Another mystery solved.
06-09-2016, 01:42 PM
#45
Team Owner
I was working on Rumblfsh and it has a PC water bridge it also has the funny idle and running symptoms need to pull it and clean the bolts and remove the powder
