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Thread: Ferrari 348 Gas Analyzer Results

  1. #1
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    Default Ferrari 348 Gas Analyzer Results

    Hi all

    I've been having an unusual judder/vibration problem with my car at low rpm and so I decided to use a gas analyzer to see how the car was behaving. What I found was a big different between the two banks. I've posted pictures of the two readings, these were at idle with the engine warm. Would appreciate it if someone could help me understand the readings. I have removed the CATs in my car and replaced them with straight through pipes.

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  2. #2
    Nosevi's Avatar
    Nosevi is offline There's an outside too? Where? Super Moderator
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    Those do seem quite out of kilter, the carbon monoxide and hydrocarbons on the first bank are way too high (if Im reading it right!). First thing Id do is clean all connections (MAFs TPCs HT leads etc), clean MAFs, check resistance across both MAFs and do a full ECU reset. If after that the imbalance remains Id start digging deeper.

    Ask on here if you need any help with any of the above

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    Allandwf is offline Del Boy's Reliant Robin Club Member
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    Default Readings

    You could easily swap the MAFs over and see if the readings follow.

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    High CO suggests to me incomplete combustion.
    Your HC is high (unburnt fuel) so almost certainly a misfire
    High Lamda reading sometimes is caused by an exhaust leak but yours seems very high so perhaps an excess of air.
    Last edited by Ian355; 24-09-2018 at 09:01 AM.

  5. #5
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    Quote Originally Posted by Nosevi View Post
    Those do seem quite out of kilter, the carbon monoxide and hydrocarbons on the first bank are way too high (if Im reading it right!). First thing Id do is clean all connections (MAFs TPCs HT leads etc), clean MAFs, check resistance across both MAFs and do a full ECU reset. If after that the imbalance remains Id start digging deeper.

    Ask on here if you need any help with any of the above
    Cleaned all connectors and checked MAF/TPCs/HT leads. Resistance across MAFs is identical and spot on. If by ECU reset you mean disconnecting the battery for 10 minutes and then letting the car idle for 20/30mins, then have tried this too.

  6. #6
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    Quote Originally Posted by Ian355 View Post
    High CO suggests to me incomplete combustion.
    Your HC is high (unburnt fuel) so almost certainly a misfire
    High Lamda reading sometimes is caused by an exhaust leak but yours seems very high so perhaps an excess of air.
    Not sure if there is a leak in the exhaust system, but the car has some bespoke exhaust so don't know if this could be issue?

    Could this be a valve timing problem? Maybe the timing is out by 1 tooth when it last had the timing belt changed?

  7. #7
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    I wouldn't say those readings are particularly out of sorts for no cats. Similar to mine, but you can't measure the individual banks accurately through the tail pipes. Ok for MOT. For tuning and diagnosis it should be done through ports on the secondary air pipes. Ref. Workshop manual. Page C 85. I presume they mean the small connector on the curved pipe in the pic. It is covered by a small domed nut although Ive not had to use these myself yet. Im also just doing a retro fit of the diagnostic buttons which connect to the main ECUs. You can fit bulbs into the spare ports in the dash and then carry out code reading for each bank. They didn't fit it to euro cars. I don't believe this is for 2.5 Motronic though. Check the video. https://www.youtube.com/watch?v=PKFhGWLM0i0

    Probably would be a help to you. There are a list of codes in the WSM.

    Ive not finished just yet but will post it in my thread. I don't know if you speak French but have a look here. http://ga68.free.fr/autre/FERRARI-34...i_348-V211.pdf

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  8. #8
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    Quote Originally Posted by Pangea View Post
    I wouldn't say those readings are particularly out of sorts for no cats. Similar to mine, but you can't measure the individual banks accurately through the tail pipes. Ok for MOT. For tuning and diagnosis it should be done through ports on the secondary air pipes. Ref. Workshop manual. Page C 85. I presume they mean the small connector on the curved pipe in the pic. It is covered by a small domed nut although Ive not had to use these myself yet. Im also just doing a retro fit of the diagnostic buttons which connect to the main ECUs. You can fit bulbs into the spare ports in the dash and then carry out code reading for each bank. They didn't fit it to euro cars. I don't believe this is for 2.5 Motronic though. Check the video. https://www.youtube.com/watch?v=PKFhGWLM0i0

    Probably would be a help to you. There are a list of codes in the WSM.

    Ive not finished just yet but will post it in my thread. I don't know if you speak French but have a look here. http://ga68.free.fr/autre/FERRARI-34...i_348-V211.pdf
    I've fitted the bulbs into the spare check engine ports in the dash and both lights go off when I start up the engine. I know they are working since if I disconnect the MAF the light on the relevant side stays on. Do you have instructions on how to retro fit the button to the ECU, my car is an early 348 so has the 2.5 Motronic.

  9. #9
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    Quote Originally Posted by haydar View Post
    I've fitted the bulbs into the spare check engine ports in the dash and both lights go off when I start up the engine. I know they are working since if I disconnect the MAF the light on the relevant side stays on. Do you have instructions on how to retro fit the button to the ECU, my car is an early 348 so has the 2.5 Motronic.
    I don't believe this will be applicable for 2.5. Do you have this loom present by the ECU? The black plug at the bottom of the picture above the test button mount. It has a blanking cap fitted here. Its on the end of approx 20cm extension coming from the main ECU loom. You need this to connect the test button.

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  10. #10
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    Quote Originally Posted by haydar View Post
    Not sure if there is a leak in the exhaust system, but the car has some bespoke exhaust so don't know if this could be issue?

    Could this be a valve timing problem? Maybe the timing is out by 1 tooth when it last had the timing belt changed?
    Never seen a lamda reading that high from an exhaust leak.
    I would have thought you would have noticed rough running immediately after the belt change if the cam timing was out
    Presumably you have the lamda sensors on what was the cat inlets. If one had gone down then it might be feeding wrong info back to its ecu?

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