Car won’t idle after changing intake, PLZ HELP!
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From: Tennessee
Car won’t idle after changing intake, PLZ HELP! I recently removed my intake, drilled it for direct port nitrous and re-installed it. I used new gaskets, attached all vacuum lines and torqued it down properly. At first it ran rough and would not idle so I did the idle re-learn procedure and now here is the problem. The car ran alright at first but after some brief driving it started to run rough again, coincidentally at the same time the temperature got to about 170 degrees. For example I am driving let off the gas to turn into the driveway and it dies. It acts like it can not find idle. After driving it I started it sitting in the driveway. It started and idled real rough. When I tap the gas it revs up then can’t find idle and wants to die. I scanned it and getting 2 codes: P0106 MAP sensor and P0101 MAF sensor. I am going to try replacing my plugs. Does anyone know what the KPA value should be from the MAP sensor? If anyone has any ideas please let me know. I have tried everything I know how. Replacing the MAP sensor is a last resort, that involves removing the intake again. And I don’t know why it should be bad, it worked fine before. Could tapping the intake and running lines to the distribution block change the internal characteristics of the intake enough to cause this problem?
Thanks for the help.
Chris
Thanks for the help.
Chris
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You...uhhh....drilled your intake for direct port nitrous. Has anybody done that with a composite manifold before? That doesn't really sound like a good idea. It sounds to me like you have a massive vacuum leak, which could be anywhere.
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From: Texas
what kind of intake is it? I had the same problem with my LSX and it turned out that you have to use their screws for the valley cover. You definatly have a air leak. You can spray around it with some brake cleaner and look for bubbles.
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From: Atlanta
I'm thinking multiple vacuum leaks. Try pulling your Nitrous nozzles out and rapping the hell out of them with some plumber's tape, or maybe some kind of sealant/gasket maker around the nozzle/hole on the outside of the intake.
a vacuum leak would likely idle too high and return too slowly to idle. Unless two ports saw a vacuum leak but 6 others didnt.
When you throw multiple sensor codes, I would make sure that all fuses are ok as well. If you pop a fuse, the 12volt power to a few sensors goes away. Make sure your MAF isnt on backwards (it can be done).
If those all look OK, then you are probably going to have to pull the intake again and look for leaks. Im trying to remember the right stuff, but you can spray something (like Xylene) at each of your nozzles and when it hits the leak the car will rev up a bit. I have been using the same spray bottle for so long that I forgot what I put in it 5-7 years ago. If you think pulling the intake manifold on a vette is a long and arduous task.... perhaps a direct port home install is not for you?
When you throw multiple sensor codes, I would make sure that all fuses are ok as well. If you pop a fuse, the 12volt power to a few sensors goes away. Make sure your MAF isnt on backwards (it can be done).
If those all look OK, then you are probably going to have to pull the intake again and look for leaks. Im trying to remember the right stuff, but you can spray something (like Xylene) at each of your nozzles and when it hits the leak the car will rev up a bit. I have been using the same spray bottle for so long that I forgot what I put in it 5-7 years ago. If you think pulling the intake manifold on a vette is a long and arduous task.... perhaps a direct port home install is not for you?
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From: Tennessee
Ricky at NX actually drille dand tapped the LS6 intake for me. He used Loctite when installing them. I do not think they are leaking and the feed lines are sealed at the solenoids so no air can get in. I agree that it acts like a air/vacuum leak but I can not find the leak. I will recheck the entire system for leaks again. Any other thoughts?
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Thread Starter
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From: Tennessee
Car update:
Checked all connections, there is not a leak. Reset the codes and did an idle relearn. The car idles OK. I let it warm up to 170 then went for a drive. Car ran OK for about 10 minutes. It then started to miss and then died. I scanned the MAP and MAF sensor and saw no noticeable change to warrant the miss. Now the car idles rough like before, however I did not get any codes this time. I bet if I did a relearn that it would clear up again for a short time. Something is causing the miss after a brief drive. If anyone has any ideas please let me know. Otherwise it is time for the shop.
