Rough start up when engine cold

BobGPz

Registered User
Having a problem with my 90' SC 5-Speed.
When I start her up and the engine has been off for a while, it feels like the engine is flooding. The car barely runs (Real low idle) and smoke (Fuel) will puff out the back for a minute until it warms up. It only does this when it is cold. After it warms up it runs fine with maybe a slight miss. I get no codes and it passes a cylinder balance test. I was thinking maybe the Cam Position Sensor on its way out or off a bit? I believe it and crank sensors are stock (14 years old).

I have replaced the following parts within the past year for other reasons, so I can more than likely rule them out: Harmonic Balancer, Both Coolant Temperature Sensors, Idle Air Control Valve, TPS Sensor, Fuel Pump, FP Regulator, Air Charge Teperature Sensor.

Tried Cleanning the MAFS Sensor and K&N Filter. Anybody got any ideas?
IF my car was a 4 barrell carbureator, then I would say it is flooding the engine and also a bad choke, but these computerized cars who knows. :confused:
 
i have a stick to and it sounds like my problem start it up cold rev it and it still wants to die but once u put it in gear and go its fine right?
 
"...start it up cold rev it and it still wants to die but once u put it in gear and go its fine right?"

It drives with a hesitation until it warms up. Then it is fine other than a slight miss once in a while. Its like the injectors are pumping too much into the cylinders or not in the correct sequence, yet I have not messed with the electrical connectors or anything. It has gotten worse over the past few months till now it is really a chore to start her. It is not bucking so the plugs are fine, and the wires are fairly new Magnecores.
 
When installing a new radiator I had to pull off my intercooler and noticed the top collar nut (Top IC Tube to SC Top) was loose. When reinstalling Radiator and IC I reefed that thing tight and it starts right up with normal idle and fuel delivery now. Guess it just wiggled it way loose. Runs much better now!
 
I had the same problem untill last weekend. When starting cold, it would not stay running without throttle attention. Except when put into drive, then everything was fine. After warm-up it would idle but would start to fluctuate slightly in park. The longer it idled the worse the fluctuation got untill it died. But it seemed to do fine when placed in drive.

I, like you, had replaced my IAC within the last year, along with many other sensors, had initially ruled it out and was looking for a vacuum leak. Nothing seemed to cure this problem. In desperation I removed the IAC and found it was very dirty. Upon cleanig the IAC, the throttle body and MAF plus re-learning the ECC My problem has gone away.

Hope this helps!! :)
 
The IAC is very sensative to what you spray or poke into them, so be careful.
I can think of 4 people besides myself that have tried to clean the IAC and ruined it.
 
rough idle with cold start

I know this is an old thread but it's the closest I've noticed to my problem.

The facts:
Shop replaces water pump 3 weeks ago. Since then idle has become erratic after cold start. Dips to 800 and then shoots up to 1400 rpm before settling back to normal rpm. This process repeats, becoming less erratic as it warms up. This is felt going down the road like a hesitation. CEL will flash sometimes. I replaced the cam sensor and DIS one at a time and observed no change. (IAC replaced less than 1 year ago.) Return to the same shop this last Friday did not identify the problem. No codes observed. Extensive forum searching has led me to an IC tube leak possibility. Found outlet tube (into lower inner cooler) flange nuts could be tightened some. Idle problem remains. Back to shop tomorrow and I will pass along IC leak theory. Anyone have similar experience and can offer solutions?

much thanks.
 
I had a similar problem and others while driving, replaced the DIS and cam sensor and no fix. I replaced the crank sensor and its been fine ever since. Might want to check all the wiring connectors around the cam sensor and DIS area to make sure they are all tight, including the one for the crank sensor which is near the cam sensor.
 
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