We have a new idea.

The plugs that weren't black were very white and clean. Too much so actually. We attribute permanently open valves to the blackening so the cylinders that did burn we suspect aren't burning right anyway.

I've looked it up on the net and it says that white clean plugs means too hot/lean. At idle the oxygen sensors show lean as you noticed, and on the passenger side very lean.

I'm already using 2 steps colder plugs (Autolite 104 gapped at 0.032").

I'm thinking maybe the engine isn't burning right and this is what is causing the surging and the rough running. What if there's not enough fuel or the chamber is too hot. I have upgraded injectors (Trickflow #30) and custom tune for all my mods, but it's mailorder still.

Any ideas on this matter?

P.S. Thanks Injuneer for all the ideas and advice so far.

 

After reading around a bit I've added to the list of things to check:
- fuel pump / regulator / check pressure (the filter is new) - besides the leanness shown at idle (140-160 LTermCounts) and even while accelerating by the oxygen sensors (135 LTermCounts) and foul exhaust smell, I could swear the car runs less badly with more fuel in the tank than with almost empty tank
- EGR Valve - used to give code all the time, we soaked it in anti-seize and gave it a few whacks to make it come back (it's kinda new), but still...

If i were to consider changing the fuel pump, what should I go for? Can I just bolt on an in-line pump after the original one without removing that one? What options do I have?

 

The fact that you have a 135 LT doesn't indicate its running lean "while acceleratiing". The PCM does not even look at the O2 sensors while accelerating (power enrichment mode). It uses either the Cell 15 or Cell 18 long term, and that LT was developed during closed loop, part load driving.

A 135 LT doesn't even show its running lean at all. If means it would be running lean, if it wasn't for the 135 LT. If it smells rich and fouls the plugs, its a "false lean", causing the PCM to add fuel it doesn't need. A 135 LT is not "extreme".... its adding 5% extra fuel. That's withing normal expactations.

 

The plugs were white and clean for the most part (except the ones with the open valves). The exhaust smell is confusing to me, doesn't really smell of gas. It stings and make my eyes water, a friend said it's the high NOx that causes this. It stings even when staying a good distance away from the pipes.

 

Do you have a cat?

 

I'm alergic to cats, I have 2 parrots though...

Seriously now, I replaced them with the Pacesetter LTs+Ypipe 1 year before this build. The way it smells and stings now though is waaay more aggressive. From what I've read high NOx comes from high temps in engine which come from leanness, so I find the gasses support the "not enough gas" theory

 

I just realized something... when I took the car out from the service after the build it pulled considerably better than it does now despite:
- the valves were done wrong - very tight, cyls were losing pressure, lifters were not filled;
- 2 injector wires were switched (2 and 4);
- there was false air from a loose PCV valve
- the TB adjuster screw was loose and changing the idle air

The engine ran a lot more rough at low rpm and felt very unstable but it pulled stronger... WTF ?

 

We did some more testing today.

1.First we checked the spark plugs - they were white with faded black areas.
2.We checked for false air with some spray - nothing found.
3.Tried changing the injector flow rate setting in the tune to 36 (ran like crap), 28 and 26 (ran ok/same, LTermCounts came down in both idle and 17 and 18 fuel cells).
4.Left it set at 27 lb/hr and went out for a ride. It ran smoother (exhaust sounds like it flows better), still surges, less violent.
5.Checked plugs again - white and the black areas went away. LTermcounts are 130 left 140 right at idle, fuel cells 17 and 18 are 126 left 129 right.

I still have to check the fuel pressure as we didn't have this tool available. If fuel pressure shows problems I'll go for a new pump, else I am thinking maybe I need even colder plugs (I have Autolite 104, maybe I should go 103/102?).

Fresh new datalog on the 27lb tune - spark advance bumps still there... Funny thing was earlier today I took it for a drive and it barely had ANY surges and now tonight they're back - possibly intermittent problem!?

 

Look what I found on some Volvo forum, quoted from the manuals :

Fault Symptoms: faulty fuel pump will cause low line pressure.
The following symptoms may arrise.
- engine difficult to start or does not start
- engine misfires during driving, under heavy load
- poor acceleration
- poor engine performance

This is spot on with my symptoms.

On top of this we have noticed the following:
- lowering the injector rating made the car run better
- in time, the car is slowly running and pulling worse
- after pushing it harder for a few minutes it runs like crap
- after reverting to the 30lb/hr tune the O2 sensors are showing even leaner condition, 150/160 at idle and 135-140 running...

 

Getting a Racetronix Fuel Pump Assembly. Should be plenty for my setup. Can upgrade it later with the harness for even more juice.

Will let you know if this fixed it.

 

Did you check the fuel pressure under load? The data logs don't show it running out of fuel. On the rare times when you take it WOT, the O2 readings are very close to, or well above 900mV.

 

Actually I couldn't find anyone with a pressure gauge, so I figured instead of buying one I'd rather replace the fuel pump and be done with it.

 

Went back to 26lb/hr setting in the tune, runs acceptable I guess... Would barely idle cold with 30lb/hr tune.

Need to make it work so I can take it to a service and have the pump replaced when it gets here. I figure even if it's not that, which I doubt, it's a good upgrade anyway for my modified engine...