A Nissan Sentra Forum banner

1 - 20 of 25 Posts

·
Registered
Joined
·
40 Posts
Discussion Starter #1
Picked up a boosted 02 spec w/ 125k miles a few days ago , and since the second day of owning it it has run very rich under hard throttle, followed by a cut of power feeling like the car is falling on it's face. I checked all of the clamps on the turbo and intercooler piping and they are all very tight and neatly put together. Next to check were the spark plugs, and they appeared to be fried. After gapping my new NGK's to .028 and replacing the old worn ones, the car ran strong the rest of the day. The car would pull to redline smoothly, and under full boost the AFR would read around 10.5. Now about an hour ago when I'm getting onto the street to my house, the car starts running extremely rich without any throttle, and is bouncing at idle. It was hiccuping and struggling to make power while the AFR was reading in the 10's while under 3k rpm. The turbo is a 57mm Borg-Warner, and is installed very cleanly and properly with all of the necessary supporting mods (to my knowledge). The car is in great maintained shape.

I'm not sure what the culprit may be... could this be an issue with the MAF? Possibly with the previous owner's tune? Boost leak?

This is my first boosted car (second spec v) so I do not have much experience with these issues. I'm doing my best to research as much as possible. Any advice would be appreciated
 

·
Registered
Joined
·
11,564 Posts
Im guessing it's tune via some sort of piggyback?? (Safc 2/neo)

With the jumping idle, I would suspect a post maf sensor vacuum leak.

On the afr issue, I went through a quite a few 02-03 maf sensors in a very short period of time on my boosted car. It would be fine for a month or so, then become suddenly rich! Would drop a new maf in, retune and be fine for a while! The last 02-03 maf I used cost me a motor. The air flow sensor part of it didn't fail. The air temp part of it failed. End result was I ate a motor!!
Definitely sounds like a maf sensor issue to me but your description was a little vague...

Also, if you are piggyback tuned, you won't be able to drive the car much in partial throttle range unless you are tuned with the primary o2 sensor unplugged. You will always be super rich at partial throttle...

Do a wot pull to see where you're at!



Sent from my XT1028 using Tapatalk
 

·
Registered
Joined
·
40 Posts
Discussion Starter #3
Yes it is tuned on a safc neo. My MAF sensor started to go on my other spec that's NA, and it feels very similar to the power cut of that. It sounds like I need to check my current MAF and replace if necessary, then get a proper tune...
 

·
Registered
Joined
·
11,564 Posts
I can't do a WOT pull right now :nervous:
If it's rich, you'll be fine!
I'm not saying do a full range RPM pull.
Put it in 3rd gear, get up to about 3-3500rpm and just do a quick wot throttle hit. Use your best judgement as how far you go.
If you are trying to do 50-60% throttle hits, it always going to be super duper rich!! This is one main problem with piggyback tuning. You can't tune midrange unless you unplug the primary o2...

Sent from my XT1028 using Tapatalk
 

·
Registered
Joined
·
11,564 Posts
And I'll just add this;

If you don't know anything about tuning with the safc 2/neo, you are about to have to learn!

Hit me up anytime and I'll gladly help!!

Sent from my XT1028 using Tapatalk
 
  • Like
Reactions: Jon

·
Registered
Joined
·
11,564 Posts
I just seen that you are gapping your plugs to .028. Thats a little low! Try up in the .030's. You maybe fowling your plugs as well!

I run one step colder ngk iridiums at stock gap on 10.5psi on a jdm qr20 TAF and I don't experience flame out.

Flame out is the reason for dropping the gap on the plugs...

Sent from my XT1028 using Tapatalk
 

·
Registered
Joined
·
40 Posts
Discussion Starter #8
Will do.

Was just outside looking at the engine bay and I noticed that the intake manifold is black with some kind of anti heat coating.. the previous owner must have taken it off at some point to coat it.. possibly there is a resulting vacuum leak from the manifold..? Could be contributing to the excessively rich conditions from the piggyback tune and/or MAF...
 

·
Registered
Joined
·
40 Posts
Discussion Starter #9
I just seen that you are gapping your plugs to .028. Thats a little low! Try up in the .030's. You maybe fowling your plugs as well!
I have NGK iridiums currently, but before I had put nickel NGK's gapped to about .033 and it ran worse... but those were nickel. Before I do anything I will re-gap my current iridiums to a little larger than .030. Also I'm on 7 psi so I'm sure it couldn't hurt if you're on 10.5 and that's what you run.
 

