rough starting

[87900turbo]

My 1987 c900 turbo convertible (just bought last week) is starting rough. If I don't give it gas right away, it dies. I have to keep giving it gas until it warms up. Once it's warm it runs fine.


I don't know when the fuel filter was replaced, so I'm replacing it. I'm also putting in new plugs and wires.


Aside from that, what else could be causing this? Vacuum leak? Any ideas?


Thanks.

[YellowBird]

I had a similar problem a few weeks ago, after taking one of my cars out of winter storage. I had to hold the gas pedal down to get it started or it just wouldn't start. Once it was in gear and running, it ran absolutely fine. However, if I hit the gas hard while idling and quickly backed off of the pedal, it immediately died.

I, too, was thinking fuel filter. Someone else suggested the oxygen sensor. Fortunately, I talked with a friend, who is also a SAAB mechanic, before I tried anything. I explained the problem to him and without hesitation, he said he was 200% sure it was the Automatic Idle Control(AIC) --- he was 200% correct!!!

It takes less than 5 minutes to put one in. I'm not sure if your issue is with your AIC, but you can swap in a used one with minimal ease and very little money -- if you are experiencing a "rough" start AND an idle issue.

[87900turbo]

I put in new plugs (NGK BCP6ES). I ordered new Bougicord wires, but they're not here yet, so I've still got the old Bougicords on. I put in a new coolant temp sensor, and an IAC that I pulled from a parts car.

Here's the video of it starting now: https://youtu.be/tXcEy4KqobQ

It might be my positive thinking, but I think it's stalling ~less~ now than it was. But it's still stalling when it's cold. I don't give it any gas until 0:37.

Aside from the wires, which should be here any day now, what should I check next?

[YellowBird]

I will run the video and your symptoms by a friend. I am far from an expert. Is it running rich? Have you checked the oxygen sensor?

[87900turbo]

I will run the video and your symptoms by a friend. I am far from an expert. Is it running rich? Have you checked the oxygen sensor?

I haven't checked the o2 sensor. I did spray an entire can of starter fluid at the vacuum lines however, but I couldn't identify any changes in idle. I did that, however, with the engine warm, which is when I don't have the problem at all.

I look forward to hearing another opinion.

[87900turbo]

Another symptom is that my turbo boost gauge doesn't work. I thought maybe that was my vacuum leak. I pulled off the speaker and it appears that the vacuum line is connected to the turbo boost gauge, though. I pulled it off, and there's no vacuum pressure (that I could feel with my finger). Is there a map of the vacuum lines behind the dash? I'd like to pull the whole dash and make sure all the vacuum lines there are good, as it seems maybe one is blocked.

In any case, that wouldn't cause my rough idle when the engine is cold.

To isolate the problem, I pinched off the vacuum line going from the plenum to the firewall, to determine if there is a leak somewhere behind the dash. It didn't seem to make any difference.

Any other ideas?

[peva]

All engines run a vacuum at some time on light throttle, NA or turbo. If you are getting no vacuum on the hose connected to the intake plenum, either the engine is not running, the hose is blocked or the the one-way valve is fitted in that hose and is installed the wrong way round. Of course in this situation the boost gauge will not work.