rough when first started

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psychrunner

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My csi runs quite rough when initially started, with some coughing and sputtering, but after a 2 to 3 minute warm up, seems to run fine. Any reason for this, or is this "normal", with nothing to be too concerned about.
Thanks
Randy
 
I assume you're running carbs - not FI in which case I think this is typical especially with engine performance mods. Certainly typical of my downdrafts. If you had manual chokes you could back off the amount of choke and probably improve the warmup idle but not much point.
 
psychrunner said:
My csi runs quite rough when initially started, with some coughing and sputtering, but after a 2 to 3 minute warm up, seems to run fine. Any reason for this, or is this "normal", with nothing to be too concerned about. Thanks Randy
Click to expand...

I would not describe your problem as "normal" although it is probably something you might live with. Depends on severity of the problem and your tolerance threshold. That being said, what you are describing sounds like an issue with the cold start setup. As you probably know, you have a cold start valve sitting high on the manifold. It is designed to furnish extra fuel to the engine when it is cold. To be sure, the valve works in conjunction with the auxiliary air valve and the temp sensors. If the valve leaks, stays on too long or something else like the air valve sticks in a closed - position you will experience an over-rich flooding situation. Some of the cylinders will not fire the mixture until things heat up, hence the missing.

There are a lot of factors at play. You might disconnect the wires to the cold start valve and try starting the engine without energizing the valve. I have found on one of my DJet equipped vehicles, the engine runs fine with or without the cold start valve connected. The difference is slight black smoke versus none AND the engine still runs clean enough to pass the local "relaxed" emissions levels. Analyzed the exhaust when trying to calibrate the ECU potentiometer with a questionable manifold pressure sender. Have car in warm climate.

Another possibility is the auxiliary air valve typically hanging down toward the throttle linkage on the left (driver side) and has a paper filter all of its own. If that valve is closed when the engine is cold - and the cold start valve is functioning properly, you will likely get the same rich mixture symptoms. I have had air valves with the opposite situation where they remain open and don't close all the way.

Good luck.
 
Are your...

distributor trigger points clean or do they "self clean" after a few minutes of running?

This isn't a high priority, but enough Djets have had difficulty that it's something to consider.
 
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