rough idle and heavy petrol smell.

Post Sat Mar 16, 2013 6:10 am

Hi all.

First post here so please be easy. I recently got back one of my old E30s, its a 1989 320i SE and back in the day when i owned it i do have to say it was a minter. I have managed to save it from the scrapper twice now and i have not given up on the old girl yet but it is in a sorry state and i cant bare to see it get crushed. Luckily ive been given it and not paid a penny so at the moment the car owes me nothing.

First job on my list is to get it running sweet again. The car fires up but is rough. There is also a smell of petrol from behind the car. I was going to firstly check the cap and rotor arm then work my way around all the hoses and finally the fuel pump relay.

Any other suggestions?

Post Sat Mar 16, 2013 6:44 am

Cap & rotor arm are well worth changing if they are old

If its running rough there are numerous things it could be - a thorough service is the first thing you should do - plugs, filters, fluids, change any hoses that look perished - fuel hoses in engine bay may be well past their best also cleaning out the throttle body and idle control valve with carb cleaner.
The blue temp sensor near the thermostat housing is a regular fail point and often the cause of rich running/poor fuel consumption.

Smell of petrol at the back of the car unfortunately may be a rotten fuel filler neck/leaking tank - very common.

Post Sat Mar 16, 2013 7:07 am

Fuel smell can start with just the perishing of the rubber O-ring that seals the fuel pump to the tank - a 50p fix you can try. Trouble is, if it's not that then your tank or filler hose is rusty...

For all your problems the Zone Wiki will have something to help. Here's what we have on rough idling:

http://www.e30zone.net/e30zonewiki/inde ... ake#Idling

Notice, all the blue words are clickable links to more info on that topic.

Post Sat Mar 16, 2013 3:16 pm

ive just changed the blue temp sensor as i took a reading off the one that was on the car and it came out at 1900 ohms and should be at least double that. found a breakers and picked one up for a tenner and poped it on and i noticed a vast improvement and the reading was 4500 ohms but its not perfect. Cap and rotor arm are next with a service.

Post Sat Mar 16, 2013 3:24 pm

A breakers? They are cheap(er) new!

Post Sat Mar 16, 2013 4:12 pm

Plus you need to test the Blue temp sensor WIRING, not just swap the sensor. Corrosion of the wiring loom under the intake manifold is a common issue.

Post Sat Mar 16, 2013 5:50 pm

FinalD wrote:A breakers? They are cheap(er) new!

Not from BMW, there £16. But unipart do them aftermarket for £7.

Post Sun Mar 17, 2013 12:46 pm

Rtaylor2208 wrote:
FinalD wrote:A breakers? They are cheap(er) new!
Not from BMW, there £16. But unipart do them aftermarket for £7.

Hence the (er) part.

For £6 more and a known working (read: brand spanking new) one though, why go to a breakers?

And then of course if you want to skimp on costs it is cheaper to buy a new pattern part as you say, so either way, the costs and benefits of buying new make breakers pointless for sensors really (at least these ones).

Post Sun Mar 17, 2013 2:48 pm

FinalD wrote:
Rtaylor2208 wrote:
FinalD wrote:A breakers? They are cheap(er) new!
Not from BMW, there £16. But unipart do them aftermarket for £7.
Hence the (er) part.

For £6 more and a known working (read: brand spanking new) one though, why go to a breakers? And then of course if you want to skimp on costs it is cheaper to buy a new pattern part as you say, so either way, the costs and benefits of buying new make breakers pointless for sensors really (at least these ones).

I agree

Post Sun Mar 17, 2013 3:04 pm

No problem with replacing the sensor with a non BMW one, as long as it's a genuine Bosch one. Some of the pattern ones don't have the correct resistance/temperature curve, and will cause running problems.
Bought a clean black 2 door 318i many years ago with a minor but significant misfire many years ago for about half what it was worth as a fully running car. 'Everything' had been tried to cure it, including a new blue sensor. One genuine sensor later, and it was running as it should.

Post Mon Mar 18, 2013 9:56 am

The reason i used one from a breakers was firstly BMW wanted £30 for a new one and as it a non stock item it would take a few days to deliver. Secondly i would never use a patern part for jobs like that. But the trip was a suscess as i also got a brand new oil cap as the old one was perished and cracked and also a clutch fluid cap as that was being held together with gaffer tape.

Post Mon Mar 18, 2013 9:59 am

Oil filler cap that actually forms a seal may have helped with your running issues