So last night i was driving my 91 rs 305 TBI, and while im just driving regular, maybe about 35 or so, she starts to sputter, and loss power when i try to gass it a little bit. So I'm sitting there thinking, WTF??? so i keep going and it keeps getting worse. When i come to a stop, she didnt want to start going again, and started sputtering more and more. So i tried to Kick it one good time, and it dropped RPM's and then after a few seconds got goin again. So i figure somethings F'ed up and ill just limp it home as best i could, and figure it out in the morning. But she cuts off while driving down the road. So i pop her in neutral, and fire it back up with no problem,a nd pull off to a side street.

My first thoughts were, miss firing, no fuel, no compression, or EAC is messed up again (I've had problems with the plug wanting to stay in the hole before) So i pull over, and put it in park and rev it all the way up. Not a single misfire, and then i let off and it idles just fine. So i get out and look at the EAC plug, and check a few other simple things. Gas reads about 1/8 of a tank. So i got no idea. So i keep one foot on the brake and one foot on the gas and get her home, and figure ill take a crack at her at daylight.

So i go out this morning and pop the hood. Check the EAC and it seems to be good, check for blockage in the Air supply and its good. So im thinking it could be either fuel pump. Bad wiring connection or *** knows what else it could be. then i see this just sitting there in the engine compartment:




and it says VAC on it. So now im thinking the vacuum system is messed up, so i go through the engine and cant find anything missing in there. But i know it has to be missing something somewhere.

Does any one know what this is.

Also today, when i fired it up the RPM's went up, the basiclly went straight back down and cut off. and i fired it up again and it did the same thing. So now its being a pain in the **** starting up.

So can someone help me out please. Let me know what you think it might be, and how to fix it. Also, what does that vacuum line connector go to.

Thanks
-Dave

 

You know, I know it has happened, but I can't for the life of me remember the last time I had a weird problem surface that I actually expected. It's usually a nearly complete surprise.

That? It's a vacuum check valve. It may have come from the cruise control or HVAC control vacuum source. It should be installed in the vacuum line from the intake ahead of the "sphere of doom" so that the cruise and heater controls maintain position under varying engine vacuum conditions. Some cars used to have them installed in AIR valving systems and the EFE heat riser behind the TVS, but I don't think your TBI would have had those.

 

does anyone have any suggestions as to what might be the problem

 

check your vacuum lines? otherwise, seeing how its only underload, maybe it is your fuel pump?

 

yeah i was thinking the same thing, but when i rev it up, she goes all the up to the top of the RPM's without a problem in neutral

So im thinking either vacuum or electrical, but i wouldnt know where to begin with the electrical

 

Check your fuel pressure. Tape the guage to the windshield so you can see it and drive around the block. If the pressure drops off then it has to be either the fuel pump or the fuel filter (try the filter first!)

Just

ALSO - that vacuum check valve didn't just appear. Either someone left it there or it came out of a vacuum line. Has the car been in the shop recently? If not, it probably wasn't just left in there. Check all those vac line very closely! It's got to be from one of them....

 

well i just went out there and check the whole vacuum system and came up short handed, i could only find 1 hose that went to nothing, but i couldnt figure out where it goes. It was right near the drivers side head lamp, Nd went off by the fender well. I'm not sure where that goes, but i dont think thats the problem. Cause i cranked her up about 4 or 5 time and then i took her for a short trip up and down the street, and i stomped on it on good time, and it sputtered at first, but that might have been because it was cold. then i went and turned around, and as i was going back up a hill, she cut off on me. O im gonna go try and get some gas, cause i have about an 1/8 of a tank, and im gonna dump some fuel system anti-freeze in there and see how that works. It might be the fuel pressure, if at certain angles, it doesnt want to deliver the fuel.

any other suggestions

I couldnt figure out where that little thing went to

 

Maybe that vaccum line to nowhere was supposed to be plugged in to the charcol canister? Sounds like the same general area...

