Sudden drop

[E30Inspired]

(86 325es, chipped)

In the last few days IV noticed a HUGE drop in gas mileage.

Before the change I was avg. are 17mpg and now I’m avg. 9.0.

I have changed my driving style if anything I have been driving more economical since I notice the change.

Also when its idling it will bounce between about 500 and 900Rpms and some times die.

It will spit and sputter for a while when cold and warm.

I have checked for vacuum leaks and everything is solid.

I recently changed the plugs, wires, rotor, and rotor cap.

Also I noticed my Limited Slip Differential isn’t doing its job. It’s slipping.

I’m think the drop in gas mileage has something to do with the LSD.

Input would be great.

Thanks,

[E30Inspired]

Its the Turner Motorsports chip.

[lennon]

86 cant do stomp test for codes unless youve upgraded to newer motronic system. o2 sensor? coolant sensor? try putting the stock chip back in just for kicks too. that low of mpg seems very very odd.

[jlevie]

That much of a drop in mileage would make me think of leaking injectors, excessive fuel pressure, bad cold start valve, bad time-temperature switch, etc. The diff, slipping or not, has nothing to do with it.

[87bimmerguy]

Maybe 02 sensor? Mine killed my mileage when it died

[E30Inspired]

Is there a way I can test my o2 sensor?

[RainierHooker]

Maybe 02 sensor? Mine killed my mileage when it died

+1, same on my eta

[E30Inspired]

86 cant do stomp test for codes unless youve upgraded to newer motronic system. o2 sensor? coolant sensor? try putting the stock chip back in just for kicks too. that low of mpg seems very very odd.

I tried putting in the old chip and it made no difference.



also when its spits and sputters i hear a metal slapping sound like its the AFM.

[E30Inspired]

That much of a drop in mileage would make me think of leaking injectors, excessive fuel pressure, bad cold start valve, bad time-temperature switch, etc. The diff, slipping or not, has nothing to do with it.

I just replaced both fuel pumps.

could it be fuel pressure regulator?

[lennon]

excessive fuel pressure would be bad fuel pressure regulator. check what jlevie listed, hes wise. get a fuel pressure gauge to check the pressure at the fuel rail. you can remove and check each individual injector for leaks if you know what to look for, it would probably be multiple injectors and be obvious if its using that much gas. do you have a bentley manual or even haynes or something? those manuals have test procedures for everything.

[E30Inspired]

I just tested the o2 and it was running between .4 and .5 so its not the o2.


My air fuel ratio gauge is telling me that its running a solid rich.