R34 running rich but code 55?

[Connorrd]

Hey all I have an 99 R34 sedan - RB25DE NEO and it’s running rich/poor but I’m not sure why. It was running poor when I bought it and the only thing the PO did before hand was drop the cat which he said caused the issue (Unsure if that’s true or not) The car has a chop while idling but once it warms up properly it runs smooth but still has the CEL. I ran the code and it gave me a MAF issue so I used sensor clean which didn’t work then replaced it with an aftermarket MAF but from a reliable seller which gave me code 55 but it still runs poor. I’ve also replaced the coil packs and checked the spark plugs and raised the O2 sensor out of the exhaust to allow it to get more air but still nothing. Any help would be great as I’ve spent a lot of time and money trying to diagnose this issue. Here’s a vid of it idling 

hope someone else has had this issue and can help fix it thanks

 

 

[blind_elk]

2 hours ago, Connorrd said:

...and raised the O2 sensor out of the exhaust to allow it to get more air ...

 

 

WTF?

What spark plugs did you use? Gap?

Have you cleaned the injectors?

Shouldn't really have caused your problem, but refit the cat.

[joshuaho96]

2 hours ago, Connorrd said:

Hey all I have an 99 R34 sedan - RB25DE NEO and it’s running rich/poor but I’m not sure why. It was running poor when I bought it and the only thing the PO did before hand was drop the cat which he said caused the issue (Unsure if that’s true or not) The car has a chop while idling but once it warms up properly it runs smooth but still has the CEL. I ran the code and it gave me a MAF issue so I used sensor clean which didn’t work then replaced it with an aftermarket MAF but from a reliable seller which gave me code 55 but it still runs poor. I’ve also replaced the coil packs and checked the spark plugs and raised the O2 sensor out of the exhaust to allow it to get more air but still nothing. Any help would be great as I’ve spent a lot of time and money trying to diagnose this issue. Here’s a vid of it idling 

hope someone else has had this issue and can help fix it thanks

 

 

Code 55 doesn't matter. The ECU can only detect a total MAF failure, partial failures or bad signal response curves are not detected. Get an OEM MAF, nothing else works for these cars. Do not "raise the O2 sensor out of the exhaust", whatever the hell that means.

[GTSBoy]

CEL is also the catalyst overtemperature alarm (which should be obvious by the appearance of the graphic in the light).

It is a better than even bet that the temperature sensor is f**ked from having been unceremoniously hoiked out of where it is supposed to be (ie, the missing cat).

[Connorrd]

5 hours ago, blind_elk said:

WTF?

What spark plugs did you use? Gap?

Have you cleaned the injectors?

Shouldn't really have caused your problem, but refit the cat.

I meant O2 spacers but forgot the wording lmao I have BKR5E-11 Copper set to 1.0 and I am going to be cleaning them soon just wondering if anyone else had any ideas. I’ll try out the cat thing also see if I can find one on ebay

[Connorrd]

4 hours ago, joshuaho96 said:

Code 55 doesn't matter. The ECU can only detect a total MAF failure, partial failures or bad signal response curves are not detected. Get an OEM MAF, nothing else works for these cars. Do not "raise the O2 sensor out of the exhaust", whatever the hell that means.

Meant O2 spacer forgot the word any reasonable places to find them? Or do I have to suck it up and pay the 500

[joshuaho96]

21 minutes ago, Connorrd said:

Meant O2 spacer forgot the word any reasonable places to find them? Or do I have to suck it up and pay the 500

O2 spacers are not going to help you here. The engine doesn't even have a post-cat O2 sensor. There is no silver bullet to fixing cars on the cheap other than giving up your own labor and time to do it.

[Connorrd]

11 minutes ago, joshuaho96 said:

O2 spacers are not going to help you here. The engine doesn't even have a post-cat O2 sensor. There is no silver bullet to fixing cars on the cheap other than giving up your own labor and time to do it.

Interesting I’ll try replacing it and installing a factory maf and seeing how that goes

[Murray_Calavera]

5 hours ago, Connorrd said:

Interesting I’ll try replacing it and installing a factory maf and seeing how that goes

If an OEM MAF is expensive (I have no idea what they go for) I would strongly consider putting the money towards an aftermarket ECU and putting the MAF in the bin. 

Also, how do you know the car is running rich? Do you have a wideband o2 sensor setup?

[Connorrd]

2 hours ago, Murray_Calavera said:

If an OEM MAF is expensive (I have no idea what they go for) I would strongly consider putting the money towards an aftermarket ECU and putting the MAF in the bin. 

Also, how do you know the car is running rich? Do you have a wideband o2 sensor setup?

Interesting ok I’ll look into that as an a new OEM MAF is around 700 USD. And it’s just based on how the car is acting such as very low mpg and a rough idle for reference

[Murray_Calavera]

6 hours ago, Connorrd said:

Interesting ok I’ll look into that as an a new OEM MAF is around 700 USD. And it’s just based on how the car is acting such as very low mpg and a rough idle for reference

Holy jesus christ! Yeah I would not be spending that on a piece of dinosaur technology. 

Surely you have plans to modify the car in future? You'll need an ECU very quickly on this modification journey anyway, way better money spent on the ECU rather then the MAF (that will end up in the bin anyway, even if it does work, once you install an aftermarket ECU. Just think how painful it will be for future you, throwing a working $700 part in the bin). 

[GTSBoy]

The other option is to go the Nistune route. Buy R35 AFM and adapter tube (for <<$700). Spend >>$700 on Nistune install. Switch from stock AFM to R35 in the software, boost off into the sunset.

Not necessarily better than the full ECU router (in fact definitely not cheaper than the full ECU route) but definitely going to be cheaper to get from "What the f**k is wrong" to "It's working now".

[tridentt150v]

How much dinero would you spend on a DE? 

IMO return it to stock, stop trying to mod it for 'powa', it is just not worth it.

[GTSBoy]

Haha. I'd forgotten it was NA.

Just put an LS into it.

[Murray_Calavera]

I assumed he would turbo it, blow up the gearbox, then put in a DET gearbox. Pretty much par for the course for new players lol. 

[Connorrd]

5 hours ago, tridentt150v said:

How much dinero would you spend on a DE? 

IMO return it to stock, stop trying to mod it for 'powa', it is just not worth it.

Luckily it hasn’t been modded a lot pretty sure only thing previous owner did was a CAI and the straight pipe - just hoping to get it running smoothly again

[Connorrd]

7 hours ago, Murray_Calavera said:

Holy jesus christ! Yeah I would not be spending that on a piece of dinosaur technology. 

Surely you have plans to modify the car in future? You'll need an ECU very quickly on this modification journey anyway, way better money spent on the ECU rather then the MAF (that will end up in the bin anyway, even if it does work, once you install an aftermarket ECU. Just think how painful it will be for future you, throwing a working $700 part in the bin). 

 

7 hours ago, GTSBoy said:

The other option is to go the Nistune route. Buy R35 AFM and adapter tube (for <<$700). Spend >>$700 on Nistune install. Switch from stock AFM to R35 in the software, boost off into the sunset.

Not necessarily better than the full ECU router (in fact definitely not cheaper than the full ECU route) but definitely going to be cheaper to get from "What the f**k is wrong" to "It's working now".

I was looking into a Nistune ECU would it be better for the AFM one or should I look into a 25det and Nistune that? I do have plans to make power hopefully in the future but no point in trying to make power when the car doesn’t run well in the first place

[GTSBoy]

Well.....it's an NA. So there is no point in spending a single dollar on trying to make it go faster, because it won't. You can make it louder, and that's about it.

Don't buy another AFM for it yet. The one you have might be a piece of shit, or it might be OK. Put that to one side for the moment. See if you can locate someone with a known good genuine one that you can test run.

The CEL issue could still be cat related, particularly the overtemp sensor problem I called out earlier that no-one seems to have noticed. I would look into that first. You should also consider the O2 sensor as a likely candidate for running rich.

Ideally you'd take it to a mechanic who has a good scan tool and you'll be able to watch the AFM voltage and the O2 sensor voltage as it is driven and see if they make sense.

[Connorrd]

10 hours ago, GTSBoy said:

Well.....it's an NA. So there is no point in spending a single dollar on trying to make it go faster, because it won't. You can make it louder, and that's about it.

Don't buy another AFM for it yet. The one you have might be a piece of shit, or it might be OK. Put that to one side for the moment. See if you can locate someone with a known good genuine one that you can test run.

The CEL issue could still be cat related, particularly the overtemp sensor problem I called out earlier that no-one seems to have noticed. I would look into that first. You should also consider the O2 sensor as a likely candidate for running rich.

Ideally you'd take it to a mechanic who has a good scan tool and you'll be able to watch the AFM voltage and the O2 sensor voltage as it is driven and see if they make sense.

Ok I’ll look into that I think - I was considering buying a scan tool also like nisscan and I’ll see what’s up with the O2 sensor someone else in person suggested I should replace it or at least give it a proper cleaning. Luckily theres a local skyline group so should be able to get in contact with someone and see if they can lend a hand

[joshuaho96]

5 hours ago, Connorrd said:

Ok I’ll look into that I think - I was considering buying a scan tool also like nisscan and I’ll see what’s up with the O2 sensor someone else in person suggested I should replace it or at least give it a proper cleaning. Luckily theres a local skyline group so should be able to get in contact with someone and see if they can lend a hand

Nissan Datascan 1 works well for logging this stuff. I use it all the time. It is a godsend compared to old Toyotas or other OBD1 cars that have zero ECU output over the diagnostic connector. It's super helpful to know what the ECU is actually seeing/commanding at any given moment.