[mattipuh]

Throwing out this question, just to know if it's normal or some sensor dying soon.
My car starts ok when cold, and usually hot too. sometimes hot starting is difficult, and without throttle car seems uneager to start. If I apply throttle, car starts ok.

Is this normal, or is there some issue looming?
Spark plugs + injectors are 2 years old (cannot see them being too old).
I'm thinking if Temp Sensor to DME or such could be bad... ? but just a guess?
Any better guesses / knowledge in this kind of behaviour?

cheers,
Matti

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[unknown4u]

check the pressure from the system. Maybe a faulty regulator or a fuel pump that is going bad.

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[94SilverCab]

This is a sure sign of a failing DME Relay. Entirely common occurance, known weak point. Most of us keep a spare in the glove compartment (costs about $30).

Regards,

Jay

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[mattipuh]

<!--quoteo(post=78268:date=Aug 20 2009, 02:57 PM:name=unknown4u)-->QUOTE (unknown4u @ Aug 20 2009, 02:57 PM) <{POST_SNAPBACK}><!--quotec-->check the pressure from the system. Maybe a faulty regulator or a fuel pump that is going bad.<!--QuoteEnd--><!--QuoteEEnd-->

Was thinking this too. There has been a whine whirring from the back of the car sometimes, the level of which varies if I use electric windows for example.
Maybe it's time to replace regulator + pump, or at least measure the pressure.

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[unknown4u]

If there is a whine from the back in according to a variarity of sound (pump revs is not stabil) , check if there is 12 volt or more at the pump available. Maybe there is a connector going bad underside the car. This can work as a resistor. Or the DME is going bad.

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[mattipuh]

<!--quoteo(post=78310:date=Aug 21 2009, 12:03 AM:name=unknown4u)-->QUOTE (unknown4u @ Aug 21 2009, 12:03 AM) <{POST_SNAPBACK}><!--quotec-->If there is a whine from the back in according to a variarity of sound (pump revs is not stabil) , check if there is 12 volt or more at the pump available. Maybe there is a connector going bad underside the car. This can work as a resistor. Or the DME is going bad.<!--QuoteEnd--><!--QuoteEEnd-->

Good point. Whining sound is not there always, which is a bit strange...
I swapped to new DME a year ago, just to play safe, and have the old one in glovebox. BTW, how does the faulty FPR (fuel pressure regulator) act, gives too low pressure or what?

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[jfrahm]

<!--quoteo(post=78342:date=Aug 20 2009, 11:48 PM:name=matti)-->QUOTE (matti @ Aug 20 2009, 11:48 PM) <{POST_SNAPBACK}><!--quotec-->Good point. Whining sound is not there always, which is a bit strange...
I swapped to new DME a year ago, just to play safe, and have the old one in glovebox. BTW, how does the faulty FPR (fuel pressure regulator) act, gives too low pressure or what?<!--QuoteEnd--><!--QuoteEEnd-->

Hot start problems are often the coil or the ignition module. I would check to see if you have a good, strong spark using a spark checker or seeing if the spark will jump a 1cm air gap when it is not starting.

A bad FPR will sometimes leak gas into the vacuum side, or it will stick and not adjust properly. The spring can also get weak. Some people hammer on them with a socket of the correct size to crush them a bit, if they are running low or they want a cheater way to raise fuel pressure in a stock racing class. I personally do not think you would have a fuel pressure problem that is causing this, you would have other problems, perhaps black plugs, etc.

Anyway when it is not starting check for spark, check the plugs for gas or fouling, and look for clues. You can also try thumping the DME or at least stomping on the passenger's footwell. It could also be an alarm system problem or even an ignition switch. If you can check a few things and let us know, that'd help.

-Joel.

