erratic idle
08-27-2018, 10:22 PM
#1
Staging Lane
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erratic idle I have a TSP 418 engine. It has a 90mm drive by wire throttle body. 2 years ago I had it dynotuned. It ran fine and idled smoothly. Last winter I insulated the air intake tube. This year when I start it it fires up immediately and runs fine. After a few minutes idling smoothly, the rpm will go up and down ever larger oscillation until it stalls. It fires right up again and in a few minutes does the same. Today I carefully checked for any air leaks, I cleaned the MAF and made sure it didn't have a vac leak around it.
I have put 2000 miles on it since the tune. I have a wideband meter and when it gets erratic the AF varies from 13 to 16. When it is idling smoothly it has much less variation.
I am not a tuner but I would at least like to know what the problem might be before I take it in.
I should also mention that it has always hated to drive in 1st gear at anything less than 1500 rpm. It surges a lot. Before and after the tune was the same.
I have put 2000 miles on it since the tune. I have a wideband meter and when it gets erratic the AF varies from 13 to 16. When it is idling smoothly it has much less variation.
I am not a tuner but I would at least like to know what the problem might be before I take it in.
I should also mention that it has always hated to drive in 1st gear at anything less than 1500 rpm. It surges a lot. Before and after the tune was the same.
08-28-2018, 08:28 AM
#2
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Sounds like the tune still isn't right.
08-28-2018, 11:38 AM
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That sounds like derivative air is too high.
08-28-2018, 07:27 PM
#4
Staging Lane
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Bit more info:Today I figured I would check fuel pressure. It was steady at 62psi. No matter idling up or down or reving it. All steady at 62psi.However, I did get a check engine light where I had none before, It showed P0174 MAF not working. Didn't get that yesterday. I cleared it and it did not come back.I do now have P0171 and P0174 lean on both banks. They keep coming back after clearing but it does not throw a check engine light.So some how things going lean. Is it MAF related? As well my test instrument is showing lights for O2 heaters but no codes. (could be not hot enough as it was just idling) FYI ECM is for a 2009 Corvette 6.2 litre manual 1G1YY26W795100446.
08-29-2018, 03:37 PM
#5
To me this is a concern:
"I have a wideband meter and when it gets erratic the AF varies from 13 to 16"
Do you know if the tuner turned off the cylinder misfire codes? Are you sure it doesn't have a mis fire or dead cylinder? If you have a infared temp gun, hit your headers once its up to temp, and see if they are all close in temps or not.
"I have a wideband meter and when it gets erratic the AF varies from 13 to 16"
Do you know if the tuner turned off the cylinder misfire codes? Are you sure it doesn't have a mis fire or dead cylinder? If you have a infared temp gun, hit your headers once its up to temp, and see if they are all close in temps or not.