Rich and Lean at the same time?????


Founding Member
Feb 15, 2001
On the Road

Part throttle bucking around 2k RPM
After hard run to anything over ~4500 RPM the RPM's will flucuate until it levels at idle ~700 RPM or stalls. Will rev to 1500 and down to 200-300 RPM

The Car has new:
Plug wires, plugs, fuel filter, front o2's, injectors that have only 26k on them.

It is burning gas like its going out of style. Its so rich when I pull into a light I can smell raw fuel wafting back into the windows!!

Any help would be greatly appreciated.

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My first guess would be vacuum leak,get some carburator cleaner in an aerosol can and spray around the gaskets (intake to heads, TB to upper intake, etc) if it speed up you've gotta leak. If nothing there, if you can get your hands ona new intake, i'd try swapping that, might have cracked it in the motor swap if you just recently finished the swap.... then maybe something more in-depth like.... blown headgasket between the cylinders?

well I sure as hell hope its not a cracked intake. Spent way to much money getting this thing running again to just put it back in the garage. oh well maybe I will just sell it as it sits and buy something else haha.

Just curious, if I were to go to autozone and hook up thier scanner to the car, eventhough the ses light isn't on would it show any "hidden" codes??:shrug:

or if I were to drive down the road would it show any codes that happen only momentarily?
same symptoms on a friends car last week. turned out to be bad MAF sensor. he replaced and no problems since. what size injectors do you have. is the MAF for those injectors?chipped?do you know someone you can switch MAF to test with? :D
Everything is stock from the intake forward. Its got stock 98 fuel system and ignition. Stock injectors and MAF. Also the computer is stock as well.

I checked for vacuum leaks and there seems to be none.

The only resolve I have got so far is that I rest the computer and it is running a hell of a lot better. Not using anywhere near that amount of gas and the idle is fine. Which brings me to think its a sensor????

Any other help.

Thanks for the comments guys.

99: As far as I know The basic AutoZone scanner is pretty much useless for what you are explaining. I think you need a higher end scanner. The autozone scanner is good enough to just scan stored codes.

High: The P0430 and P0420 are catylist under efficency as well. I am not worried about that I am worried about the 1130, and 1150s.

I used to work at a ford dealership and had a MAF sensor go bad on my car. We unhooked the MAF and drove the car and thats how we determined the MAF was bad. Try unhooking the MAF, it puts the computer in "limp home mode" and see if it runs any better. You might also want to try unhookin the Inlet temp sensor too at a different time, i've seen those do some crazy things before too.


Started a new trick on the way home from work tonight. sputters when I am on the gas when I get off of it, it idles down real quick in a half miss half sputter way. Very hard to explain. Like when I am on the gas its fine and anything else it just falls on its face when I am not on the gas.

Who knows.

I am going to try to tinker with it tonight.

First of last week I put a ProM MAF on the car. It was used but still in excellent shape. All this did was move the bucking to a different RPM now at like 1100-1200 it really bucks. And it seems like its down on power throughout the whole rev range. It hasn't stalled yet. But it doesn't matter the weather now it will buck anytime.

Any more ideas?