darek_u

Idle seems little uneven, just slightly up and down, I can barely see it on the tach, more on oil pressure gauge. But first of all I can hear it. My buddy asked is the engine is misfiring. Please see below Rogue logger screenshot. Spark advance - is this normal or there is something wrong? Slight vacuum leak? I checked for leaks and there is nothing except for slight leak from top of AOS above 12-13PSI. Hot idle shows 9.2 PSI (18.5 mmHg roughly), I think it is pretty good. Idle around 840 RPM +/- 40. Any suggestions? Car behaves ok, it just buggers me that it is not idling perfectly smooth...
Car is 88 951S with A Tune, Rogue DME, straight 2.5" exhaust (gutted cat). Otherwise stock.

darek_u

I was watching it little more tonight, from cold start for approx. 30 mins. It looks like it gets worse as the engine oil gets hotter. It is more uneven (spark advance varies from 9 to 15 deg.). What is really strange AFR goes richer and richer. Once it goes to closed loop it bounces around 14.7 than gradually drops down to around 13.8 - 14.0, sometimes comes back for a short period of time to 14.7 than again rich. What does it tell? I'll post another screen shot later.

darek_u

With disconnected O2 sensor it still idles unevenly, AFRs go down to 12.5

darek_u

This is my warm idle graph. Rich and engine seems to work unevenly. Anybody has any idea why? Where to start searching?

refresh951

If you pull the O2 sensor and car idles at 12.5 the car is running rich. The closed loop will have to struggle to get to stoich therefore idle will not be as smooth. You need to figure out why you are running so rich in open loop. Once you idle close to 14.7 in open loop, closed loop will be much smoother.

darek_u

Thanks for your answer Shawn. I was suspecting the car is running too rich as my fuel consumption is around 15 ltrs/100km - thats roughly only 15 mpg, regardless of driving conditions. When cruising AFR is around stoich but at WOT it drops down to 10 - 11.
I'll check fuel pressure tomorrow but if it stays at 3 bar where to look next? Injectors have been cleaned and flow matched, chip is A Tune from Josh, what should I check next?

refresh951

May want to take a bit of fuel out, FQS Position 2

Tom M'Guinn

Does the idle still hunt with the stock chips?

darek_u

Unfortunately I do not have stock 951S chips... Car came with unknown tune giving 270HP but as far as I can remember it was also hunting a little. I'll check this too.

fejjj

Daren,

I have a set of stock chips from my 89 if you want to use them for testing.

Just pay shipping both ways and you can borrow them.

darek_u

Thanks Fejjj, I really appreciate. It would be much easier to get bin file or mirror or whatever format they are so I can burn them myself...

darek_u

I have checked fuel pressure. Results are as follow (car fully warmed up, closed loop before test):
43 PSI with engine off and pump running
36 PSI ish with engine running and -9,2 PSI vacuum, it does not change much when revving up, maybe 1 - 2 PSI, first drops down then comes back up.
46 PSI with vacuum disconnected
Does it sound right? FPR is brand new (maybe 2 kkm) BOSCH.
I also tried FQS 2 - with lambda disconnected AFR goes up from 12.5 to around 13 - 13.1. Still way too rich. My next move is change to 2.5 bar FPR when engine cools down.

darek_u

I checked engine again with 2.5 bar FPR. It reads 2,6 bar with pump running, 2.1 with engine running and again 2.6 with vacuum removed.
When car idles AFR reads 13.2, with FQS 2 it reads 13.7 - 13.8. Better but still far from perfection. All readings with lambda disconnected. Engine still hunting...
I wanted to use my old chip but car does not want to start with it placed in Rogue DME. Any idea why? I thought Rogue DME will work with ANY tune? Do I need to switch something on the motherboard?
I will try using Bosch DME and read AFRs directly from LC-1 but I need to calibrate it again, it just decided to quit... I hate this Innovate piece of ****, from time to time it just stops working - readings are all over the place with no error indication and I need to calibrate it from the scratch.

hally

Reducing fuel pressure is probably just masking the problem. Have u tried pressure testing the intake, also failed dme temp sensor is another candidate?

darek_u

I stated in my first post that the intake is tight except for slight AOS leak above 12-13 PSI. NTC sensor has been replaced a week ago - it failed and showed 20 degC lower temps causing rough starts. Easy fix with logger.
On the other hand intake leak would rather cause lean condition with lambda disconnected, am I right here?