After driving around with a deteriorated fuel line in my tank causing low pressure for 5 months I've finally got the pump and hose replaced and can spin the tires from a stop any time I want! I finally get to experience some real power, when I bought the car in June it was good but then the pump started going and acceleration just sucked after that.

Problem now is that I've gotten three codes out of it: 23, 32, and 34. MAT sensor, EGR, and MAP sensor. Haynes has a possible vacuum leak as a problem listed for every one of these codes, along with a defective ECM and open/short in the circuit but I have to check into the possibility that the TBI unit has no leaks. It starts harder in the mornings now too, something else that confirms my suspicion. Anybody's thoughts on this?

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'91 Firebird
305/TBI(L03)/700R4/T-tops
Mods: Catco high flow cat - B&M Shift kit - K&N Air Filter - Trans Am tail light conversion
Stereo: Pioneer DEH-P8200R - Pioneer 6x9's - Kenwood 8" Tube

'87 Firebird
2.8L/MPFI/700R4/220K
Totalled it but saved a bunch of parts before it went to the junk yard.
Firebird parts

 

gona guess, high miles??
tune it up,
replacing all that could save you many troubles down the road.
maybe the guy who had the car before you never did any scheduled maintance to it.

after buying a car its always good to do a full over inspection and replace anything that is bad. (common sense i guess)

 

Yep, almost 121K to be exact and I've already replaced several items. I checked it out with Carfax before I bought it and its been through several owners, more than 4, and I was definitely apprehensive about buying it, but it was a good deal and I needed a car. I've given it a full tune up and its due for an oil change again. The engine runs perfectly its just tired and I really have no clue as to what was rebuilt or not. Like working on it blind.

 

I'd start by pinching each vac line by the throttle body, and yes sounds like a vac leak or the EGR not fully closing.
If #6 spark plug shows some oil on it, then probably a leaking intake manifold gasket, might try tightening it up and see if its real lose.

 

I had a problem a while back when my "Service Engine" light kept coming on while cruising. Code 32. Turned out the diaphragm in the EGR valve had dry rotted and wouldn't hold vacuum. This can cause a rough idle and or unsmooth engine performance when on the highway at constant speeds. I replaced mine and never had the light or the error code 32 again.

 

You can spin the tires easily huh? I have a 305 TBI in my 89 RS and have a tough time getting the wheels to light up... unless its raining. But then again I have posi rear. I assume you have limited slip maybe? If so why did you say "tires" plural. Sorry to nit pick, just curious if my pump is going as well.

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89 RS V-8

 

Uhh, ok you got me there... I can light up my TIRE on demand now better? No, its a peg leg with 2.73's and drums... a 3.73/posi/disc rear is on my wish list though.

 

egr sounds like a suspect.
otherwise, im not a drivability master.
anyway, since it is brought up.
ok, ive got a 92 rs, ive seen this discussed before. both of my tires spin. but ive never done anything to the rearend. does that mean the owner before me put in posi.
when i spin one tire on the lift, the other goes in the opposite direction.
both spin on demand(when i floor it), till about 30 mph.then they wont spin anymore. also, they are 1 year old tires.
whats going on. do i have limited or posi.

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IM: snflupigus | ICQ: 96787192

ENGINE SPECS:
305 TBI,Open Element,K&N 14x3,Hypertech Stage I,160 Deg. Thermostat,454 GM TBI

STEREO SPECS:
JVC Kalmeleon kdlx3,Infinity Kappa 2way 6x9's,PPI 4x6 Coaxials,PPI PC2400 AMP @ 2ohm
DEI Studio 12" 4ohm DVC,Custom Box:Exactly 1 Cubic Foot

 

Well I thought limited slip was the same thing as posi - posi just being the GM name for it. When I was getting tires for my car though, they had the whole back end up in the air and I spun the tire one way and noticed that the other tire spun opposite. I've read other discussions before where you lift one tire off the ground, take the emergency break off, and put it in neutral (pretty sure) and spin one tire. If you have posi then it will engage after a couple of rotations even when the car is stationary and not running.

So I'd say you probably have an open rear end (non-posi), like me. But I've never seen my left tire spin, even in a break stand. Its the one-stripe wonder!

[This message has been edited by pianiy (edited November 25, 2000).]

 

Peg-Leg Posi blows. Invest in an auburn posi or something. Traction is a lot better, espically if you have a modded LO3. Cause personally, I remember when my LO3 was basically stock and I don't remember ever getting the back tires to spin but maybe just a small chirp. Not a very powerful engine.

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Eric Natzke
91 Firebird 305 TBI (ZZ5 summer of "01")
ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-Accel Cap & Rotor-MSD Blaster Coil-Rapidfire Plugs-265/50/R15 Tires-Emmison's all Gone
http://members.aol.com/j007golden/91firebird.html

 

Your ECM probably isn't defective. If it was, you'd probably be seeing a LOT worse drivablility problems along with no codes :-).

A short in the wiring is unlikely because the MAT and MAP are on different circuits. The MAT shares a ground with the TPS and CTS. In fact, the MAT problem is probably unrelated to the MAP/EGR problem because it's a fairly seperate sensor.

The MAP/EGR are probably related. The computer uses the MAP sensor to tell if the EGR is opening. If the EGR opens, engine vacuum drops a little. So if the MAP is bad or otherwise reading wrong (vacuum leak for example) the computer can't tell the EGR is working, and throws code 32. I would recommend heading to your favorite parts store, picking up 10 feet of vacuum hose, and replacing all the hoses you can find. Quite a number of mine were well-rotted, so leaks were quite possible. While you're there, rent a vacuum pump. You can use it to test for leaks, but also to check the EGR valve. On the L03, the EGR valve should open when you apply vacuum to it (just hook it up directly to the vacuum pump). Put your finger under the valve (engine cold obviously, the EGR gets very hot!) and you should be able to feel the diaphram move when you apply vacuum. Also, it should hold vacuum for at least 20 seconds. If the EGR fails these tests, buy a new one FROM A GM DEALER. Autozone, PepBoyz, and Trak Auto all gave me the wrong kind (there are like 6 different EGR valves for our years of SBCs, all will fit but they work differently).

To test the MAP, just hook the vacuum pump to it and a voltemeter to the wires (there are three, it'll take a bit of trial/error to tell which two wires to read). Turn the key ON, and apply vacuum with the pump. The readout from the sensor should change smoothly as the vacuum changes (I forget if it reads higher or lower as the vacuum increases).

Good luck!