8v running lumpy

[inthecity77]

Alright all! not been on here in a while.

Anyway, need a bit of the old advice.
My 93'L 8v is running a bit lame, in that, it goes ok, but got the following symptoms

-slightly lump idle, not enough to raise or lower the rev counter, just sounds  a bit lumpy
-the power isnt too smooth on acceleration, feels a bit lumpy accelerating
-Sometimes seems less powerfull than other times.

dont get me wrong, its not really bad, just seems like it needs a service, but it only had one 3-4months ago (less than 2k), it had a fully 30k job, after which it ran great. Any ideas? as i heard that this particular year of 8v engine has idling issues and can run a bit lumpy.

What are the top say 5 things I could do to help this?

Cheers dudes

[monkeyalan]

clean the throttle body

replace ecu relay

replace fuel pump relay

check for vacuum leaks

check oil breather pipes aren't blocked

[adyh]

All of  the above and have you tried taking the car on a long run ? Works for me when my car is lumpy .

[Len]

Check the relays first!

Warm car - bout half an hour or a quick blast. Stop/switch off, bit obvious but there are some numpties out there!
Take out the relevent relays E30 and E??? i think and hold em next to cheek is best. If warm they are ok if cold even on one side then replace!

[monkeyalan]

relay numbers 30 and 167

part numbers are 165906381  and 191906383C

did mine today £32.74 .

[inthecity77]

thanks guys, will check and keep you posted

[inthecity77]

I know these are the fuel and ecu relays, but, and sorry for being thick, what do they actually both do? and what fails in them for them to need replacing? I would have thought they either work or not, and if they didnt work, then how does the car still go? sorry for being a pain

[AudiA8Quattro]

If all of the above fails, look at the airflow meter.

[mowgli]

I know these are the fuel and ecu relays, but, and sorry for being thick, what do they actually both do? and what fails in them for them to need replacing? I would have thought they either work or not, and if they didnt work, then how does the car still go? sorry for being a pain

A relay allows a small amperage circuit to switch on a circuit that requires big amps.  So, for both these relays the ECU and the Fuel pump require big amps to work so use a smaller feed to energise a small electro-magnetic circuit which in turn attracts the switch that enables the big amps to go through.  If this is teaching you to suck eggs, sorry, gotta start somewhere and they may be someone interested who doesn't know this bit 

What can happen over time is the contacts inside the relay can become gunked up with deposits from a slight amount of sparking that occurs when the circuit is made - have a look at the inside of the dizzy cap and you can see the same stuff on the 4 electrodes.  This build up leads to a resistive joint so some of the voltage available (12 - 13.4v ish) is dropped across this relay.  This in turn reduces the voltage available at the ECU/Fuel pump and using ohms law (V = I x R, voltage = current x resistance) if the volts available drops and the resistivity of that circuit stays the same the current must also drop.  So, the item needing the high current doesn't get it and operates under par, leading in this case to hesistation and stuttering.

[inthecity77]

i didnt know any of that but i do now!
techie talk rules!
cheers dude