Rebuilt my engine ... having running issues - input appreciated

I posted here last year about my engine throwing a timing chain. When I took it apart, there was very little collateral damage so I decided to challenge myself and rebuild it (dealer said new engine). It�s now up and running ... but I have a few issues. I wonder if any of you serious gearheads can help diagnose these problems: 1) The engine seems to run fine but won�t rev past idle more than a few hundred rpm. (timing? computer?) 2) After the third test start-up, white smoke (ie: coolant vapor) slowly started to appear out the exhaust. Could this be the AOS ... or more likely internal (ie: head gasket)? I've only run the engine three times for about 3 minutes each. I thought the problem might be that the computer needed time to re-adjust so the last time I ran it I was aiming to let it get up to running temperature and run for a while to see if it would rev ... then I saw the white smoke (well, steam) and shut it down - I�m worried about damaging something like the catalytic converters. Any thoughts appreciated .... (As an aside, the secondary air injection pump died within the first few minutes of the initial startup (high whine, white smoke, giving me a heart attack) and I took the unit out .... so the engine is running without it. I don�t think it has anything to do with the issues I�m having - as I understand, it just blows fresh air into the exhaust for a few minutes during start-up as part of the pollution controls.)

What year is your car (egas or cable)? My cabled '99 had no problem revving when I re installed it last fall. The steam could be condensation from the exhaust.

Imo - It's a 2002, so e-gas. As for the condensation - maybe that's what it is. I'll see if it's still there when I figure out the rev problem and restart it. BTW, thanks for putting your rebuild on - it was encouraging and I got some good tips!

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Having a hard time with what could keep the engine from revving past idle. If there is some timing or DME problem I can't think what it would. Not a common abnormal behavior in my experience. One explanation is the e-Gas system is not working right and the throttle is not opening. There's fuel supply of course. Pinched line. Or just a going bad fuel pump or a fuel pump relay. (Long shot but what's the fuel level like? And how long has that fuel been in the tank?) There is of course an intake blockage possibility. Lose a shop rag in the air box? (Long shot and not sure if it is even possible with an interference engine -- there's a limit to how wrong the timing can be and the engine still turn over without the valves making contact with the pistons -- but super wrong cam timing could be an explanation.) How did the engine react when you tried to rev it? However, I'm not sure you should run the engine any right now. First an engine that has been apart is going to smoke from the assembly lube (oil) used to lube the pistons/rings/cylinders. (When assembling an engine I was taught to dunk the assembled piston with its rings and rod into a bucket of clean engine oil to let the oil get everywhere then put the assembly in the cylinder. Obviously some of this oil runs away/down but enough remains that upon the first start the engine smokes likes a two-cycle engine.) But you need to be sure there is no coolant leak into the engine. Did you smell antifreeze in the exhaust? How's the coolant level? The oil level? Drain some oil out into clean pan and look for signs of water/coolant in the oil. The engine has not run enough to perhaps make an oil analysis of any value. But it is cheap enough to have a sample tested for any presence of anti-freeze chemicals in the oil. Also, "reading" the plugs may not be of much value but you want to use everything at your disposal to know for sure the engine coolant is staying where it should. I would get the secondary air system working right. The DME expects additional air being injected upon cold start and it adds extra fuel so the air and fuel burn in the converters to help warm them up. It would be the white smoke you saw was the result of excess fuel without the extra air. But first you have to be sure there is *NO* coolant leak.

Thanks Macster. The gas is a year old now - guess that could possibly be it. Don't think there's a rag in the air box ... hmmmm. When I try to rev it, it goes up a few hundred rpm and then kind of bogs. Take my foot off the gas and it settles back into a good idle. Yes there was a lot of oil on assembly - could be it just burning off. I drained all the oil to inspect it and saw no indication of coolant visually. Coolant level is static. Oil level seems fine. Had to add more than what the manual listed but I just assumed that with a rebuilt engine, it has more nooks and crannies to fill than with a regular oil change. Will check plugs and get a new air pump to complete the system - good point. Thinking of buying a diagnostic tool - don't know anything about them, what should I get - Durametric or OBD11 ...?

I'm not familiar with the 996 egas but if its anything like the Audi with the egas then there is a procedure to synchronize the gas pedal with the throttle servo on the engine. Find out if this exist with the 996.

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Yes I did the synchronizing procedure ... but I just reread the manual and they mention the power supply has to optimum. I was dealing with a weak battery at the time so maybe that's part of the issue. I just bought a new battery so will try again. Thanks.

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Poster Imo000 raises a good point one -- the e-Gas needs to be re-calibrated -- that I intended to raise also in my post but forgot. I do not know what if any effect this can have on an engine if it is not done but you should do it and do it right to eliminate it as an explanation for the abnormal behavior. The amount of oil in the (owners?) manual is not gospel. The factory supplies the correct amount which is tied to the car's VIN. In the factory manual there is an amount given for a oil/filter service with a drain time of so many minutes and with other preconditions, but there is also the engine's complete or total oil capacity the amount of oil that is needed the first time to bring the level to its proper, well, level. As you now realize by having the engine apart the engine was quite dry and the engine was very similar to the condition it was at in the factory when new thus the amount of oil needed was higher than the usual amount for just an oil/filter service. The main thing is you do not want to run the level too low nor overfill the engine will oil. And in this case you want to make sure the oil stays in the engine.

