Desparate need of ENGINE EXPERTS

[harrisracing]

Here's the deal. I rebuilt my own 2003 Boxster 2.7L 5 speed engine after IMS failure. VERY clean rebuild, new shaft that was remachined for the triple row bearing upgrade. Followed factory rebuild specs, new valves on the head that jumped time, new lifters, etc. I can't get the engine to stop the "misfire bank 4-6" on this car.

Let's start this off thinking I am EXPERT level with engine rebuilds. My high end racing motors are ALL still together to this day and I have rebuilt at least 20 racing engines for overhead cam type motors. This includes a Subaru 2.5L engine that makes 400HP to this day on road-racing season #4. I am "familiar" with what it takes to build a modern-ish boxer engine.

This car cranks just fine, but it coughs and sneezes when it runs at idle and has a very rough idle. It cleans up a good bit at higher rpms 3-6k, but runs like crap and makes very little power when trying to drive it. I have checked the cam timing by going to TDC 3 times. The green plugs look good, I followed the factory timing layout by threading in the tensioners while the cam pulley bolts are loose and rolling things into timing positions before tightening cam bolts. I am quite confident that I have everything timed right...

A couple of things to note:
1) I was sent the wrong gasket kit for this engine. Things I noticed specifically were the orings that go between the lifter guide plate and the cylinder head were thicker than factory and a different color...but they went in. Brown was what came in the car, green is what went in the car. I DID reuse one side of brown ones because they just looked perfect and my engine was only 24k miles before IMS failure. I tore one of the other brown ones so on the other side I used green ones. I honestly can NOT remember which side had green and which had original brown, but I know they are different. When it comes to the lifter guide plate, would this cause the plate not to seat well enough?

2) I think the oil light comes on at idle, but I don't know if it's because its SO LOW of an idle and the engine is new.

3) The brand new lifters in one bank did NOT slide in nice and easy...they were kind of sticky and I NEVER should have run them in like this in hindsight. It should have been evidence of an issue, but I thought being NEW lifters they would run in a bit. Is the the source of my problem??? Do those guide plates warp? Maybe the thicker orings were on this guide plate and it's warped because of that?

I am asking these questions just to make sure there is nothing I missed electronically, etc before pulling the engine back out to check the lifters, etc. I'm quite confident the bottom end is together very well and I know that all the wristpins, etc went in fine (checked all with borescope).

I'm out $5k on this so far and I'm exhausted with it. It is SOOOO MUCH work to get done and I just don't want to do more than I already have so far.

ANY input is greatly appreciated.

Patrick Harris

[James Brown]

no help but, these are fantastic engines, the engineering is very cutting edge. what test equipment you using?

[Cajundaddy]

Caveat: Definitely not an m96 expert but I have been through a dozen other motors and understand your frustration.

Observation: Low oil pressure light is a bad sign on a fresh motor.

In the absence of error codes directing my search I would apply a basic process of elimination to the problem. First pull the plugs and see if they or visual inspection of the combustion chamber offer any clues:

Signs of oil intrusion

Signs of coolant intrusion

AFR too rich/too lean

Detonation

leakdown test

One of these should point you where to look next. Good luck.

[derfo]

[QUOTE=harrisracing;7503142]

ANY input is greatly appreciated.

Hello Patrick
I hope the experts chime in for you soon, "come on experts help this guy out". In the meantime have you ever looked at the website "986 fix". This guy successfully rebuilt a 986 a while ago now. There are very detailed videos on his site of the complete rebuild, it may help you, I don't know.

[harrisracing]

The compression is perfect on all cylinders and all plugs look great. Actually compression is very high like the valves are not opening all the way (closed for too long while running) The backfiring indicates the same. Maybe something wrong with the VANOS on that bank? Computer isn't picking up that though...

The oil pressure light is only on at VERY low rpms (where it "idles" at right now) and flickers with engine revs at idle only. It is OFF at anything over 500 rpms (this honestly seems normal). I don't think the oil pressure drop could be anything but in the cylinder head for some reason. Again, we haven't run it very long so maybe it needed to prime up more.

The scan tool is a SNAP ON solace scan tool - one of the best in the business from what I understand. I did try swapping sensors from bank-to-bank and it did not change anything.


Keep the ideas coming! I appreciate it!

[VirginiaF1]

Originally Posted by harrisracing

Keep the ideas coming! I appreciate it!

Sorry for your issues mate..
We 944 guys often try to eliminate the DME ( 80's-vintage CPU) as a contaminant whenever rebuilt engines run like slog.
Any same year/Engine code friends near you for a swap test?

If same result, how bout crank and throttle position sensors?

[Sapientoni]

I agree that perhaps something is amiss with the vario installation and timing, but I have not progressed to the reassembly on my current 987 project. Sticking lifters when new is not good. Low oil pressure is terrible on a newly rebuilt engine and sign of major problem. EG. 944 oil pump does not have a drive "key" in the crankshaft. My friend didn't pay attention when putting the bolt in, captured the washer out of position, torqued it down, had no oil pressure. Taking it back apart he had almost punched a half moon crescent out of the washer. Replaced it properly and had oil pressure again. It's all in the details and proceed slowly to prevent hard lessons.

Best of luck and we will be observing to learn with you.

