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Stumble, Rumble, Hard-to-Start

hmmm - i thought it was from day one.



well then, the decision is whether or not to diagnose it yourself, requiring purchase of tools, or to take it to somebody who has the tools.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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"well then, the decision is whether or not to diagnose it yourself, requiring purchase of tools, or to take it to somebody who has the tools."



That qualifies as the quote of the day, either within the context of this thread's discussion, or in very general terms.
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I'm all for buying tools, the question is whether or not I'd need a degree to use the AF meter. I have planned to get a durametric for some time, so now I should just pull the trigger. I've sent them messages and called but have no response back, which doesn't make me feel great. I just want to know if it will help with my questions about the <acronym title='mass air flow'>MAF</acronym>, Hall Sender, Crank Position Sensor, etc. I believe it would show "actual values" but I don't know how those are derived. I'll try to call again today, and I'll try one more shop that has good reviews and is independent.



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I'm sure you've said somewhere in this thread, but I'm assuming the blink test show nothing, right? Just displaying my ignorance here, but since I assume the durametric and the blink test get their information from the same source, would the durametric be expected to provide any useful information if the blink test isn't showing anything?
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it does show actual values on the MAF. it picks up the voltage readings from the ECU. i'm not sure how it does what it does, since there are only 4 wires for everything. i do know that i have looked at cylinder head temp and MAF voltage though. i can't remember what else i have looked at.



as for the A/F, they are actually pretty simple to operate.



regarding getting ahold of durametric, i haven't had that problem, but then it has been over a year too. keep trying via phone.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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Finally got through at lunch, but it was less than helpful. The fellow wasn't sure what it showed or what "engine temp" was shown, so I'll read through the manuals and pick one up anyway.



@MB968, are you talking about a gauge for AF mounted somewhere in the cockpit?
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Tama, sorry wasn't on the site yesterday. Spent the day at the track watching the "historic" races.



Yes I was referring to a gauge for both A/F, and exhaust gas temp. so you can watch them real time. I prefer putting them on the pillar post (can just see them my Mazda pic). This way they are always in the field of vision. They do get in the way a bit when autox since you're always looking sideways and the thicker pillar is a little more to look around. But, in my opinion well worth the loss of vision. Though I haven't seen any 968s with pillar post gauges, I think they are available. Or, maybe there is something available for a pro looking dash mount?





   
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'92 Midnight Blue 968 Coupe

'94 ProbeGT, Eaton SC@9psi, Quaife, TecGT ECU, 300+HP, body sold, parting out

'98 3000GT VR-4, 400+HP AWD beast, didn't fit w/race helmet, Sold

'93 Bone Stock MX-6 Sold (in '05) sadly to the crusher in 2010

'61 Triumph TR-3, White with red leather interior; My First Car
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i make a 3 gauge plate that goes below the deck, if you have a single din deck. if you are like me though, with a double dine, you're screwed.



i've seen the a-pillar gauge mounting piece for the hardtops. they don't make one for the cab though. personally, i can't stand the sight of gauges on the a-pillar. way too ricey for my tastes, no matter how functional. i wrestled with that one for a long time, when i was trying to get my oil temp gauge set up. i'm still a gauge short, but i really don't want to put it in the a-pillar



i have no need though for an A/F gauge mounted in the car, and i'm squeaking things more than others. just as i did with the kits, i tuned it with plenty of room, and as long as everything is working, there is no need to see the mix. sure, if i had the space, i'd put one in, but since i don't, i've learned to trust my tuning.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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I'm tracking down a code on my daughter's E46 3-Series that is typically caused by a vacuum leak, and in my research, most people recommend using a smoke machine to drive some smoke at fairly low pressure into the vacuum system (after you've sealed off the intake), and look where it leaks out. It's a common technique, actually, and there are several posts on youtube about how to make your own mcahine. Or, if you have a fog machine used at Halloween, that works too. You might want to do a search on youtube for how to trace down vacuum leaks using a smoke machine. Even if this turns out not to be your problem, repairing and/or ruling out vacuum leaks is probably a beneficial thing to do.
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[quote name='flash' timestamp='1372524353' post='145052']

. . . and as long as everything is working, there is no need to see the mix.[/quote]



Flash, my comments are no reflection on your tuning which I'm sure is great. I agree, no need to normally see the A/F ratio. I wish things were always working as they should.
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'92 Midnight Blue 968 Coupe

'94 ProbeGT, Eaton SC@9psi, Quaife, TecGT ECU, 300+HP, body sold, parting out

'98 3000GT VR-4, 400+HP AWD beast, didn't fit w/race helmet, Sold

'93 Bone Stock MX-6 Sold (in '05) sadly to the crusher in 2010

'61 Triumph TR-3, White with red leather interior; My First Car
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Durametric on the way. Looking at LM options, they're pricey for a one trick pony.



