Kroon Harness for 944 Turbo

[Tom]

Let the engine run long enough for the oil pressure to drop to 3 or lower at idle, then tell us what you are seeing for 1) RPM, 2) AFR, and 3) vacuum on the diagnostic gauge.

Just did the above. Here are the results as well as a compression test:

Compression Test (Engine Warm)
Cyl 1: 155
Cyl 2: 155
Cyl 3: 149
Cyl 4: 150

After letting car run for 20 minutes
Idle RPM: 880 RPM
Vacuum: Steady at 15 in HG, dead steady - no bouncing
AFR: Between 14.7-15.0 (both AEM gauge and reading in ODB+
ICV: 93% Open (according to ODB+)
Ignition Advance: 4.1 (according to ODB+)

Here's another test I did. I removed the oil fill cap and NOTHING happened. No change in RPM, no change in AFR, nothing. According to Chat GPT (I looked for CarBot but couldn't find any such chatbot?) that would mean I'm already getting air introduced into the crankcase somewhere. I'm thinking it could be the dipstick tube as I doubt that seals properly (even though I have the o-ring and the plastic spacer and it's bolted to the IM. Any thoughts on that?

Lastly, if I were to go "old school" on this, the vacuum gauge literally says "slow ignition timing" between 14-17 in HG. I checked my timing marks and they seem "ok". Any thoughts on this?

CarBot is still under development (as I add Porsche info to the back end), so is only available in its own subforum for now, located here:
https://www.carpokes.com/viewforum.php?f=65

On the ignition timing, I think you are mixing apples and oranges. It sounds like the gauge is talking about when the spark plugs fire (ignition timing) whereas the timing marks on the motor relate to when the valves open and close. I'd park all that for now. If you cam belt is aligned, you're good. The ignition timing is set by the DME and out of your control for this purpose. If it's retarded, that's a result of whatever is going on, not a cause.

On my F9 DME, I believe my ISV duty cycle reads backwards -- i.e., 93% open is really 93% closed. I'd flagged that for Joe but never got a response. I'd park that one for right now too as a result. (You could test it by turning the throttle screw on top of the throttle body, and then checking to see if the reported ISV duty cycle compensates in the right direction -- but I'd say that's a rabbit hole not worth going down right now.)

Your warmed up numbers are not 'that' bad, but do still point to a vacuum leak. I went out and warmed up my car to replicate the oil cap removal test and can indeed confirm my motor stumbles quite noticeably when I remove the cap. So, if yours does not, it likely means you already have a leak that the DME is already trying to compensate for. It also may point to that leak coming from the crankcase and AOS hose. Easy enough to check: pull the AOS hose off the j-boot and seal off both sides. If the leak is coming from the crankcase via that hose, your vacuum should go up and AFR should richen up.

If plugging the AOS port improved vacuum and makes the AFR hunt above and below 14.7 -- then I'd start by checking for the thick, light brown o-ring inside the oil cap. They can come loose and disappear. Also, how is the seal at the top of the AOS? It is not officially replaceable, but people have been known to pry off the top and replace the seal ring (not always doing more good than harm). If yours is leaking, you'll often have a mess of oil mist around it. Those would be my top 2 suspects if the leak is coming in through the AOS, since smaller leaks wouldn't produce the magnitude of problem you are seeing -- though I suppose there are plenty of possibilities.

If plugging off the Jboot/AOS port does not fix the issue, then the hunt continues for the source of the leak/problem...

[NCGermerican]

Let the engine run long enough for the oil pressure to drop to 3 or lower at idle, then tell us what you are seeing for 1) RPM, 2) AFR, and 3) vacuum on the diagnostic gauge.

Just did the above. Here are the results as well as a compression test:

Compression Test (Engine Warm)
Cyl 1: 155
Cyl 2: 155
Cyl 3: 149
Cyl 4: 150

After letting car run for 20 minutes
Idle RPM: 880 RPM
Vacuum: Steady at 15 in HG, dead steady - no bouncing
AFR: Between 14.7-15.0 (both AEM gauge and reading in ODB+
ICV: 93% Open (according to ODB+)
Ignition Advance: 4.1 (according to ODB+)

Here's another test I did. I removed the oil fill cap and NOTHING happened. No change in RPM, no change in AFR, nothing. According to Chat GPT (I looked for CarBot but couldn't find any such chatbot?) that would mean I'm already getting air introduced into the crankcase somewhere. I'm thinking it could be the dipstick tube as I doubt that seals properly (even though I have the o-ring and the plastic spacer and it's bolted to the IM. Any thoughts on that?

