Okay, time to go "whole hog"
09-30-2014, 12:48 PM
#1
Pro
Thread Starter
Okay, time to go "whole hog"
1991 S4 with 77K on the odo.
First, thanks for all the helpful advice troubleshooting my recent stall and lack of restart with tach jumping around wildly. Seems I probably have a bad CPS. I got in there today and looked at what I'm faced with, and it is apparent that I'm going to tear up all kinds of stuff behind that intake trying to get the CPS out. So, I've decided to remove the intake and replace everything in sight that matters. Here is my current list:
- CPS
- Fuel dampers
- Fuel hoses (already have a set of Greg Brown's ready to go)
- Knock sensors
- Vacuum hoses in the area
What am I missing? Should I do the MAF sensor? Does everyone powdercoat their intakes when they are out?
EDIT: Oh, and I guess I'll address the "flappy" while in there.
I'm planning to leave the injectors alone for now. The car had BG induction and BG fuel system services done 2,000 miles (15 mos.) ago. I have no indication of any injector problems, and I believe they can be done with the intake in place anyway, right?
I don't know if I'll try to tackle the in-tank fuel pump while the car is out of commission. Should I? Should I replace with a strainer? I'm in North Carolina.
I'm also planning to take out the CE panel and do some panel cleaning and replacing relays, as necessary. I have water getting into my passenger footwell, and I need to figure that out. Will that be as easy as cleaning my sunroof drains? I don't know anything about those.
And, of course, I'll find as many ground points as possible and clean those up.
What else? I've got a set of engine mounts and transmission mounts, as well as steering rack bushings. I also have a new silicone oil pan seal.
Timing belt was done 2,000 miles ago and recently re-tensioned--it hadn't stretched.
I need to bleed the PSD and flush the differential. Tranny was flushed 2,000 miles ago. Air filter replaced then too--it's still clean. Cooling system also underwent a BG flush then.
My guess is it will be late next spring before this car sees any more mileage. All I have are Race Ramps and two jack stands.
Time to call Roger. Any advice is appreciated.
Louis
First, thanks for all the helpful advice troubleshooting my recent stall and lack of restart with tach jumping around wildly. Seems I probably have a bad CPS. I got in there today and looked at what I'm faced with, and it is apparent that I'm going to tear up all kinds of stuff behind that intake trying to get the CPS out. So, I've decided to remove the intake and replace everything in sight that matters. Here is my current list:
- CPS
- Fuel dampers
- Fuel hoses (already have a set of Greg Brown's ready to go)
- Knock sensors
- Vacuum hoses in the area
What am I missing? Should I do the MAF sensor? Does everyone powdercoat their intakes when they are out?
EDIT: Oh, and I guess I'll address the "flappy" while in there.
I'm planning to leave the injectors alone for now. The car had BG induction and BG fuel system services done 2,000 miles (15 mos.) ago. I have no indication of any injector problems, and I believe they can be done with the intake in place anyway, right?
I don't know if I'll try to tackle the in-tank fuel pump while the car is out of commission. Should I? Should I replace with a strainer? I'm in North Carolina.
I'm also planning to take out the CE panel and do some panel cleaning and replacing relays, as necessary. I have water getting into my passenger footwell, and I need to figure that out. Will that be as easy as cleaning my sunroof drains? I don't know anything about those.
And, of course, I'll find as many ground points as possible and clean those up.
What else? I've got a set of engine mounts and transmission mounts, as well as steering rack bushings. I also have a new silicone oil pan seal.
Timing belt was done 2,000 miles ago and recently re-tensioned--it hadn't stretched.
I need to bleed the PSD and flush the differential. Tranny was flushed 2,000 miles ago. Air filter replaced then too--it's still clean. Cooling system also underwent a BG flush then.
My guess is it will be late next spring before this car sees any more mileage. All I have are Race Ramps and two jack stands.
Time to call Roger. Any advice is appreciated.
Louis
Last edited by L_perm; 09-30-2014 at 01:07 PM.
09-30-2014, 01:14 PM
#2
Shameful Thread Killer
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Look up cleaning the ISV. They get sticky sometimes. Causes car to idle hunt.
If you do ANYTHING to the intake it has to be spotlessly clean inside and out before installation. Several stories of engines being ruined by sand or other media left in the intake. It's a complex casting.