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[Cloud9...68]

My car behaves exactly the same way, but I don't think it's the DME relay in my case, as I have upgraded mine to the newer style. When it's really hot, I have to partially open the throttle in order for it to fire, but even with this, I have to crank it several times, and say a quick prayer or two. This has been going on for years, though, so as with a growing list of issues with the car, I've just lived with it, as it hasn't gotten any worse. I figure it'll get fixed when I make my eventual pilgrimage to RS Barn for my complete rebuild/make-the-car-truly-track-worthy experience. Just need to see the market string together about 20 consecutive days like today [img]style_emoticons/<#EMO_DIR#>/rolleyes.gif[/img]

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[Lonestar968]

My symptoms are exactly the same as Cloud's. Sometimes it'll start without issues when warm/hot. Other times it acts as if it's laughing at me saying... "I'm not starting dude, forget about it, I'm not starting. It's too freaking hot, I'm not starting. No really, crank away sucker. I'm not starting".

Normally if I crack the throttle about 1/2 to full for just a second or two while cranking, it'll start when hot. "Normally". But day by day it still seems like I'm cranking longer than what you would consider "normal" in most other cars.

I have had times when it simply didn't want to fire up. After waiting a minute or so, the crank-with-throttle-open-method works. Normally.

I've got to figure this out.

My 1998 Explorer fires right the heck up the moment you just bump the ignition switch.

Frustrating AND embarassing for a Porsche owner to say the least.

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[unknown4u]

under all conditions my 968 fires right up! even with a poor battery. . Maybe your idle stabilizer system is a bit faulty?

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[flash]

i wold be looking at the coil wire - we are seeing them starting to fail - when they get old and get hot, they won't spark enough

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[Cloud9...68]

Lonestar - great description of the problem. Very funny, too. Must be a Texas thing...

Flash, good suggestion about the coil wire. Not sure if it will show anything, but I'll try the running-in-the-dark test to see if it's spewing any stray sparks. I replaced my plug wires about three years ago, though, and I'm pretty sure the coil wire came with the set. Would be an inexpensive and easy fix if this were the problem, as I'm sure I could just replace this one wire without having to replace the whole set.

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[flash]

i am referring to the actual coil, not just the high tension lead - they start reducing in output over time - a lot of the 944 guys are having the same problem, and it often turns out to be the coil

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[Cloud9...68]

Ah, I see. Yes, the coil has been long on my list of things to replace as a preventative measure. Is there any way to test one to make sure it's bad before I just replace it? Last time I checked, they weren't terribly expensive, but not exactly cheap, either. I have no problem replaing it if I know it's marginal, but I'm too crazy about replacing it just because it's one item in a long list of things that may be contributing to the hot start problem. Also, it's strange that the problem isn't getting any worse. As Lonestar described, it's highly intermittent.

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[flash]

yes

of course there is the "big fat blue spark" test:
http://autorepair.about.com/od/troubleshoo...test-manual.htm

then you can test the resistance:
http://autorepair.about.com/od/troubleshoo...il-test-ohm.htm

i am having trouble finding the specs on the coil - the only bosch black coil specs i can find are:
100 turns
primary 3.0 ohm
secondary 9.83 ohm

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[Johannvb]

<!--quoteo(post=78450:date=Aug 23 2009, 01:22 AM:name=flash)-->QUOTE (flash @ Aug 23 2009, 01:22 AM) <{POST_SNAPBACK}><!--quotec-->i am having trouble finding the specs on the coil - the only bosch black coil specs i can find are:
100 turns
primary 3.0 ohm
secondary 9.83 ohm<!--QuoteEnd--><!--QuoteEEnd-->

Are all coils equal, or are some more equal than others?

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[flash]

all coils are NOT equal - there are actually quite a few different ones out there, each having different specs - that doesn't mean that there aren't substitutions that can be made, just that you have to do some homework to see if the one you want to use will work

there is nothing wrong with the OEM coil for this car - specs are fine - spark is fine - likely not a lot to be gained by switching, and no idea what other things might go bad as a result of the increased spark

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