 

so im pretty sure that the problem is fuel flow relate, or lack there of

I was rackin my brain tryin to figure out the problem and i was out side and i cranked my engine over, and it idle just fine for a few seconds and then the rpms would drop and the thing would cut off, so then, i didnt it again about 15 more times or so, and sometimes i would tap the gas, and it would cut off immediately. So i pulled off the airfilter cover, and looked down in the throttle body,and i reached down and tapped the throttle, and the injectors just kind of sputtered

So that means 1 or 2 or all of 3 things, fuel pump, fuel filter, or injectors

so lat me know if it could be anything else, also, i could never figure out where that vacuum valve went?

 

I have a 1990, and a 1992 - both TBI 305's - and I never seen that check valve stock in either. On my 1990, I installed the VaFPR in the TB unit, and it comes with a check valve like that, but I've never seen that check valve under a stock TBI hood. I'd say someone dropped it in there by accident, unless it was actualkly connected to a vac line - they don't just "fall off" the end of a rubber vac line. Put the valve aside for now, make sure no vac leaks (spray carb cleaner around all vac connections while it's running), and go from there.

Have someone turn key on while you have your ear on the back deck in the trunk, and listen for FP before you assume it's dead (it's a PITA - make sure you need it before you change it). Replace fuel filter, install FP guage inline and make sure you have pressure, swap pump relay with fan relay and recheck pump operates. Sorry, I'm rambling - mind works faster than fingers - but there's a few simple things to try before you just go tearing tank out for pump replacement.

 

well im pretty sure the punmp and filter are in the engine compartment, and not in the tank, because that would be a pain in the **** to change, so im gonna break into the fuel system tomorrow and see what happens

I think the first thing im gonna check it the punp, the the fiulter then the lines then the injectors last, if i dont solve the problem by then, i wont know what to do

-Dave

 

the pump IS in the tank.
the filter is inline near the rear axle under the car.

 

I've had my pump go south on me before! It will rev. up to red line in N & P but will take forever in gear under a load. That was at 7lbs of pressure. No doubt there! I put in a new pump and got 13.5 lbs and it ran like a new car. Granted, a fuel pressure test gauge will cost as much as a new pump at AZ but it will remove all doubt about the fuel pump condition. My Formula fuel gauge is a little off too, when I get down to 1/8th of a tank, it likes to sputter around a right turn but will still go 10 or 15 mi. till the next station. Just try a couple of gallons to check it though, it might save you some grief of a full tank if you have to drop it for a new pump.

 

sounds about EXACTLY what happened to me Saturday night

my car is a 3.1 v6 with TPI

i haven't done much, but i need to get out there and do some more troubleshooting...

FYI

I put an Accel coil in mine, and it would run again without boggin, albeit roughly, so i think it is an ignition problem

if you have any updates i'd appreciate it if you posted them up

i'll update my thread with anything i find, i'm gonna tear into the ignition system a little more today, it's been about 9 months since I've done cap,rotor, wires, and plugs, so i'm starting there

 

$10 for an inline guage, just cut line and stick it in

$65 for a fuel pump at CarQuest, with pickup. I wouldn't risk an AZ pump after all the hassle to install it.

 

well it was raining and sleet all day today here, so tomorrow morning ill crack into it and see what i can find, i think ill go spend the money on a fuel pressure guage, i want one of them any way

thanks everyone for your responses

 

I was talking about the fuel test gauge (49.00) at A/Z not a pump. No way would I buy a pump from A/Z. When my pump went bad I continued to drive it while putting up with all kinds of problems ( loss of power, start and die several times before it would stay running). I was so convinced it was ignition I put up with it for a few months before my wife got tired of me bitching about it and bought me a test gauge. By that time I had replaced everything but the dist. itself. For the price of everything (plugs, wires, cap, rotor, module, and other things) I could have got the gauge and pump for less money!!