Crackership

So, I fixed a BUNCH of vacuum leaks that were due to the vast majority of my vacuum lines and hoses having turned to dust. FWIW, the LR venturi delete /w vacuum line kit and the AOS kit are worth every cent, IMO.

So, since I've gotten all the vacuum leaks fixed, and vacuum is back to where it should be, I've developed new problems with my AFR's. Not that this is entirely surprising, but I have no idea how to fix it.

So here's what's going on. At cold idle, I'm somewhere between the high 13's and the low 15's. At warm idle, I'm closer to mid 13's to mid 14's. At PT I'm usually right at 14.7. At very light throttle (like going down a slight grade and keeping speed), I'm usually right around mid 12's to mid 13's. WOT seems to be fine, except there is an occasional hesitation which I really dislike. And then the weirdest bit is that when I let off the throttle (either to shift or just coming to a stop) AFR's will jump into the 9-10 range for a brief second before going lean and the car will backfire.

Now it's important to note that the momentary richness and backfire on lift was there before fixing the vacuum leaks. In general, the car runs like a new car since the vacuum fixes, but there's just these few things left over that are bugging me.


Any ideas?

Oh yeah, here's the setup:

Vitesse MAF
3" DP-back w/ 3"Cat (you think it could be the cat loading up?)
Tial 38mm
83# injectors
3bar FPR
MBC
k26/6 @ ~15psi
zt-2 w/ WB O2

thanks in advance for your help!

86 951 Driver

Is the MAF clean?

What do the plugs look like?

Crackership

Plugs are new, and look pretty good. Wires are new Magnecor.

As for MAF cleaning, what is recommended for cleaning a Vitesse MAF? I know some MAF manufacturers are very particular about how to clean them?

I was also, considering that my cap/rotor look less than stellar. I mean they look OK, but they definitely don't look fantastic... and my coil looks OEM (read 25 years old)

toddk911

New cap and rotor and coil will do wonders. Upgrade to an MSD coil.

Also, in between shifts or letting off at wot, etc. and seeing sudden rich or lean spikes is pretty common.

For the maf there are some special electrical/maf cleaning sprays. The damage potential is not really in which one or type you use, but just let it fully dry before running the car.

schip43

Did you confirm your fuel pressure settings?

Crackership

I'm sure that the cap and rotor will to quite a bit for me. It's very high on the list of got-to-get-done stuff. And definitely MSD coil. I put a Blaster 2 on my Alfa and the car came alive... especially at high RPM's

I kind of figured that the sudden rich spike when letting off at WOT was pretty normal, but when slowly easing off and when downshifting? Although, afters years of Alfa ownership, I can't stop myself from heel-and-toeing on downshifts (synchro's suck in the Alfa transaxle).

And I'll try cleaning the MAF.

Crackership

Um... forgive me for my ignorance, but how would I do that?

schip43

Ok your gonna need more parts! An adaptor on the fuel rail and a gauge, I belive you pull the hose of the FPR and pull the hose and at idle your pressure should be 45 psi with a 3 bar.

For the parts: http://www.9xauto.com/944a.htm or http://pauertuning.com/index_files/f...ssuregauge.htm

I went with Pauertuning setup with a t for an in cabin FP gauge. The nut backed off on my AFPR so I'm kinda going with overkill.

86 951 Driver

Clean the MAF first. A dirty maf can cause all kinds of weird issues.

Crackership

The pauertuning fuel line/gauge kit is also pretty high on my stuff to get list... after seeing the state of my vacuum lines, I'm on a mission to replace all old rubber underhood. But without an AFPR, what is the gauge really going to do for me?

Crackership

Will do today.

schip43

If it's not adjustable a gauge will only tell you if it's working or not ie in spec. Mine is adjustable and the nut backed off. But yeah try cleaning the MAF first.

toddk911

The gauge will only cofirm if you 3BAR FPR is in fact 3bar, as some are off by 2-5psi one way or the other.

I would say that is step 5 or 6. Preceeding steps being clean maf, new cap, rotor and msd coil. All of those are failry inexpensive and failry easy to change out. The cap is a PITA to get back on sometimes though! lol

The fact that your issue is a richness/back fire issue (and it isn't that big of an issue) makes me feel more certain your ignition system is leaving some un burnt fuel and then the exhaust takes care of it; backfires. Also, while you have the electrical spray out go ahead and clean all your electrical connections.

Do you get backfires in between wot shifts? 2nd to 3rd or 3rd to 4th?

schip43

PS... No guy the bar has been set pretty high for ignorance, I don't think anyone is gonna beat "How do I change my oil filter!"

But he did get it done and was smart enough to ask!

blown 944

One idea that hasn't been mentioned is to check the tps adjustment or function. It is used for an idle switch, fuel cut, part throttle mapping etc. It may not be adjusted and that would cause a rich condition when lifting the throttle. Just a thought