Removing emissions gear

[texaninmass]

I have a 95 Discovery with a 3.9. Has anyone disconnected the emissions equipment for one of these….O2…..MAF ….and such? If so does it have a negative effect on mileage? I thought I saw an older posting with someone that had done this but, could not find it when I went back and did a search. Any info would be appreciated.

Anthony

[Disco]

I cannot imagine why you would want to do what you contemplate. Yes, I have bypassed the O2 sensors and MAF on both my D1's but then, these functions are controlled by a Motec computer as both my vehicles run high performance engines. If you did bypass the MAF etc, without an alternate system to control the air/fuel ratio, not only will you get crappy mileage, I doubt your vehicle would run at all.

[Disco Mike]

Beside the fact it is against both the State and Federal law, why the hell would you want to do it, you would have no engine management, the truck would run like crap and you couldn't resell it in most states with out all the parts attached.
Mike

[texaninmass]

I have a 95 Discovery with a 3.9. Has anyone disconnected the emissions equipment for one of these….O2…..MAF ….and such? If so does it have a negative effect on mileage? I thought I saw an older posting with someone that had done this but, could not find it when I went back and did a search. Any info would be appreciated.

Anthony

So you think it's a bad idea?: It’s the Texas outlaw in me!.... Okay, no more stupid posts.
Luckily the person I just bought the LR from just replaced the CATS as well as the exhaust y pipe’s on it. I suspect that the O2’s are bad.

The symptoms I am having is the truck starts and runs great while cold but, after it warms up it is hard to keep it at idle when I pull up to intersections. It is not consistent as sometimes it does do this and other times it does not.

The check engine light is on as well. I know I need to get the codes read but any direction to look would be welcome.

Anthony

[me.guevara]

FWIW: I have the Australian package Disco I (no O2 sensors, no evap system, no cats) - the ECU runs the engine with input from the MAFS. The Worshop Manual says that it only requires changing a resistor on the ECU, but it only gives approximate location and color, no other info.

Speaking only from what I've experienced and read on this board, I think I'd like to have the O2 sensors' input to the ECU - folk who have them are consistently reporting fuel consumption I could only dream of.

Your idle problems could be any number of issues, including the MAFS and IACV (those are relatively easy to check if you have a buddy who'll loan you his good ones). You may also want to check your plugs, wires and ignition coil (not to mention the ground and battery connections).

Welcome to LRO!

[Adam in NYC USA]

Hello from Adam in NYC

I have the NAS 4.0 and went thru quite a bit to get me to work fine. I changed the MAF (without needing to), changed the 02 sensors, then the shop that originally worked on the oxygens sensors destroyed the circuitry that read the oxygen sensors. Went thru four ECUs until I found one that worked with my truck (went to the dealer twice for the security wipe).

The symptoms sound like you are in limp mode. Get a cheap codereader (umm, I think you are OBD 1 since the 96 is OBD 2). Read the codes and start on your merry way (NOT!).

If you want to get rid of the o2 sensors, there are plenty of fooler sensors on eBay that would trick the ECU into thinking your emmissions are okay.

http://search.ebay.com/oxygen-sensor...sPageNameZWLRS

Adam in NYC

[300bhp/ton]

A MAF or Mass Air Flow meter is not an emissions control it's there to tell the ECU how much air flow there is so it can add enough fuel accordingly.

If you want to keep EFI without a MAF you would need to go for a SD (Speed Density) setup. This would use preset custom tables to tell the ECU how much fuel to add for any given rpm. A setup like this would have to be custom, using something like Megasquirt.

In the muscle car world it seems to be the norm to get rid of CATS, EGR, AIR and other emisisons controls but it's all down to the State you live in on whether you'll get away with such antics.

Another possibility would be to swap on a 4 brl carb conversion. Webber/Edlebrock 500cfm is a common swap and works well off road. Holley 390cfm is another possibility and better for WOT performance but suffers fuel starvation off road due to the location of the floats.

A well sorted carb setup will normally out perform the standard EFI setup and should return similar or better mpg also. A sorted custom EFI setup will provide the most control of fueling and thus optimum performance and fuel economy, but the standard EFI setup is probably not going to be able to achieve this.