Lastly, if I were to go "old school" on this, the vacuum gauge literally says "slow ignition timing" between 14-17 in HG. I checked my timing marks and they seem "ok". Any thoughts on this?

CarBot is still under development (as I add Porsche info to the back end), so is only available in its own subforum for now, located here:
https://www.carpokes.com/viewforum.php?f=65

On the ignition timing, I think you are mixing apples and oranges. It sounds like the gauge is talking about when the spark plugs fire (ignition timing) whereas the timing marks on the motor relate to when the valves open and close. I'd park all that for now. If you cam belt is aligned, you're good. The ignition timing is set by the DME and out of your control for this purpose. If it's retarded, that's a result of whatever is going on, not a cause.

On my F9 DME, I believe my ISV duty cycle reads backwards -- i.e., 93% open is really 93% closed. I'd flagged that for Joe but never got a response. I'd park that one for right now too as a result. (You could test it by turning the throttle screw on top of the throttle body, and then checking to see if the reported ISV duty cycle compensates in the right direction -- but I'd say that's a rabbit hole not worth going down right now.)

Your warmed up numbers are not 'that' bad, but do still point to a vacuum leak. I went out and warmed up my car to replicate the oil cap removal test and can indeed confirm my motor stumbles quite noticeably when I remove the cap. So, if yours does not, it likely means you already have a leak that the DME is already trying to compensate for. It also may point to that leak coming from the crankcase and AOS hose. Easy enough to check: pull the AOS hose off the j-boot and seal off both sides. If the leak is coming from the crankcase via that hose, your vacuum should go up and AFR should richen up.

If plugging the AOS port improved vacuum and makes the AFR hunt above and below 14.7 -- then I'd start by checking for the thick, light brown o-ring inside the oil cap. They can come loose and disappear. Also, how is the seal at the top of the AOS? It is not officially replaceable, but people have been known to pry off the top and replace the seal ring (not always doing more good than harm). If yours is leaking, you'll often have a mess of oil mist around it. Those would be my top 2 suspects if the leak is coming in through the AOS, since smaller leaks wouldn't produce the magnitude of problem you are seeing -- though I suppose there are plenty of possibilities.

If plugging off the Jboot/AOS port does not fix the issue, then the hunt continues for the source of the leak/problem...

Thanks so much for all the help, Tom. This is great. I did replace both the AOS (with a brand new one $$$) as well as the oil fil cap about a month ago (have a video on it - replaced without removing the turbo!). Regardless, I'll be re-testing by isolating the AOS system tomorrow - I should have included that in my latest testing video. My adult ADD brain often has me going in a million directions, so eliminating some possibilities and setting some clear steps helps a lot.

[NCGermerican]

Update. Pulled the AOS to jboot hose and blocked both sides. Car ran horrible and I pulled the dipstick. It almost shot out of the tube. I immediately pulled the plug out of the AOS side and a ton if air came rushing out. It made zero difference in vacuum though.

That tells me there is too much crankcase pressure. Since my compression test was good, I think I’m getting air in the crankcase somehow. That might also explain why I have a LOT of oil in the intake system (charge pipes and intake) to the point where I’m getting blue smoke (while light) from the tailpipe.

I think it makes sense as having that much pressure in the crankcase would act as a vacuum leak and push unmetered air into the intake system through the jboot. The question is….where is it getting into the crankcase.
? The short block, AOS, AOS seals, turbo oil vent line, oil cap…..all brand new. Smoke test on the intake system coming tomorrow.

My question is… how in the world do the LR catch can/breathers work, unless they have a check valve?

Im scratching my head. I have ZERO oil leaks. The only thing I can think of is could the turbo (Raptor X) be pushing air through the turbo oil vent line?

[Tom]

The only thing that can create positive pressure in the crankcase at idle is ring blow-by. Combustion gases blow past the rings and pressurizing the crankcase. Static compression tests don't rules out blow-by unfortunately, as the pressures in a running engine are significantly higher than when just cranking the starter.

That said, all motors have some blow-by, and by capping off the AOS, what you saw may have been just a normal (or not extreme anyway) amount of blow-by that was bottled up in the crankcase. The longer it was bottled up, the more pressure that would be normal. There's no practical way to say how much is too much, but in general you would expect some pressure, and you would expect that pressure to build the longer is stays bottled up. Since you are seeing blue smoke, you might want to do a leak down test, which is better at detecting bad rings, but my guess is that this is another rabbit hole not worth going down right now. Excessive blow-by would be a concern, but probably not the cause of your low vacuum and lean AFR -- or at least the sole/primary cause. I'd park that for now.