Put rags in the intake runners on the head the instant the intake is off the car. Don't want anything falling in - ask my how I know this.
Although the MM, rack bushings and OPG can be done on jack stands(I've done it), the job is half the time if you can get the car on a lift for a half day or so. Well worth driving a while to use a lift, even more important when you are on the back side of 50.
If you do ANYTHING to the intake it has to be spotlessly clean inside and out before installation. Several stories of engines being ruined by sand or other media left in the intake. It's a complex casting.
Put rags in the intake runners on the head the instant the intake is off the car. Don't want anything falling in - ask my how I know this.
Although the MM, rack bushings and OPG can be done on jack stands(I've done it), the job is half the time if you can get the car on a lift for a half day or so. Well worth driving a while to use a lift, even more important when you are on the back side of 50.
09-30-2014, 03:06 PM
#4
Pro
Thread Starter
Look up cleaning the ISV. They get sticky sometimes. Causes car to idle hunt.
If you do ANYTHING to the intake it has to be spotlessly clean inside and out before installation. Several stories of engines being ruined by sand or other media left in the intake. It's a complex casting.
Put rags in the intake runners on the head the instant the intake is off the car. Don't want anything falling in - ask my how I know this.
Although the MM, rack bushings and OPG can be done on jack stands(I've done it), the job is half the time if you can get the car on a lift for a half day or so. Well worth driving a while to use a lift, even more important when you are on the back side of 50.
If you do ANYTHING to the intake it has to be spotlessly clean inside and out before installation. Several stories of engines being ruined by sand or other media left in the intake. It's a complex casting.
Put rags in the intake runners on the head the instant the intake is off the car. Don't want anything falling in - ask my how I know this.
Although the MM, rack bushings and OPG can be done on jack stands(I've done it), the job is half the time if you can get the car on a lift for a half day or so. Well worth driving a while to use a lift, even more important when you are on the back side of 50.
Louis
09-30-2014, 04:02 PM
#5
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If you decide to powder coat, see Powder coating intake/cam covers/etc. best practices. You'll find numerous other threads on the topic as well.
Yet another top-end refresh (WAS: Trying to fix irregular/poor idle ...) (especially starting at about post #47 in that thread) might be useful, too.
Yet another top-end refresh (WAS: Trying to fix irregular/poor idle ...) (especially starting at about post #47 in that thread) might be useful, too.
09-30-2014, 07:11 PM
#6
Rennlist Member
Louis,
There are a couple different schools of thought here. One is the "WYAIT" theory, which says that when you take something apart, you ought to do everything else in the neighborhood while you are in there because it will save time later. This makes a lot of sense, especially if time is in short supply or expensive. The problem with this approach is that the cost can get out of hand in a hurry. None of that stuff under the intake is cheap, and most of it-- perhaps everything given the 77K miles-- is going to be just fine for another 100K miles.
The other approach is the "surgical strike"-- dive in and fix what needs fixing. Check other components while you are there, but if a rubber hose under the intake feels like a rubber hose, i.e. rubbery and flexible, then it is probably fine. Of course there is always a chance of something falling apart the week after, but that can happen to new parts also. And there are some things to not take chances with, like fuel hoses.
I tend to subscribe to the second approach. Parts are expensive, time can be managed. In your case, unless there was something in particular under the intake that needed fixing, I would leave it alone. Pull the MAF and replace the fuel-line under it, and take apart what you need to in order to get to the CPS. Then see if that fixes the stalling issue.
At 77K your MAF is getting a bit aged, but probably OK for a while depending on how the car was driven (it's the number of start-stops that ages MAF's, because of the burn-off cycles when the engine is stopped).
The in-tank pump is a concern because the short rubber hose that attaches the pump to the fitting can split (not compatible with ethanol), allowing the main pump to suck in debris and jam. This can get you stuck on the road. So it is a good idea to drain the tank, remove the fitting and in-tank pump and have a look. The hose can be replaced with a short piece of fuel hose, I believe that Greg B has the proper stuff.
There are a couple different schools of thought here. One is the "WYAIT" theory, which says that when you take something apart, you ought to do everything else in the neighborhood while you are in there because it will save time later. This makes a lot of sense, especially if time is in short supply or expensive. The problem with this approach is that the cost can get out of hand in a hurry. None of that stuff under the intake is cheap, and most of it-- perhaps everything given the 77K miles-- is going to be just fine for another 100K miles.
