payforyourebay

Hello... this is my second post to this board.... I have owned my 86 951 for about a month now, but have yet to be able to drive it. I am fairly mechanically inclined, but I am REALLY stumped here.
Here is what is going on. I start the car, and get some black smoke (rich)... smells like gas when running... turns plugs black. The car seems to run fine the first mile or so, but when it starts warming up, and it starts to get a little boost, it starts to stumble, then goes to what feels like a complete miss, that gets a little violent at higer rpm's/boost.. It continues this mis like feeling that is worse and more harsh the more pedal you give it..... then, when the car cools down, it repeats this cycle of starting out really rich, running decent (not well), for the first mile, then as it warms up and you get into it a little, it starts into this mode all over again. The car is running very rich.... and has maybe a popping like sound under boost while this is happening.
I have replaced the injectors, plugs, wires, cap and rotor, and tried to look for loose connections. Is this an electrical problem, wastegate?, computer???
I live in Florence, KY near Cincinnati, OH. Anyone near that would like to lend a hand or some advice? I would like to get to know some local 944/951 people here anyway. Anyone know of a good mechanic here? (I hate the thought of going to a mechanic, as I usually do all of my own work) . Please help.
Mike

NZ951

Bad FPR? Vac Leak... start there. Got a Mitavac? (sp)

jsonnen

You mentioned a popping sound under boost , that sounds like detonation to me, if you are also fouling plugs abnormally I'd say it could be your headgasket or a possibly a hole in one of your pistons. I would not drive the car until you sort this out as you can cause serious damage very easily from detonation or running too rich. You might need to take it to a Porsche specialist to sort this out before you possibly frag your motor.

Good luck

NZ951

Not sure how you can be detonating and running very rich on that car. How do you know for sure its running very rich?

payforyourebay

It is running rich because is it fouling plugs, smokes black, and smells like gas when running. The popping noise I was talking about is not detonation.... It is hard to describe.... it is like all power cuts out.

jsonnen

If your engine is stumbling or cutting out while underboost either A- theres not enough fuel and you are detonating or B- theres too much fuel, but why would you be rich? Do you know if there are any mods IE chips etc? Also normally a popping sound is detonation or pinging maybe you are hearing something else. Its hard for any of us to try and diagnose over the internet whats going on, maybe Danno will chime in and point you in the right direction.

NZ951

I still think vac and FPR may need to be looked at. Its not your wastegate.

payforyourebay

I hope so.... From what I have read Danno is quite the man when it comes to these cars... I am quite certain I am not leaning out.... I probably shouldn't have said a popping noise... let me take that back.... that just makes it confusing. It may be modified, I am unsure.

hosrom_951

I too suspect the FPR and a vacuum leak.

payforyourebay

I will check these out... I do have a mightyvac... any suggestions on techniques or other advice welcomed. At least I can rule one thing out.
Thanks,
Mike

NZ951

Also test your FPR... is it a 3.0 or stock 2.8? You should list your mods in the sig if you know them, that helps lots.

porshhhh951

Jsonnen...you can't detonate under rich condition's. dentonation sounds like mables pinning inside of his engine...I highly doubt he is getting detionation. Especially if he is smelling fuel and describing back fire. It wouldn't be his headgasket either...that would mean alot ...I mean alot of white smoke along with water and oil problem's. Which he has not described any of. And where in the heck do you get that he might have a hole in one of his pistion's. I guess what I am trying to say here is if you don't know then don't post.


On a personal opinion. I would have checked and changed all the thing's you have already done. Cap,rotor,plugs,wires. The stumbling and smell of fuel along with backfire or poping noises mean's you aren't using your fuel somehow. You could be essentially flooding your engine. So the real question is why aren't you using your fuel. No spark,bad plugs,faulty wires,bad coil???

the first thing I would suggest since you have already done all the basic's is check for vaccum leaks. A vaccum leak can cause all the syntom's you are describing above and then some. Do you have a after market boost gauge? If you do these are great at helping determine wiether or not you have one. If you do what's your HG reading at idle. Normally you should be anywhere from high teen's to low 20's. I myself run around 23. You could also tell if it was a vaccum leak if you ilde was irregular. say to high or fluxing.

You could also change some of the other usual's. Like fuel filter, check your fuel pump relay's. I had a bad fuel pump sender once...and it only acted up when the car got hot.....took forever to track down.


I am chaising a problem myself right now. I think we have to narrowed down to the speed refference senor's or maybe a bad dme.


Tell us more about the car. Mods? service history? Check for vaccum leak's, check your fuel filter, maybe even a bad damper for fuel pressure regulator perhaps. Either your system is sending too much fuel or you can't use the fuel you have. Either way it sounds like a fuel use problem.

