You can block the vacuum line to the EGR and the controller solenoid if you want to. The '87 has no way of knowing if it's working or not. Mine has a plate under the EVR and the vacuum hose has a bearing in it before the vacuum controller. No codes for it ever, I just ran a check the other day with the new code reader that replaced the old beeping and flashing one I had from the stone age.

My truck will not surge in warm weather, but sure will in cool and cold. Not near as much as it used to though. Unless I let it warm up for 5 minutes or so in real cold weather, it won't try to stall. When I first go it, it would stall out from surging at 60 degrees.

 

Yardbird,

So you saying the truck will be fine without the feedback from the EGR Position Sensor to the ECM? Hmmmm may be a way to go then. The EGR valve is blocked between the exhaust and intake port now for testing and because the EGR valve would not clean up and let the it seat 100%.

I have done all but sit this thing in river and look for air leaks. I have not found any other than the broken nylon tubing for the heater controls and 2 rubber lines on the engine. Guess it time for a smoke tester.
I went back out yesterday evening and started it up. It surged stalled for about 2-3 minutes. If I kept it up to 1k rpm it would stay running. As soon as temp gauge started to move truck idle fine from that point thru 20 minutes or until I cut it off.

I am going to pull ECM and do the caps in it when they arrive. Got a full tune up kit coming for it,plugs,wires,cap,rotor,pcv to replace whats in there as they at least 14 years old. I do not feel any of that is going to fix my cold start surge as it purrs fine when warm however I may be wrong. Took me at least three times of forcing it to get up to temp and cooling off to find the bad Air Charge sensor and Engine Coolant Sensor. Air filter ,fuel filter was done when I replaced the rear fuel tank,pump sender assy.high pressure pump,fuel reservoir valve.

 

The way I have kept mine from surging is I have the idle set to 1000 rpm. Still will if I let it warm up a few minutes when really cold, but does good now otherwise.

I also put in a cut off switch to the IAC valve so that when I start the engine cold I can keep the rpm down until the oil pressure comes up.

 

I done a MAP sensor test today:
Manual Specs Mine
1.) 0 in. Hg ...... 152 Hz. 158Hz

2.) 5 in. Hg ...... 141 Hz. 144.9

3.) 10 in. Hg .... 127 Hz. 130.8

4.) 15 in. Hg .... 115 Hz. 118.5

5.) 20 in. Hg .... 101 Hz 105.5

 

Smoke test today and saw smoke rising around #3 intake runner. Could not pinpoint if it was at head or where the manifold splits. Will do some more investigating next day or so. Got intake and exhaust ,valve cover gasket,IAC gasket,TBI gaskets on order.

 

The computer looked good no leaking or bulging caps. 3 new caps going in it this week. Then will back up and start again from ground zero testing and checking things.

Tim

 

The ECM back in truck with 3 new electrolytic caps. Still a surging idle when cold start. Back to the drawing board for more testing and probing. Replacing the TAB an TAD solenoids when I can figure out which one goes where for the wiring harness plugs.

 

Keep fighting! There's a lot of interest. If you figure it out you'll be helping a lot people with this common issue with these trucks.

 

So, just some thoughts to throw at you...

The cold surging may be the computer trying to prevent a stall or it is a malfunction from a faulty/incorrect component.

So, what is the condition of the basic tune up parts? Spark plugs, wires, air filter, fuel filter? Is the gas good? Base ignition timing?

By the way, did you note what computer is installed?

 

TAB/TAD are keyed differently, no chance of error.

 

I have tested an retested components. After the truck warms up it purr like a kitten. Will go back and get it to warm back up and check the components again and let it cool down over night and check them again.


All brand new and gas is only month old at most and is non ethanol. Have not put the timing light on it as when it is up to temp it runs great. Will be checking the timing next but it was running great when it was parked 14 years ago. It may very well need the injectors cleaned and tested.

Base Ignition timing is 10° dead center of the deep V notch. That stingy timing mark hard to find.


Yes I took picture of the label on the ECM.

 

When it rains it pours.
Now I have brake light and rear anti lock warnings on dash.

Frustrated yesterday I pulled the TB off the intake to see if I damaged the gasket after removing to clean it. No damage to gasket but cleaned it a second time while it was off. Now my idle is staying around 1000rpms after it warms up. Still some surging when cold start had to start it 3 times before it would stay at 1200/1300 for couple minutes then started to settle at about 1000 and stayed running.I am thinking maybe someone as monkeyed with the throttle stop screw way back along time ago. Hard to tell as it has been down for 14 years so no fresh marks on the screw.

 

When the Red Brake lamp is turned on that will also trigger the Yellow ABS lamp. Check the fluid level in the master cylinder. That is the most common cause of the Red Brake lamp. The brake fluid level float is also known to sink.

 

I did a quick check and the float is up and fluid is full.
I watched it this am and when I start it the rear light comes on first then about a minute later the Brake 1 turns on. So now more gremlins to chase.

 

possible unrelated park brake or wire failure on switch combined with ABS actual malfunction