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DrMems
I think this cam timing is where it's at, you shouldn't get one bank nearly zero deviation and the other on the limit at around six degrees just after a build, that bank isn't times right and I'd bet if you sort that your car will be right!
DrMems
I think this cam timing is where it's at, you shouldn't get one bank nearly zero deviation and the other on the limit at around six degrees just after a build, that bank isn't times right and I'd bet if you sort that your car will be right!
I'd love to set the cam timing to where it belongs, but it costs something like $3K just to pull the motor out, which apparently is needed to fit in the Porsche special timing tool. Correcting the timing is additional cost. Unless anyone has a method of setting the cam timing with the engine in the car...
I'd love to set the cam timing to where it belongs, but it costs something like $3K just to pull the motor out, which apparently is needed to fit in the Porsche special timing tool. Correcting the timing is additional cost. Unless anyone has a method of setting the cam timing with the engine in the car...
No offense intended (well maybe a bit), but if you have signs that say you have a timing problem and you've already done just about everything else possible, then why not get the timing set properly?
I get that you've spent an insane amount on it already and don't want to spend more if you don't have to, but if it really is the timing then you'll just keep chasing your tail trying other things.
You have a known issue that could relate to the problem you are trying to solve, seems logical to me to get the issue solved properly.
The timing tool isn't so big, I can't comment myself without looking under my car, I did mine on the engine stand, I'm sure someone will comment. I think maybe you could just lower it down a little to give access, go and buy a hydraulic motorcycle lift and buy a porsche 996 timing kit off eBay and do it yourself, 3k to pull the engine , that's a lot , it takes half a day ??
The timing tool isn't so big, I can't comment myself without looking under my car, I did mine on the engine stand, I'm sure someone will comment. I think maybe you could just lower it down a little to give access, go and buy a hydraulic motorcycle lift and buy a porsche 996 timing kit off eBay and do it yourself, 3k to pull the engine , that's a lot , it takes half a day ??
$3K includes reinstalling the engine, refillling the coolant and A/C, etc., so I think it's about two half days of labor by a mechanic who has done it many times.
I might try your suggested eBay timing kit method. To answer Gnat's suggestion, I don't have any more thousand-dollar bills sitting around to fund a mechanic.
A 6* deviation won't cause poor running. It takes double that much to set an out of range CEL, and even then the engine will be an issue... You can have a 3 degree deviation advancement on one bank and 3 degrees of retard on the other to net a 6* deviation, according to what sensors you are looking at. I see the cam reluctors slightly bent, causing more deviation than this.
The REAL way to check the cam timing accurately is with a lab scope with at least 2 channels of capability, then scope each sensor and overlay the plots. I have seen the DME be absolutely wrong before.
A 6* deviation won't cause poor running. It takes double that much to set an out of range CEL, and even then the engine will be an issue... You can have a 3 degree deviation advancement on one bank and 3 degrees of retard on the other to net a 6* deviation, according to what sensors you are looking at. I see the cam reluctors slightly bent, causing more deviation than this.
Thanks, Jake. That's the bit of information I was looking for. Based on this, trying to reduce the Bank 1 camshaft deviation would be a waste of time and money.
Thanks, Jake. That's the bit of information I was looking for. Based on this, trying to reduce the Bank 1 camshaft deviation would be a waste of time and money.
Absolutely. 6 degrees is still barely within the Porsche spec.
It's been eight months and I'm still working on fixing the rough idle. To recap, I had a sticky intake valve lifter in cylinder 1. That was replaced at 100 kmi and most of the rough running was gone, but the car still vibrates randomly at idle. I don't feel anything wrong when driving. Here's what I've tried since then:
* 103 kmi: Looked at throttle body. Only a tiny bit of dirty film on it. Cleaned it with CRC brand throttle-body cleaner. No change.
* 104 kmi: Replaced vent valve between canister and throttle, P/N 996.110.129.33. Little if any change.
* 104 kmi: Replaced fuel tank vent valve, P/N 996.201.143.01.M100. No change.
* 105 kmi: One of the cats had low efficiency, so I replaced them with used stock cats.
* Somewhere in there I installed new stock Porsche engine mounts. No change.
* Also replaced all six spark plugs again. No change.
* My German-car mechanic suggested that a mismatch in fuel injectors due to minor clogging could be causing the rough idle.
* My local indy-car mechanic did a smog check (passed) and checked items on their list, including fuel pressure and flow rate. Everything looked fine. Their next steps, if I wanted to pay for them, would be shot-in-the-dark leak-down tests and scoping the cylinders. I'll wait. They said that if there were a misbehaving fuel injector, it would show up in the fuel trim, but those numbers looked fine, so they didn't think the problem was with the fuel injectors.
