(Q) Is that the TAB and TAD valves?
Yes the backfiring is coming from the exhaust with a loss of power at the same time. The vacuum hoses that I capped off were the two that plugged into valves along the hose coming from the smog pumg to the heads and crossover tube. Is that the TAB and TAD valves? I capped off the tube going to the xpipe and the tube going to the heads. It runs a lot better now. It still has occasional loss of power and misfires. I am going to run codes and check for vacuum leaks. If the EGR is stuck open could that cause the problem? It is the original EGR so it probably isn't working correctly. What are your thoughts of removing the EGR and putting a plate over the holes? Do I need the plug that fools the computer into thinking the EGR is working properly? If I don't get a code for the EGR I will just leave it alone. I had a problem similar to this once before but with the smog pump working. I unplugged the 02 sensors and the problem went away. I later replaced the 02 sensors. Do you think it could be bad 02 sensors but didn't make the car run bad with the smog pump operational? I am going to try to resolve the problem but will just replace the smog pump if I can't.
(A) Yeah those are indeed the TAB/TAD valves you removed the vacuum hoses from. (Q) If the EGR valve is stuck open could that cause the problem?It is the original EGR so it probably isn't working correctly.What are your thoughts of removing the EGR and putting plate over the holes
(A) If the EGR valve is stuck open,it will essentially create a vacuum leak,which causes a lean condition.A few things to note about the EGR system and the EGR
Eliminater plug.When the EGR valve is open,it triggers the ECU to lean the fuel mixture and advance timing.Anytime a code is set for the EGR system,it triggers the ECU to delete/bypass EGR function in the EECIV,so that the fuel and timing values will remain normal vs being altered like stated above.What the EGR Eliminater does is,it outputs a voltage equivalent (0.50) to the value of a closed EGR valve,so that the ECU will see a always closed EGR valve and run normal fuel and timing values and it also prevents the cel from coming on,if the code is one that triggers a cel.The cel would not affect you anyways since the 86-88 models didnt come with a cel.You dont need the Eliminater anyways,since the ECU shuts the EGR function off with a code present.All youve gotta do is remove the vacuum hose from the EGR valve and plug the hose.This will trigger a code,which will trigger the ECU to delete the systems function and fuel/timing values will remain normal.A free trick that can be used for someone having a cel on due to the EGR is to remove the EVP sensor from the EGR valve,push the sensor rod in until the sensor reads a value around 0.50 volts then wrap tape around the sensor and rod to hold it in that voltage position,super glue the rod then once it dries,remove the tape,bolt the sensor back on the EGR valve (unless you'd rather use a blockoff or delete plate to totally delete the EGR valve) reinstall the EGR valve (or just the plate by itself) then plug the wiring harness back in.If youve got a blockoff plate or delete plate,just leave the EVP sensor off the valve and ziptie just the sensor up out of the way somewhere.This trick keeps you from needing the Eliminater plug.If your EGR valve is leaking,just get rid of it and install a plate or you can make your own out of a piece of sheet metal. (Q) Do you think it could be bad 02 sensors but didn't make the car run bad with the smog pump operational?
(A) Alot of time,o2 sensors will set a code (41,91,42,92) if they're defective,but these codes can also be caused by many other issues too,so dont go replacing the o2 sensors everytime a code pops up for them.Test them first.As an example, something as minor as a lean or rich condition will set those codes.A loose or disconnected hego ground wire could cause a lean o2 code also.The possibilities go on when it comes to things that can cause codes for the o2 sensors.Its very important that o2's react quickly to the changes in the exhaust, which indicates whats going on in the motor or efi system.They need to switch from lean to rich to lean,etc rapidly to keep the afr stoich.As o2 sensors age,their ability to measure o2 in the exhaust and their reaction time slows down,which is referred to as a lazy sensor so when the ECU tries to compensate for the o2 readings (by richening the system if the o2's are reading a lean condition or leaning the system if the o2's are reading a rich condition) its imperative that the o2's read correctly and quickly.If not,the changes the ECU makes will run behind somewhat because of the speed at which the o2's are operating at,if they're lazy.IOW - by the time the ECU sees a lean reading from a lazy o2,it might have already changed to a stoich or rich reading by the time the ECU has gotten around to compensating for that lean condition.The following link details how to properly test the o2's. O2 Sensor Codes 41/42/91/92 Troubleshooting