hot start issues

[ziopinulo]

hi guys,
as the title suggests my s2 suffers long cranking when engine is hot. no problem with cold starts.
i have to push a bit the throttle for help the engine to start.
i thought the ISV could be the guilty. Firstly i've tryed to clean it, but nothing. Then i've bought one, not original, from carpart online on ebay, but it's rubbish, the car wont idle with it..
any suggestion ? I might check something else?

happy new year's eve!!

[DEREKCO]

Hot start

Hi I had the same problem turned out it was the camshaft sensor there is a link on here somewhere that gives direction how to change it

[ziopinulo]

Hi I had the same problem turned out it was the camshaft sensor there is a link on here somewhere that gives direction how to change it

thanks i'll try

[ziopinulo]

i've done some tests, the problem still there.
cam sensor seems to be ok.

other information about the problem:

rough warm idle
rich mixture
lambda adaptation over 165 on vagcom (all other values are good)

car performance are good, maybe slightly high consumption

what do u think guys, MAF? or o2 sensor?

[UrS4boy]

rough warm idle
rich mixture
lambda adaptation over 165 on vagcom (all other values are good)

G62 Coolant temp sensor might have failed making the ECU think the engine is cold = rich running, etc.

Click on this Engine Bay Device link and bookmark it. Then click on the G62 label at the top of the diagram (all the links are hot links to more info)

http://members.shaw.ca/ajmills/UrS%20Engine%20Bay%20Device%20Map.html

[RichLV]

G62 Coolant temp sensor might have failed making the ECU think the engine is cold = rich running, etc.

Click on this Engine Bay Device link and bookmark it. Then click on the G62 label at the top of the diagram (all the links are hot links to more info)

http://members.shaw.ca/ajmills/UrS%20Engine%20Bay%20Device%20Map.html

Wasn't this unique for AAN? 3B's & ABY's have coolant temp from the big, 4 pin sender in the water manifold?

[Dynasty]

Should be possible to verify that the coolant temp sensor is ok by checking the coolant temp value in the ECU (with VCDS etc.)....

[UrS4boy]

Wasn't this unique for AAN? 3B's & ABY's have coolant temp from the big, 4 pin sender in the water manifold?

Close but no cigar. The 3B and ABY MFTS under the intake manifold in the water manifold are connected to the ECU at pin T55/46 but only for safety reasons (overheating = ECU goes in to safe mode, no boost). The AAN MFTS does not do that.

However, the 3B, AAN, ABY and ADU all use the 035919369M "Thermal Switch" (coolant temp sender) to inform the ECU of the coolant temps.

REFERENCE: http://audi.7zap.com/en/rdw/audi+cou.../919-919066/#9

F76 MFTS = http://forums.quattroworld.com/s4s6/msgs/22584.phtml

[ziopinulo]

Should be possible to verify that the coolant temp sensor is ok by checking the coolant temp value in the ECU (with VCDS etc.)....

yes in fact from vagcom coolant temp is ok. it isnt the problem

[ziopinulo]

What else could enrich the mixture?

[newsh]

hot start issues

Try cleaning MAF connector properly as detailed on here or replace pins.

Test for boost leaks and leaks in pcv system

Try changing Lambda sensor.

[SteveH]

i've done some tests, the problem still there.
cam sensor seems to be ok.

other information about the problem:

rough warm idle
rich mixture
lambda adaptation over 165 on vagcom (all other values are good)

car performance are good, maybe slightly high consumption

what do u think guys, MAF? or o2 sensor?

O2 sensor gone bad. Have you checked exhaust emissions at idle?

[ziopinulo]

O2 sensor gone bad. Have you checked exhaust emissions at idle?

yes, too rich

[ziopinulo]

Try cleaning MAF connector properly as detailed on here or replace pins.

Test for boost leaks and leaks in pcv system

Try changing Lambda sensor.

no boost leaks. i'll try to clean maf connector

[mike74]

Before buying anything try just unplugging lambda sensor and see if its any different