Seems like my car is running lean at certain RPMs (1600, 2100). The computer shows that that it goes back and forth from the EGR to the O2 sensor, rich, lean, rich, lean, and tends to stay lean at those RPMs. On the road the car tends to jerk around this time and can only be corrected by letting up or stepping on the gas (to either decrease or increase RPMs past 1600 or 2100). I suspect either the O2, or more probably the EGR is bad (carbon buildup on the EGR diaphram perhaps?).

Okay, I've changed an O2 sensor before, so that's no big deal. But how in the hell am I supposed to get to the EGR? Does the entire intake have to come off, or just the plenum? Also, will I need any extra tools to do this? Or is it a straight bolt-off, replace, bolt back on?

Thanks a lot.

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Maverick
1989 Formula 350 TPI
5spd Tremec 3550/TKO
several suspension mods

 

One other thing -- I was told that it might be possible to loosen up some of the carbon on the EGR by "tapping it with a piece of wood and a hammer" (use the wood to reach the EGR since the hammer can't fit). Is this safe? The person who told me this used to be a GM tech (retired now). He said just to tap it a bit, not bang on it.

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Maverick
1989 Formula 350 TPI
5spd Tremec 3550/TKO
several suspension mods

 

I dug out the Chilton manual for more info. So, I all gotta do is unbolt the plenum from the runners and the intake, pull it off, swap off the EGR, replace the runner gaskets and bolt the plenum back on? That doesn't sound too difficult.

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Maverick
1989 Formula 350 TPI
5spd Tremec 3550/TKO
several suspension mods

 

Mav,

The EGR is not too difficult to access. A few hints, however. If you've never had the intake plenum off, start soaking all the fasteners in penetrating oil right now. Apply more a couple of times daily until you are ready to perform the job. Get some antiseize compound and use it on all the fasteners that thread into the aluminum when you reassemble.

Purchase a good quality Torx bit for the plenum bolts. One of those Pacific rim brands that comes in a complete set for $4.99 will only **** you off by ruining the fasteners. Use a torque wrench to reassemble the system, and torque all the plenum and runner bolts to 18 ft/lb. Throttle body bolts are 10 ft/lb.

While the plenum is off, soak the distributor hold down clamp bolt, remove it, and apply antiseize to it as well. They are a ***** to get loose with everything assembled, and the compound will make it possible to move later with a distributor wrench.

Use GM or FelPro gaskets. They fit and seal very well.

Before you install the plenum after replaceing the EGR, make sure the throttle cables are routed correctly. One of them might be installed behind the intake runner tubes, and can be difficult to install with the plenum bolted in place.

While it's apart, take a look at the plenum opening behind the throttle body, and see why you might want to port the plenum in the future.

Good luck.

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Later,
Vader
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