Rough running problem (long)
09-01-2011, 11:10 AM
#31
Rennlist Member
I am going to guess false air leaning out the mixture past the point where the LH/Narrow band O2 sensor can compensate. The Wideband/Shark Tuner will tell us this in short order.
Have you tried to pressurize the intake with the kit that Roger sells (the one with the big MAF rubber boot/PVC/Pressure gauge)?
And.....I wouldn't want to spoil you Jim not having to shift all those gears all the time
Have you tried to pressurize the intake with the kit that Roger sells (the one with the big MAF rubber boot/PVC/Pressure gauge)?
And.....I wouldn't want to spoil you Jim not having to shift all those gears all the time
09-02-2011, 12:34 AM
#33
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
I need to get an oscilloscope on the outputs of the injector lines for both batches. It sounds like an intermittent short in the injector harness.
A failing ignition problem will create either the IMS shutdown, or it will backfire with unburnt fuel in the exhaust. I'm pretty sure this is a fuel metering problem. It can also be causes by incorrect resistance on the injectors themselves. Either a short, or an open circuit can affect all four injectors in the batch. That will make it run funny, without any IMS trigger or backfiring.
<edit: I think my Oscope is at Rogers house if you want to use it yourself. I can find the test points for you, or we can connect and do it together.>
A failing ignition problem will create either the IMS shutdown, or it will backfire with unburnt fuel in the exhaust. I'm pretty sure this is a fuel metering problem. It can also be causes by incorrect resistance on the injectors themselves. Either a short, or an open circuit can affect all four injectors in the batch. That will make it run funny, without any IMS trigger or backfiring.
<edit: I think my Oscope is at Rogers house if you want to use it yourself. I can find the test points for you, or we can connect and do it together.>
My understanding is that all the injectors share one ground. The IMS circuit is separate and does break the injectors into two batches. The short would have to be in the IMS circuit, not the injector harness, to knock out only 4 injectors.
09-25-2011, 01:18 AM
#34
Thought I'd update this thread for Jim.
Jumped in to it this weekend with a clear mind and wanted to start from scratch. The first thing I wanted to do was re-pull the intake as the last time we did it we installed new GT cams, sharkvent and as anyone knows, when you pull cams, you are doing an *** load of other things.
When I pulled the intake I found a couple of things that could cause a crap idle, which could in turn foul up the rest of the running. ISV to boot hose. This is turning out to be an issue since Porsche seems to think that if they supply a hose that is 1/2 an inch shorter than what they put in there, it would be ok. They failed there. This was part of the issue on Jims car and we had to fix it.
Nology wires. They look really good. Nice and blingy. When you buy them and are all happy that they look good on the car, don't worry about what it will cost you in a few years to replace them because they are a crap set up. Not worth loosing sleep over. The stock Beru's only lasted 19 years.
When you do an intake refresh, replace all the rubber, not just the ones you think seem bad, do it all. That is just advice. When we did Jims 2 years ago when we did the cams, we did replace everything we just did not clamp down all the hoses in the intake. Porsche didn't so we figured it wasn't a big deal. Clamp them, even on the MAF boot.
As of tonight the car is a freaking beast.
Jumped in to it this weekend with a clear mind and wanted to start from scratch. The first thing I wanted to do was re-pull the intake as the last time we did it we installed new GT cams, sharkvent and as anyone knows, when you pull cams, you are doing an *** load of other things.
When I pulled the intake I found a couple of things that could cause a crap idle, which could in turn foul up the rest of the running. ISV to boot hose. This is turning out to be an issue since Porsche seems to think that if they supply a hose that is 1/2 an inch shorter than what they put in there, it would be ok. They failed there. This was part of the issue on Jims car and we had to fix it.
Nology wires. They look really good. Nice and blingy. When you buy them and are all happy that they look good on the car, don't worry about what it will cost you in a few years to replace them because they are a crap set up. Not worth loosing sleep over. The stock Beru's only lasted 19 years.
When you do an intake refresh, replace all the rubber, not just the ones you think seem bad, do it all. That is just advice. When we did Jims 2 years ago when we did the cams, we did replace everything we just did not clamp down all the hoses in the intake. Porsche didn't so we figured it wasn't a big deal. Clamp them, even on the MAF boot.
As of tonight the car is a freaking beast.
09-25-2011, 01:21 AM
#35
Oh, oil leaking in the valley? Use the early paper gasket along with the rubber o-ring, all your oil leaks will be solved.
09-26-2011, 12:28 AM
#38
Rennlist Member
Thread Starter
Guess I need to chime in here. I haven't even driven the car yet except to pull it into the garage. Worked all day (late) and was exhausted when I got home. I did get a call, at work, from Roger who delivered the car to my house. I don't remember his exact words but it was something like "Wow your GTS is so much faster and better than my Roger Box GTS." Anyhow, I owe Sean a debt of gratitude (in addition to the bill). My schedule is busy enough that it would have been weeks before I got to the issues he found. Thanks Sean!
09-26-2011, 05:44 PM
#41
Rennlist Member
Join Date: Jul 2002
Location: Deep in the Heart of Texas!
Posts: 3,267
Likes: 0
Received 5 Likes
on
4 Posts
So it turned out to be the 'ISV to boot hose'? And maybe one or two other things (i.e. Nology wires)? Makes me a little nervous since I did the manifold refresh job in 2010 ...
And did Roger actually drive it (post says 'delivered') ... didn't know he knew how to work a stick ...
And did Roger actually drive it (post says 'delivered') ... didn't know he knew how to work a stick ...
09-26-2011, 06:17 PM
#42
Rennlist Member
I have also had a very similar problem, intermittently, with my white 86.5, but it would never happen in front of my mechanic, so it has not yet been addressed.
The pattern I noticed with mine, was that it only happened when the A/C was on.
The A/C is usually on in Florida of course, because it is almost always hot, but I know it is in Texas also (maybe hotter there, but more humid here).
Would there be a reason for it to only occur with the A/C on, other than it just being hotter outside?
I started thinking that the condensation build up that happens under the center console, next to the passenger package tray was leaking down and shorting something in the wiring harness (like the 4 cylinder relay or similar on 86.5)?
The pattern I noticed with mine, was that it only happened when the A/C was on.
The A/C is usually on in Florida of course, because it is almost always hot, but I know it is in Texas also (maybe hotter there, but more humid here).
Would there be a reason for it to only occur with the A/C on, other than it just being hotter outside?
I started thinking that the condensation build up that happens under the center console, next to the passenger package tray was leaking down and shorting something in the wiring harness (like the 4 cylinder relay or similar on 86.5)?
09-26-2011, 07:08 PM
#43
Jim, let me know when you drive it, I want to know what your impression is. I didn't hear from anyone last night and was getting nervous.
09-26-2011, 09:14 PM
#44
Rennlist Member
Thank you, Sean, I took a look, and there is something mounted there, with an adjusting screw on it and what looks like a vaccuum line, as well as a line to the oil filler.
I would post a picture, but the engine compartment is embarrassingly not purtty - it wouldn't hurt the white car to get an intake refresh. I may just do that, or have it done. Has a procedure been written for the 86.5, as nice as Dwayne's for the 87+ ?
Thank you, again,
I would post a picture, but the engine compartment is embarrassingly not purtty - it wouldn't hurt the white car to get an intake refresh. I may just do that, or have it done. Has a procedure been written for the 86.5, as nice as Dwayne's for the 87+ ?
Thank you, again,