'95' Chevy Blazer,surging idle

[Donna DuRocher]

My 95 Blazer is surging at idle speed, but when I get it on the highway to drive, it smooths out. It does miss going uphill at 50-60 or up mph. I got the codes off of the check engine and the only thing they said was the MAP Sensor, so I changed it but there was no difference in the performance. I also changed the fuel filter already. Please help ASAP if anyone can... Greatly appreciated,Thanks!
Donna

[old_master]

Welcome to the forum!

What code was retrieved from your vehicle? There are several MAP sensor DTC's. When a MAP sensor code is in memory, it doesn't necessarily mean the sensor is bad. It means there may be a problem with the sensor or its circuit, or something else that affects MAP sensor operation. How many miles since the last major tune up, (spark plugs, distributor cap, distributor rotor, spark plug wires)? Have you checked fuel pressure? How many miles are on the vehicle now? Many things can produce the symptoms you are experiencing. Repair history is important for us to know, so that we can help diagnose the problem.

[Donna DuRocher]

Hi, Thanks for the welcome and the info. In reply; the car has alot of miles on it 195297. It was totalty tuned up in August,I had all new parts up in itie plugs ,wires,rotor,all the right stuff. Also has new Flow Master dual outlet Muffler System.After clearing the computer, all I could get out of the read out was:2-3,3-3,3-3. I have cleaned the injectors, changed the Fuel filter,changed the map sensor as you already know,sorry about repeating myself!!!It had an oil change in December. Some one said that it might be the EGR valve, could that be it? There is black stuff coming out of the tail pipes. Thanks so much for your time and help. Please reply again if you can. Again THANK YOU For Trying To HELP Me, Donna

[old_master]

In your list of parts replaced, I didn't see distributor cap...very important. If it hasn't been replaced, do it now. As for the codes: 23 indicates a problem with the IAT, (Inlet Air Temperature sensor). This could mean either the sensor itself is faulty, or one of its circuits has a problem. The sensor is located in the air intake hose between the air filter and the throttle body. It has two wires connected to it. The code 33 refers to the MAP, (Manifold Absolute Pressure sensor) and its circuits. When troubleshooting DTC's, (diagnostic trouble codes) always start with the first code given, in your case, the IAT. The fact that the MAP sensor has been replaced, and the code is still present, may be due to the IAT problem. Troubleshooting will require the use of a digital volt ohm meter. The IAT sensor is inexpensive and easy to replace, if you choose the "trial and error" angle of attack. Hope this helps.