Both banks running lean and now running rich?

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I am not sure if the make and model of the car is important. The initial code indicated both banks running lean at load. I instructed to check for the vacuum leak and then clean MAF. Afterwards, fuel trim is indicating that it is running excessively rich on both banks. Is it possible that too much cleaner on the MAF can make it give false rich readings to computer? A modern fuel injected car would suddenly start running rich on both banks only if the fuel pressure regulator malfunctions. Other causes such as exhaust leak before O2 sensor can be ruled out because it is unlikely that similar leak would develop on both banks simultaneously. O2 readings on the scanner indicate that both O2 are functioning correctly. Air cleaner element is NOT clogged With MAF disconnected short term remains pretty much in neutral territory and car run reasonably well. So changing MAF is already planned for. But most MAF when they go bad, the engine starts running lean and not rich. OEM MAF is $$$$ for this "mistress" so first attempt would be made with a ebay MAF as it costs 10% of the OEM money. Of course, if that does not fix it, we would have to decide if we need to shell the big money for the OEM one or to approach different diagnostic strategy. Any suggestions?
 
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Originally Posted By: Vikas
I am not sure if the make and model of the car is important.
It would be helpful.
Originally Posted By: Vikas
The initial code indicated both banks running lean at load. I instructed to check for the vacuum leak and then clean MAF. Afterwards, fuel trim is indicating that it is running excessively rich on both banks. Is it possible that too much cleaner on the MAF can make it give false rich readings to computer?
It generally shouldn't, but timing is important. Cooling hot things too quickly can break them. Is there any chance he unplugged it to clean it, then failed to get the connector on all the way when putting it back?
Originally Posted By: Vikas
A modern fuel injected car would suddenly start running rich on both banks only if the fuel pressure regulator malfunctions. Other causes such as exhaust leak before O2 sensor can be ruled out because it is unlikely that similar leak would develop on both banks simultaneously. O2 readings on the scanner indicate that both O2 are functioning correctly. Air cleaner element is NOT clogged With MAF disconnected short term remains pretty much in neutral territory and car run reasonably well.
This sounds likely enough. The sensor should be replaced if your guy was lucky enough to clean a dirty MAF so hard that he broke it.
Originally Posted By: Vikas
So changing MAF is already planned for. But most MAF when they go bad, the engine starts running lean and not rich. OEM MAF is $$$$ for this "mistress" so first attempt would be made with a ebay MAF as it costs 10% of the OEM money. Of course, if that does not fix it, we would have to decide if we need to shell the big money for the OEM one or to approach different diagnostic strategy. Any suggestions?
I think that the most obvious thing to check before replacing the MAF sensor would be to compare it's reading (engine warmed up) at idle and at 2500RPM with no load against a known good vehicle if available, or if no such reference is available, just do a quick sanity check.
 
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What vehicle is this, it does matter. Some Ford trucks for example with show some bizarre readings with no CEL if the band clamp holding the air cleaner housing together isn't on properly (easy to do). What are the fuel trims? Any codes? It sounds like he may have screwed the MAF but who knows.
 

Vikas

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99 Porsche Boxster 5speed aka "the Mistress". The whole thing started when he opened the "logical hood" on this engine the very first time and looked at the air filter. Because of the design and location of the air filter and MAF housing, it is possible that some dirt did end up in the MAF and initial lean codes and very poor running of the engine at load lead me to advice him to clean the MAF. This unfortunately also happened immediately after he filled the gas tank. So bad gas has been one possibility. So once again on my advice, he threw Techron in the tank. Is there even 10% probability that strong Technron dosage could lead to rich burning? One of the strange complaint that he has been making is that car runs great until first time he does WOT and from that point onward, it changes the personality and starts bucking and nearing to stall etc. At that point I had him hook up the scanner and relay the live data to me. Currently, both STFT starts trending down to -20% range and he had both banks lean at idle pending codes although the car is driving very well. He is convinced that if continues to drive, the codes will change from pending to stored. He will be on the 3rd iteration of ebay MAF. The first one did not come with the built-in IAT, so the car threw that code when he did the swap. The replacement ebay MAF had the IAT but the electrical connection did not match. Now he is waiting for the 3rd one to arrive. The $30 handheld scanner has its own quirks and limitations. For example, he can monitor 4 PID's in one screen and he has no choice about which 4s. He can scroll the screen for the next 4 etc. Fortunately, trims were on the single screen but unfortunately, O2 voltage are on two different screens, so it is little bit tricky to monitor the voltage but from his observations, O2 sensors are functioning as expected. MAF readings are in the ballpark but my prior experience playing with MAF suggests that there is a vast difference between a good MAF and what factory manual says is acceptable MAF. He purchased Porsche specific PC-based cable but has not been able to get that cable to work on the laptop yet. I was pretty confident about my ability to guide him remotely when he first started getting the initial lean codes but after transitioning to the rich codes, I am running out of ideas. He is now almost on the 1/4 tank of that gas and I am inclined to tell him to run out of that gas and fill it and just continue to drive and see if he gets CEL.
 
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So many things going on here. Until he gets the correct MAF sensor in this car there is no point in going further. Can you get the OE number of the sensor? I have a few here, it will a number like 0 280 217 007, 99660612300. I cant see Techron causing an issue.
 
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reman MAFs usually cost much less than OEM sensors, and I never had a problem. I'd rather use than than some random used unit. I have never seen a reman MAF at a dealership, only at auto part stores. I wouldn't be surprised if the MAF on your car is found on several other cars that use Bosch MAFs.
 
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