Thanks
Checked all connections, there is not a leak. Reset the codes and did an idle relearn. The car idles OK. I let it warm up to 170 then went for a drive. Car ran OK for about 10 minutes. It then started to miss and then died. I scanned the MAP and MAF sensor and saw no noticeable change to warrant the miss. Now the car idles rough like before, however I did not get any codes this time. I bet if I did a relearn that it would clear up again for a short time. Something is causing the miss after a brief drive. If anyone has any ideas please let me know. Otherwise it is time for the shop.
Thanks
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TECH Junkie
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From: Melbourne, FL
Take a really good look at the pins on the MAF electrical connector. That seems to be a source of problems for some, and I've had issues with it in the past and had to replace the entire connector. That wouldn't really explain the problem appearing to be temperature related like you describe, though, but it's something to check...
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If its an intake area leak, the car should idle real high. Otherwise, its computer related. Mabey a sensor, there are two idleing sensors in the side of your throttle body that are cheap and wouldnt hurt to replace. I never had this problem and dont know what exacty the car would do, but the little sensors inside your MAF could be messed up. Whatever it is, its something stupid and simple.
Last edited by MakoLS1; Nov 27, 2004 at 02:37 AM.
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Originally Posted by MakoLS1
If its an intake area leak, the car should idle real high. Otherwise, its computer related. Mabey a sensor, there are two idleing sensors in the side of your throttle body that are cheap and wouldnt hurt to replace. I never had this problem and dont know what exacty the car would do, but the little sensors inside your MAF could be messed up. Whatever it is, its something stupid and simple.
Here's what I think has happened ->Your PCM is adjusting/Learning your Idle Airflow via the Long Term and Short Term Idle Trims ( that's basically what an "Idle Relearn" does) - i.e. it's pulling down the airflow at idle to compensate for an increase in airflow at idle. Learned Idle AirFlow then further adjusts as you drive and conditions change. On the "Electronic Throttle Control/Fly by Wire" Vettes the Running Airflow (RAF) is critical. If the RAF is too low the car will stall - unable to stabilize the idle. So,although your RAF was fine before it is now too little/low due to the Adaptive Learning ( if it was too high the car would have a criuse control-like effect).
Bottom Line - look for a source of increased airflow....at least the MAF thinks there is an increase in airflow. Check your MAF output at idle now -compared to a previous value. Ported TBs can cause this same problem.
FWIW. Hope this helps some.
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From: Tennessee
Thanks for the help guys. And for the record pulling the intake is an easy 15 minute task. Something I am comfortable doing. But I have never ran into a problem such as this. A leak should have showed up when spraying carb cleaner around the intake. Also a vac leak should be there all the time at idle and at cruise. The computer is doing something time/condition related.
-Bink I tihnk your assesment makes a lot of sense. What determines the RAF value? I will check the MAF output. But if the MAF sees the increase in airflow then the computer should adjust the LTRIMS correctly. Unless of course the MAF is not seeing the correct value to begin with. The throtle body is not ported BTW.
Thanks for the help.
-Bink I tihnk your assesment makes a lot of sense. What determines the RAF value? I will check the MAF output. But if the MAF sees the increase in airflow then the computer should adjust the LTRIMS correctly. Unless of course the MAF is not seeing the correct value to begin with. The throtle body is not ported BTW.
Thanks for the help.
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RAF is a Value which can be edited with Hp Tuners, LS1Edit or the new FlashScan. Although the LTRIMS will change with airflow changes I was talking about AirFlow Trims. We can't monitor these yet - hopefully soon. Did you change anything else? If not and there are No Leaks then it's either your Engine Coolant Temp Sensor, MAF sensor or MAP. If your not getting the P106, P101, or P1514 codes I would think the MAP and MAF are Okay. Make sure you drive it long enough for the PCM to go through the MAF/MAP gut checks - I don't remember how long the drive cycle needs to be. Temp Sensor??
-joel
-joel
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From: Tennessee
Update: Pulled the intake and checked all hoses again. No signs of leaks. Replaced the MAP sensor. Re-installed and now the car seems to run good again. Idles well and I have drove it about 20 miles without any codes or trouble. Also when scanning it yesterday the MAP consistently read 80-90 kPA, while the new one reads about 30 kpa, which I believe to be more accurate. Anyway after all that searching for leaks it turned out to be a $40 sensor. Thanks for all the help.
Was it installed properly the first time? 