To get back to Daeron's problem:

 

It sounds like you proved that it runs fine in open loop. So that means MAF or O2 sensor, or both. I am not absolutely sure it does ignore the MAF when running open loop, but a funky MAF will run better with more air flow.

 

So, yes, I think your idea of combination MAF/O2 sounds about right.

 

Good luck finding it.

OMG ROFLMAO heheh, ROFLCopter... absolute absurdity, I have never done this before.

 

So I had a thread about an EFI question, whether coasting in gear with no throttle burned less fuel than idling in neutral for the same coast... The reason that came up is, I am (was) flat broke pending today's check, and SUPER low on gas in the tank.. I had a jug today with about a gallon of low-test in it "just in case" and sure enough, i needed it when i got to work to pick up my check.

 

I went to pour it in before I left to cash the check.....

 

and.....

I have no gas cap!!!!!!!!!!!!!!!!!!!!!!!!! :clap:

 

I must have left it behind last time i got fuel, well over a week ago. I can't remember when or where, but i think it may have been christmas day or the day after.

 

The entire time this problem has been occurring I have had less than a quarter tank.. and now ive got just over half, and it seems to be at bay. Obviously I am going to the JY to get a new one tomorrow...

 

What are the odds that THIS has been a contributing factor to my problem???????? I still haven't had the time to run a D-check mode, although I may go ahead and do that tonight.. Chances are I will wait and do it tomorrow night after i get my new gas cap

 

 

 

So yah, commence with the mockery and laughter. I've earned this one :-p

It is entirely probable that it was your problem. And don't feel so bad, we all make stupid mistakes(like me with my old Toyota:banghead: ).

Oh, I don't feel "bad" at all, beyond a slight smack in the forehead over the "blonde moment" that led to losing my gascap....

 

It took me a few moments after seeing it, but within 5 seconds of noticing its absence, a BIG smile was slowly creeping across my face. I thought, well.. (turn on retarded voice) "Hey USMB, why is my car running like butt?????"

 

There is no feeling quite like discovering this problem you have TOTALLY made into a huge deal in your mind, is in fact something as simple as a disty rotor screw, or two components with identical connectors getting the plugs swapped, or (in my case) realizing that your fuel system isnt being pressurized properly because you left the cap somewhere out in France....

Hhhmmm - I doubt that the cap would cause that. I've driven my Brat (SPFI) without the cap, or with it cracked open and it was fine...

 

Some newer cars this will cause issue, but the SPFI shouldn't give a crap - as long as the pump has fuel flow and the tank doesn't build vacuum due to a clogged breather line..... it really shouldn't matter if there's a cap at all.

 

GD

well the one example I have yet of its behavior with a decent amount of fuel is positive.. but the condition has been anyone's guess at any time. Sometimes it runs "fine," and sometimes it doesn't...

 

-as I said, I do have a background o2 sensor problem according to the last d-check about four or five months ago, and one or two other codes like neutral switches and speed sensors... but this anomaly is wholly above and beyond any of that. All I "notice" (its really not manifesting much issue at all) is a vague lack of power at mid throttle.. and thats not a good description. If I had a stickshift I could feel what the motor was doing better, but as it is I can't feel much.-

 

..BUT when it doesn't, it is bucking and stalling at any throttle position other than wide open. Believe me, once I got the cap on it I was investigating everything thoroughly anyhow.. but I have had a mess of old "stuff" that has needed eliminating, and a broken water heater, and I've been staying up too late on the internet If i can make it happen tomorrow before 5, the D-check etc will be run then.

 

For now, must read on MAF and think on acquiring one tomorrow at the boneyard..... Can the MAF itself be removed from the large aluminum housing that all the air feeding the engine runs through??? Thats one of the things I am going to read about, but I thought I would ask while I was here.

 

I have talked about this far more than I have actually worked on it.. Time, I need more Time!!!

For now, must read on MAF and think on acquiring one tomorrow at the boneyard..... Can the MAF itself be removed from the large aluminum housing that all the air feeding the engine runs through??? Thats one of the things I am going to read about, but I thought I would ask while I was here.

 

Yeah - just be really, really careful of the heating and sensor elements - without the housing they will be exposed and easily broken.

 

GD

Well, i haven't logged enough miles since I put a gas cap on it to say for SURE, but that would appear to be my answer.. It will take a day or two to rule out the possiblity of a relapse, but it seems to have fixed my sputter!!!

 

I still desparately need to run a D-check and determine/eliminate my O2 sensor issue.. While I was in the boneyard, I snagged a MAF, as well. That was actually easier than the cap.. the cap wasnt on the tank! my local junkyards have become real nice about things like that, removing dipsticks, oil caps, radiator caps, brake fluid reservior caps, etc etc... as a RULE!!! so I grabbed the MAF off the '88 DL that I found (quad headlight setup??? was that stock for a DL still in '88?? the VIN said 88 and there were four headlights..) I walked the WHOLE rest of the yard, then started checking other cars near the DL to see if maybe a nissan cap or something would fit... then on a hunch I checked the backseat.. yoo-reeka! I can't believe they do that.

 

Anyhow, will update tomorrow and let y'all know what happens. My butt-dynamometer tells me I am back to "normal," though.. and the butt-dyno has felt this issue from its inception, before it got severe at all. I had to tell the butt-dyno it was imagining things, until the first time I got bucked...

Okay.. not TOTALLY gone, but a VAST improvement, again JUST from replacing the gas cap. I only make the update because I was told it shouldn't make much of a difference..

 

The issue was intermittent, and it has only recurred once since I put the cap on. Not only has it become less frequent (it was at LEAST 50% of the time before) but it is also much less severe.

 

Thats all for now, I just want this info out there so that people hear that yes, their soob DOES need to have a gas cap on to run perfect. Well, mine does.

Awesome, glad to see you finally found (mostly) the problem. Gas caps do amazing things, sometimes

...Anyhow, any thoughts or tips are appreciated.. I have good ideas where to be looking, just wondering if anyone has any good ideas I haven't thought of, or stories like this complete with the ending. "I did this and this and this, and then finally did this stupid thing and THAT fixed it..."

---------------

FUEL PRESSURE REGULATOR???!!!

Hhhhmmm!...just a thought.