Help with poor fuel economy, and CEL codes 16, 17

[JPv6]

*update* I forgot to post what car this is for. 1993 MX-3 GS

Hi all.

Hoping to get some advice about my car. Since purchase I've noticed it's hard on gas, especially after replacing the engine with another K8. Very occasionally it also feels like I'm not getting any power. Here is a brief history of the car.

-unknown # of previous owners, purchased at auction, seller was a dealership.
-160K on body presently
-replaced engine at 150K due to letting oil run dry, replaced with another K8 engine from Tiger Japanese in TO, guessing it had less than 100K.
-after replacing engine, CEL light comes on at speed (80+)
-mechanic that did swap said it was a sensor, advised replacing. Didn't say what sensor, but pointed to small tubing connected at rear of engine bay under the throttle body. Said it was ok to drive like that, so I never looked into it cause he said the sensor was probably $100-$200. From my chilton manual it seems like that might be the idle speed controller valve or something, but that doesn't seem right since the light is coming on at speed only. My interpretation from the manual may be incorrect.

After reading up on the forums I tried shorting TEN to GND on the diagnostic box, got codes 16,17
From the codes list on this forum I saw
16 Exhaust gas recirculation (EGR) system
17 LHO2S inversion error

My chilton repair manual doesn't list anything for 16, just 17.

*update*: My Chilton repair manual lists 17 as Oxygen Sensor (inversion): Sensor output continues unchanged 50s after engine exceeds 1500rpm

Soooo, I could just replace the O2 sensors, but it's an expensive guess. What does everyone think? I can get my Chilton manual out of the car and provide more details on what it lists for code 17. Would that be helpful?

[Daninski]

Order new O2 sensors from Rockauto.com they're about $40 each, you'll have them in three days. If you got the Engine from Tiger it's a JDM K8 and they don't use EGR's but if you ensure yours is connected it saves you getting a code. Weather it's connected or not has no bearing on the engine performance because there's no port going into the intake for the exhaust gasses to go through. They don't use EGR's in Japan. Without the EGR working you may not pass an Etest as the EGR is what reduces the NO. You could go to the Dealer and they may sign a paper that will allow you to be tested Hot Rod status.

[JPv6]

Thanks for the nfo about no EGR on my engine. For the o2 sensor they have some ranging $57 for BOSCH Part # 15733 universal, up to $150 for ac delco. Also, I'm confused about upstream, downstream, towards radiator, in exhaust manifold. Should I just get 1 upstream and 1 downstream sensor? Total for both from Bosch is going to be about $160, much better than what I found, aside from a UK site.

[fowljesse]

There is one in each exhaust downpipe.

[Daninski]

I just bought Denso's they're original equipment. Unless your car is a 96+ you only have one O2 sensor per side. RH is closest to firewall, LH, closest to rad. If your car is a BP then ony one O2 of course. Go to Google and search Rockauto coupons. There's always a 5% off coupon. Here's an O2 cross reference chart if you like. I used it to convert bosch to denso.
http://home.att.net/~ngksparkplugs/wsb/ ... e_Rev1.pdf" onclick="window.open(this.href);return false;

[JPv6]

I forgot to say what car it was. Updated original post.

For those Denso parts, they show Front, and Front Left, and Rear. What does that mean?

[Daninski]

Order Denso 2344143 Front and 2344606 Rear. The other part number was for a Delphi O2 sensor, not required. Use that chart I sent you the link to to cross refer Denso to Bosch if the Bosch are cheaper. I heard Walker works really well too. Not sure why the Denso's are so expensive, the ones for my MX6 we're cheap $43 and for my 96 GS they we're only $56.

[davmac]

Daninski gives good advice. Part numbers for Denso are correct. I've had good luck buying O2 sensors here. The universal one requires you splice wires in order to reuse the connector. The universal sensor works just as good as the OEM style with the factory connector included. The front sensor in the exhaust manifold (pre catalytic converter) - usually up by the radiator is the one that provides primary input to the engine control unit. If you could only replace one that is the one I would replace.

[JPv6]

Rockauto lists the front (# 234414 ) $10 cheaper. I'm considering getting the universal for $60, oxygensensors.com has universals for front and back. I don't mind some solder work. I should probably inspect mine first though, since I'm re-using my connector.

[JPv6]

Quick question, Rockauto lists two different 1.8L mx3 on their site. Under MX3 they show V6 FI, under MX3 GS they show v6 MFI. I thought all mx3 v6's were the GS trim. MFI is multiport fuel injection right? Or Mechanical? Anyway should it matter or should I go with the GS section, keeping in mind the engine is from Tiger Japanese, so JDM right?

*update* Oh, I just used that PDF to convert denso to bosch, and rockauto doesn't have bosch I need, yet they list a few that they say will work. Sorry to keep asking I just won't want to buy the wrong thing.