* 107-108 kmi: If clogged fuel injectors really are the problem, then fuel-injector cleaner might help. I fill with Chevron premium with Techron 90% of the time, but I gave it a try. I ran through two bottles of Techron Fuel-Injector Cleaner (not Techron Fuel-System Cleaner), then two bottles of STP Complete Fuel-System Cleaner. I think it's idling smoother, but is not perfect. I changed the oil (Joe Gibbs DT40) afterward based on reports of poor used-oil analyses after using fuel-system cleaner.
* I brought the car back to my German-car mechanic to have the fuel injectors pulled and sent out for flow-rate and spray-pattern analysis. The mechanic found cylinder 1, 2, and 3 misfires, which I have not seen with my Durametric or experienced myself. He then didn't want to pull the fuel injectors and wants think about what might be causing bank-1-only misfires.
* In his book, Wayne Dempsey says it costs about $200 for fuel-injector testing. Well, six new Bosch P/N 0.280.156.053 fuel injectors (which on Pelican parts I've ordered as Porsche P/N 996.606.122.00/14 and P/N 996.606.122.00/114) and, which are the same part number as I now have in the car, cost a little over $200, so it makes sense to try replace all six with new ones. I'll try that this weekend.
Last edited by DrMEMS; 11-28-2016 at 12:37 AM.
Reason: Typos. Added info.
Using my Durametric to look at engine acceleration when each cylinder fires (they call it "rough running"), I can see that cylinder 1 accelerates the crankshaft speed when it fires (see plots below). Maybe this is because I replaced the cylinder 1 fuel injector a while back and it outputs a bit more fuel and the other five injectors.
After the engine briefly warms up, cylinder 1 accelerates the engine speed when it fires. This is only at idle speed; when the engine is turning over faster, the acceleration disappears, which correlates with the roughness I feel disappearing when revving it up.
I couldn't figure out how to get the left fuel rail out. The supply line comes from the rear, unlike the photos in two books I have. Instead of replacing all of the fuel injectors, I pulled the new one from cylinder 1 and replaced it with the old one that I pulled a few months ago. That seems to work. I'd say that the rough idle I feel is 80% gone in limited testing. The graph below shows that, at idle, the cylinder 1 acceleration has dropped from about 3.5 (above post) to about 1 (graph below).
After swapping in the old fuel injector to cylinder 1, the measured roughness at idle has dropped.
Very nice and looks promising! This one was truly a puzzle. So your Cyl #1 misfire was caused by the stuck lifter first, and then by a bad fuel injector. Does that summarize it pretty much?
Very nice and looks promising! This one was truly a puzzle. So your Cyl #1 misfire was caused by the stuck lifter first, and then by a bad fuel injector. Does that summarize it pretty much?
Its always possible to have two problems, on the same cylinder at once... You can even have one problem spawn the other.
Bad intake lifters breed injector issues, since the intake charge travels back up the tract, and fouls the injector tip while the bad lifter does its thing.
Injectors are causing all sorts of issues these days with these engines, and they are often overlooked. I need to write a 5 page post about this..
Very nice and looks promising! This one was truly a puzzle. So your Cyl #1 misfire was caused by the stuck lifter first, and then by a bad fuel injector. Does that summarize it pretty much?
Not quite. I just had a stuck lifter in cylinder 1, which caused cylinder 1 misfires. In trying to resolve the problem, I replaced a lot of parts, including the cylinder 1 fuel injector. I think that the new injector was putting out a little more fuel than the other five, causing the rough running. When I put the old injector back in, the idle smoothed out. I caused one problem when trying to fix another!
It's been a week and a few hundred miles and the rough-idle fix is still working. I find myself lingering longer than needed at stop signs and when parking to feel the car doing...nothing, just idling smoothly.
It's interesting that the rough-idle problem didn't show up in the fuel-trim values, as one mechanic said it should.
Before, with a new cylinder 1 fuel injector, I had:
Bank 1 FRA = 1.04, RKAT = 0.94.
Bank 2 FRA = 1.06, RKAT = 0.84.
Afterward, with the old cylinder 1 fuel injector back in:
Bank 1 FRA = 1.06, RKAT = 1.03.
Bank 2 FRA = 1.10, RKAT = 0.75.
I think this means that the bank 1 injectors have a little longer pulses now (both FRA and RKAT are higher), so I might end up with a little more power. For bank 2, I can't tell whether the DME is sending more or less fuel. If anyone can shed some more light on this, I'd be interested in hearing it.
07-11-2016, 06:26 PM
