Stock '89 T/A 305/TPI

My EGR vacume hose has been disconnected for ages. I always get an SES light on the first start of the day (3-5 seconds after and stays on). Subsequent starts that day give no light but I know a code 32 hiding in the ECM. Otherwise runs fine for a 270,000+ mile 305. But, idles at ~1000 RPM instead of the desired 600-750 RPM.

Just for grins, I went out today, disconnected the battery to reset the ECM, and plugged the EGR back up.

Runs like a turd. Still idles a little high, but has a definite power shudder at around 1500 to 2000 RPM under acceleration (is fine in park/nuetral). Beyond that and up to WOT, I feel no shudder but some power loss.

Could this just be a plugged/dirty EGR, or the solenoid? Or both?

Can the EGR be cleaned.... Seems to be stuck open/closed?? (thats where I'm lost)

I'm not against dropping bucks for a new one....just to get thing back to original.

I also had an A.I.R. tube break at the collector, has a temp fix and leaks a little. I did replace the check valve. Don't flame me but I had to JB rig it together....Looking for replacement tubes right now.

The air tube into the CAT was also broke, used muffler patch to temp fix that (no leaks there). Wish I could just yank that stuff, but Illinois would't be too happy 'bout that.

Could these things collectively be setting the code 32 and power shudder?

Anyone...

RB

 

Slack,

The EGR valve has a pilot valve as well as the main valve. If the pilot valve is stuck, the main EGR will open when it is not supposed to. And that sounds like your description of the problem. If the engine runs acceptably with the EGR vacuum line disconnected, but stumbles when it is connected, the EGR is likely opening at the wrong time. The EGR solenoid is operated by the ECM, and is pulsed rapidly (duty-cycled) to regulate the amount of EGR gas. The EGR valve itself determines whether the conditions are right for opening the main valve via this pilot valve. Most of the EGRs on our TPI engines are a negative backpressure type. You could remove the valve and try to clean the main pintle, valve seat, and pilot valve bleed hole. If the problem is simply a restriction, it may work. If the problem is a failed pilot valve diaphragm, it would be futile. Since repairing an EGR valve internally woudl be delicate, and repair parts would basically be non-existant, you might as well not even try.

 

Vader, so say the EGR solenoid allows vacuum to the EGR valve. The EGR valve decides for itself whether or not to use the vacuum? Wow. I'm 99% sure we 2.8'ers have the same EGR as you v8 guys... I know it's a neg backpressure unit. I'll have to check my GM manual on it.

Slight tip; my EGR was sticking open, I bought a replacement at Pep Boys for $45. It was a universal sucker. The vac line was aimed in the wrong direction- I didn't want to cut my plastic line and patch in a rubber hose to make it work. Problem #2; the underside was not "open" like the GM one- you couldn't feel the diaphragm, kinda makes it hard for diagnostic. Problem #3, it wasn't painted, and was a bright brass color. I took it back. (They gave me crap, as usual.)

I bought a replacement from GM for $65, fit perfectly, vac line mated up exactly, diaphragm "test" hole was there, and, it was painted a nice gloss black. So don't get a generic EGR valve, go to the dealer!

 

Think I'll just get a new EGR. Its the original one that came on the car...So I ain't complaining.

Been years sing I've removed a plenum but...
1. Remove torx bolts
2. remove throtte body
3. slide plenum up and out
4. do the EGR (might as well put a 180 stat in while I'm there)
5. get new plenum gaskets
6. loosen a runner, easiest side (Prolly drivers side) to make room for plenum and new gaskets.
7. tighten it all back down
8. re-install thottle body

or have I forgotten anything..........

RB

 

Slack,

1. Remove UPPER T-40 Torx bolts and loosen the lower runner bolts on one side (the right/passenger side is usually a litte easier. Use a good quality T-40 Torx bit for this instead of one from a Pacific rim manufacturer, or you'll be sorry;

2. Remove throtte body bellows, cables, and four bolts into the plunum. Remove the three (don't forget the hidden one) cable anchor bracket bolts and bracket;

3. Slide plenum up and out (that's optomistic), unplugging the MAT sensor electrical connector as you lift;

4. Replace the EGR and any other components you may feel inclined to replace. Use anti-seize compound on all bolt threads entering aluminum (in other words, all of them);

NOTE: If you ever wanted an AFPR, this would be a good time. This may be interesting reading: TPI-AFPR Conversion.pdf

5. Install new plenum gaskets;

5A. Port the plenum if you have the inclination and time. More interesting reading: Plenum Porting.pdf ;

6. Loosely install the plenum in place, remembering to reconnect the MAT sensor electrical connector again. You should also check the routing of the throttle cables before installing any fasteners, since the transmission TV cable should be routed INSIDE the left runner tube set;

7. Coat all fasteners with anti-seize, reinstall them loose, then torque them to 18 ft/lb final torque;

8. Re-install thottle body (Never-Seez again);

9. Did I stress using anti-seize compound enough?

 

And if you're considering a 180°F thermostat, this might also be interesting reading: TPI Cooling.pdf

It has instructions for a cheap, non-invasive fan control for less than $25.

 

Looks like Vader's putting your butt to work! LOL

Gotta agree tho'......now's the time for any of these things if you want them.

 

Your manual should have a diagram a little like this: