System too rich - Engine Hesitates Under load
Hi Guys
I have 2 issues according to VAGCOM: Load Calculation Cross Check Fuel Trim Bank 1&2 System too rich - Intermittent The Purge valve threw a CEL a couple of months ago and was replaced, then recently the MAF did the same, it was replaced (MAF cleaner didn't help) It felt much smoother after the new MAF but now its 'lumpy' again and noticeably the engine hesitates and surges when under load. Is this a vacuum issue? I've looked at the diagram under the hood and frankly i'm lost all that spaghetti of black tubing in the engine all looks the same to me :( and i can't find a decent photo of which line is which. I don't mind systematically changing the Vac lines, but i'm not sure what is and what isn't Vac, and does anyone know what diameter it is so i can just buy a reel of the stuff? Cheers |
Which engine do you have?
Anyways, I don't think is it vacuum related since vacuum related trouble usually gives you lean condition, not rich. Anyways the following website contains a wealth of information regarding the fuel trim. There is also a PDF attachment which deals with more stuff that you would ever want to know. http://robsaudiworld.com/fueltrim.htm |
Its the 2.8 with 121k, thanks for the link, i'm assuming it isn't the MAF as that's new, but i may have to explore the Coolant Temp sensor and Fuel Pressure regulator.
Useful info thanks |
If I were you, I would try the simple stuff first. Obviously see if you have any intermittent codes which are not throwing a CEL yet. Also clean the throttle body and run it through the calibration. Then the next thing is the CTS. It is pretty cheap and each to replace. Other than that, I would think it is 02 sensor related.
Just disconnect the front 02 sensors and see if the car runs better. |
Originally Posted by hxgaser
(Post 1126305)
If I were you, I would try the simple stuff first. Obviously see if you have any intermittent codes which are not throwing a CEL yet. Also clean the throttle body and run it through the calibration. Then the next thing is the CTS. It is pretty cheap and each to replace. Other than that, I would think it is 02 sensor related.
Just disconnect the front 02 sensors and see if the car runs better. Thanks for the tips, although i have 2 questions. 1. How does the temp of the coolant affect the fuel being too rich, is it a default cold start/choke type thing. 2. How do i disconnect the front 2 O2 sensors, do i do it from the exhaust or from in the engine? I Managed to get a copy of the VAG ElsaWin but i have a 64bit OS and it won't work. I will get round to installing it on my old laptop that runs VAGCOM. Cheers |
1. CTS sends motor temperature info to ECU to adjust the fuel trim in addition to many other readings. If the CTS is sending the ECU that the motor is cold when in reality the motor is warm, the ECU will add more fuel than it is required to get the proper combustion ratio.
2. You can just unplug the engine side plugs above the bank 1 head. |
Not tried driving with O2 sensors unplugged yet, but i did measure resistance across pins 1&2 of O2 sensor plug it read '0 ohms' ElsaWin says should be between 0-19 ohms.
Have ordered a new Coolant temp sensor and will be getting the wife to fit it cos there is zero space for my hand. I note the turbo boys have it easy 'cos the air intake isn't in the way for them ;) |
You can disconnect the intake air hose. Even with that it will be snug. Just make sure the motor is completely cool, then release pressure from the reservoir by opening the cap. Re-tighten the cap and replace the CTS. The plastic clip holding the CTS tends to become brittle. Just order one and a new o-ring as well. I found it easier to disconnect a couple of brackets holding some vacuum lines to get access.
|
Well i replaced the Temp coolant sensor, man what a bugger that was, luckily my wife has small hands as there was noooo room to move, even with the flexible hose removed.
Curiously once it was replaced we got a CEL, i cleared the 'Engine codes' and used it today in normal driving. We got a CEL again and i just pulled the codes. Both trim banks : System too rich Load calculation cross check: Implausible value Fuel Pressure sensor?? O2 Sensors?? Visit to my local independent?? ;) |
What is the actual code number?
|
Control Module Part Number: 4D0 907 551 AH
Component and/or Version: 2.8L V6/5V MOTR AT D04 Software Coding: 06252 Work Shop Code: WSC 02324 3 Faults Found: 17535 - Fuel Trim: Bank 1 (Mult): System too Rich P1127 - 35-00 - - 17537 - Fuel Trim: Bank 2 (Mult): System too Rich P1129 - 35-00 - - 17549 - Load Calculation Cross Check: Implausible Value P1141 - 35-00 - - |
17549/P1141/004417 - Load Calculation Cross Check: Implausible Value Possible Causes * Mass Air Flow Sensor (G70) OR Manifold Pressure Sensor (G71) faulty * Vacuum Lines faulty Possible Solutions * Check Mass Air Flow Sensor (G70) OR Manifold Pressure Sensor (G71) * Check Vacuum Lines * Check Engine Operating Conditions => Meas. Blocks Special Notes * Uwe: I think this code is set when the airflow being measured (or otherwise calculated) by the ECU doesn't make sense given other operating parameters such as RPM and throttle opening, manifold pressure, etc. I would also look at the vacuum line going to the fuel regulator. Most are vacuum referenced in order to keep the pressure at a certain value above manifold pressure. |
I would check the MAF once more. I heard some cases where new MAF sensors were bad. Check out the following website.
http://www.ross-tech.net/vag-com/adv...AF_TechTip.pdf Other than that, the only thing that I can think of is to check the vacuum going to the fuel pressure regulator. It is a small cylinder looking thing above the intake manifold toward the driver side rear. Yes I know I said the vacuum may not be the issue before, but I am running out of options. |
Hey Jim beat me to it as I was typing.
|
At least we're thinking the same thing :)
Ahhhhh! get outta my head!! |
Speaking of fuel pressure regulators, it could just be bad too ....121k is about right for it to go.
|
1 Attachment(s)
Thanks Guys
I checked the vacuum line to the fuel pressure regulator it looked OK (still supple not brittle) but it was difficult to see the other end of it. It disappears under a bunch of connectors in the middle of the back of the engine. Where does the other end go? If i have to replace the fuel pressure regulator is it a straight forward job? Am i gonna get covered in fuel? I looked at the article you posted about the MAF and did a block group 032 it seems out of tolerance Attachment 42170 cheers |
It is just telling you that you are burning rich. One way of check is to just disconnect the MAF and check the measuring block 32 to see if you get the same result. If you do get the same result than it probably is not a MAF. If the o2 level goes up, then you probably have a bunk MAF.
|
I disconnected the MAF and ran it again. Both 032 values dropped to -25%
The 001 O2 banks fluctuated between -5 & +10% |
All times are GMT -4. The time now is 03:59 AM. |
© 2024 MH Sub I, LLC dba Internet Brands