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Twin Turbo troubleshooting


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Hi, my 1999 BH5 GTB has been having some issues recently.

 

First, whenever I start it up, the car struggles to maintain a steady idle throughout the heat cycle. It doesn't shut off, but will consistently alternate between the usual 1500 rpm on a cold start down to about 700-1000, and the exhaust note is dramatically different, almost as if it is down a cylinder.

 

Second, the car seems to misfire/cut boost throughout the primary turbo. It still accelerates fine and is relatively driveable, but it feels down on power between 2000-3500 rpm; the car feels 'clogged up', almost as if I am accelerating up a hill or into a headwind, until it hits peak boost on primary during which the car accelerates fine and transitions to secondary as usual. This is especially noticeable in 4th and 5th gear, and maintaining 110km/h on vacuum is difficult and makes highway driving especially uncomfortable. Going through the powerband onto secondary makes this issue less dramatic the next time I accelerate on primary, and the car seems to misfire/cut boost less and feels more confident.

 

As such, I've started to drive it by accelerating on vacuum until about 3000 rpm, then rolling into it and getting up to speed.

 

All of this occurs with no check engine light.

 

I've replaced the spark plugs with NGK BKR7EIX gapped to 8mm, and the stock coilpacks with Napol Performance 22433AA421 2.0 turbo coilpacks. I am running Shell Rotella T6, and a generic apexi cone filter which came on it from japan. I run Husky 94, with no additive on the stock tune, but I intend to get the ProjectLAMBDA tuner.

 

I have tried to clean the maf, but I've read it is better to just find a replacement, which I have had trouble sourcing.

 

I've read that this could be anything from an O2 sensor/catalytic converter issue, to a boost leak in the wastegate/recirc valve area, although being a pre-OBD2 model I am unsure as of how to diagnose this issue.

 

Anyone encounter a similar issue? Any help would be appreciated, else it will be going into the shop. Thanks!

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I think you should start with a smoke test, then check the turbos to see that both are OK. Also all the pipes - inlet and exhaust to ensure that you don't have a stuck wastegate or something similar.

 

 

A boost gauge could also give you some indications of how well the system behaves.

 

 

And even if you have a pre-OBD2 you have some codes to look at.

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I think you should start with a smoke test, then check the turbos to see that both are OK. Also all the pipes - inlet and exhaust to ensure that you don't have a stuck wastegate or something similar.

 

 

A boost gauge could also give you some indications of how well the system behaves.

 

 

And even if you have a pre-OBD2 you have some codes to look at.

 

Sounds good. I've yet to comprehensively inspect the the turbo system. I currently have a boost guage and everything is relatively consistent to what I've seen other users post, but when the car does the stuttering, boost will build quite sluggishly compared to other turbo cars I've driven in.

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  • 2 weeks later...

if you look under the dash on the drivers side there should be two black connectors. plug those in and turn the ignition on. The engine light should start flashing. long flashes are 10 and short flashes are 1. so example two long flashes and three short flashes would be code 23. Start by checking that out. Currently I am having similar issues with my legacy b4 and it has the code 23 for the maf stored but never actually throws a CEL. Replaced the maf, o2 sensor, fuel filter, smoke tested twice, and had the MAP and all the solenoids checked and it still hasn't fixed it.

 

If you plug the green connectors underneath the dash as well and turn the ignition to on then that will put the car into test mode. you should hear the solenoids click and the the rod for the wastegate on the primary turbo should move as well as the exhaust control valve on the intercooler, and the exhaust control valve on the secondary turbo. Let me know if any of this helps!

 

Also... did this happen before the Napol coil packs? I'm just wondering as I am starting to think that my issue is related to the Delphi coil packs I had put on the car about 2 weeks before my issues started.

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  • 1 year later...
  • 8 months later...

Also... did this happen before the Napol coil packs? I'm just wondering as I am starting to think that my issue is related to the Delphi coil packs I had put on the car about 2 weeks before my issues started.

 

I also put delphi coil packs in and have been having the same issues. are you in Canada as well? I have been suspicious that our cars just can't run properly without a lambda 94 tune

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