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.

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?