Starts but won't idle
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Starts but won't idle 1998 Trans at 6.0 LQ4 swapped. Got it started. But it won't idle longer than a minute, sometimes you can feather the gas and it'll stay alive. But won't just idle. It's getting a low signal from the cam sensor code but that's it. I know that won't help but it shouldn't keep it from running. But I could be wrong. I was thinking it could be the security system cutting fuel but it wouldn't be able to stay running with giving it gas then would it? I also thought idle air control solenoid but haven't had the time to check it and see what it looks like. It has been tuned, and it is on its second pcm so it is not a computer thing.
It has been tuned for the swap?
Sounds like you need more base airflow as it warms up. So to me, it seems like the tune isn't right. That's the easiest thing to fix.
Another thing to try would be to open the set screw on the TB up 1/8 or a turn or so. If you have to feather it to stay alive, you need more airflow. Pure and simple.
And the cam sensor doesn't help, but won't cut off the fuel. It makes startup harder.
And VATS cuts fuel at startup. So it's not that.
Sounds like you need more base airflow as it warms up. So to me, it seems like the tune isn't right. That's the easiest thing to fix.
Another thing to try would be to open the set screw on the TB up 1/8 or a turn or so. If you have to feather it to stay alive, you need more airflow. Pure and simple.
And the cam sensor doesn't help, but won't cut off the fuel. It makes startup harder.
And VATS cuts fuel at startup. So it's not that.
Thread Starter
Teching In
Joined: Sep 2016
Posts: 20
Likes: 0
It has been tuned for the swap?
Sounds like you need more base airflow as it warms up. So to me, it seems like the tune isn't right. That's the easiest thing to fix.
Another thing to try would be to open the set screw on the TB up 1/8 or a turn or so. If you have to feather it to stay alive, you need more airflow. Pure and simple.
And the cam sensor doesn't help, but won't cut off the fuel. It makes startup harder.
And VATS cuts fuel at startup. So it's not that.
Sounds like you need more base airflow as it warms up. So to me, it seems like the tune isn't right. That's the easiest thing to fix.
Another thing to try would be to open the set screw on the TB up 1/8 or a turn or so. If you have to feather it to stay alive, you need more airflow. Pure and simple.
And the cam sensor doesn't help, but won't cut off the fuel. It makes startup harder.
And VATS cuts fuel at startup. So it's not that.
Put a mechanical fuel pressure gauge on it. Although I had a bleeding line from the pump to the hat in my fuel basket, and it made starting hard... it would idle once the pump was primed. It would just lean out up top.
The other things to check are the coils/plugs and make sure you're getting sufficient spark.
Always start with the big 3 - fuel, air, and spark. And troubleshoot each before moving to the next.
The other things to check are the coils/plugs and make sure you're getting sufficient spark.
Always start with the big 3 - fuel, air, and spark. And troubleshoot each before moving to the next.
Thread Starter
Teching In
Joined: Sep 2016
Posts: 20
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Put a mechanical fuel pressure gauge on it. Although I had a bleeding line from the pump to the hat in my fuel basket, and it made starting hard... it would idle once the pump was primed. It would just lean out up top.
The other things to check are the coils/plugs and make sure you're getting sufficient spark.
Always start with the big 3 - fuel, air, and spark. And troubleshoot each before moving to the next.
The other things to check are the coils/plugs and make sure you're getting sufficient spark.
Always start with the big 3 - fuel, air, and spark. And troubleshoot each before moving to the next.
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I wouldn't tighten it - I'd open it up more. Typically when the motor warms up, the IAC motor closes down... so at cold start you may have sufficient airflow to keep it alive, but as it warms up and the IAC counts start to drop, it may drop too much and kill it.
So I'd open the TB some more to allow the IAC some control over the idle.
So I'd open the TB some more to allow the IAC some control over the idle.
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Huh?? 
Thread Starter
Teching In
Joined: Sep 2016
Posts: 20
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I wouldn't tighten it - I'd open it up more. Typically when the motor warms up, the IAC motor closes down... so at cold start you may have sufficient airflow to keep it alive, but as it warms up and the IAC counts start to drop, it may drop too much and kill it.
So I'd open the TB some more to allow the IAC some control over the idle.
So I'd open the TB some more to allow the IAC some control over the idle.