The other approach is the "surgical strike"-- dive in and fix what needs fixing. Check other components while you are there, but if a rubber hose under the intake feels like a rubber hose, i.e. rubbery and flexible, then it is probably fine. Of course there is always a chance of something falling apart the week after, but that can happen to new parts also. And there are some things to not take chances with, like fuel hoses.
I tend to subscribe to the second approach. Parts are expensive, time can be managed. In your case, unless there was something in particular under the intake that needed fixing, I would leave it alone. Pull the MAF and replace the fuel-line under it, and take apart what you need to in order to get to the CPS. Then see if that fixes the stalling issue.
At 77K your MAF is getting a bit aged, but probably OK for a while depending on how the car was driven (it's the number of start-stops that ages MAF's, because of the burn-off cycles when the engine is stopped).
The in-tank pump is a concern because the short rubber hose that attaches the pump to the fitting can split (not compatible with ethanol), allowing the main pump to suck in debris and jam. This can get you stuck on the road. So it is a good idea to drain the tank, remove the fitting and in-tank pump and have a look. The hose can be replaced with a short piece of fuel hose, I believe that Greg B has the proper stuff.
09-30-2014, 07:20 PM
#7
Nordschleife Master
Just get a new ISV. Consider it a wear item. Not expensive, and Roger has new ones. Easy peasy once you have the manifold off.
Also get new O rings (upper and lower) for the injectors - Roger has them in kit form - also another easy peasy while you"re there.
Also get new O rings (upper and lower) for the injectors - Roger has them in kit form - also another easy peasy while you"re there.
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09-30-2014, 08:52 PM
#8
Pro
Thread Starter
Louis,
There are a couple different schools of thought here. One is the "WYAIT" theory, which says that when you take something apart, you ought to do everything else in the neighborhood while you are in there because it will save time later. This makes a lot of sense, especially if time is in short supply or expensive. The problem with this approach is that the cost can get out of hand in a hurry. None of that stuff under the intake is cheap, and most of it-- perhaps everything given the 77K miles-- is going to be just fine for another 100K miles.
The other approach is the "surgical strike"-- dive in and fix what needs fixing. Check other components while you are there, but if a rubber hose under the intake feels like a rubber hose, i.e. rubbery and flexible, then it is probably fine. Of course there is always a chance of something falling apart the week after, but that can happen to new parts also. And there are some things to not take chances with, like fuel hoses.
I tend to subscribe to the second approach. Parts are expensive, time can be managed. In your case, unless there was something in particular under the intake that needed fixing, I would leave it alone. Pull the MAF and replace the fuel-line under it, and take apart what you need to in order to get to the CPS. Then see if that fixes the stalling issue.
At 77K your MAF is getting a bit aged, but probably OK for a while depending on how the car was driven (it's the number of start-stops that ages MAF's, because of the burn-off cycles when the engine is stopped).
The in-tank pump is a concern because the short rubber hose that attaches the pump to the fitting can split (not compatible with ethanol), allowing the main pump to suck in debris and jam. This can get you stuck on the road. So it is a good idea to drain the tank, remove the fitting and in-tank pump and have a look. The hose can be replaced with a short piece of fuel hose, I believe that Greg B has the proper stuff.
There are a couple different schools of thought here. One is the "WYAIT" theory, which says that when you take something apart, you ought to do everything else in the neighborhood while you are in there because it will save time later. This makes a lot of sense, especially if time is in short supply or expensive. The problem with this approach is that the cost can get out of hand in a hurry. None of that stuff under the intake is cheap, and most of it-- perhaps everything given the 77K miles-- is going to be just fine for another 100K miles.
The other approach is the "surgical strike"-- dive in and fix what needs fixing. Check other components while you are there, but if a rubber hose under the intake feels like a rubber hose, i.e. rubbery and flexible, then it is probably fine. Of course there is always a chance of something falling apart the week after, but that can happen to new parts also. And there are some things to not take chances with, like fuel hoses.
I tend to subscribe to the second approach. Parts are expensive, time can be managed. In your case, unless there was something in particular under the intake that needed fixing, I would leave it alone. Pull the MAF and replace the fuel-line under it, and take apart what you need to in order to get to the CPS. Then see if that fixes the stalling issue.
At 77K your MAF is getting a bit aged, but probably OK for a while depending on how the car was driven (it's the number of start-stops that ages MAF's, because of the burn-off cycles when the engine is stopped).
The in-tank pump is a concern because the short rubber hose that attaches the pump to the fitting can split (not compatible with ethanol), allowing the main pump to suck in debris and jam. This can get you stuck on the road. So it is a good idea to drain the tank, remove the fitting and in-tank pump and have a look. The hose can be replaced with a short piece of fuel hose, I believe that Greg B has the proper stuff.
Thanks again for the thoughts. I guess I'm of the mind that: 1) at 23 years old, it seems a good idea to replace some things, especially those that are subject to a lot of heat; 2) I need to do all the fuel lines anyway; 3) I didn't particularly enjoy wasting my whole day Friday stranded in a Lowe's parking lot--which was a lot better than it could have been and may be the next time.
I bought this car thinking that the basic, big parts were robust and that I could restore something like new-car reliability by overhauling the "little" stuff. If I can't do that, then I'd just as soon sell the thing, as I'd like to drive without worrying about what's going to strand me next.
I understand new parts can fail too, but we are talking about reducing the probability of failure.
My automatic transmission shifts like s#%t too. The symptoms are complicated--not likely to be fixed by a Bowden cable or vacuum modulator. I have to do something about it at some point. I'll probably have another $25K in this thing before it's worth the $20K I paid for it. But, at least then I'll have a reliable car that works the way a 928 was meant to work. At least that's what I'm hoping. At this point, I wouldn't buy it again.
Louis
10-01-2014, 02:20 AM
#9
Nordschleife Master
I would send the injectors out for testing and cleaning, time in an ultrasonic tank is vastly more effective than any juice you can run through the motor, and two of my injectors didn't meet spec even after cleaning.
10-01-2014, 05:31 PM
#10
Pro
Thread Starter
I'm also going to see how I feel about opening up the cam covers and water bridge once I have the intake off. Not sure if I want to go there.
Thanks,
Louis
10-01-2014, 05:37 PM
#11
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I and others have been happy with WitchHunter. (See my results, including the before/after injector performance report.) There are a few other services that are good, too; I'm sure some other people will mention them.
10-02-2014, 10:57 AM
#12
Rennlist Member
I've decided to do something with the injectors, either replace with refurbished ones, or send off for cleaning. Who is recommended for injector cleaning/service?
I'm also going to see how I feel about opening up the cam covers and water bridge once I have the intake off. Not sure if I want to go there.
Thanks,
Louis
I'm also going to see how I feel about opening up the cam covers and water bridge once I have the intake off. Not sure if I want to go there.
Thanks,
Louis
Oil leaks from the cam covers? Any coolant leaking into the valley?
Do you have a camera? How about some pictures of the engine bay?
10-02-2014, 11:51 AM
#13
Pro
Thread Starter
I and others have been happy with WitchHunter. (See my results, including the before/after injector performance report.) There are a few other services that are good, too; I'm sure some other people will mention them.
As for the injectors, I don't know if all of them are working to spec, and I don't know how I can determine this. Therefore, I was thinking I would send them off to be cleaned and tested while I have them out. 23 years of gasoline from probably every state east of the Mississippi has probably taken some kind of toll, wouldn't you think? Not to mention heat cycles and 77K miles of combustion. It makes sense to me to have them cleaned and tested, as it will cost less than $200. If they are all fine, then at least I'll know, but I can't imagine a cleaning won't help at least a little.
As for intake removal, a couple of the vacuum lines that run under there (left throttle-to-venturi and right front cam cover to oil vent and maybe the right rear cam cover to right throttle) seem a bit soft. Let me say this: when I check the various vacuum lines around the engine bay, they have--in some cases--significantly varying degrees of softness/hardness. I haven't ordered any of them yet, as I want to get in there and see what seems right and what seems compromised. It's hard to tell without taking a few off. Are the soft ones good and the hard ones bad, or vice versa, or both bad, or both good? How does one know without pulling a few off?
