Hi all!

I am very confused why my car is running so rich and my MPG is so awful bad. I tried to figure it out, but cant find the reason


First of all my Setup:
L69 (v8 305 H.O.) 1984 sitting in 1987 (ex. v8 305 LG4) thirdgen Firebird
Cam: Jones Cam Designs H66299-67300 (details here: http://i59.tinypic.com/t8kp77.jpg)
Rest of the Engine is stock.
Hedman Hedders (this one: http://www.summitracing.com/parts/hed-68470) with heated 3 wire o2 sensor (recomended one from the board) running on stock exhaust pipe (2 1/4" ?) back to flowmaster 80.

Default Computer Controlled Quadrajet connected to L69 Computer.
Gave it to a shop for overhauling (gaskets and stuff).



Now what I´ve done already:

- checked the fuses (all ok)
- tried to use an other computer (the old LG4 - car runs worse)
- checked error codes / status codes (nothing else than code 12)
- checked o2 Sensor (running rich as hell 0.95-0.98)
- checked TPS Sensor

I´m not sure if the TPS Sensor is okay..
I used this guide to check it: http://easyautodiagnostics.com/gm_tp..._van_tps_1.php

it says there, with ignition on, it should read 0.5 - 0.9 V
mine reads 0.95 V

further they say, with full throttle it should read 4.5 - 5 V
mine reads 4.32 V

and then they tell you, that the voltage should read 5 V for voltage testing, and mine says 5.10


So... any other Ideas why my car is running rich ?
by the way, the o2 Sensor reads well, the car smell as hell and throws out gas.

 

Probably, the plugs in the bottom of the fuel bowl under the primary jets are leaking.

Their purpose is to plug up the holes left after drilling several of the passages through the casting. They are spun into the casting. They are made of aluminum; the casting is chinesium. The dissimilar metals in contact result in electrolysis. This eats the chinesium, allowing fuel to be sucked into the intake manifold directly from the bowl, completely bypassing all metering and control.

If the carb has ANY evidence if white powder ANYWHERE on it, then this is surely the cause.

The only cure is to sand or wire-brush the area down to clean bright shiny corrosion-free metal, STERILIZE the entire scene of the crime with some solvent that evaporates COMPLETELY such as lacquer thinner or MEK - NOT "brake parts cleaner" or "electric motor degreaser" for example - and coat everything thoroughly with epoxy. Unfortunately it is not permanent; the chinesium continues to corrode, and eventually the epoxy will fail. So it has to be re-done from time to time.

The plugs in question are quite small; maybe 4mm dia. There are 8 of them. The 2 large plugs in the center of the bowl that are about the size of a .10 euro coin are NOT a factor.

The TPS voltage being slightly out of spec is a symptom of this problem, not a cause. Fix what's REALLY wrong and the other will take care of itself.

Also, BE SURE the timing is set to AT LEAST 8° BTDC WITH THE CONNECTOR DISCONNECTED. Re-connect after setting it, of course. The timing should go to around 24 - 26° BTDC at idle with the connector re-connected.

 

now thats a great and helpful reply
Thanks a lot for this! I´ll check this tomorrow again.
I am very sure that the white powder exists in this quadrajet.
Before I took it to the service, I unscrewed it myself, and was wondering how clean it looked and thought this white stuff is some kind of sediment of the gasolin.

what time frame is "from time to time" ? are we speaking of several month or more of once in 3 years? this is not a daylie driven car... just a fun in the summer car

thanks for the tip with timing. it already set at 9° (set disconnected) thats where it was running smooth

 

From time to time = a couple of years; depends on how much moisture it is subject to. If it sits around for long periods without driving it might even be every year.

 

hi again!
upcoming week I will unmount the quadrajet and try to reseal the plugs, as I am switching in a new intake manifold at the same time and want to save time unmounting it twice (and maybe kill a gasket more :-P )

what came up to my mind today, do you think that may my hanger and rod combination is the fault for running so damn rich in idle? could that be?

I currently use N hanger and DR rods.
Think my secondarys dont open well too, which I think is the fault of the AV settings / spring ? When I shift manually by locking gears (1 > 2 > D) I can hear the engine sound changing at about 4000/4500 rpm, which would mean the spring is too tight, right?

But anyway, as far as I understood how hangers and rods works, they are *just* for the secondary´s which dont affect the idle, correct?

with my setup as described in the first post, do you think this combination fits well?
I have a collection of N, K and I think its a C Hanger and DR, CH and I think it was CK Rods. The Primary Jet Seal is also gone and it seems the pre owner did "tune" it. Is there a easy way to tune it right?

this quadrajet thing gets me crazy :\

 

Hangers and rods are only active when the secondaries are open (foot on the floor); not at idle.

So, no. No effect on idle or gas mileage.

The air valve has a spring that controls its tension. For nearly all practical purposes, the "ideal" tightness depends on the engine displacement, and little else; which is convenient, because once you know the engine size, you just set it to match, and you're done. For the 305, it's about 7/8 turn. Loosen the little set screw underneath the air valve shaft, on the side opposite the throttle linkage; let it go completely loose; tighten the spring, using a small screwdriver in the slot at the end of the air valve shaft, until it just barely begins to hold the air valve closed; tighten it some more, and stop at 7/8 turn; tighten the set screw back up.

If it's too tight, it will run extremely rich whenever the secondaries open. If it's too loose, the secondaries will open too soon and the engine will run lean, which produces the LOOOOONNNNNNNGGG bog/flat-spot when you try to use them before the engine RPM is high enough (i.e. the air valve doesn't control itself properly).

Most people seem to hallucinate that loosening the valve makes their car "run better", mostly I suspect because the carb then makes more noise, which re-calibrates their butt dyno. Actual power output measurements such as time slips at the track tell a different story.

As far as hangers and rods, you can make any hanger into any other hanger just by bending it. Rods, you can change out in like 13 seconds if you're slow like me, you're probably faster than that, so just try whatever ones you have and use whatever ones you like best.

Don't worry about the gasket. Just smear some dielectric grease on both sides of it. It'll last through about a million times of remove and re-install.

There's no primary jet seal that I know of.

 

Hi again..

Today I opened up the quadrajet.

here is a video of it, after I took off the top:
The car was driven about 48hrs before I took this video.

I guess these are the plugs you were talking about?


Here a closeup.. is this correct, how its mounted?



and another shot from the top




by the way, the secondary´s where waaay to tight.
its a huge difference after setting it the way you told me, but I didnt drove the car yet.

still no clue why its running so worse.
I can get only 5 to 10 mpg.. and I dont lose fule under the car :-P