Fault codes on a 1999 W202

[bedwards1966]

I've a 1999 C230k auto that is giving some fault codes on my EBD reader:

P0170 Fuel (Trim Bank 1)
P0700 Transmission Control System (MIL request) PENDING
P0170 Fuel (Trim Bank 1) PENDING

In English, what does this mean?
I've had the car about 2 years and have cleaned the MAF and air pipes a few times when it stops performing properly, the last time I cleaned the MAF I plugged it in and got these readings.
If I clear them then as soon as I start the engine they reappear immediately.

Any ideas? I can get live data off the scanner if there is anything in it that will mean something to anyone.

 

[Pendragon]

P0170 Fuel (Trim Bank 1)......This code often crops up with incorrect fuel mixture so likely causes could be many IE air leak, sensor fault, seriously blocked air filter, MAF fault.

Basically it needs a full check with live read outs to see exactly what's causing it, maybe even an emissions test it could just be a sensor fault

The bank 1 part usually points to a RICH mixture so the car has compensated as much as it can and now has thrown the fault code. you need to look at the Long term fuel trim or LTFT on a scanner and it should be 0 or -1% that is fine, if its say 7% either side of 0 then its way off as close to 0 as possible is normal running.

Keith

 

[bedwards1966]

Thanks for the reply.
I went out and got some live data reading, I've attached some pictures of the readings so hopefully you'll be able to see them.
The LTFT was about 32% (first picture), what does that mean? The engine was cold when I started it for the test, will that matter?
I forgot to add it's had a new air filter quite recently, so it's not that.
With the LTFT reading like that, what could it be? Air leak perhaps, or still possibly a sensor issue?
The fuel consumption is about 18mpg round town, all short trips, it'll do 28, maybe 30 on long runs, so I take it from those figures it's not using vast amount of extra fuel?

 

[bedwards1966]

Out of all the experienced MB mechanics on here are there no more suggestions as to what could be wrong, surely someone must understand the readings I've posted?
Or is it just that new members aren't welcome on this forum?

 

[Pendragon]

P0170 Fuel (Trim Bank 1) PENDING....You have 2 possible faults that will kick out a P0170 code:

1- change the crank case vent valve- is it leaking/hissing?

2- the MAF is faulty.

 

[martyz]

I think it's time to get a new MAF, don't bother getting anything other than Bosch.
Cleaning them does more harm than good.Hope this helps you.

 

[bedwards1966]

I take it the crank case vent valve is the little black box fixed to the top of the engine near the air cleaner/by the coolant tank? With a hose into the engine, dipstick tube and air cleaner?

How much is a new MAF likely to set me back? I had feared it could come to this...

If I leave it and continue using it am I likely to have any problems? It seems fine on power and the fuel consumption seems about right (to me), is it likely to make much difference?

 

[bedwards1966]

After a quick look on eBay, £180 seems rather steep, what is the actual difference between Bosch ones and cheap ones such as this
MERC C200 C180 C230 CDI & PETROL MAF AIR FLOW METER | eBay which claim to have the same Bosch part numbers?

 

[streethawk]

Hi there. Your crank case breather or check valve is under the inlet manifold! This splits to two pipes which go into the head under the inlet via two brass little jets! These get blocked and cause engine to hunt while on tickover and also contaminates maf with oil via your cam case breather or swirl chamber as I think its know! This oil goes into the airbox and then intercooler and maf. The little jets and check valve get blocked and the breathing system can't handle it so you get excess oil through the top end which causes contamination of maf. Don't know about your engine codes though.