MAF sensor replaced to cure hesitation, but now it's back :(

[kpm197]

hi, i replaced my maf sensor on sunday (leon fr) and the car felt really good, but only for about 30 miles! i had been getting a hesitation/ sluggishness around 2500 rpm when accelerating normally, especially in 2nd. roll on to this morning and it's still much better than before, but i'm starting to notice that hesitation creeping in again and the car not feeling as responsive. it's an obvious hesitation, not placebo

the maf is a new bosch item from euro car parts.

thanks

 

[nd-photo.nl]

Have you scanned the car for errors? Also, are the crankcase ventilation pipes all in good condition? The original ones are known to split.

 

[kpm197]

Hi, yeah it came up with an error yesterday, I had the ECP and the triangle warning light. The error it gave related to throttle position B. I cleared and reset and they haven't come back after another 30 miles of driving. I looked into it and a garage on a Skoda forum mentioned they had seen this issue on a couple of customers cars after changing petrol stations, and unfortunately I had to fill up at Morrisons on Sunday (before the MAF was changed). I've put it down to that until the light comes back.

The ventilation pipes were rotten on my car, both upper and lower. I've replaced them all with silicone hose (diy, not direct replacements)

 

[nd-photo.nl]

Did you fill it up with RON98 or...? You might also want to reset the throttle body alignment (via vagcom)

Procedure for performing a Throttle Body Alignment on DBW Cars using KWP-1281:
(Check to see if the engine speaks KWP-1281 by looking in the top left of the Open Controller Screen Some examples of KWP-1281 engine controllers are 2000+ Golf/GTI/Jetta/New Beetle/Audit TT 1.8T)

Turn the key on but do not start the car.

[Select]
[01 - Engine]
[Measuring Blocks - 08]
Group 060
[Go!]
[Switch to basic settings]
Once you do this you will see the top right display say ADP RUN. The TB adaptation is being done as soon as you switch to basic settings. You will see the values change and hear the TB cycle for the first few seconds then it will stop. Leave it in Basic Settings for about 30 seconds.
[Switch to Meas. Blocks] button and you're all set.

Be sure not to touch the accelerator and make sure the engine is NOT running when you do this!

 

[kpm197]

No, normal unleaded. I've asked on the vag-com thread if anyone has it in my area. I want to clean the tb anyway so needs to be reset.

 

[nd-photo.nl]

I live in the NL, so no experience with Morrisons. Do they provide crappy fuel? If so, the car maybe retarding its timing even further (your car is supposed to run on RON98) then needed for RON95 fuel.

 

[kpm197]

Morrisons is a supermarket, and a cheap supermarket. Generally one of the cheapest fuels you can buy. And I filled it up to the top! 50 litres

 

[nd-photo.nl]

That was prolly a bad idea then...Drive it hard so you need can put in some proper BP Ultimate/Shell Vpower asap

 

[kpm197]

I've noticed it doesn't do it in the mornings on way to work, but it does it a handful of times on way home. It's colder in the morning but only by 8°C. 20 in the evening, 12 in the morning. If cheap fuel was the issue, I would expect it to be the other way around- ie the cheap fuel isn't rich enough for the denser air. I'm not really sure how the whole map thing works though.

 

[kpm197]

I've compared some of my engine parameters in the morning and evening. The yellow cells are evening when car has issues, the blue cells are morning when car is fine. Data presents a 10 second gentle acceleration in 3rd from around 22mph. Each row of data represents 1 second intervals. Something I picked up on from the yellow evening data is the ignition timing jumps to -4.5 degrees during acceleration for a couple of seconds before returning to where it was, and at the same time the boost jumps in psi before dropping back. Might be nothing but it looks odd. Any thoughts? I'll continue running tests on my travels

 

[kpm197]

car is still playing up. i start to accelerate and you can feel it pulling well, then it noticeably holds back, like someone suddenly pulled the handbrake on a couple of clicks. it still accelerates all the way and it doesn't struggle to get there, but it's not responsive. it doesn't seem to do it from cold, only once it's warmed up.

 

[virdi]

Test your MAF when the car is running bad.

 

[Seatmann]

Buy some of this

http://www.ebay.co.uk/itm/380370452070?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

And do this to your maf plug

It's known to cure things on the tdi, smoother running and acceleration

 

[kpm197]

Thanks, I've ordered some of that grease.

The problem with testing the MAF is that the problem is intermittent.

Has anyone ever replaced a MAF and found the problem to return quickly? Would a Bosch MAF from Seat be better than a Bosch MAF from Eurocarparts?

 

[morf101]

Have you checked your plugs? I had a problem very similar the other week, power would start to drop.. changed the plugs and shes running perfect again. no garage could sugest anything because the fault code/management light would only come on for periods of time. might be worth just checking condition of them?

 

[kpm197]

plugs are good. a couple of days ago the temp started dropping from 90 down to 75-80 and back up again. it did this a few times. i'd only changed the thermostat and cts a few weeks ago. i whipped out the cheap ebay cts and put the original thing in and car was great... for 20-30 miles before starting to go pants again.

i've also noticed that if it's running pants and i turn the engine off and restart, its fine.

 

[mty12345]

Are you using the proper (98/99ron) fuel now?

 

[JDUB 20V]

i've also noticed that if it's running pants and i turn the engine off and restart, its fine.

A friend of mine has this same issue, when runs poo switch car off and then on again and it will be fine. 180 Cupra btw.. Tried to change vacuum pipes to the rear right of engine, MAF, N75, cleaned throttle body and adapted today, see how it goes.

 

[kpm197]

Are you using the proper (98/99ron) fuel now?

yeah, it ran worse and mpg dropped!

 

[kpm197]

A friend of mine has this same issue, when runs poo switch car off and then on again and it will be fine. 180 Cupra btw.. Tried to change vacuum pipes to the rear right of engine, MAF, cleaned throttle body and adapted today, see how it goes.

be good if you could let us know how it goes, cheers

i also cleaned the throttle body, felt different for a while but back to normal. i had this same problem with my old integra. whenever it went to a garage it came back feeling great but slowly went worse again. never did get to the bottom of it.