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ARGH !!!!!!! Need an engine guru

B

Blazin Obsession

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My 88 Blazer is running like a piece of sh*t!!
Can some one give me some advice on what to do??
The problem is black carbon coming from the exhaust,rough idle, engine shakes bad, very poor performance.
the compuer codes are 1-2 and 4-4 and it is a TBI.
I have recently replaced
o2 sensor
map sensor
pcv valve
plugs
ig. wires
rotor
cap
set timing to 0
inspected and cleaned most electrical connectors
inspected and replaced some vac lines.
cleared the computer codes.

What the h#ll is going on ???
Ken
 
Try replacing the EGR valve. Mine is not running right either and I am stumped. Mine is not as bad and I am not getting any codes to come up.
 
A code 44 means the 02 sensor is detecting a lean exahust mixture. A bad or dirty EGR or EGR solonoid can cause a code 44. The EGR solonoid is the little black box by the MAP sensor. You can trace the vac line from the EGR valve going to it.
A code 12 means no trouble codes stored in the memory
 
A code 12 will always come up, it is telling you that the system is working. The computer will always flash a code 12 then whatever other code(s) there may be then revert back to a code 12.
 
I dunno alot about codes but how does it run at speed? Is it crappy at idle or all the time? I would guess vacuum. It's the dagger in my side anyway. Also what's the correct timing for your motor? 0 degrees?
 
when the EGR's go bad in our big Detroit diesels they blow tons of black smoke and lose lots of power.
 
If you have the air pump setup check the air control solenoid. Its up by the air pump. Its suppose to allow air to the exhaust manifolds during idle only. If it fails and allows air all the time the computer reads the mixture as lean while the engine is running rich. Plugs foul and it runs like crap. The dealer wanted like $125 for the solenoid (that was with a discount) so I just plugged the hose comming off the solenoid valve. Better to pull the tubes off the manifold and put plugs in the manifold. I found the metal tube that goes around the back of the motor was broken letting air into the manifold even though the hose was plugged. If thats not it check your EGR valve.
 
First, here's the codes link -

http://216.121.161.76/files/GMError.pdf

Second, get a scanner. No way to troubleshoot by replacing part after part. Could be a combo of things, and a scanner allows you to 'read' the ecm on dozens of readings to see what is not right. Codes are one problem (and you have one to deal with) but drivability stuff usually does NOT throw codes. www.autoxray.com has good scanners for about $150 that you can buy at your local Shucks/Kragen/Checker auto parts store.

Your symptom of black exhaust and a LEAN code don't jive............hmm.
 
I've rented the xray a few times and its great. Probably buy one, but just remember the scanner will not replace basic trouble shooting. I think I even rented it for the air solenoid problem, but for that it can't help you, except to tell you there are no computer or sensor problems. Take your time and think it out. Sometimes its a pain but follow the service manual steps to the letter instead of jumping to conclusions.You can drop tons of money replacing parts.

If I remember the basics right, the O2 sensor reads oxygen in the exhaust as lean. If the exhaust comming out of the engine is black with no oxygen (rich mixture) and oxygen gets into the exhaust before the O2 sensor, the sensor will register the oxygen and the computer will think its a lean mixture. This equals black smoke, fouled plugs and lean mixture trouble code. The air can get in from the scavenging effect of the exhaust pulses. The air injection tubes have check valves which keep the exhaust from flowing backward through the tubes. The tubes connect right on top of the exhaust manifolds right over the #1 & #2 exhaust ports. Once the exhaust pulse ends, the check valve opens letting air in, even without the air pump belt on. I guess the same thing could happen even if you don't have an air pump but have an exhaust leak before the O2 sensor. Good luck.
 
Thanks for all the help, I am going to look at the egr and possible air leak. I have noticed another possible hint.
the EGR $$$ unit that is between the EGR valve and the maifold has a strong vacum going into it but no vacum to the EGR. Should vacum be present al the time at the EGR valve or is the $$$ a vacum switch? I also thought the air pump was the problem and have removed the diverter valve and plugged all lines.
Ken
 
By $$$. Do you mean the EGR solonoid? If there were problems with that you would be getting a code 32. The EGR solonoid is controlled by your Computer(ECM) It uses input from the throttle position switch, coolant temprature sensor, and MAP to activate it. It usually wont let vacume thru till the engine is completly warmed up. And the ECM recieves a signal from the Coolant temp sensor telling it so. After the engine is warm it(the EGR solonoid) is controlled by the TPS and MAP sensors. Which open and close the EGR depending on the demands to the engine.
The EGR is normally closed or almost closed at idle. So there should be little vacume going to it thru the EGR solonoid.
The EGR sould be closed when no vacume is going to it.
Sometimes the valve in the EGR gets dirty and gets stuck open. This allowes Exhaust gasses to enter the intake all the time This will make your engine idle very rough and have poor acceleration. it also leans out your fuel/air mixture possibly causing the code 44. The ECM trys to correct this lean condition by dumping more fuel to the mixture. If that still wont correct the lean condition the ECM will go into bypass mode. Some people call this "Limp Home mode" When the ECM is in bypass mode it ignores all the input from the sensors and runs on a pre-programed settings.When it is in bypass mode it usually runs rich and kind of rough and gets bad MPG. Alerting you that something is wrong and to get it fixed. The check engine light may not be on when in this mode.
The EGR also has a valve in it that regulates how much it is open according to engine vacume and exahust back pressure.
I hope I havent confused you. But thats how it works as I understand it for the TBI.
I think your problem is in your EGR valve its self. It is probabally stuck open. You can try pulling it off and cleaning it up and spraying it with WD40 or something. While it is off check the diaphram for leaks. You can put a line on the port and suck on it and see if it moves. If it is free it should be Ok
You can also see if your installed EGR is working right by starting the engine when warm. And reving it up to around 2000 then back to idle. You should be able to see or feel the little rod in the EGR go in and out. If the rod doesn't move and the EGR is getting vacume it may be stuck or have a bad diaphram.
 
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