Hi folks,long time no talk to... Well a few weeks ago my '89 firebird 2.8 auto started acting up outta no where. Basically it'll start right up but if you try to give it gas (warm or cold) it starts sputtering and acting like its flooding (not sure if it is) but if you let your foot off the gas peddle a bit the car will say,catch up and then you can slowly accelerate.

I'm pretty sure my fuel system is ok cause I checked it not to long ago and a mechanic friend (who recently did the fancy scan at his shop and looked the car over good and said I was good to go) suggested a sensor issue (map or tps?)... I did try searching but didnt see much helpful. I have that little black box you plug in and it tells ya the codes and such,and no codes!

Any help would be greatly appreciated.

 

Does your tach flutter when this happens? If it does, I'd have the ignition module tested. That problem left my car stranded at school for 2 weeks while a bunch of idiots worked on it (we weren't allowed to do that sort of work in that class ).

 

Has it been a while since you changed the fuel filter? You would be surprised of the EVIL power a dirty fuel filter possesses!

 

Oh, and have you tried disconnecting the MAF and seeing if it runs better? MFI 2.8's don't have a MAP, btw, only the 3.1's and carbed 2.8's.

 

When was the last time she got new plugs, wires, rotor, and dist. cap? I replaced those and my fuel pump relay on my 91' bird after simmilar problems. She runs like a champ now! good luck!

 

Hi, my tach doesnt flutter and the ignition module was just replaced a few hundred miles back (the original gave up around 136k) and the car ran great ever since. It really hasnt been that long since I did a full tune up although the fuel filter could use a change but really isnt that old. I'll try that maf trick and check everything over again.

Thanks again guys .

 

Do you have a fuel pressure gauge? That would be a good starting point after you find out if the MAF is screwy or not.

 

Fuel filters are pretty cheap, just a hassle to change out on some rides. Wierd things happen to driveability with a funked up fuel filter.

One of my favorites is a worn out Oxygen Sensor. The probe becomes glazed over and give false readings to the computer... car drives weird!

Keep checking, the force is with you & don't forget to post what you find.

 

SO ive got a 1991 rs wit the lil 3.1...and number for in my collection of beautys i have for of them...and ever since winter my brightwhite has being doing this...i have changed and done every thing you guys have said and she still does it no codes...last time i check fuel pressure it was 90 psi...ysterday i replaced Ignition module , fuel filter...plugs...before winter every thing else??? got any ideas???

 

90 PSI? I think you should check that one again. That REALLY don't sound right. If that is the actual reading, then there's your problem right there. When you hit the gas, you're flooding out the engine due to the excess fuel pressure behind the injectors, if it even runs at all without throwing a code 45 for being so excessively rich...

 

this was last year it has ran fine ever since my last test...and i know...it should be 45 psi so i dont think its that...got any other i deas....it clears up with tps off...but still not right...ever since the winter when i parked it its been doing this

 

my old pickup did similar things, can be a number of things as im certain u r aware of! Stab in the dark>>>> clogged "catalytic"? put new screens in injectors? I.A.C. ( idle air control)? You said u did the plugs but did u do the wires, dist cap & most impotantly the rotor? Fuel pressure regulator???? Good luck!

 

the worst part is i put a brand new cat in last year ...when i put my 80series on so it would be a lil smoother...i havent changed the regulator...but yea ive done every thing

 

Check the voltage on your TPS with the engine not running. Should be .55V at closed throttle. Also check the feed line to see if you are getting somewhere within about .5V of 5VDC.

:edit: And after you are driving (if possible), pull a couple plugs and tell us what color they are.

