OK guys, I just picked my car up and my tech went over everything with me for about 30 solid minutes. He performed ALL of the tests that everybody on this thread had mentioned with the exception of measuring the pre-cat & post-cat temp as well as the 4-gas analysis. One of the somethings (sensors?) in his machine died and he didn't have time to go buy a replacement part. The secondary air pump was completely disassembled, tightened, and then tested in 3 forms and he said that he smelled a slight hint of burning plastic inside the unit itself. So, it looks like I will be replacing that. So, this leaves the other cat efficiency codes (which just triggered the CEL after installing Hyper-Flows) and the p1130 LT-Fuel Trim code for Bank 2 that has plagued my car since I bought it in 2008 (7000 miles ago). We looked at the cats, O2 sensors, fuel trim, etc with his machine and everything is working as it is supposed to at idel, 2500rpm, and 5000rpm. He thinks that it is possible that something at an even higher rpm might be triggering the LT Fuel-Trim. His ONLY question was this: Attached is the readout from from the display. Notice that the LTFT for Bank 2 is substantially higher, which means the car is running lean at times. Is this 15.6 number the number from when the car is NEW? If so, would this trigger a CEL even though the problem may have been recitified? Is it possible that this has NEVER been reset by an SD1, and can it even be reset by an SD1? If the SD1 can reset this, would the fault code (p1130) disappear? Guys, my tech is honest and factory-trained on the 355. He spent 4 hours on my car and charged me for 2. If i can't get this resolved I will be shipping my car up to Carlo at Alfa Tacoma in May (his first opening). Thank you all for your input. Image Unavailable, Please Login
BLAMPEE, What mods (besides the cats) are on your car? I don't like to see LTFT's and STFT's with different signs. Something isn't "right". Jim
Bank 2 long term fuel trim at 15% is a problem. It could be a weak injector, lazy o2, or exhaust manifold leak. Misfires will throw off fuel trims as well but that would be rather noticeable. Basically a car that is running correctly will have short and long term fuel trims within a few percent of zero and be close to equal on both banks. In your case the ecu is adding 15% fuel to bank 2 in order to reach stoich
Only mods are Hyper-Flow cats, rebuilt QV London headers, and Quicksilver Exhaust--all installed June 2009. The p1130 code has been a problem since August 2008. All replacement parts replaced OEM equipment. Thank you for the response. The LTFT was a problem before the cat codes triggered the CEL. When was the start date of this LTFT reading?? When the car was new? Or, is resettable by the SD1 and was it ever reset?
I was in a pinch and used the Bosch approved equivalent "universal" pre-cat O2 sensor on my 355. I did not use the splicing block that was included, and chose to solder and individually heat shrink each connection, then heat shrink the entire bundle. It has been on my car for about 3 years, with no problems. I don't have all the equivalent Bosch "universal" pre and post O2 sensor part numbers handy, but I have posted them several times before and you can probably find them with a quick search. I don't believe just any "universal" will work as there are some specifics to them...I recall "Loser" accidently used Motronic 2.7 precat O2 sensors by accident on his 5.2 Motronic (due to an error in the Bosch online look up used by every parts house in the USA and still in use!) and it created all sorts CE lights, codes and wierd graphs when he printed the output wave forms I have been using the following Bosch part numbers for Motronic 5.2 F355 (1996-1999): Pre cat #13819 Post cat #13820 I needed a pre-cat O2 sensor once late on a Friday, and simply bought a Bosch, four wire "universal" from the local auto parts store (as recommended by Bosch on their 800 customer service #), ditched the provided "splicing block" and soldered my old plug onto the new sensor, then used heat shrink tubing over all four solder joints, and one big piece over all four joints. Okay, checked on the Bosch "universal" O2 sensors: Pre cat is #15730 Post cat is #15738
BLAMPEE, OK, you have an M5.2 car - one MAF. It is unlikely that an unmetered air leak for only ONE bank would be possible, but I'd still check for one - time for the smoke machine. (I use n-Heptane in a squirt bottle - I DO NOT RECOMMEND THIS - it is very dangerous!) So, if you have no air leaks on the INTAKE side - and fuel pressure is correct on BOTH banks then I would look at... Injectors (flow and spray pattern) Exhaust leaks Something is causing your LTFT on one bank to go WAY rich - which means that there is a decently large "enleanment" on that bank. Things like - low fuel pressure, clogged injector, exhaust manifold leak, intake air leak. Jim
The LTFT uses a rolling timeframe. If there is a problem, and it seems there is, resetting the LTFT is not going to fix it. What did your tech say about that LTFT? I see that as a bigger issue than the cat codes. I'd spend my money getting that fixed and ignore the cat codes. Since the check engine light is on all the time I'd get a OBDII reader and periodically check to see if there are any new codes.