As it's already been said hopefully danno or one of the more expeirence guy's on the board will chime in and add more insight. Always kinda hard to help if we aren't there. Internet is only good for so many things..lol.


Hope everything get's sorted out.

jsonnen

[QUOTE]Originally posted by porshhhh951
[B]Jsonnen...you can't detonate under rich condition's. dentonation sounds like mables pinning inside of his engine...I highly doubt he is getting detionation. Especially if he is smelling fuel and describing back fire. It wouldn't be his headgasket either...that would mean alot ...I mean alot of white smoke along with water and oil problem's. Which he has not described any of. And where in the heck do you get that he might have a hole in one of his pistion's. I guess what I am trying to say here is if you don't know then don't post.

Hey John chill out guy I am only speaking from past expeirences bud I never claimed I knew ****, so instead of you telling me I don't know what I'm talking about try helping the guy out and keep your opinions of what I know or don't know to yourself. I had a hole in one of my pistons from a lean situation and kept on fouling plugs so similiar to what he had said, so why don't you get off your high horse Mr Noob mechanic.


Registered: Feb 2003
Location: dallas
Posts: 1127 Okay got some serious question's(Please take it easy on a newbie)

"Okay I am a newbie mechanic. I have just performed my first major mechanic endevour(my headgasket). I thought I had a leaky seal towards the end of the head gasket....but, now I am not so sure. It start's up fine it was really rough at first consider the car has sat for several month's and now with the recent over haul I thought nothing of it"


Ya john your a freakin expert now?


Up until now I thought you were a pretty cool guy.

hosrom_951

The fuel smell could be from the fuel canister system, check the vacuum over there. Also make sure that the thermo vacuum valve (a little valve with two pongs under the intake manifold next to the oil filler cap) are not cross switched. I have my vacuum lines switched there, and got fuel/vapors inside the cabin. To the right of the valve (right pong from driver's side) should have a vacuum heading towards the fuel canister system, while the left pong should to to the throttle body.

porshhhh951

[QUOTE]Originally posted by jsonnen
[B]I am new at ripping into the 951 engine. I am by no means new to car's or mod's.I have always been a spec guy....a guy with number's or modding knowledge. When it comes to okay lift this here while unscrew this here kinda of stuff....this is what I am a newbie at. Moreover to some of these guy's on here that know so much and have built motor's are the guy's I am looking for advise from. I would most certainlly consider myself a newbie when it come's to that. Other than that...I have owned and driven my share of sport's car's. I have been around this kind of stuff since I started racing when I was 7. It was by no mean's a personal attack on you in anyway shape or form. Although it's hard not to take it personally so I understand your response.
The reason why your post was so off was because you were discribing lean condition's ....of which he has none. A hole through the piston??? don't you think your being a little dragstic....a little too early.

Look what you have to understand is that people on here take what is said pretty seriously. If you give some adivse chances are people are going to give real concern to it. So when I see someone that might get potentially freaked out by reading a post that's not really true...like

jsonnen
I'd say it could be your headgasket or a possibly a hole in one of your pistons. I would not drive the car until you sort this out as you can cause serious damage very easily from detonation or running too rich

while running too rich can be harmful it's not a blow a hole through your piston type of thing. Dentonation under rich condition's is just plain false. And telling someone they might have destroyed there entire motor when not really knowing there circumstances is very extreme. Remember my reason for posting as I said earlier. People take what is said here to heart. I didn't want him to read what you wrote and freak. Get on the phone with a dealership and tell them people on the board said his motor is toast. This was just simply outta place. Once again nothing personally because I don't know you. But, telling someone there motor needs serious work without knowing is just plain harmful. That's why I said if you don't know then don't post. Opinion's are fine everyone is full of them. I just knew your's was way off and didn't want him to freak out when he read it. Without being there is no way to know for sure what his problem is. So we tell him to check thing's and by process of elimination hopefully it get's solved. This is what rennlist is all about.

You don't just tell someone they are looking at 1000+doller's in repair's and shoot off your mouth without having a serious basis for your diagnoisis.



Ofcourse this is all kinda a moot point.....because it's all simply speculation and opinion. Your's and mine. We just happen to differ. I am willing to bet though his motor isint in the kind of shape you feel it is. I just wanted him to know that he has lot's of stuff to check out first before flipping out and calling the dealer.


As with my problem I think we really have it narrowed down...so hopefully she will be running soon. Just more flustrating than anything. I know how not having a car running right can get to ya. Just want to have him check the obvious stuff first before throwing in the towel. I hope you can understand.