Possible Vacuum Leak?

no1biscuit · 04-08-2002, 09:14 AM

Ok,
First off I have a 86 951 and I know this is the non-turbo area but they aren't helping me. Ha Ha.
Here is the problem. When I start the car it seems to do OK but as the car warms up more the car begins to back fire and hesitate a little. By the time the car is at normal operating tempeture all hell breaks loose. When I take off the harder I push the accelarator the slower the car goes. But if I keep the rpms low and shift really (really) early and don't let the Turbo spool up I can get up to a max rpm of 3K. Some times I can hit the accelarator and it will hesitate and eventually it stops spuddering and takes off like a rocket. (Zero boost then full boost all at once. Kind of hard on the kneck.) I have fresh gas in it and I have also drove it around to see if it was just something to do with it sitting for a couple of weeks but there is a problem.
Any and all Help would be much appreciated.
Thanks
Thom

no1biscuit · 04-09-2002, 06:20 AM

Doesn't Any one care that my car is not running.

drew1 · 05:57 PM

Yeah Thom, we care but we are ignorant, too.

I haven't worked on a 951, but first I would try to think the differences in the way the computer, DME & I believe KLR on 951, acts on hot & cold. Well as the motor warms up, the computer is susposed to see a changing signal from the coolant temp sensor, & opens the injectors less time. It problably also shuts down the idle speed motor or solenoid & draws less air through the airflow meter causing the injectors to open less time.

Next I would look at what controls boost. The KLR?, waste gate & bypass valve (wife's 924t has it built in the compressor side of the turbo but I think it's separate on a 951). Bypass valve draws boost off from the pressure duct to the turbo inlet when the throttle is closed. To do this it has to compare the pressure before & after the throttle.

I would check this pressure valve because it could be the cause of an airleak & could be preventing boost from coming on.

drew1

edit : this ought to get you back up top where Lawrence (who's sharp on these), Ahmet (he's got one now), or Britwrench (he's worked on them all) can help.

no1biscuit · 04-09-2002, 06:12 PM

So Should I unhook the battery and see if that resets the computer? If not how do I check those?
Thanks for putting me at the top.
Thom

drew1 · 04-09-2002, 06:17 PM

I don't think the bypass valve has any connection to the computer, probably just two hoses I'd guess about 1/2 " dia.

I'll look in Water Cooled Parts & Ref to see if I can find what it looks like & where it might be.

drew1

no1biscuit · 04-09-2002, 06:47 PM

Thanks I appreciate it. Seeings how no one wants to help.

drew1 · 04-10-2002, 04:34 PM

Thom,

Think I was wrong about # of hoses, it's probably 3. 1 from intake pressure duct, 1 from somewhere before turbo enrty, & 1 (maybe small) from intake manifold.

Did not find anything in Parts book.

drew1`

xero · 04-11-2002, 12:47 AM

hey i was having a similar problem in my non-turbo 944 (absolute 0 power untill full throttle and a bad idle) and drew1 told me that the O2 sensor is not used at full throttle. so i unpluged the wires to the O2 sensor and not my car is fine

so you may want to try that?

drew1 · 04-11-2002, 03:20 PM

check O2 as xero pointed out, then chech Paragon Products web site in catalog, 944, boost. There is a picture of the bypass on a car. It is by the coolant tank.

drew1

no1biscuit · 04-17-2002, 04:45 PM

I just had my o2 sensor replaced less then 2 months ago. Also the pictures at paragon parts are bad links. Please help. I will unplug my o2 and take her for a drive.
Thom

no1biscuit · 04-17-2002, 05:26 PM

Just unplugged the o2 got about 2 miles away from my house and then I bairly made it back. When I got home I couldn't even keep it running. Just kept dying.
Thanks
Thom

kcturbo · 04-18-2002, 12:15 AM

Hey have you found anything yet? Im just curious do all the gauges work ok, check the temp sensor? The problems that you are describing seem common for many things. Hey by the way Im only 45min north of you.

no1biscuit · 02:48 AM

No I haven't. It is like as soon as the car warms up it just falls apart. I wonder could that be a choke issue. that my choke is sticking and flooding my car? Just guessing.
Thanks
Thom

Oh by the way kcturbo you are correct. I live next to North Kansas City and Harrah's, thus it is about 45 minutes. Who is your mechanic? Small world huh?

geoffbaltz · geoffbaltz's Garage

Timing Valve....these help the car run cold and then adjust when the temp is at normal operating range. It could be bad or is not getting the proper temp signal.

I just replaced the bypass/blowoff valve on my 86 951 with a piston based Forge unit. You won't really notice when it is bad and it definitely wouldn't cause the problems you are talking about. All it does is maintain boost in the system when shifting or letting off the throttle a bit.

Hope this helps.

-g

drew1 · 04-19-2002, 04:44 PM

Thom,

First time I've been here in a while & I was hoping you had it figured out.

With the O2 sensor disconnected & running worse you probably were too rich like you said. I don't think you have a choke. Maybe a temp sensor is bad or has a bad connection & makes the computer think it is cold & keeps the injectors open too long.

drew1

no1biscuit · 04-19-2002, 05:25 PM

Where do you think the temp sensor would be. Also drew I hoped it would be fixed as well.
Thom

geoffbaltz · geoffbaltz's Garage

It is in the top of the motor on the driver's side. The one on the pass side is the temp sending unit for the guage.

I would definitely check the timing valve too!

no1biscuit · 04-19-2002, 06:23 PM

Sorry guys.
I forgot to mention I know very little about fixing my baby (I am trying though). So how do I check the temp sensor and/ timing valve as well as where is the timing valve?
Thanks for your patience.
Thom

drew1 · 04-20-2002, 01:02 AM

Getting ready to go turkey hunting so I will tell you what is in my head. Hope you can get some replies to either verify or say I'm wrong.

The temp sensor has a plug about like an injector plug. On an na it is blue. I don't know where it would be in the plug to computer.

Instead of taking a bunch of stuff off to get to it, it would be good if you could check it in the plug. I think it should ohm about 450 to 500 ohm when cold & less when hot. If you pull it out, it you can check it in hot water by heating & cooling.

drew1