Since the vacuum remained low and AFR remained lean, what the test did show is that the AOS hose is not the source of your issues -- so things like oil cap and AOS seals can come off the list. When you removed the oil cap and nothing happened, that's probably because your DME was already offering its max compensation for lean conditions, so adding another leak was just another drop in the bucket.

Hate to say it, but I think all this means the search goes on.

You can try the same test with the other hoses going to the j-boot and I/C pipe, especially the one from the brake booster. If you disconnect and plug any of them and that increases the vacuum and AFR, then you found the source...

[NCGermerican]

Hi All - just an update. I posted my latest video this morning and I wanted to give some more color in this thread for those following along.

Basically, I installed the Storch MAF kit. It was EXTREMELY easy to install. The thing that took me the longest was soldering on a custom single pole connector along with an in-line fuse. If I were to just use the piggy back harness (to the ICV) that came with the kit, the whole process would have taken less than 30 minutes.

I fired the car and it ran exactly the same as how it did with the AFM. While it didn't solve any of the issues (except possibly the dead spots), it tells me that it's working like it should - disguising the fact that there's a MAF to the DME (instead of an AFM). Unfortunately, I didn't hit the record button on my phone so I don't have any of that footage.

After that, I sort of went "back to the drawing board" and did a lot of thinking. Here is a full list of the issues I have had, both long term and shorter term:

1) Low engine vacuum (10inHG Cold, 15inHG Warm) - this was an issue before AND after the motor replacement
2) Lean condition on warm start - this issue started about 2 months after the motor replacement
3) Oil pressure cold is 4.5 bar, fully warm is about 3.8-4 bar - this was an issue before AND after the motor replacement
-head rebuilt, short blow rebuilt, replaced OPRV, Oil pressure sending unit and dash gauge with no change
4) Excessive oil in the charge pipes (and probably now the intercooler as well)
-I disregarded this because I have always read "there will always be SOME oil in the charge pipes". What I didn't realize is that "some oil" should only be a slight film, not to the point where oil will pour out of the charge pipes, even after only idling.
5) A high pitched "squeak/squeal" from what I thought was the throttle body, but using my stethoscope didn't pinpoint the sound to that are. - this happened before and after I replaced both the motor and the throttle body.

So, I decided to investigate the charge pipe oil issue. I thought maybe it was coming from the AOS into the J-boot. I disconnected the AOS line to the j-boot and plugged BOTH lines (a big mistake). About 30 seconds after starting the car, it started freaking out - it went extremely lean and the ICV seamed to have no idea what it was doing.

I pulled the dipstick and the force of air coming out almost blew it through the hood. My mistake was that I blocked off any way for the crank to release any pressure. I then noticed a very light bit of blue smoke from the exhaust while the car was idling.

My only thought that maybe the issue is with the turbo (Evergreen Raptor X). I called up Charlie and talked through my issues. He thinks that with my previous motor, which had extreme blow-by and pressurized the crank case to the point it blew my RMS, AOS seals, etc, it could have blown something inside the turbo (seals, bearings, etc). He also said that "chirping" noise when I blip the throttle could very well be the impeller wheel making slight contact with the housing. So - the turbo has been sent to Evergreen to investigate.

If I truly roached the turbo, then that could explain a lot. I'm not sure if any of the following is correct or a possibility, but I'm wondering if something broke internally and either A) allowed outside air (from hot side?) to enter into the the air and/or oil system. If into the air, that would definitely be unmetered air. If into the oil system, then that could explain consistently "higher than expected" oil pressure even when warm. The additional oil in the intake system could also through off combustion. EVERY time I pull off the intake manifold, some of my gaskets are oil soaked.

I'm going to do a leakdown to see if anything in the block or head is leaking. As crazy as it sounds, I HOPE that the turbo is broken and therefore, would be the source of my issues. Since many of these issues happened before and after (essentially) a full motor rebuild, the lowest common denominator is the turbo.

Oh, and I'm going to change the oil thermostat to see if that does anything..........

[Tom]

Ug, sorry. A bad turbo can leak oil and make noise, but it won’t create crankcase pressure or explain such low vacuum. Based on your description, it sure sounds like your engine is building excess crankcase pressure. It may have other issues as well, but that’s the piece I’d focus on first. What exactly changed and what stayed the same with the swap, and what was the condition of the replacement motor? Excessive blow-by seems quite possible. A leak down test would be a good next step.

