voltage fluctuation and wideband reading
 

After a few CASs and a new CAS harness I have my sync loss mostly cleaned up. However I have noticed usually when I'm cruising I get a random miss or something, aslo I'm having a hard time with part throttle under load. Seems like anything less than 50% throttle maybe it gets real jerky and bucks. After some logs I noticed while cruising my voltage wondered all over, I also noticed the wideband had pretty much the same path. So I'm gong to try and change my alternator tonight and see if it clears up. Anyone else have this issue? Can post a log when I get home this evening.

If the alternator doesn't fix it, then it sounds like a grounding issue.

Are the ECU and wideband grounded to the same point? Good solid engine grounds from the engine to the chassis? This is especially important if the ECU is grounded to the engine.

New ground cable from new battery. MS, wide band, and everything else grounded to rear housing from same bolt on rear housing (another cable goes from the rear to the front housing) to chassis and starter. If I get time tonight I may check resistance between them all.

Had 0 from chassis to battery and .1-.5 chassis to engine. I may just make a new main engine ground or clean it again and see what I get.

Have you checked the alternator and battery cables for loose connections or corrosion?

Battery and cables are new, alternator I just rewired to switched 12v+ and seems to have made the volt meter in ms better but the wideband still jumps, I guess it could still be a miss?

The wideband will jump around if the engine misses. Typically it will show a lean spike.

Yeah that is what it does now while I'm cruising or at idle, random lean spike and engine misses...

At idle the O2 will bounce around leaning out of range, while at a cruise the O2 will go all.over and car will buck.

Are you sure you aren't getting sync losses?

How are the basics? Like plugs, wires, etc?

Plugs new, wires less than a year, injectors new id1000, only other issues I can think of is vacuum leak or noise in just wideband ground. I can watch the sync logger and it does absolutely nothing, wideband goes completely out of range. I'm going to see if I can snag a smoke machine and check for vac leaks this week. I took a very short log I'll post later.

This one is older and shows sync loss when I rev it but that sync loss has been taken care of and it still shows the random lean spikes towards the end. The other logs are too big.

Also hooked up the laptop to my wideband since I dont have a dedicated gauge yet and the gauge in log works shows the spike too.

Smoked the intake, no vacuum leaks at all...

If you don't have zero resistance from engine to chassis, the grounds aren't sufficient.

I would loop grounds to the battery negative myself.

Neg term to engine and chassis, chassis to engine and Neg term, and engine to chassis and Neg term.

Sometimes even zero resistance doesn't mean the grounds are good, checking resistance won't indicate how much load you can apply through the ground circuit anyways. You just know you have some kind of connection, that's it.

I'm still leaning towards and intermittent connection somewhere.

Could dirty map signal or too rough of a fuel table cause issues?

Imagine removing all your grounds and replacing them with one tiny 18ga wire.

Does it work? Yes.

Is it sufficient? No.

You have everything grounded at the engine. I would drop what I'm doing and at least achieve zero resistance between the engine and chassis.

Would a 18 ga wire create zero resistance? Yes.

Is that better than 0.1 - 0.5 ohms? Yes.

Is it sufficent? .....

It sounds electrical. The giveaway is the fluctuating voltage.

Both a dirty MAP signal and rough VE table could cause the engine to run poorly but won't fluctuate voltage. Also since the VE table is interpolated, there would have to be an obvious and large "bump" in one bin to cause a misfire like that.

Blck13b I completely understand, I have 00 awg grounding my engine to the chassis. Pulled the tranny lastnight (bad input shaft seal) so I'll take my ground and clean it up and test resistance again.

Aaron did you look at any of my logs? Do the map or voltage signals look alright? Started getting some good time with the computer over the weekend and have made a big difference in the running of the car. Idle is still kinda questionable here and there. Also as far as my VE table goes I'll upload it tonight and see how horrible you think it is.

Had a friend on the laptop making adjustments and pretty much all the lean spikes are gone, it stays in pretty stable in the ve table now at cruise.

My table

Spent most of the night doing highway pulls and getting lower load cruises down. Redid the Ve table,, when I loaded it from Aarons website it was oddly spaced all over. Had a fellow board member smoothing everything out. Still have absolutely zero luck with idle! The lean spike is gone now. I'm not sure where to go now, checked base timing, rewired grounds with 0 resistance, alt is charging properly, smoked the intake, moved the line for the map signal, tried messing with throttle stop screw, adjusted ve table in the idle area, EVERYWHERE else the car is great, idle just won't smooth out at all...oscillates in a 3x3 area no matter what I try. I'm using stock tps, would a constant change in the tps value cause this? It's only +/- 1

Can you post your VE table?

Is closed loop trying to correct your idle?

A smooth idle relies on all the surrounding bins having a very gradual transition. If it's too lean, it will oscillate. Make sure the bin which the car idles on is in a little valley surrounded by a bit more fuel on all sides. Also, decrease the timing in the idle bin a little and then run a few more degrees of timing just to the left and above it. That will stabilize the engine if it starts to wander.

If you are using the BAC to control idle, don't even try until you have a stable idle otherwise.

Closed loop disabled,I think I've found the issue. Tpsaccel and decel are constantly blinking at idle. So I'm assuming this means it's constantly adding and removing fuel? Regrounded tps to make sure it had zero resistance, nothing, put a cap at tps with no results...