Engine's gone a bit odd

[tom_burnley]

Hello all

I seldom post, but just today I've noticed a peculiar development with my S160, so I thought I'd ask for help:

The engine seems to have just developed the following symptoms:
1) When cold - under load it backfires at about 4-5 K rev's
2) When it warms up it seems to loose power at 4-5K revs - this feels like a car that has run out of fuel ( it IS full ).
3) It gets warm far too quickly - now this one is difficult to explain: because I know temperatures vary wildly - the STACK reads between 82-97 degrees, and I long since spotted a dodgy earth on the temp sensor, not that I've sorted it. BUT, now the fan, which runs on the other sensor ( which was previously OK ) seems to kick in more readily - even on a mild day. It can still cool itself but it does take longer!!!
4) A colleague has just parked next to me and noted how increadibly hot the engine bay is, and it does seem exceessivly warm - its not something I've noticed on 3 years of ownership so I'm sure its worse then it should be.

SO

What could this be?
1) Fueling problem? Pump / injectors something like that.
2) HGF - please no not me - not now.
3) something else?

Please, PLease Please apply all those years of your collective wisdom to figuring this out...... if there is something - i'd like to catch it early...

Thanks
Tom

[MiniDiva]

Sounds like it's running a bit lean - that will make it hot and could cause a number of other problems like burning out the valve seats. Maybe a problem with fuel mixture, fuel blockage, dodgy fuel pump, injectors...
I'd get it looked at and drive it as little as possible.

[Gooby]

Remove a spark plug - if it is a white colour it is running lean, if it is black oily colour then it is rich. Personally I would start by checking all the plugs and gaps and rpelacing the HT leads....

[Altrezia]

tom_burnley said:

Hello all

The engine seems to have just developed the following symptoms:
1) When cold - under load it backfires at about 4-5 K rev's

Please dont rev it that high when its cold!

[tom_burnley]

Altrezia said:

tom_burnley said:

Hello all

The engine seems to have just developed the following symptoms:
1) When cold - under load it backfires at about 4-5 K rev's

Please dont rev it that high when its cold!

This was just experimental.... its not something I'd do normally

[tom_burnley]

Altrezia said:

tom_burnley said:

Hello all

The engine seems to have just developed the following symptoms:
1) When cold - under load it backfires at about 4-5 K rev's

Please dont rev it that high when its cold!

This was just experimental.... its not something I'd do normally

[Trixster]

I suggest you get some expert advice from a local specialist

[tom_burnley]

Trixster said:

I suggest you get some expert advice from a local specialist

I thought the people on this bulletin board were the specialists

Seriously - the only response : check its not running lean... ?

[stevie111s]

Maybe ... if you've visually checked the obvious (HT leads, rotor arm, coil, loom) then it could point to a problem with the ECU, which one are you running? I have just had a failure on my S160 ECU, an EFI Technology unit installed as part of the driveability kit. The IACV (Idle Air Control Valve) driver MOSFET (chip) was blown to bits (symptom - the engine wouldn't tickover) I have now installed an Emerald M3D.

Backfire is usually a symptom of too far advanced ignition or over fueling but this shouldn't happen if the ECU is ok although it is possible that if the ECU temp sender is faulty it will cause the ECU to incorrectly MAP the engine (e.g. by applying the cold MAP values when the engine is hot and vice-versa) you could check the resistance of the ECU temp sensor when cold and hot, just to see if it's in spec. Also check the throttle pot for linearity, by that I mean that it's resistance changes linearly as the throttle is opened - an ohm meter across terminals 1 and 2 will show this.

Resistance values are all in the freely available manuals ... can look up in mine if you need.

HTH

Edited by stevie111s on Friday 24th August 13:18

Edited by stevie111s on Friday 24th August 13:19

Edited by stevie111s on Friday 24th August 13:20

[tom_burnley]

Thanks stevie111s

From your description I'm betting that its the temp sender ( given that the fan plays up ): it explains the funny heat thing - it explains the backfire.... ???? and maybe the throttle at 4-5 K problem????

Thanks
Tom

Update: just talked to the 'specialist' garage - and they insist that the temp sender is pretty reliable :-( Need more ideas

Edited by tom_burnley on Friday 24th August 14:41