Talk to Charlie, but my concern is the turbo is a victim here, not the root cause, and you risk damaging it again if you bolt it back on before sorting out the crankcase pressure. When the crankcase is pressurized, the turbo can’t drain properly, oil backs up, gets pushed past the seals, and ends up in the intake -- pretty much exactly what you’re seeing. That pressure wasn't coming from the turbo (even if it does, indeed, need repair at this point), so I'd hate to see you get it rebuilt only to have the same thing happen again.

Leak down is a good next step. Changing the oil thermostat feels a bit random...

[chrischrischris]

You wrote about a new oil filler cap. Do new ones come with the seal ring or do you need to install it separately? Basically just checking it has the seal.

Is all of this pointing to an issue with the rebuilt short block?

[NCGermerican]

Ug, sorry. A bad turbo can leak oil and make noise, but it won’t create crankcase pressure or explain such low vacuum.
Based on your description, it sure sounds like your engine is building excess crankcase pressure. It may have other issues as well, but that’s the piece I’d focus on first. What exactly changed and what stayed the same with the swap, and what was the condition of the replacement motor? Excessive blow-by seems quite possible. A leak down test would be a good next step.

The head was rebuilt with new valve guides, seals and springs about 2 years ago. The short block was replaced in August of last year (right before 944Fest). It's actually an 86 block (car is an 87) and was machined/sleeved with Wossner pistons (100mm bore). If there was a "weakest link" in the reassembly, it would be the head gasket. Due to time constraints, I had to go with a factory/Reinz 104mm "factory style" head gasket (both block and head were resurfaced). I really wanted to go with a Cometic steel HG, but the lead time was too long. The new short block has around 1,000 miles on it.

Talk to Charlie, but my concern is the turbo is a victim here, not the root cause, and you risk damaging it again if you bolt it back on before sorting out the crankcase pressure. When the crankcase is pressurized, the turbo can’t drain properly, oil backs up, gets pushed past the seals, and ends up in the intake -- pretty much exactly what you’re seeing. That pressure wasn't coming from the turbo (even if it does, indeed, need repair at this point), so I'd hate to see you get it rebuilt only to have the same thing happen again.

I definitely think the turbo was the victim and I'm hoping it was victimized by the previous block and not the new one. The compression test was very good (155, 155, 149, 151), but I think the leak down will tell more. I'm also going to remove and flush the turbo drain and vent lines in the engine carrier arm.

Outside of that, I don't know what else it could be. When I talk to Charlie, I'll ask him if it's possible for outside air to enter into the system if the seals or bearings are bad. If so, then that could be the mysterious vacuum leak which could lead to both low engine vacuum and lean idle.

Leak down is a good next step. Changing the oil thermostat feels a bit random...

Oh it's definitely random. BUT, I'm going through the process of updating any components that were shared from the old block to the new one as it relates to the crank/oil system. I reused my oil filter housing (after giving it a thorough cleaning), but didn't touch the thermostat. On the Lindsey Racing Website, their listing for the oil thermostat states "
We suggest you replace this when doing an engine rebuild to be on the safe side." For $100, I figure why not. I did remove and flush out the external oil cooler when the motor was out, so I don't think there's any blockage/constriction there. I plan on removing and flushing out the intercooler (LR Stage 2) this weekend as well as test it for leaks.

[NCGermerican]

You wrote about a new oil filler cap. Do new ones come with the seal ring or do you need to install it separately? Basically just checking it has the seal.

Yep - the new cap came with a fresh gasket already installed.

Is all of this pointing to an issue with the rebuilt short block?

I sure hope not! The fact that most of the issues started before the block was changed makes me "hope" that it must be something that was not changed (lowest common denominators, like the turbo).

[Dkraven]

NG, if I could hijack your thread a little - I just dug into my new to me 86 951 with milky coolant with a plan to change the head gasket, took off the head, and found bore scoring. Now I'm looking at sleeving and am curious about your experience. If you want I can start a separate thread to discuss this, but my main questions are -

Did you use flanged or straight sleeves? Assuming steel? What material were the rings on your pistons? I understand OEM rings meant for alusil cylinders don't vibe with steel liners. I'm kind of wanting to reuse my pistons but am starting to accept that I might need to get new ones.

Anyways, any tips you can give me, I'm suddenly in deeper water than I'd hoped and trying to find a lifevest.