abf 16v idle problems

[paultownsend]

so 4 months ago i fitted the said 16v lump into my mk2 golf. using the digi 3.2 full management. the only sensors i didnt use were the charcoal evap and gearbox sensor for the speed readout (im using my existing 020 with cable drive). these errors obviously show up through vag-com.

the install went perfectly, in in a weekend, and 4 months of perfect, quick driving
until one night i got a terrible idle. iv a solid mount (as the idle was perfect before. very smooth). it really shakes the car around.
it also hesitated badly and would not pull. i think iv put the hesitation down to a very loose p/s bracket. only 1 bolt. since it re-torqued it the hesitation has gone. i think it was knocking and the knock sensors saw this and pulled the timing back.

so, the idle. start the car, and its perfect (ish). then it'll get rougher and rougher. really shakes the car around. drive up the road 100m, pull over. and it'll idle as it should. problem gone. well, not as it should. im sure even at its best it doesnt idle lke it used to. it does it warm or cold too. its intermittant. if its idling rough, if i turn off the ignition and restart, it'll idle perfect again. hmm

when i did the car, all parts were new. cam belt and ignition parts. all from tps vw. iv cleaned up all the earths and contact points. i suspected the coil, but after checking a few others, and resistance through autodata, its perfect. so is the isv. new vw relays (ecu+fuel pump). all new vacume hoses too.
no fault codes are showing through vag-com, im lost!

any ideas chaps? iv got a spare tb, crank sensor and dizzy and leads to try next week.
annoying as i was ready to get the head done, aswell as mapped. i wanted to make sure everything was sorted and correct before i started tuning.

btw it seemed healthy just before the idle started. dyno_dynamics machine read 149.5hp and 139lbft

cheers in advance guys
Paul

 

[Fl@pper]

checking the coil at a point may reveal all is well but you say the faults intermittent ?

for what it takes to do i would change it anyway if you access to one then test it

 

[paultownsend]

iv had 3 coils on it. mine, a new beru item and a used coil off a friends abf that runs perfectly.

 

[basssound]

Defo get the coolant sensor checked or replaced first.
Sound like a sensor fault thats breaking down over time, doubt it would be wiring fault as it would be intermittant, switching the ignition off wouldn't change this.

Also is the fuel filter or the air filter old, the Air mass sensor ok??

All these could cause your fault.

 

[paultownsend]

no maf on these. they use a map in the ecu. fuel filter is new oe. thanks for the data. i have a spare sensor. il get it checked. there expensive new!

 

[paultownsend]

it was the blue ecu temp sensor! causing it to run far too rich at idle.
cheers fellas

 

[oldeboi]

Hello mate, do you have a part number for this, it sounds like the problem i have.

 

[rubjonny]

ECU temp sensor is white on the abf, party #:
026 906 161 - 29.52+VAT

 

[Fl@pper]

if you want a cheaper one try a local motor factors for either

Intermotor - 55504 or QH / Commercial Ignition - XEMS39

should be no more than a £10 at the 'very' most

i have a list of all 3 aftermarket sensors for the ABF 16v with MFA at home as i'm just about to change all mine for winter

*edit* see below for list

 

[oldeboi]

Thanks for that one rubjonny.
Is there a way of testing my old one as im extremely short of funds and id like to be sure that this is the culprit of my rough idle.
Cordoba 2.0 16 valve, cleaned up the throttle body, im fairly certain the hoses are ok but every so often when idling it jumps from 800rpm to 1500rpm, up and down several times then settles for a while. blipping the throttle clears it for a while until it goes again, wits end is an understatement!

 

[oldeboi]

Cheers fl@pper, money talks!

 

[Fl@pper]

if you 'really' wanna test it you can use some water and a thermometer and a multimeter to test resistance

temp in degrees = resistance in ohms

0 = 4800-7000
10 = 3250-4400
20 = 2200-3000
30 = 1500-2100
40 = 900-1400
50 = 700-950
60 = 535-670
70 = 400-500
80 = 275-375

 

[rubjonny]

you can also plug in vag-com and use the measuing blocks to read what the ecu sees, compare it to dash and mfa oil temp. if they all agree then you can be reasonably sure its ok. run engine from cold too, make sure temp rises steady like. you can also monitor the intake temp, rpm, throttle angle etc

 

[oldeboi]

Thanks guys,
Its starting to get to me.
What kit do i need to get my own vag-com set up?
Needs to be cheap as chips.
What i really need is a local expert to show me then i can be competant and self suficient.

 

[rubjonny]

if you have a laptop its cheap, get on ebay and do a search for 'vag-com' you'll get a massive list of cables. go for the cheapest USB one you can get, usually sent from hong kong and shouldn't cost more than £15.

If you dont have a laptop then its not so cheap unfortunately

 

[oldeboi]

Yeah, i have a laptop, of sorts.
Is it just the cable i need? No software?

 

[rubjonny]

you need version 409.1 of vag-com, but thats freely available to download plus it'll probably come with the cable on CD

 

[oldeboi]

Thanks rubjonny.
If only you lived next door!
On reflection its probably a good thing you dont.
Il get on ebay.

 

[paultownsend]

turned out it wasn't the temp sensor. but it was the dissy and hasn't happened in 3 weeks!
top banana!

 

[paultownsend]

its back with a vengeance! right so the only options left are the crank sensor and ecu.
its defo an electrical fault.
start the engine from warm or cold and you get the terrible idle and hunting. put your foot down and it'll hunt and kangaroo. like theres no spark or fuel.
turn the ignition off/on and its perfect. even if its coasting.
my local vw master tech can re-programme a spare ecu i have to the immobiliser chip

he recons the ecu may be changing maps. cut the power and it changes