[Sapientoni]

The oil pressure at idle cold should be 5 bars. After warm up 2.5 bars. I'd put a gauge in the oil sender port and get a direct reading. Low oil pressure is a killer and severe $$$$ depletion.

[bell]

Just a random thought.......did you check the coil connectors are on the correct coils on that bank? I did this once.......

[howe00]

The fact that the engine has no power suggests that maybe the cam timing is out.
When we built up a race engine we would always check inlet and exhaust opening and closing degrees before and after TDC. This is difficult with the box because the cover is the cam bearing housings. But if you were to remove the cover with the locking tools in place and then 2 temporary bearings caps on the end journals you could then check the timing exactly. A degree card can be fitted to the front pulley, dial indicator to the lifter cap. ...just a thought

[harrisracing]

I will definitely be doing this when I pull it down next time.

(This is assuming I don't find a buyer for it before I have time to do this next).

Thanks for the input. I'll be looking for the cam timing specs.

I was personally wondering about the lifters in this case. If they are collapsed or stuck they will not be providing the proper lift for this test....but either way I should see the issue while looking at all this stuff. I have all the dial indicators / degree wheels, etc for this testing so I'm sure I can get some solid numbers.

Thanks for the solid advice!

Patrick

[JJK78-951]

**no expert here** Sorry for the dilemma you are having... Just to back up a step, you said this is all because of an IMS failure... How bad of an IMS failure? Did you just find bearing material in the filter or did it fail and jump time? We have had some strange stuff happen on these motors at the shops I've worked at...
If you are not getting a check engine light then I doubt your problem is electrical as they will usually throw some sort of code if the electrics are out of whack... if it is electrical I doubt it's a loose plug~ Can the snap on tool show actual values for cam deviation etc? If not maybe try to borrow a Durametric if you can and see if it tells you anything.
Does your oil pressure read all the way up to 5 bar when revving? What is it at when revving at 700~? If it is only dropping when the motor is below 500 rpm then it is probably right, cause it's not supposed to run that low~ The o-rings could be suspect but once you get it running right I think it may take care of itself... Good luck.

[harrisracing]

So...I still have the car. FINALLY after moving, moving shops, building a shop, etc I'm back on finishing this project.

It will run on the 1-3 bank only and when revved to 2-3k it really doesn't sound bad BUT the 4-6 side never gets hot (even over ambient). Coils are sparking but seemingly wrong time as I am hearing intake backfires when it runs which points to cam or ignition timing, coils in wrong spot, or some other stupid issue I haven't found. Plugs are covered in fuel and CLEAN so I think fueling is good...just wrong spark timing.

I'm wondering if anyone has pictures of the intake cam on the 4-6 side specifically with the metal camshaft timing plate on the rear of it referenced to the two camshaft timing marks. I am maybe thinking mine may have been bent or something to cause it to maybe be out of time, but everything else looks good mechanically.

[harrisracing]

New plugs, swapped cam sensors, rechecked cam timing again at TDC (OT) (pics attached) runs exactly the same. Lifters all sounds good mechanically, traced coil wire colors and they are in the correct spots. Stumped aside from resetting time in the car including the variocam part. What else should i try before pulling the motor?

[bell]

when you assemble these engines, the cams should be installed at tdc for that bank......so when you installed bank 1 cams engine should be at cylinder 1 tdc, when you install bank 2 cams engine must be at cylinder 4 tdc....meaning you spin the crank 1 rotation to get cyl4 at tdc.......
I have built many of these engines....and would call myself an expert....pm me for my cell as in not on the forums a lot....and texting is easy along with pics you would need to send.
to me it sounds like bank 2 cam timing is way off or b2 is 180 degrees out.....

[bell]

sent you my info via pm.....text me....

[harrisracing]

I think you are right!

I have been doing all cams on same tdc...which is independent of ignition tdc. Duh...thanks. does ANYONE have a picture of all 4 cam locations at one TDC pin location?

I'll text after christmas. To verify this i will be able to run 2 compression testers on opposing cylinders and have someone roll by hand to see if they are both on compression stroke at same time. I'm betting you are correct and they are one tdc out.

This would be the first engine in my life that i missed timing setup ever. This includes my latest RB26 which i built and tuned myself which just put down 629 whp and 485 tq to the wheels on pumpgas. I know that may sound "know-it-all"ish but I followed a procedure and didn't like not being able to verify valve timing events, etc when i got it together.

Thank you and merry Christmas.

[harrisracing]

Can i swap the cams with the engine in or should i pull it?

[harrisracing]

Well that's amazing. Did a compression test on the opposing cylinders at the same time (1 and 6) and yep they both compress at the same time. Threw this idea out the window a long time ago because I've had strong compression on all cylinders from day 1...never checked at the same time but they were all paired up on the compression strokes.

https://youtu.be/XDwlfZHyhLc

Enjoy that disgusting video!

Pulling motor tomorrow. I'll have it back together hopefully monday. Can anyone think of anything else that may be went wrong because of this?

[bell]

no need to pull the engine......set engine at tdc1..... (will need to get a/c comp out of way) follow procedure to remove bank 2 cams.....
rotate engine 1 rotation, reinstall cams....
6 hour job max....