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Car running RICH, then LEAN.

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Banned Member
Aug 30, 2004
ca, Central_America
This is so frustrating. My car had some boost leaks which was causing it to run rich. And it was the connection from the top outlet of the SMIC to the uicp. I fixed it and now it runs hella lean. I been running rich for about 4 days so my guess is I clogged up the fuel filter. I bought one and I'm about to install it but was wondering what you guys had to say. Lemme know what's up.
I don't think your fuel filter will care what AFR you're running. It's job is just to filter the fuel before it gets to the fuel rail. I think the recommended service interval is somewhere around 10k miles, so it probably wouldn't hurt to change it, but I wouldn't put a lot of faith in it as the single cause of your problem. When you installed the 190 lph fuel pump, did you rewire it? Exactly how lean is "hella lean"? Also please specify part throttle closed-loop or WOT.
oldman- I'm using an a/f ratio gauge. I know the rep on this, but it was given to me.

donmagicjuan- It shows lean both ways. And the 190 is a wish part but I did re-wire the stock pump for better flow. I'll check the connections soon on my relay.

I haven't changed the filter in 2 1/2 years so I know it's time to replace it. I can't hit 2 1/2 grand w/out it jerking. I read about this member who had the same problem. Come to find out his alternator wasn't producting enough voltage. So you think it could be a electrical prob?
Well, it could be that you're not getting enough pressure to the fuel rail, which could be either a flow restriction or an electrical problem to the pump. However, if your AFR gage is pegged lean at least some of the time or all of the time, I would suspect a faulty O2 sensor.

S Ranger said:
And the 190 is a wish part...
So it is. My mistake.
Yeah, the flow restriction. That's what makes me think it's the fuel filter. I'm gonna relieve the pressure for the gas work, d/c battery, then check my connections. If that passes I'm going to install my fuel filter. Assemble everything and start it up. If that fails next step is to look into a new 02 sensor because I do have a CEL but then again I have a test pipe instead of a cat. Anyway, I'll keep you guys updated. Thanks for the input.
S_Ranger said:
oldman- I'm using an a/f ratio gauge. I know the rep on this, but it was given to me.
Not much to work with there, discribe why you consider it lean or rich. Give us details of the gauge readings during idle, part throttle and WOT before and after fixing the boost leaks.
If it's the blinky light gauge, it's useless for anything. Even an O2 sensor reading from a logger would be more helpful at this point.
If you have the fuel filter you should try to replace that right away and see what happens. At worst nothing bad.
I replaced the fuel filter and same results. It runs lean at idle and at WOT. When I did the boost leak test I got air coming out of the TPS. The screw on the intake manifold that adjustes the idle. So I'm assuming a throttle body rebuild kit is necessary. I'm going to replace the upstream 02 sensor and see what's up. Any words?
So what happened my car seems like it has been doing the same thing. I had boost leaks then i fixed them and now it feels like i am running lean.??
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