Black51

So my car is pulling 12-13 inches of vacuum at idle. It sporadically shuts off too. I pressure tested the intake and found a leak at the thermo vacuum valve. Ok. But there is also a massive amount of air flowing in the #1 cylinder area of the cam housing. I turned the engine over several times, thinking it was probably just air rushing past open valves in that cylinder. No change. I couldn't feel air coming out anywhere in that area, including the header. I also poured soapy water on the small space where the cam gear housing mates to the camshaft housing. There were a few tiny bubbles... I will be doing a compression test next week to rule out the cylinders.

My question is can a leaking camshaft seal be the cause of my low vacuum? This problem has been driving me nuts since the fall, and renders the otherwise awesome car undriveable.

black944 turbo

Did you pressurise the j-boot? If so, did you disconnect and plug the line running to the Aos? if you pressurise the j-boot area you have to disconnect and plug that line as it is always supposed to be under vacum and by pressurizing it you are in turn pressurizing your crank case. Not a good thing.

F18Rep

Its a pain to do a thorough boost test. Here's how I do it...Bruce

Black51

I intentionally pressurized the aos because I suspected it was leaking. I may end up pulling it and visually inspecting it also. Test pressure was not high enough to blow oil seals. But i need to find the problem here. Again, the only area where i could hear air was at the #1 cylinder around the cam housing. The car does not burn oil btw.

black944 turbo

You should not ever pressurise the Aos. That is my opinion and several people have differing opinions on that. It never sees boost on that end at all and as you say it can blow seals. How much pressure did you apply?

Auto_Werks 3.6

removing the AOS is not fun.... turbo out procedure.

Black51

I have a vband exhaust and turbo. IMO, the exhaust is the worst thing to deal with on this car. So I built it so assembly and disassembly is like lego. Removing it and the the aos will not be a problem once I have a chance to get under the car.

Pressure was as much as 15psi. But for the most part, I was running a trickle of air to listen for leaks but not have air rushing through the earlier mentioned area. It was too loud to hear anywhere else.

NCLA951

I had this happen the last time I pressure tested, it seemed to hold pressure all right, but I could hear it like a valve was open on cylinder 1. Compression test was ok so I don't really know where it was going, valve guide maybe?

Black51

Soooo, some development...

Today I was poking around under the hood looking for vacuum leaks/anything out-of-place looking, etc. Couldn't find anything unusual, as usual. Then I decided to pull the TPS plug out of curiosity. Aside from the idle going up, the vacuum goes up to 17ish inches, the car runs absolutely smooth (no coughing, hiccups, or misses like before), and didn't shut off in about the 15 minutes I had it running without the TPS plugged in. As soon as I plugged it back in and the idle went back down, the coughing, hiccups, etc. returned. The car only shut off once on me today. And that was with the TPS plugged in. Another quick test I tried was with the TPS still plugged in, I adjusted the idle up to approximately where the idle sat without TPS. The car still showed the aforementioned symptoms with the TPS plugged in. A couple of other things I noted were that the vacuum at idle was lower than unplugged, and engine deceleration vacuum was lower.

The vacuum comparisons were:

At idle - TPS - 14in, no TPS - 17in

TPS plugged in & matching no TPS idle - TPS 16in, no TPS 17in

Engine decel - TPS - split second at 16in, then 14in, 18in when injectors kicked in, then 14in, no TPS - 19-20in, then 17in

I hope those comparisons make sense. I might make a vid tomorrow to show this. The engine definitely runs perfectly smooth with no TPS, and stumbles with TPS. So my next step will be to test the TPS. Hopefully I've found the culprit.

Black51

Tested the TPS today. It checked out within specs. Also pressure tested from the IC inlet and found some leaks. Thanks for the suggestion F18Rep. The ICV was leaking pretty badly. So I pulled it, glued the bottom of it with epoxy, and put everything back.

Vacuum now is at 15-16in with TPS, and steady at 18in with no TPS. The car still runs rough with the TPS plugged in. I was doing another pressure test and heard something leaking, but then the IC hose decided blow off and one of the gear clamps went flying somewhere. I'll have to find it, put it back together and pressure test it again tomorrow to find what's leaking. Time to switch to T-bolt clamps...

My thoughts at this point as far as the rough running is either a bad ICV or TPS, even though the TPS checked out. The symptoms seem to come on once the temp gauge needle hits the first line, and the TPS is plugged in. But I'll fix this leak and go from there before making any more decisions.

Black51

All vacuum leaks fixed. Still no change. Going to borrow a working TPS to see if it makes a difference.

Tom M'Guinn

Have you set your base idle? You'll get more vacuum as the idle RPM goes up, so that may explain why it goes up with the TPS disconnected. Do you have a wideband? Would be useful to see what's happening with the AFR. Did it start after making mods or repairs, or just start out of the blue? Which m-tune do you have? There were some threads on the LR version worth reading.

Black51

I've set the idle several times, as in checked and re-checked. Understandably the vacuum goes up with a high idle. But it's also the fact that with the tps plugged in, it fluctuates now between 14-16in, which correlates exactly with the stumbling/skipping beats etc.

Wideband shows about 15.1-15.4 qhen the engine struggles. Then it returns to 14.7 and sounds like it should. It keeps doing that cylce constantly.

Yes, this has only happened since doing mods last year/year prior. Although this problem didn't happen right away. It seems like it came about over time. The engine was out. Did the oil seals, built an exhaust, popped in a gt30, wired in new LR injector and engine harnesses. New HV fuel pump. The car has had an m-tune direct fron Rogue with no issues. New Rogue ECU, tuner and logger put in. All directly from Rogue. All sensors except tps are new.

I'll try to put up some vids to help show what's going on.

Black51

Ok here we go:



The vacuum shows 13-14in in the second vid, but that was taken prior to fixing some vacuum leaks. The engine still behaves the same though, and the afr's are the same as in the vid.

Black51

Swapped the tps out for another one. No change. Ran the engine for an extended period with the isv bypassed. The engine still struggles. I'm running out of ideas.