largecar379

old drag racing trick for setting timing (does not require timing light):

make sure distributor vacuum hose is connected properly

loosen distributor lock nut

bring engine revs to approx 3000 rpm's

rotate distributor slowly, back and forth, until you hear (or see, if you can see a tach) maximum engine speed.

tighten lock nut


reason for doing it this way:

crank balancers will, over time, slip the outside donut on the balancer rubber, causing the balancer timing marks to be "off". (How old is your balancer???)

This way, you get maximum advance dialed in at it's maximum application rpm.

(And be sure to keep your fingers out of the fan....)

--Russ

Solid Snake

I took some vacuum readings tonight. At the crappy 450rpm idle, I get 3 in/hg. I tapped the meter plate to get the highest possible RPM (750) and the reading was 5 in/hg. Then after going nuts, clamping, listening, etc, I decided to pull the hose going from the outer connector of the thermo valve to the EGR valve and what do you know? RPM jumps up to a smooth 650 rpm and vacuum stabilizes at 8 in/hg. Now when I tap the meter plate, idle jumps further and vacuum hits 14 in/hg. Finally she's idling smoothly, but throttle response still sucks. I'm not really partial to the EGR system, in fact, I'd have torn it out if the garages around here didn't check for it.

I'm fairly certain I have the hoses right. One EGR hose goes to the thermo valve, the other goes to the vacuum regulator on the right bank. What do I have to disconnect to eliminate exhaust recirculation? Although it runs 100% better, throttle response is still sluggish, I suspect some EGR crap is still slipping through.

Anyway, thanks for the responses so far. I think after two long years of watching it sit, my baby will be on the road by next week Excuse me while I go put some ice on my EGR-burned finger.

Lizard928

Holy cow, that is REALLY REALLY low,

even at 14" of vacuum you still have alot of leaks to take care of.

Solid Snake

I think it's possible that I may have the two EGR vacuum connections reversed. Why do our EGR valves have two connections and how are they used? Does the valve operate on the pressure differential between the two vacuum sources?

Dennis Wilson

Where did you measure the vacuum. Some of the ports on the throttle body are pre throttleplate and some are post throttleplate. If you attached to the pre your vacuum will be low. Also, check the vacuum advance/retard lines to make sure the aren't reversed. That would account for the low vacuum reading and the sluggish throttle response.

Dennis

Solid Snake

I measured the vacuum off the brake booster line. My distributor has only one vacuum connection and that line is shared by the evap control valve.

RngTrtl

I'd say check the plug wires just to make sure. Sounds just like when I had some plugs wires reversed on my truck. Double check them.

Solid Snake

I never took the wires off the distributor. I didn't mix up the banks either and since all the wires are the right length, there's no way they could be in the wrong place. Above 600 rpm, the engine is smooth as silk, so I highly doubt the firing order is incorrect. I'm going to do some leak testing with propane tonight.

I'm still unsure of how to disable the EGR, and what exactly the two hoses leading to it are.

SharkSkin

If you disable the EGR you may have to get the advance curve on the distributor altered to avoid pinging under certain load/part load conditions. Or, back off the timing and end up losing power. A properly functioning EGR should not rob power; it should be inactive at full throttle. Since it should also be inactive at idle, the fact that unplugging it affected your idle points to a problem, perhaps incorrect hose connections as you suggested. You should have a third connection down there(D in the first diagram), a long thin tube that connects to the amplifier for sensing exhaust back pressure. If that long metal pipe is broken off you will need to find an alternate way to transition from hot exhaust to rubber hose for that connection.

Here's some more info on vac hoses and EGR:

Dennis Wilson

Since you measured the vacuum off the brake booster, try plugging the line where it enters the booster and remeasure. If it comes up to 14-17, the vacuum leak is in the booster. The vacuum line to the distributor should be a direct connection to the front of the throttlebody as in Daves diagrams.

Dennis

Solid Snake

Yes, I know what you mean. It's the one that runs up to the passenger side valve cover and it's connected. The thing I fear I might have mixed up is the two that go directly to the EGR. Would mixing these two up cause the EGR to open at idle? I may still disable the valve if only to keep all that crud out of the motor. Perhaps doing so will extend its life a bit.

I'll give it a shot when I get home, Thanks.

What's not shown in the diagram is the evap system. From what I can gather, that line increases vacuum with engine rpm, so I T'd it into the advance line.

BTW - Thanks a lot for that diagram.

SharkSkin

I think that having the lines reversed will make the EGR misbehave, yes. Are the other connections correct?

I don't think you're going to extend the life of the motor much by defeating the EGR. Most particles coming out of the combustion chambers will tend to go straight out the exhaust rather than make the sharp turn into the EGR valve. The resulting pinging would reduce the motor's life to a greater degree, I'd think. Or, as I said, you would have to retard the timing and lose power, or get the distributor modded.

Obviously we have a difference of opinion as to whether it's more trouble getting the system to work as designed as opposed to removing a key part then adjusting other things to compensate. You're going to end up with the same amount of power at WOT either way, unless you do it half-assed(e.g. simply retard overall timing).

Sean79 5spd

It might be time to check primary fuel pressure and flow. If the in-tank and external pumps are original it is time they were replaced. You can use the same equipment to check the control pressure and establish if the WUR is functioning correctly. Also, check the cold start valve to be sure it is not leaking.

Try this link for the test equipment.
http://www.closeout.com/we-ta-33865.html

Dennis Wilson

Connecting the EGR vacuum line into the distributor advance line could be causing a problem with both systems. The vacuum line to the distributor should be pre throttleplate and the EGR should be manifold vacuum. Also if the EGR diaphram is bad, the distributor wouldn't advance when the throttleplate is opened.

Dennis

docmirror

No one has mentioned the old fashion way to check for vac leaks. Get a can of carb cleaner with the little red nozzle. Let the car run, and warm up some. Spritz each intake joint, vacuum port, air intake line, etc with the carb cleaner. If the car picks up RPM when you spritz, you have a vac leak at that point.

It doesn't take much of a spritz, in fact a small amount is better than a flood. To test, pull a vac line, and spritz in the port to see what it sounds like. Then, go around all the fittings on the intake one at a time. I think you'll find some more leaks.