Bomb Factory

Ill definitely check out the relay. That would be nice if the fix is that easy.

I have not changed the oil since I got it but PO kept it impeccably maintained. It is running Mobile 1 15w50

1996 S4S Runs like a top. Notice that my pressure warning light comes on at low RPMs. Plenty of oil. Was planning on just replacing the sender (same as pressure switch?) but I was reading on some other posts that it could be just the light. Im about to replace my boost gauge with an updated VDO that has more range and also vac. While Im in there wondering if there is a way to test the oil pressure light to be sure that is not the issue. I see a transducer listed on a dealer parts site - see below for PN. But it is $317 and I dont want to just throw parts at the problem. Any experienced advice is appreciated. I dont believe there is a real issue with the pressure but it is very unsettling none the less to see the light come on knowing the criticality of proper oil flow. Plus literally everything else on the car works (I hate to even mention this fact because it is tempting the universe to blow something on the car up) and I want to get this issue sorted. Thx Charles TRANSDUCER-OIL PRESSURE Part Number: A082N4038F

Found it ordered it. Looks like the rear one is a real pain in the ass to change out!

Link provided says part no longer available. But since I have the PN I am sure i can find one. thx!

Finally got time to remove the BOV and replace with a new silicone tube/hose. That seemed to do the trick. I can now peg the boost gauge at its 1 bar limiter. PO on mine had the gauge recalibrated since he has a red race chip that ups the max boost under the right conditions. I want to get the car on my dyno and I am thinking that Id like to have a more precise boost gauge before I do. Any advice on replacement/upgrade boost gauge that others have found to be of good quality and functionality? Also- I noticed that one of the little rubber mounts that holds the charge cooler to the head is severed. This would be the one towards the back of the car and is hard to see since it is obscured by the charge cooler. Id like to replace it but dont know what to call the part to search for it. Any info on what the part is called or a PN is also appreciated. Happy to have all my boost back. Now I need to learn how to use the boost properly- I find this car requires you to wring the power out of it- vs the large V8s in the rest of my cars. Im getting to know it slowly so I can feel the limits and keep better control.

@jonwat so its just the one part number that gets me both parts of the gasket or do I need to order two?

Makes sense. It looks like only modifications to the stock vacuum lines to accommodate the BOV is a T that goes into one of the lines running on the back side of the engine. It seems pretty simple to just pull it and place a cap on the T or even just use a barb splice to reconnect the stock hoses. The vent tube is external and just hangs down so that is pretty easy. Suggestions on where to get a good replacement hose to span the intake to the charger cooler? I will definitely test the plenum too. @ramjet thanks for the tip there.

No havent checked the plenum gaskets- I know you are urging me to do so. So I will do it. Are you suggesting a visual inspection without taking the manifold off? If so I reckon I better get some new gaskets no matter. Do you recommend a good source for those? I recall its a two part gasket? @jonwat Could it actually be that easy? Certainly a good place to begin the journey. cheers!

After a busy few months I was finally able to get back on the diagnosis of my boost leakage. I took a look at the cat which seemed fine but while I had part of the exhaust off- I just went ahead and removed the cat. I live in Louisiana and we dont have any inspections to worry about. I figured it would add a tad better flow - less restriction. I test drove the car and the issue is not solved. When you push the revs hard - during prime turbo time the boost hits .5 bar or so and there is a loud whoosh- which is not the same sound as the blow off valve makes- and the boost gauge falls to 0 and then starts its journey to build back up again once the throttle is applied again or pushed further. Now that the cat is off it seems that there is more cackling and a bit of popping when I lift off the gas after accelerating. None of it sounds bad per say- Ive had lots of cars with glass packs or even no mufflers at all and the noise is similar. But I want to be sure it is not a sign of something being wrong. This being my first car of this type- and having only logged a hundred or so miles with the car- Im still a newby. My next step in diagnosis is to map out all the blow off valve/turbo piping and vac lines to make sure I know what is going where and what its function is. Then I can try removing the blow off valve and replacing with a new piece of hose that spans the gap left between the charge cooler and the air intake. I dont want to just start pulling stuff off until I know what all the connected lines do and where they go. This process will also allow me to do a more thorough inspection of the tubes, clamps etc. From my visuals thus far- all seems snug and tidy. Maybe I will find a break or loose fitting that I missed before. I have all the service manuals for the car- binders of them- but would like to ask here if anyone has a nice, easy to follow map of the vac lines that relate to the turbo and the installation of a BOV that is not adjustable and externally vented (as mine is). I am sure I can find it but I appreciate the collective wisdom of this group in shortening my research process. thx Charles

I guess I can just replace the gaskets anyway. I am checking the cat first and foremost as well as second deeper look at all the BOV hoses etc. Is there an upgraded plenum gasket set? And if so where to procure?

@andydclements I was definitely informed that the BOV hoses can slip. Mine seem quite firmly in place. But I am going to take a deeper look and I can have a mate stand over the motor while I rev it and get boost flowing. @Sparky Is there a reference you can point me to in regards to the process for changing intake plenum gaskets and a good supplier for them? Ive changed many gaskets so its not about the basics but more any specific things to know when doing the service on this car. Ive not learned my way around it yet. First thing I need to shrink my hands.

Have not checked the plenum gasket. What would the best way to do that be? Push air through it somehow? I guess is starts with making sure the fasteners are tight. Advice on that is appreciated. I didnt realize the intercooler was the red box on top. I am still learning my way around. Ill check that out. I did see that there is a little rubber bushing where it is attached to the motor and I can woggle the red box back and forth a bit. My thought was that the rubber bushing was there to help it flex due to vibration. Am I off base here? I'm used to working on American v8s in giant engine bays- this is a new situation for me. -Charles

Thx for the good ideas. Exhaust not new, PO installed it years ago. It is a Larini single exit with a Larini cat. It is stainless and in nice shape so Im not sure how likely the cat is plugged but I will check this first. I plan to unbolt the cat and do a visual as well as blow some air through it to see if it is clogged. I have not been able to locate visually the charge cooler but I have not tried very hard yet! All I can see are the pipes- I am going to get it on the lift though so I can look more carefully then. I'm going to order a regular hose to replace the bov and see what happens. The vacuume lines coming off the BOV are a bit hard to trace as I am still getting familiar with the engine area and it is very tight in there. Where could I find a diagram that shows which ones are typically added for a BOV and what stock config should look like? Thx! Charles

I have a very well sorted and maintained S4s (Thank you Bruce Tatusko!). I have only put about 200 miles on it since purchase. It runs really well and had no issues. I have been slowly pushing the car harder as I get used to it. On my interstate high speed drive yesterday I think something changed. On any throttle position it wont build boost past about .5 bar. The car has a red race chip which should allow it to hit 1.25 bar I've been told. When it gets to right below .5 bar there I hear a loud whooshing which I am sure is excess pressurized intake air being blown out, and the boost falls to 0. Nothing else seems out of whack. The car runs fantastically but I want my extra boost! I have done some research on this issue and that allows me to report the following: Blow off Valve- the car has a Samco Sport blow off valve. It appears to be non adjustable and externally vented. I am not sure how many flappy things it has- likely one. PO does not know when it was installed but he had the car for 17 years so it is at least that old. I know the valve was working before because I could hear the slight "chuffing" sound on my shifts. I was told that the hoses for these valves can be an issue- coming loose and such and this could cause the inability to build boost. I did a visual inspection and mine appear to be quite tight. All looks normal on visual. Turbo housing and wastegate- I have only done a visual on this system- there is no rust or corrosion. I tried to actuate the wastegate with my hand - moving the bar that goes from the capsule to the housing. Stiff resistance there, could not get it to move. Unsure if that is normal or not. The issue would be if it were stuck open, not closed. I could also not make it rattle but maybe I need to have it running and get someone to hit the gas? I was by myself so I could not do that test. Check engine light- I verified that this is not burned out. It has not come on at all. I read that if it is on the ECU will not allow full boost. A clue? - The only other potential clue is that I did manage to blow a shift on the interstate and went from 5 to 2 instead of 4. I realized it before I let the clutch all the way out and fully loaded the drivetrain. The tach pegged at redline for a fraction of a second and I pushed the clutch back in fully and let the revs drop. I felt no adverse effects from this mistake. It probably could have been a disaster if I had let the clutch out fully. I was doing about 80 MPH. I wonder if the quick hit to redline could have blown out a seal or something that contains turbo pressure? Two things I am going to try now- 1. Removing the blow off valve and seeing what happens. I will need to get a new hose and figure out the right way to cap or restore the vac lines to stock. Once off, I'm on the fence about replacing it- if I do I will use a more modern one that is adjustable and has two flaps. Ill make that call once I remove it and see what happens. 2. Testing the wastegate function- I found instructions for doing this on the tech talk site and I am capable of doing this test. This is my first post and I am hoping to tap into the collective wisdom of everyone here for some guidance. Starting with any other ideas that I might have missed here. I cant say enough about my S4s. It is a real joy to drive. I read all kinds of stuff before I got it about what people dont like when driving it. I fit fine, I can see behind me fine, the shifter is not a Ferrari - but it works fine- although 3 to 2 can be a bit indirect. Thanks in advance. -Charles Handler