The behavior reads like a lack of air. If it were a lack of fuel or the wrong fuel pressure the mixture would be wrong and the engine would react differently is my take. I have to stress that you must be sure there is nothing in the intake, or the exhaust interfering with the flow of air into, through, and out of the engine. Do you have kids, or kids that like to visit your workshop? Or possibly a friend who helped you during the rebuild process? Someone might have for some reason tucked a rag or something else into the intake or even the exhaust. A blockage in either could very well account for the behavior.

I'm away for the weekend (long weekend here) but when I get back I'll re-calibrate the e-gas with the full battery and if that doesn't work, I agree, it seems like an obstruction. I may have to drop the engine down again so I can the intake runners off and check inside. I don't have kids but maybe this big kid did something dumb. I was watching the oil level carefully, being aware that it was 'drier' than normal after a rebuild. Thanks for your input! Will be back to it Tuesday.

What happens when you push the throttle plate open with your finger?.

Sounds like it needs a system adaptation or "hand over" to me. You also may have left one of the brown ground wires in the main harness disconnected and it has the system pissed off. Or the cam timing is off and it mechanically will not rev. Post a video of the occurrence. The car isn't a tiptronic by chance, is it?

Hey, thanks for all the input everyone - the car is now running fine. I think it was a collection of small things (like the throttle body plug not seated just right) but in the end I think the real culprit was old gas ... 15 months old to be exact. I drained the old gas out and put in fresh hi-test and it now starts easily and revs freely. As for the white smoke, it has completely disappeared so I guess it was just assembly oil burning off, or condensation. So, she runs well and there are no leaks. Feels good! A few pics of the build:

Nicely done! Congrats on your rebuild. Thanks for posting pics and updating us all. Best, TomF

Great to hear. Gives some of us courage to rebuild when our motor pops.

Glad you were able to trouble shoot your engine idle issue. Thanks for the rebuild pics. You should be pleased that your Porsche is happy and healthy again.

Great to hear of your successful rebuild story. Nice job.

Congratulations Bill. You're indeed an inspiration to all of us amateur wrenches. Pardon me for being gauche...but what did you end up spending on the rebuild? jasper

Do you have a pic(s) of how the pistons and cylinder walls looked? Some more details on what you did would be great. Awesome job!

That's some old gas. I got a chance to experience 6 or more months' old gas with a new Infiniti. The tank was filled up in Jan of 2012 and then not filled up again until July of 2013. The car sat with very little usage, like maybe no more than 30 minutes of run time (and most of that just one drive) over that time. Then in July I went and picked up the car to use for some personal business, personal business for which my Porsches were not at all suited. The engine didn't react too badly. It started and idled and run ok, though on the road I thought the engine was down on power but not being that familiar with the car just believed it was the nature of the car. So I drove the car around until the tank level got pretty low and as the owners manual stated I filled up the tank with premium (Shell). Wow! The engine really perked up and its performance and throttle response was like night and day different from before I filled up the tank. I guess with another 9 months or so of aging the engine might have refused to run above idle, maybe not even run at all. Anyhow, glad you got it all sorted out.

Thanks Tom, Mhenry, Barn, Alpine, Macster and Jasper. I took my sweet time but I�m pretty happy with the results. Jasper, I haven�t added up all the bills but I think it�s under $5000 and that includes maintenance items (clutch, tensioner pads, IMS bearing, etc) replacing damaged parts, plus specialty tools. Not bad considering, plus I quite enjoyed the project. KrazyK - the bores and pistons were really good as were the bearings. The car has 130,000 kms (80,000 miles) on it. Basically I had to replace the timing chains (one broken); a scavenge oil pump because it had a piece of broken chain jammed in it; the IMS shaft because the chain chewed up the gear (that was the costliest item at $1300 but it came with a new bearing, not that mine was bad but I would have changed that anyway); and a few bent valves. Those were the only damaged parts. The rest was just cleaning and checking and making sure no bits of chain remained. And of course, all new seals, gaskets, bolts and tensioner pads throughout. Hats off to local Rennlister pterfloth who loaned me tools and expertise and time. Thanks tons Pat. Some more assembly pics below: Cleaned half case; installing wrist pin clips blind in the middle of the block (sheesh!); lowering the crank cage into one case half; rebuilding a head; keeping lifters sorted; crank cage apart. Clean, clean, clean!

But this is my favourite picture: back down on the ground!

Thats what else I was wondering. So it CAN be done blind. Great info and pics!

Excellent job, not only on the rebuild, but also on the starting problem diagnosis and fix. Congrats!

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There are special tools for the install but you can still mess up if the clip isn't seated properly ... or you drop a clip inside like I did and you have to split the cases again to find it. You need a snake camera to check your work. Macster - interesting gas story. We don't often leave new cars sitting. I'm used to having older sportscars that have sat for 6 months through the winter and always start up in the Spring. (But decidedly low horsepower and low tech) Take a new(er) hi-performance car, plus let it sit for over a year ... different story. I should have been on it much sooner.

billyboy, great to hear you have finally got around to fixing that engine of yours, I almost wondered if something had gone wrong with your rebuild as mine has been on the road for a year since my build and I think both our chains expired about the same time last year although mine needed many more parts than yours, you lucky fella. I'm glad its sorted, and I'm made up for you, I konw only too well the satisfaction of firing it up after a self build,...enjoy. Did you time it up yourself? Bad fuel can turn into treacle and isn't good when its been sat for a while.

Thanks Chris. No excuses, it was a slow rebuild ... but partly in my defence, I was shipped the wrong timing chains and had to tear the engine right down to the crank and start over so that put a damper on things. Damn, I know that engine inside out now! Yes I timed it myself ... you need a(nother) special tool but it's pretty straightforward in the manual.