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Uncle niluca,
Why we REALLY need a proper Volvo 240 FAQ.
Please use the almost useless brickboard search tool for codes. The error codes suggest all sorts fault conditions. You may want to search through my message log (click on the blue hyperlink kittysgreyvolvo; please ignore the bombastic commentary and thread titles - I do this) as I've had answered this very same issue about a dozen times in the last year period alone.
I trust you have a Bentley, Volvo green, or somewhat maligned Haynes, or even a Chilton service manual for your 240, yes?
Well, why we need a 240 FAQ.
Did you clear the codes after installing the AMM/MAF and the new headerpipe?
So look here at the http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm
You scanned the Bosch LH 2.4+ Jetronic codes at the black LED diagnostic box through socket 2. You MUST also check for fault codes in the Bosch EZK ignition system (socket 6). The two systems work together. Post back your results.
Causes:
- Failed AMM/MAF or fault in electrical connection (you say you back probed at LH-ECU connector and all's well.
- You have air intake leaks anywhere downstream of your rebuilt MAF/AMM. Locate and seal these. All vacuum lines, all piping, all connectors and unions including the PCV system).
I doubt a failed fuel rail control pressure regulator. Yet check this. Pull the vaccum line and check for fuel leak from the fuel rail control pressure regulator and into the intake port (manifold).
Inspect and remedy the exhaust for leaks. Any leak ahead of the 02 sensor will induce poor fuel economy and performance. If an exhaust leak way upstream of the 02 sensor, that may appear as a lean running condition. If the exhaust leak is in front of the 02 sensor, like at the header pipe output to catalytic converter input flange, that may induce a rich running condition.
Your brickboard account post/thread history indicates your have an EGR-equipped 1989 Volvo 240, so the EGR piping and unions are secure and do not leak.
You may have a weak oxygen sensor. I'm unsure. Replace it every 60k miles. If the 02 sensor has suffered a rich running condition, the 02 sensor can prematurely fail. The newer Bosch 02 sensors are of more robust construction than ever. I just bought three new for Bosch LH 2.4 equipped Volvo 240 like yours from Autozone. Yet verify whether yours is good, weak, or failed, before spending the $ for a new one.
Try this - http://www.brickboard.com/FAQ/700-900/EngineFuelinjection.htm#Oxygen_Sensor_Diagnosis
Heh-heh-you'd never find it in the 700-900 FAQ TOC or Index.
Remember kids, a Bosch LH-Jet and EZK equipped Volvo 240 runs best when the emission controls are in optimal operation and condition. Meaning all performs best when the emissions controls are operating optimally.
Questions?
Hope that helps.
MacDuff the Bastard and SOB.
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