I have a buddy that has a MPFI 3.1 and he is experiencing a lot of missing and hesitating at a stop. It does it only when it is idling and coming to a stop. It never does it when the car is at more than 1000 RPMs. I think it may be a bad fuel injector or fuel pump. But I know it is a pain to drive around like that. Especially if it dies on him. If anyone has any ideas or need some more info on what its doing I would be glad to know or give anymore info that may seem like the problem...Thanks guys.

 

Sure; has he done anything resembling a major tuneup to it? (And I don't mean just plugs and wires!) He probably hasn't; at least do the major tuneup, then you know the car's in tip-top tuned condition, and can start going after the big stuff.


------------------
-Tom P (Hot rodded 1986 Firebird 2.8l)

 

Also, how do I check codes, and does anyone think that disconnecting the battery would have done anything to make it do this.

 

Pulling the bat cable can cause a small idling problem for a short while, and I do mean short.

The 3.1L need to relearn the IAC and TPS sensor inputs. The ECM will figure it out after driving it for about 3 - 5 miles. If the problem continues after that there is a larger problem.


I would do as TOm said give it a real good tune up. The fuel filter can give you a similar problem.

One thing to check is the EGR valve. The 3.1L has a digital EGR so you can't test it like a older EGR, but you can pull the 2 bolts off that conect it to the intake and check if for exsesive build up. It is normal for there to be black coating inside the tube, but you will want a quick look for chunks. Also check the gasket it can collect the carbon and plug it up. The gasket is a dealer part, but it can be reused. A little B-12 and a soft bristle brush will clean it up nice. The 3.1L doesn't idle that well when the EGR isn't working correctly.

But I wouldn't be supprised if it is a plug, wire,cap, or rotor, or all these that is causing the problem.

[This message has been edited by BitchinRS (edited October 04, 2001).]

 

yea, it may sound stupid but to start check your plugs and wires and diagnose them correctly. i spent four months trying to target a bad hesitation and it was a cracked boot that i hadn't noticed a while back...

------------------
1990 Firebird 3.1
------------------
- Auto Trans, TA Body Kit
- Home Made C.A.I. (KNN-RE-0810)
- ASP Underdrive Pulleys
- MSD 8.5mm Superconducter Wires (custom-cut)
- MSD GM Blaster Coil (8226)
- AC Delco Cap & Rotor
- Bosh Platinum +4 plugs
- Mobil 1 Synthetic Fluids
- 2.5" Hooker Aero-Chamber Cat-back (27121)
- 2.5" Hooker Elite Stainless Extension Tips (31503)
- GTS Blackouts (stickers removed - #GT034)
- TB Bypass

KILLS = Dodge Daytona, 2000 Toyota 4 Runner 4WD,
1999ish Explorer XLT, "older" Jeep Cherokee, 68ish Mustang (died completely when the light went green )

LOSSES = 300zx (took me in 2nd )

"The racing dice added 5hp...I SWEAR!"

 

It seems to idle ok once it is idling if that makes any sense, but when you are coming to a stop, instead of holding about 700-800 RPM it drops below 500 then recovers and it is just fine, then when you take off sometimes it will hesitate before it will move. You still think that could be plug and wire related? I will check them for anything that looks bad. It was just odd that it did this right after the battery disconnected

 

Then I would definetly go after the plugs wires, and stuff. Pull a couple of spark plugs and see how they are. Mine had problem like that and what happened was I thought I change the plugs, but forgot about and there were bearly any electrodes left on the plugs.

Also this may sound stupid, but if it doesn't happen all the time the next time it happens have him look at the gas gauge. There are no baffles in the gas tank. So even if you have 1/8 of a tank left it will try to die when you come to a stop and when you accelerate away from a stop light as the gas sloshes back and forth.

 

Maybe the ECM learned the car poorly... our old Oldsmobile 2.8 MPFI was like that... it'd take a long time to relearn itself.

Disconnect the battery for a few minutes again. When you start the car, head for the highway- drive 1/2 hour away at highway speeds (with a few stop lights thrown in), and then 1/2 hour back home.

And look into the major tuneup.


------------------
-Tom P (Hot rodded 1986 Firebird 2.8l)