It is a learned value which is always adapting. Once the short term fuel trims remain positive the long term fuel trims will start to increase until the short terms return back to zero. Lets say for instance one of your injectors isn't flowing correctly, or there is a leak in your exhaust manifold. If you were to correct whatever the problem is without resetting your current learned fuel trim the next time you ran the car you would see the short term fuel trims running negative until the long terms were brought back down to zero. Alternatively, if you reset the fuel trims to zero and ran the car in it's current condition you would quickly see the stft's go to 15% and then soon thereafter the ltft's would climb to 15% to bring the stft's back down to zero. (same as you see now)
He did not check the fuel pressure but will when I get home from my 14-day business trip on the 20th. He has smoke-tested my car 4 times and there are no leaks anywhere. If the fuel pressure is good, is there anyone on this board I can send the injectors (ALL of them) to for testing? My tech doesn't have the capabilities to test them but he said he can pull them out easily. Is it possible I have an exhaust manifold leak, even though I replaced the OEM ones last June with rebuilt QV Londons? Also, the exhaust is Quicksilver and new, too. We only replaced one O2 sensor last year (upstream Bank 1, I believe. The common theme on this board is that I should replace the other 3. However, my p1130 code has been a problem since I owned the car in 2008--remember that I did my 30k in June 2009 and thought I would get rid of that pesky little reoccuring code. Could it really be that GD simple as an O2 sensor that may freak out on RARE occasion but functions fine by testing...? This will be the first thing I do when I get home. My tech said that he cannot reproduce anything that would show why the LTFT is so lean. What he said was that he can't get the STFT to change. He says that it is possible that something is happening at high rpms while the engine is under load while driving. I have an OBDII reader, but it just shows codes (fault and pending) ONLY if there is a CEL as well as the readiness items for OBDII testing. Should I buy one of the more expensive ones? I paid like $35 for mine and I know that the $100+ OBDII readers show live data. Is the 15.6% an AVERAGE...or is that the MAXIMUM that the LTFT has reached in correcting the leanness of the engine over time? Educational, yes...but not fun when its your car, Sean. BTW, I decided to upgrade my subscription to Rossa for the sole reason that I have learned so much about cars and my 355. The knowledge in this chat is phenomenal.
Possible, but not that likely. Doubtful. I'd just change it since they are relatively cheap. If that was the case then the LTFT would go back down when you are driving normally. The window of time for the LTFT to adapt is not that long. I'm starting to wonder how good your tech is if he is suggesting that. Not testing fuel pressure is a red flag too. That one should be fine for engine codes. It should still show you codes that have not tripped the CEL though. Pending codes should still show up. It's a little tough to grasp at first but the two fuel trims are what the computer adds or subtracts from it's main fueling map to get the engine to stoich fueling, 14.7:1 air to fuel ratio. If you reset the fuel trims they both start at zero. For whatever reason your bank 2 is showing a lean condition. When the computer sees a lean condition it adds fuel via the STFT. After a certain time period the LTFT will ramp up and the STFT will ramp down. Short term is supposed to be centered around 0. That 15.6% is the amount of fuel that is being added on top of the regular fuel map all the time. It's not a max or average.
Correct, there's nothing that needs to be "reproduced". If the LTFT is at +15% on one bank that in itself is a problem. I doubt it's the o2 sensor but you could swap the sensors between b1 and b2 and see if the problem follows the sensor. (could do the same with injectors if you want to be certain of the problem before sending them out) As far as fuel pressure I thought only early 95's had separate fuel systems for each bank. If this car has a single fuel pressure regulator than fuel pressure wouldn't explain the problem being on only one bank.
Is your 15% LTFT measured at idle conditions? The 5.2 seems to have different LTFT cells according to the running conditions (RPM, load). Try to record the LTFT value while driving at different RPM (1500, 2000, 2500, ...., 4000) and different loads. If its value decreases significantly at higher RPM and loads, you may face a small leakage (exhaust or intake) which has more effects at idle and less effet when gas flow increases, or some misfires at idle which increase the oxygen content in the exhaust. If it stays the same, it could be due to fuel starvation in all the running conditions (fuel pressure, injectors), or continuous misfire.
Yes, that measurement was at idle, 2500rpm, and 5000rpm...but the car was not being driven at the time. My car did have a misfire problem before we did the 30k. However, the service seemed to resolve it. It may be possible that it is still misfiring vary rarely at idle. Occasionally, when I am sitting at a stoplight it feels like the engine "shutters" a little bit and it moves the entire car. Is that a misfire?
Hmmm, So going back on my old threads, the code on the 355 I work on is P0432. I have always just ignored it thinking it was a bad cat. It still has the OEM cats and I'd heard those go bad a lot. Maybe I have another issue? Same as you?
Why do you say that Jim? Once the LTFT has reached its final positive value (to compensate for the apparent lean condition measured by the O2 sensor) it seems normal to see the STFT swinging around 0% to stay close to stoechiometric condition ... seen by the O2 sensor. As it swings, it has sometimes the same sign as the LTFT and sometimes the opposite. No?
You have to drive the car if you want to see the LTFT changing, you need to put more air in it and increase the load. I made some experiment on my car this WE because I am also chasing a LTFT which is a bit too high on one bank. What I have learnt is that the 5.2 stays in closed loop if the RPM is below #4300 RPM AND the throttle is below #23% (OBD data). If RPM OR throtle exceed these limits the ECU goes in open loop. I made some LTFT recording, while staying in closed loop, and was able to see that its value decreases when air flow increases. I tried to explore different running conditions, light throtle and RPM increase or almost constant RPM and throtle increase. The result is the same and, in my case, LTFT is air flow dependent and goes down to 0 at about 53g/s. This is a low flow value, the engine is able to breath more than 260 g/s! That makes me confident I am facing a small leak somewhere which has no impact on the fuelling conditions under (high!) loads. May be you can try some similar investigations and report your findings ... Image Unavailable, Please Login Image Unavailable, Please Login
Curious.. if one has a power improving addition like say a hyper-flow cat (which publish decent power benefits) how does the ECU manage fuel corrections to richen up the AFM sufficiently to account for the added HP/TQ once the engine goes into open loop mode (ie: above #4300 RPM and 23% TP)? .. or does the engine simply run lean(er) than it should?
Small improvements in horsepower/airflow will be measured by the mass airflow sensor and additional fuel will be delivered. More substantial modifications (such as cams or displacement change/etc) will require ECU recalibration in order to maintain the proper air/fuel ratio.