Thanks MB, I'll look for something temporary for now, and maybe a multi-purpose gauge eventually like the one I always put in my trucks - the Evolution Edge or Insight.
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mb - no worries. on this car, things are pretty simple. the fuel system either works, or it doesn't. when it doesn't, it's always related to poor maintenance (i.e. dirty injectors, etc) and it always tells you. an A/F meter won't really help you much on that stuff, other than to confirm you screwed up and should have done something you pushed off. unfortunately it won't generally prevent a problem in such an instance.



tama - yes, they are pricey. but, they can help with diagnosis, in that they provide logging and such which might point to a particular problem. if i were just trying to fix my own car, i'd try to borrow one or something



this is that line between hobbyist and mechanic. it should not be crossed lightly. anybody can buy tools. only a few can actually use them well. using them wrong will bring you nothing but headaches. so, sometime the answer is to hire somebody who knows what they are doing. i do that all the time.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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Some vacuum leaks plugged and verified twice with a smoke test (orange vacuum hose was loose-fitting where it enters the firewall). I need to go back in and try different combinations of the heater on / heater off kind of thing to make sure I am testing all the circuits completely, and then I'll recheck vacuum again at the <acronym title='heater control valve'>HCV</acronym> and near the fuel pressure regulator. For now, it's between 14 and 15 psi at the fuel pressure regulator, cycling up and down every few seconds (along with the quality of idle).



Car ran stronger as a result, but tomorrow morning will tell (cold). I still suspect some <acronym title='mass air flow'>MAF</acronym> laziness for some reason...
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that shows a definite vacuum leak. besides the low reading, the cycling is the tell-tale.



disconnect ALL vacuum lines. check again. then ONE BY ONE reconnect them.



under no circumstances should you have less than 16" of vacuum
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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Day 2 of trying to find the vacuum leak. I took each circuit in turn and tried to test it thoroughly with vacuum, pressure, and smoke.



- Verified the car has only 16" at idle.

- Verified the climate controls, including the <acronym title='heater control valve'>HCV</acronym>, are airtight on all settings.

- Verified the evap circuit is airtight. Although I could not pull a vacuum with the MityVac on the large hose after the valve, I think that goes straight to the gas tank?

- Verified there is a loud general hiss and diffuse smoke coming from the exhaust manifold area.



For the life of me, I can't pinpoint the leak, but at least it's not for lack of trying. I tried the stethoscope method, too, with a hose up to my ear. It's time to take it in to someone who's more experienced with finding these things! It's actually time to have the VarioCam pads inspected anyway, so maybe I'll plan on having that done and all the gaskets replaced at the same time.
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a loud hiss at the exhaust indicates worn valves or, in our cars, an improperly set exhaust cam. if there are no leaks, 16" of vacuum can indicate the same thing. it is very common in hot rods to have low vacuum with performance cams.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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When tracking down some of my Vac. leaks ( using the pressure method) I found the Idle control valve leaking up at the electrical connector. I had to remove the ICV, disassemble it ( PITA) and found two brittle and cracked O-rings that separate the armature area from the actual valve. After replacing I am now up to a solid 16,, Still looking for 17 and just a note not getting the full 5 boost, 4.3 to 4.4 max. I'm thinking timing now also. I just need a better timing procedure,, because there was a big difference in my dial gages, when pressurizing the Vero cam with air, then doing it with oil!
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yup - cam timing will cause a boost leak, as well as a vacuum leak. cam overlap is a wonderful thing in normally aspirated engines, but not so much in boosted ones.



make sure your hose camps are fully seated outside the ridges. having them on the ridges can actually cause leaks. they should shown up though by ear under a pressure test.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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[quote name='KRAG50' timestamp='1374003599' post='145707']

I just need a better timing procedure,, because there was a big difference in my dial gages, when pressurizing the Vero cam with air, then doing it with oil!

[/quote]



Wha???!! You figured out a way to pressurize the variocam with oil? This is way off topic, so an IM is on its way.
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I've spoken to both the local dealer and the only trustworthy shop in the area, neither of which wants to tackle timing my car, so it may not be too far off topic after all...
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