Installed new intake and now car idles rough and turns off

Svt_mean98

New Member
Nov 5, 2019
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Stockton
I recently had a stock intake i bought the JLT Performance Next Generation Ram Air Intake (96-98 Cobra) installed it and my car started idling rough and check engine light came on says its running lean in bank 1 and 2. Also while driving if i put clutch in the rpms just drop and cars dies out it said a tune wasn't required so im lost any suggestions?
 
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wmburns

SN Certified Technician
Aug 14, 2009
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Houston Texas
Just wondering....... What have you done to rule out a common intake vacuum leak?

Do you have an ODB2 scanner? If so, monitor LTFT/STFT's at idle and under load. Typically a vacuum leak will show up as adding fuel at idle but adding less fuel under load.

ForScan ODB2 scanner w ELM327 USB
 
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Svt_mean98

New Member
Nov 5, 2019
4
0
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Stockton
Just wondering....... What have you done to rule out a common intake vacuum leak?

Do you have an ODB2 scanner? If so, monitor LTFT/STFT's at idle and under load. Typically a vacuum leak will show up as adding fuel at idle but adding less fuel under load.

ForScan ODB2 scanner w ELM327 USB
Someone told me to just spray carb cleaner on all the hoses and intake to see if it idles different but i didn't notice any change. I dont own one myself but a buddy of mine has one ill try that out next and see what its doing. Thanks man
 

wmburns

SN Certified Technician
Aug 14, 2009
5,842
505
194
Houston Texas
Don't over look some of the "other" possibility for a vacuum leak. For example:
  • power brake vacuum booster vacuum source.
  • EVAP purge vacuum line.
  • Fuel pressure regulator or FRPS intake vacuum reference line.
  • PCV valve
  • PCV make up air line.
  • oil dip stick tube seal.
  • Valve cover gaskets.
  • injector O-rings
  • EGR vacuum operated solenoids.
  • The vacuum line that goes through the firewall to operate the vacuum controlled vent damper motors.
 

Svt_mean98

New Member
Nov 5, 2019
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Stockton
So i decided to try and put stock intake back on to see if it made a difference and all of a sudden my check engine light turned off and car hasn't died out. so could that mean i have a vacuum leak on the actual filter or piping itself?
 

tsemmett

Active Member
Jul 2, 2019
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If it's only an issue with the new intake, I would suggest that you have a leak between the MAF and Throttle Body. Some potentially "dumb" questions: Are you moving your MAF and IAT sensor over to the new intake or using new ones (maybe one or the other is bad)? Are you connecting both of the smaller tubes to the new intake (PCV and IAC)? Do the rubber sleeves seem to fit well on the TB and MAF?

On my car, I have a worn out rubber sleeve that sometimes causes my intake to come apart right past the MAF (the engine torques away from it, and pulls it apart). When it does, the car behaves in a similar manner; pulling air the ECU doesn't know about and all.
 

Svt_mean98

New Member
Nov 5, 2019
4
0
1
23
Stockton
If it's only an issue with the new intake, I would suggest that you have a leak between the MAF and Throttle Body. Some potentially "dumb" questions: Are you moving your MAF and IAT sensor over to the new intake or using new ones (maybe one or the other is bad)? Are you connecting both of the smaller tubes to the new intake (PCV and IAC)? Do the rubber sleeves seem to fit well on the TB and MAF?

On my car, I have a worn out rubber sleeve that sometimes causes my intake to come apart right past the MAF (the engine torques away from it, and pulls it apart). When it does, the car behaves in a similar manner; pulling air the ECU doesn't know about and all.
I was using the old MAF sensor but then got a new one and it did same thing. I did notice the sleeves where you plug in the IAC and PCV hoses were kinda loose has a lot of wiggle room so I wonder if that can be the problem, ill probably go to autozone today nd see if the have better sleeves. Could i use like Teflon or electrical to seal the tubes better or am i better boff getting better seals
 

Hudson N

Member
Aug 7, 2018
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Queen creek Arizona
I was using the old MAF sensor but then got a new one and it did same thing. I did notice the sleeves where you plug in the IAC and PCV hoses were kinda loose has a lot of wiggle room so I wonder if that can be the problem, ill probably go to autozone today nd see if the have better sleeves. Could i use like Teflon or electrical to seal the tubes better or am i better boff getting better seals

Try electrical tape for now and see if that fixes your leak, It worked for me.