I also noticed some wet gasoline on the vacuum line attached to the left rear fuel damper when I reached down to the CPS. Why would there be fuel on that vacuum line. (I had wiggled it a little getting to the CPS.)
I should also mention that a significant factor in my deciding to even purchase this car, and certainly to do the work I'm doing now, is my need for a hobby. I have no golfing buddies. I have no fishing buddies. No one to shoot the **** with. I work out of my house and have no contact with anyone most days. If I have something sitting in the garage that I can go tinker with, then my life is much better. If I end up with a car whose condition I know like the back of my hand--because I've addressed/investigated pretty much everything--then that is also a positive. I have a baseline reference. I'm also better equipped to troubleshoot if I do have a problem.
I'll get some pics taken and posted soon. I need to finish up a work project today--work I'm actually paid to do.
Louis
10-02-2014, 01:18 PM
#14
Rennlist Member
Louis, thanks for the perspective, that makes sense. Agreed, if the cam overs aren't leaking then there is nothing inside that otherwise needs attention for many miles.
Injector problems are rare, they can leak (causing difficult warm-restarts after sitting for a few minutes), or they can get clogged-- but those are rare with brand-name fuel (i.e. decent additives).
But certainly, if you have the injectors out for any reason, then send them off for cleaning/testing and replace the o-rings (the tops are standard, the bottoms are not -- get those from Roger).
Replacing them with the same 19# injectors doesn't make sense, from Porsche they are expensive and aftermarket is a crap-shoot, the specs need to match. If you want to go looking for horsepower and get into tuning then that's a different story.
Vacuum lines: There are two types, rubber hoses which I think are the ones you describe-- brake-booster venturi on the (car's) left side, and cam-cover breather on the right-- are pretty soft rubber. If they are uniformly soft then I wouldn't worry, but if they have particular soft spots then check more carefully. The small vacuum lines (fuel regulator/dampers, heater valve, etc) are nylon and pretty firm, and get hard and eventually brittle with heat and age. Unmolested they are usually fine, but if you are working around them then they sometimes crack and need replacing.
Wet gasoline is a problem-- was it inside the vacuum line when disconnected? That indicates a leaky damper. Dampers (and the regulator) are basically small chambers divided by a rubber diaphragm, fuel on one side and a spring and engine vacuum on the other side. So if the diaphragm develops a leak, then fuel leaks into the intake manifold and screws up the idle (too rich). (This might be your idle/no-start problem except for the bouncing tach).
If the vacuum lines connecting the fuel regulator and dampers are wet inside, or smell of fuel then replace the regulator/dampers.
Injector problems are rare, they can leak (causing difficult warm-restarts after sitting for a few minutes), or they can get clogged-- but those are rare with brand-name fuel (i.e. decent additives).
But certainly, if you have the injectors out for any reason, then send them off for cleaning/testing and replace the o-rings (the tops are standard, the bottoms are not -- get those from Roger).
Replacing them with the same 19# injectors doesn't make sense, from Porsche they are expensive and aftermarket is a crap-shoot, the specs need to match. If you want to go looking for horsepower and get into tuning then that's a different story.
Vacuum lines: There are two types, rubber hoses which I think are the ones you describe-- brake-booster venturi on the (car's) left side, and cam-cover breather on the right-- are pretty soft rubber. If they are uniformly soft then I wouldn't worry, but if they have particular soft spots then check more carefully. The small vacuum lines (fuel regulator/dampers, heater valve, etc) are nylon and pretty firm, and get hard and eventually brittle with heat and age. Unmolested they are usually fine, but if you are working around them then they sometimes crack and need replacing.
Wet gasoline is a problem-- was it inside the vacuum line when disconnected? That indicates a leaky damper. Dampers (and the regulator) are basically small chambers divided by a rubber diaphragm, fuel on one side and a spring and engine vacuum on the other side. So if the diaphragm develops a leak, then fuel leaks into the intake manifold and screws up the idle (too rich). (This might be your idle/no-start problem except for the bouncing tach).
If the vacuum lines connecting the fuel regulator and dampers are wet inside, or smell of fuel then replace the regulator/dampers.
10-02-2014, 01:33 PM
#15
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Cam chains and pads are a wear item, and under the cam cover(of course). At 77k miles should not be an issue, but if they wear prematurely the failure mode is massively expensive.