I have a 1996 Blazer thats showing a PO code 507 Idle Air Control (IAC) System RPM Higher Than Expected . Thats is followed by a PO code 300 random misfire...Iv done my best to tune up the engine plugs wires cap cleaned map sensor throttle body seaform though the brake boost ect. I replaced what i believed to be IAC sensor on the rubber boot between the Air intake and throttle body. The Code came up again so i assume that the senor is working.I dont know were to go from here i read thier may be a motor? for the IAC that could be plugged with carbon but do not know where it is located or even what it would look like or if the engine 4.3 throttle body even has one. I know i need to fix the 507 code before the missfire. Looking for advice photos on IAC system what to replace and how any advice would be helpful as i am running out of ideas. My Haynes manual shows IAC motor pug on what looks to be the AC motor i have no idea if thats right or how to work on it. Any help would be greatly appreciated.
Ok to amend my post dose the IAC sit on the right side of the throttle body? Held in by two hex screws and a connection?

 

First step, get rid of Haynes manual. The sensor in the "rubber boot" is the IAT, (Inlet Air Temp) sensor. The IAC (Idle Air Controller) motor is on the driver side of the throttle body, next to the throttle position sensor. Remove the IAC and clean it with carb spray. DO NOT move the pintle valve. If that doesn't help, try this: https://blazerforum.com/forum/diagno...plained-35140/

 

Thanks found it removed it cleaned it with carb cleaner not sure what a pintle valve is hope didnt damage it. I read your reply to a prior po 300 question your remarkes were great it good having someone with such knowlege on here.
Thanks again

 

The "pintle" is the the actual valve on the "business" end of the IAC. The IAC motor moves the pintle in and out to adjust idle speed by introducing more or less air to the plenum. The drive mechanism in the IAC is fragile, so don't try to move it by hand. Buy BWD Idle Air Control Valve 31023 at Advance Auto Parts

Always diagnose and repair the first DTC that is retrieved, then clear the memory and perform a General Motors Driving Cycle to confirm the repair, (and to make sure the SES light stays off). In most cases, the first DTC can cause others to set, so you might end up chasing a ghost if you don't start with the first one.

 

So i performed the General Motors Driving Cycle. During step 4 "Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed." The check engine light began to flash, missfire. Is there anyway you can help diagnose what might be casuing the miss fire from this information it seems to mostley miss fire at highway speeds around 80-100 km? But some times miss fires at lower speeds. It does not set a DTC code

 

Did the P0507 set in memory? If it did, you need to diagnose & repair that one first.
Did you look for pending DTC's in memory? (possibly P0300)

P0300 is almost always caused by a fault in secondary ignition: spark plugs, plug wires, distributor cap, rotor, and ignition coil. It can also be caused by low fuel pressure and incorrect camshaft retard adjustment.

 

When i use the ob2 scanner to scan for DTC codes nothing comes up..however when i use the ob2 scanner and go into the enhanced dtcs. It says present dtc PO507, when i check pending dtc in enhanced dtcs it say PO300. Does this mean i didn't clear the DTC properly or the vehical hasent run though enough driving cycles to set the code on the cluster>

 

There should be a menu on your scan tool that shows "I/M Readiness" or "Readiness Monitors". After each monitor it will tell if it's complete. If all monitors are complete, the DTC's are current and the drive cycle was performed correctly. During the drive cycle, P0507 was detected and the SES light should be on. The P0300 was also detected and it is stored in the "pending file". If it occurs again within the parameters programmed in the PCM, it will be moved to the "current" or "hard fault" file where the P0507 is now. NOTE: "Pending" DTC's will not turn the SES light on.

 

The DTC 507 went off on my way back to work going to replace the iac and see. Thanks for the advice

 

So i replaced the IAC and i am still getting the DTC code 507 coming up. I cleared the code and it came up again. I made sure their were no codes or pending codes in the scanner. Could this be caused by an air leak at the throttle body? I seem to have cleared the missfire bad plug on the driver side middle, pain to remove. Replaced all the plugs and wires seemed to clear the miss fire. Just got the 507 left to deal with any help would be appreciated.