'87 II 2.9 codes and jerking

[Ottieotter]

Hey all, got a issue with my '87 BII, 2.9 V6 5-speed.

Recently it's started jerking under throttle, acting like its cutting fuel or spark for a second before coming back, along with sometimes almost dying when taking off from a stop.

Harassed the ECM for codes, got a code 10(?), code 30(?), code 33 (EGR Valve fault), and code 77 (Operator error during dynamic response test/wide open throttle not sensed).

The code 33 I suspect is either the vacuum sensor on the EGR valve or the solenoid that sends vacuum to the EGR as I just replaced the EGR valve less than a month ago, everything else is a mystery to me.
Any advice would help

 

[franklin2]

If it idles smooth, you can disconnect the EGR vacuum line and plug it off with a screw. That will take the EGR out of the picture to make sure it has nothing to do with the problem. I have run for years without the EGR.

There is no code 10 or code 30. You can pull the codes again, it is very easy to get mixed up when counting pulses.

 

[Ottieotter]

If it idles smooth, you can disconnect the EGR vacuum line and plug it off with a screw. That will take the EGR out of the picture to make sure it has nothing to do with the problem. I have run for years without the EGR.

There is no code 10 or code 30. You can pull the codes again, it is very easy to get mixed up when counting pulses.

I had went out and bought the code reader, those are the codes that it's giving me.

 

[SenorNoob]

IDK about reading by hand, but I have had my reader give me a 10.

 

[Ottieotter]

I went out a drove it a bit this morning (around 2 miles to get it up to operating temp,) couldnt get it to give me anything other than that code 10 and code 11 during a KOEO scan, got the code 33 and code 77 during a KOER scan

 

[Ottieotter]

If it idles smooth, you can disconnect the EGR vacuum line and plug it off with a screw. That will take the EGR out of the picture to make sure it has nothing to do with the problem. I have run for years without the EGR.

There is no code 10 or code 30. You can pull the codes again, it is very easy to get mixed up when counting pulses.

Got the line plugged off, cleared the codes, and took it out for a drive. It's still throwing code 33, idle does seem to be surging a bit now too. Wont go below 1k RPM and tries to die when it does

 

[franklin2]

You will definitely and always get a code 33 with the EGR disconnected. One of the failure modes of the EGR is it can get a piece of carbon stuck in it and it will be like a huge ugly vacuum leak internally. The only way to take it completely out of the picture is to make a solid metal gasket out of a pop can and put that underneath the EGR to really block it off. Of course you will still get the code 33.

The only thing the computer will do when it recognizes the EGR is not working, it will set the total timing back a little bit to reduce the chance of pinging. You can easily compensate for this and set the inital timing at 12 BTDC instead of the factory 10 BTDC.

All of this is reversible, and right now is mainly a troubleshooting exercise.

 

[Ottieotter]

You will definitely and always get a code 33 with the EGR disconnected. One of the failure modes of the EGR is it can get a piece of carbon stuck in it and it will be like a huge ugly vacuum leak internally. The only way to take it completely out of the picture is to make a solid metal gasket out of a pop can and put that underneath the EGR to really block it off. Of course you will still get the code 33.

The only thing the computer will do when it recognizes the EGR is not working, it will set the total timing back a little bit to reduce the chance of pinging. You can easily compensate for this and set the inital timing at 12 BTDC instead of the factory 10 BTDC.

All of this is reversible, and right now is mainly a troubleshooting exercise.

I found the problem, cracked the EGR sensor open and found a blown out resistor. Got a new one on order, should be in Wednesday

 

[Ottieotter]

Late update on this
The new EGR sensor cleared the code 33, it is now throwing a code 32c, EGR pressure feedback fault. I did throw a new EGR vacuum solenoid in it as the old one was literally falling apart, and made sure the vacuum lines going to the solenoid from the intake and the reservoir were holding vacuum. As of typing this, it's been holding about at about 12 inches of mercury for about 10 minutes. Scratching my head at this point, half tempted to parts cannon a ECU at it and see where that lands me

Edit: Tested the wires at the EGR sensor. Getting 5v at the orange/white wire (pin closest to the upper intake), assuming thats the 5v refrence for the sensor. The black/white wire (middle pin) tested at 200 ohms resistance, .05 volts, and the brown wire (outer most pin) tested at .54 ohms, .05 v

 

[franklin2]

You can use your vacuum tester on the EGR sensor. What it does is measure the pressure in the exhaust tube feeding the EGR. Depending on conditions, it measures backpressure from the exhaust when the EGR valve is closed, and can actually read a little bit of vacuum from the intake when the EGR valve is opened. This is how the computer verifies the EGR is working. If you have modified the exhaust and taken the cat out, it will most likely never work, there is not enough back pressure for the EGR to work properly.

But I think you are wasting your time and money on this. These engines run fine with no EGR on them. Yes they will have codes, but beyond that they run fine with the EGR having a block-off plate under it.

 

[Ottieotter]

You can use your vacuum tester on the EGR sensor. What it does is measure the pressure in the exhaust tube feeding the EGR. Depending on conditions, it measures backpressure from the exhaust when the EGR valve is closed, and can actually read a little bit of vacuum from the intake when the EGR valve is opened. This is how the computer verifies the EGR is working. If you have modified the exhaust and taken the cat out, it will most likely never work, there is not enough back pressure for the EGR to work properly.

But I think you are wasting your time and money on this. These engines run fine with no EGR on them. Yes they will have codes, but beyond that they run fine with the EGR having a block-off plate under it.

As much as I would like to just permanantly bypass the EGR and move on with my life, I am in Cali so I need it for smog, and not having it kills my MPG. The only reason I even give a damn about the EGR and MPG in this truck is because it's my only vehicle at the moment. Exhaust is all still stock with the cat.
Vacuum gauge is jumping between 0 and 5 inches of mercury on the EGR vacuum port

 

[franklin2]

Vacuum gauge is jumping between 0 and 5 inches of mercury on the EGR vacuum port

I would do this same test during a cold start. During a cold start and warm-up, the EGR is locked out, the computer will not activate the EGR till the engine is fully warmed up and in closed loop. If you get the vacuum to the EGR going on and off during warm-up, something is definitely not right.

P.S. Also during a warmed up idle, the EGR will not be activated. The engine cannot handle any EGR during idle or it will try to stall, cold or warmed up.