When I started my '90 Miata last night I noticed that I was idling very lean, like 19 AFR, so I increased my VE table by about 10 pts before I got the AFRs to the appropriate level. As I slowly started to drive off I noticed that EVERYWHERE was really lean so, again, I increased the entire VE table until I saw the appropriate AFRs. This increase was about 30pts everywhere else just so I could drive the car without it detonating on me. I should also mention that a similar event happened about a week ago where I needed to increase the fuel table. As it is I am scared to drive the car when I don't know what's wrong with it. My first thought is maybe the fuel pump is going bad so I'm not getting the proper fuel pressure which is why I would need a linear increase for the entire VE table.
Has anyone else has this problem? Does this sound like the tell-tail sign of of a catastrophe waiting to happen? What are some tests that I can do to narrow down the problem?

Details about my setup: 1990 JRSC 1.6, DIY MS2, stock injectors, still have the old thing that is attached to the return fuel line to increase fuel pressure (part of the old piggyback system the previous owner had).

 

Check the fuel pressure.

also, strongly recommended to get bigger injectors and drop the rrfpr.

did you ever need to reduce the VE after the first time this happened?

 

Is this a new MS install or has it been running for a while?

 

Happened to me with clogged fuel filter.
Otherwise it could be misfiring, and reading lean.

 

I'll be leaving to AutoZone soon to rent a fuel pressure kit.
I know, I really want to get some good fuel injectors and ditch that rrfpr. Is there a recommended injector for only 7psi of boost? I was thinking these ones from Deatschwerks.
No, its just slowly gotten worse from when it started happening a week ago. At first it was only 3 or 4 points higher to get the correct AFR. Within the last day and a half its only gotten worse.

No, it is not a new MS install. I've been running a standalone MS2 for a little under 2 months and 1200 miles.

 

check your MAT corrections.

 

You can check a log for fuel Pressure yeah In tuner studio?

 

no.

post the msq. and post a log.


honestly the FMU + MS2 isn't a big deal. the increase in fuel pressure is predictable -- I HIGHLY doubt its the issue.

 

Attached are my MSQ and a log file. I don't have a good VE table right now because nothing is consistent. My car was driving fine for the past month so I don't think that the answer would be in the MAT settings but please do take a look.
Also, the log file here is with a fuel pressure gauge attached in between the hoses where my FMU sat before. For some reason I could not get a reading on the gauge at all tonight, always stayed at 0 even while the engines was running. Maybe the gauge has to be on the feed line instead of the return line? Maybe a faulty gauge. Not sure but Ill try swapping it. I'd really like for this pressure gauge to work so I could decide to buy the EV14 Deatschwerks if the injectors are the problem.

 

FP needs to be measured on the fuel rail side of the regulator(s). This can be done between the hardline and the fuel rail.

 

For some reason I was not getting a reading when the gauge was hooked up between the fuel regulator and the hardline. I did get a reading of 30psi while the gauge was between the fuel rail and the feeding hardline while at idle. I'll try to flip it again to the regulator side and try to get a reading.

 

No, the location with 30psi is correct. 30psi also sounds line ballpark for idle. What do you get when you remove the vac line to the regulator?

 

The psi jumped to 40 when I pulled the vacuum line then when I put it the vacuum line back on the regulator the fuel pressure went back to 30.
So sounds like the fuel pump and regulator are fine. Does that leave the fuel injectors as the culprit?

 

are you MAT and CLT sensors reading correctly? I can't open the log, away from TS.

speed density or AFM?

 

All the sensors are reading correctly. I'm using MAP for my calculations.

 

Wow I feel dumb. I just checked my warmup enrichment curve and, sure enough, the answer was there. Somewhere within my noob tuning I accidentally got half of my curve below 100%.
Thanks for all the help guys.

 

Yup. Gotta check all the things like that when stuff starts going wrong. Somehow my start up enrichment curve was fine down to 40f, but then jump to 500% below there. First cold day flooded it right out. Woops...

 

I win.