·
Registered
Joined
·
11,564 Posts
Will do.

Was just outside looking at the engine bay and I noticed that the intake manifold is black with some kind of anti heat coating.. the previous owner must have taken it off at some point to coat it.. possibly there is a resulting vacuum leak from the manifold..? Could be contributing to the excessively rich conditions from the piggyback tune and/or MAF...
This is where it opens the can of worms with piggyback tuning!

If you have a post maf sensor vacuum leak, the ECU will add fuel in the short term fuel trims. Once it has added fuel long enough on the short term, it will now make a correction to the long term fuel trim! It has now added fuel the your base fuel schedule which has now pretty much richened the fck out of your tune....

Sent from my XT1028 using Tapatalk
 

·
Registered
Joined
·
40 Posts
Discussion Starter #12
This is where it opens the can of worms with piggyback tuning!

If you have a post maf sensor vacuum leak, the ECU will add fuel in the short term fuel trims. Once it has added fuel long enough on the short term, it will now make a correction to the long term fuel trim! It has now added fuel the your base fuel schedule which has now pretty much richened the fck out of your tune....

Sent from my XT1028 using Tapatalk
Hmm.. so that could explain how the car is running strong under 50% throttle? Let's say there is no vacuum leak and it is the MAF.. would the piggyback make the AFR react the same?
 

·
Registered
Joined
·
11,564 Posts
Hmm.. so that could explain how the car is running strong under 50% throttle? Let's say there is no vacuum leak and it is the MAF.. would the piggyback make the AFR react the same?
Nope, all the piggyback is doing is tricking the maf signal to the ECU....

If the maf is reading incorrectly, the tune would be incorrect as well!

Sent from my XT1028 using Tapatalk
 

·
Registered
Joined
·
11,564 Posts
I'd listen to KJG, he knows his schitt about piggyback tuning!
Thanks for the boat of confidence Shan!!!
Hahahahaha
Guess I've been at it a while...
First piggyback tuning experience was back in like 1999 or 2000????
Some 17-18 years ago I would say...

Sent from my XT1028 using Tapatalk
 

·
Registered
Joined
·
40 Posts
Discussion Starter #15
Thanks for the boat of confidence Shan!!!
Hahahahaha
Guess I've been at it a while...
First piggyback tuning experience was back in like 1999 or 2000????
Some 17-18 years ago I would say...

Sent from my XT1028 using Tapatalk
Thats 18x as long as me so I'll gladly take the advice. Lol.
 

·
Registered
Joined
·
40 Posts
Discussion Starter #17
So to reiterate... my course of action should be:

a. regap spark plugs to .030<
b. check for post MAF vacuum leak
c. replace MAF if the problem persists
d. retune?

- - - Updated - - -

Hit me up anytime man!!

Sent from my XT1028 using Tapatalk
Will do bro thanks
 

·
Registered
Joined
·
11,564 Posts
Good course of action!
I would replace the spark plugs, and gap the new ones accordingly just to rule out a fouled plug because of how rich you have been running.

And yes, retune will needed either way!

Question, did you change altitude from where the car was originally tuned?

Sent from my XT1028 using Tapatalk
 

·
Registered
Joined
·
40 Posts
Discussion Starter #19
No I did not change altitude. So I regapped the NGK Iridiums I bought earlier to about .031 and still nothing. Ugh... look like I have to search for a vacuum leak..
 

·
Registered
Joined
·
19,790 Posts
i am not a tuner
however

def eliminate any vac leaks


personally i have had a very bad time with the 02-03 mafs
went thru a bunch on my vq swap

even when i carried a spare
they were so sensitive, they would be bad when i went to use them.
if i carried them in the car

oem did not last very long

imo buy guaranteed, used, [junk yard,] and get a bunch


i'm running .035" gap @16lb boost no flame out

and use no additives in your gas
93oct is fine if properly tuned

or oil based aircleaners prior to the maf


make sure there is 8" between aircleaner and maf
and 5-8" between maf and tb

these things gave me the most stable maf voltage readings


please understand though i could tune a carb
never efi

so i cheat
lol

running rich all the time?
to a full tank say 10 gal add 1 gal of e85

please do so at your own risk



i am not a tuner




imo
 
1 - 20 of 25 Posts
Top