issue when cold
 

Hello,

I am quite new here but this forum seems to have a very good technical knowledge, better than the ones at home.

I have a 87 3.2. When cold, it bogs really heavy between 1500 and 2000 rpm. Starts and idles good, pulls good over 2000, but the whole car shakes between the said rpms. After 10 minutes of driving, oil temperature has left the lower white segment, it goes away. Seems to get worse / more pronounced the last couple of drives.

Any ideas?

Thanks in advance and greetings from Bavaria!

I had a similar problem in my 88. Both the oxygen sensor and ignition wires were bad. However, it's hard to say that the symptoms are the same. My car wouldn't shake, but it did run roughly at lower RPMs until warmed.

Todd

I have an '87 also, but only for the past 8 months, and have never had this issue, so I will be interested to read what the problem might be. Sounds like tulliotk has some good information, thanks for sharing.

Appreciate the first feedback/hint. This is my first Porsche and I have less than 2000 miles experience with it.
I might want to start with the oxygen sensor then, I understand it is a (not cheap) wear item. Car has about 100k miles but I don't have any service records to determine if it was ever changed. In fact it started life as a non-catalytic converter motor and was later upgraded to the original Porsche cat. At what mileage I don't know.

On a cold start, the O2 sensor does not start sending a signal for a couple minutes until it warms up. And even then the ECM ignores the O2 signal until the engine reaches a specified temperature. So you can always rule out the O2 sensor when troubleshooting cold engine driveability problems.

It could be electrical like plug wires, although that would be more likely to affect driveability all the time, not just cold. More likely your air/fuel ratio is off and so your idle is too low, but why is it off? Probably an air leak. I'd start looking for disconnected/damaged vacuum hoses, there's only so many to check on a 3.2 but some are hard to get to and inspect without really digging into the back side of the engine. But first, what is your idle at when you start the car? What does the idle settle down to? Does it hold the idle steady? Do you have a stock or modified chip in the ECM?

real quick check. unplug the cht sensor when cold . the top white connector on the left. if it then runs fine until it warms up ( then plug it back in ) . the sensor is bad.
if it runs the same, then plug it back in and move to the next item.

it has a modified chip. I installed it. The german equivalent of a Steve Wong chip (both exchanged data) The issue did however show up later, makes me think it is not directly related.

When started cold, it idles for a short time above 1000 rpm, it will then drop shortly thereafter below 1000rpm. It does not hunt very often. If it does, after 2 or 3 oscillations it will smoothen out. When the engine is warm, it will drop really low, below 800rpm according to the instrument, too low in my opinion. It is so low that it not super steady anymore. When starting from a stop/idle, it would come of from idle good but than acts up at around 1500-1700 to 2000. What you think?

Edit: while posting Iceman replied. Thanks for that hint. Of course don't want to start throwing expensive parts at the problem, so any hints in ruling out those are very welcome. So this would rule out the NTC2, right?

i think hou sbould have put that info in hour original description :)

sounds like you dont have a cold running issue. but a general running issue that has been masked.

put your orignal chip back , check for leaks and have your base CO adjusted. also check your timing.

I agree with Iceman, although putting the stock chip back in may not be necessary, it can at least help you rule that out as a cause. Your car should hold a steady idle at 880rpm (assuming the aftermarket chip is set correctly). Regardless, the idle should never bounce. I'd start by looking for vacuum leaks by checking all hoses to be sure they're connected tightly and have no cracks. It helps to remove the whole airbox and AFM and use a small mirror and flashlight to inspect all of the hoses at the back side of the engine. There's a hose that attaches to the back of the airbox too though so be careful with that one if you pull it out. You should have the "Vacuum Hose Routing Diagram" sticker in your engine bay showing all vacuum hoses that need to be inspected.

Sorry about that. One reason I did not was that it ran without any issues and having the modified chip (put that in last year) in and the low idle. I was very happy with the behavior of the motor. The idle hunting happens maybe every one out of twenty starts.

But I am here to follow experienced advice. So I will put the original chip in and report back if that made a difference on idle and cold drivability.

No sticker as mentioned. Might be not present on a Euro car?

Not every car has all the stickers:

http://forums.pelicanparts.com/uploa...1333400906.jpg

And I'm not sure, but your Euro car may not have the carbon canister or the hose that runs into the back of the airbox from it. Not sure how that works on Euro engines...

Thanks for the diagram. Certainly some stuff on it I was not aware it exists (Venturi tube, temp switch at throttle housing).

Putting the original chip back removes that variable as pointed out. I would leave the original chip in until you get things squared away

Wilco.

On my way to Asia now but will report when back and messing with the car.