So I bought this pain in the *** '93 z28. Its been one headache after another with this car. To make a long story short I got the car on the road but its not running right. Replaced the head gasket so at the same time did new plugs and wires. started the car and it runs. but does not always start up on first turn. Then when it is on it idles rough. ONce in drive it goes but real rough until after 1500 RPM then everything is fine. Until I go to slow down and come to idle then its sluggish and rough until I pick up speed. OH and when cruising on the freeway say at 65 and go to accelerate same response as if I was in idle again until the RPM's come back up.

Any suggestions?

New Cap
New Rotor
New ????

 

Have you checked the fuel pressure, including rate of loss of pressure when you shut the engine off? Have you scanned it for codes? Have the injectors ever been cleaned? Have you checked the critical speed-density related sensors, like the IAT and MAP sensors? A faulty coolant temp sensor can cause problems with hard start, rough idle. Have you checked the EGR valve for leaks.... again, causes rough idle and similar problems.

 

I have not. I thought for sure it was a iginition issue. There are no codes popping up as of right now. What is the IAT and MAP sesnors? Are one of those the temp sensor?

I knew I should of changed the EGR valve when I had the head and intake off.

 

IAT is inlet air temperature. The sensor is located on the 90-degree bend in the inlet air elbow (bellows), immediately in front of the throttle body. MAP is manifold absolute pressure. It measures the pressure of the air in the intake manifold, and is the black domino-shaped plastic piece on top of the intake manifold, passenger side, right behind the throttle body. Your 93 is the only year LT1 that runs in speed-density mode. The ECM (computer) calculates the mass of air entering the engine from the speed (RPM) of the engine and the density of the air. To calculate the density of the air, it needs to know the absolute temperature and the absolute pressure of the air entering the engine. If either the IAT or MAP sensors are giving bad readings, the ECM doesn't get the air mass flow correct, and doesn't add the correct amount of fuel. It may cause the engine to bog, particularly when the air flow is changing rapidly.

You can also have a problem due to several other inputs to the ECM, inculding the TPS (throttle position sensor) or the CLT (coolant temp) sensor. Or. maybe the O2 sensors are not in good shape and the engine is leaning out or running too rich on transition.

Looking at the sensor readings and ECM parameters with a scanner, or logging the data with something like TTS DataMaster or FreeScan will sometimes allow you to pick up on where the problem is.

 

Is the air cleaner new? Check your PCV valve and see if it needs replaced. Possible air leak in manifold.

 

thanks for all the help!!!!!

I'll look at those sensors this upcoming weekend.

 

So things got better after taking sensors out and expecting them and reinstalling. However, now things are even worst.

I am probably going to start a new thread in a hour or two if no one responds.

The same symptons are there as before but, now depressing the gas too much the car rattles like it is too lean (old school carb). Then, if I feather up to speed it swallows gas. I must be burning almost 10-15 miles a gallon.

I am going to try to replace all sensors but, if it may be something other than a sensor then I don't know.

 

If it is not the sensors it could be a vacuum leak. Engines run badly when excess air gets into the system from a place where there should have vacuum. Then when they are at high RPM it evens out. If you don't have a vacuum guage you may hear the leak and close it. Places to check are the rubber 90 degree elbow. These degenerate over time and tear, the donky dong falls loose from the elbow or the edges are not properly sealed to the throttle body. Loose hoses and polution systems can be the problem. This may be an inexpesive fix.

 

Yeah is been fun checking all the vacum lines. It is almost as if everytime i fix one problem I create another. Would a vacum leak also cause it to backfire. There is a real strong gas smell from the exhaust and when I go to accelerate "heavy" it feels almost like its flooding but, if I feather the pedal it acclerates OK but, this is a camaro I should be able to punch it and it should respond accodingly. LOL.