 

providing i did it right my voltage is right...i got a pressure gauge fuel pressure is 37 psi now....seems odd that last year it was 90 psi...it doesnt seem like spark either im sure its fuel...or it must be a dead cylinder!...(im a marine mechanic by trade) i know some stuffso any other ideas....i'll check plugs tomrrow pain in *** at night

 

About the only other thing you can do at the moment is to disconnect your injector harness at the rear and probe the injector terminals. One set is pink/black and light green (2,4,6), and the other set is pink and light blue (1,3,5). Your DVOM gets connected between the pink and the other wire, and you should come up with around 4 ohms (within about 1 ohm). Any different, and you have either an open (high resistance at the very least) or shorted injector on that bank. That will tell you if your injectors are electrically sound. As for whether they are flowing fuel or not, you would have to pull the rail and look as you crank the engine.

:edit: If you have an electrically failed injector on one bank, then you have to ohm out the injectors to about 12.6 ohms. Someone is going to say different, but every GM injector I have ever tested has come out to 12.6 ohms if good.

 

well i did that i had 4.1 ohms ...finally pulled plugs they where(black) all richer than a ***** on humpdayits all most time to take her to GM i guess...unless you got some more ideas??

 

This is AFTER you were driving, right? Because, if it was when you were just sitting in your driveway idling to operating temp, they will end up that way after a while, as the ECM is programmed to enrich the idle, similar to a carb.

Anyways, since your fuel pressure is right on (37 PSI running), and you have black plugs, I would assume either your spark is weak (dying coil) or your fuel injectors are leaking into the cylinders, but ALL SIX injectors leaking at the same time just isn't possible, so I would take a shot at a new coil. Have you ever replaced the coil, and when?

 

put a accel or what ever coil in just before winter..and yea it was sitting it wound even run any more it coughs evry like 10th revolution or so...and yea it wasx 37 psi running on the gauge last time ....cranking pressure is 40psi...and i checked all the plus i got spark at all 3 days ago i did ignition module... and tps are new...map sensor last year...plugs last week...fuel pumps a year old

 

From personal experience and the $45 or whatever I spent on the damn thing, Accel coils are JUNK. Mine lasted around 4 months, and, I believe, is now in a junk pile somewhere (or it's in one of the remaining trash bags in my garage), but either way, I'd go and grab a stocker for $20 and see what happens. You've either got WAY too much fuel in the mix or you have a VERY weak spark. Try cranking the engine with a plug out and see what color the spark is. If it's not white, you need a new coil.

Those performance coils aren't really meant for full-time street use, only for quick, 1/4 mile, WOT runs.

 

went and got a stock coil..65 bucks...list100 down where i am i wish it was 20 bucks...but yea it was a lil week...replaced the plugs again....it fired up but ran really rich...only at about full throttle sounded like a miss...but it wasnt electrical miss...fuel pressure was good the hole time....so i pulled the injector rail im going to swap out the injectors from my rebuild 2.8 i did that is going to waste...if that doesnt work i think im gunna flat deck her to GM....i cant beileive this i just wanted to sell it...

 

So0o0o0o....i finally changed my injecotrs(so do you know the diferenct between 3.1L injectors and 2.8 cuz the ones in the 3.1 where diff they are like the difference between an innie and an outy and the tip....? but she fired right up....hooked that old accel coil back up for now runs great lil lean it sounds like ....and sounds like a smaller motor now...just cuz of those injectors!!! ****en things!!!!

 

full tune up, plugs wires n all, these cars eat ign parts.
had similar once, neded new wires though they were not that old.

 

Ah, you're in Canada, didn't see that before. Mine was $17 the last time I had to replace it, difference probably being that yours most likely had to be imported. The difference between the 2.8 and 3.1 is minimal in injector size. Actually, pre-87 2.8's had bigger injectors on average (15 lb/hr as opposed to around 14.7 IIRC, have to look it up, and anything from 88 up to the 3100 and 3.4 had the same size injectors), but they had the pintle cap type injectors that were more prone to deposit fouling (so they made innie injectors instead of outies). However, most of them, of either design, are prone to internally shorting due to their design.
But, I'm glad to hear you're running again, even if you have to sell it.

 

N.W. Ohio? Toledo here. With all do respect I asked him about a full tune up and he said all is good!