Low idle, slight miss not throwing codes?
Thread Starter
Registered User
Joined: Oct 2013
Posts: 18
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From: Schofield barracks, HI
Low idle, slight miss not throwing codes? I have a 2000 camaro z28 completely stock, the only thing I have done is a muffler delete and has 93,000 miles. I went ahead and replaced plugs (tr55)and wires (ac deco 7.5), air filter with regular fram, fuel filter, changed oil to full synthetic, radiator flush with new thermostat and housing, I put dielectric on all plug connections, flushed break fluid, and seafoamed the intakes with their intake cleaner, cleaned maf with maf cleaner, cleaned iac and iac port. Iac is working, IAT is working, cleaned TB. Before I did all this it had a very slight miss and idle lows, at a stop light while I'm in gear the idle drops to around 480rpm. I sprayed the vacuum lines, around injectors base, around intake with starting fluid to look for vacuum leaks. When doing this it didn't show signs of any leaks the rpms never raised when doing so. Pulled the plugs the porcelain part is white, and the spark plug prong had a light coat of whitish residue, I'm told that it could mean its running lean as well. I m stumped on what could be causing the slight miss, and low idle car runs good real well. The factory idle is suppose to be 550-600 so showing 480-490 is def low. If any body has any ideas that would be great?
Thread Starter
Registered User
Joined: Oct 2013
Posts: 18
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From: Schofield barracks, HI
Im having to order a fuel pressure tester couldnt find one on the island. It threw a code today po420 (Catalyst System Efficiency Below Threshold (Bank 1). I used the scan tool to test the o2's. 02 sensor 1 bank 1 read at CL (.250v-.480v)constantly flucuating in that range, 02 sensor 2 bank 1 was reading (.000v-.180v) flucuating with sensor 1 on bank 1. Bank 2 for the o2 sensors was pretty much identical. With what the spark plugs read and what the o2 sensors are reading the motor is def in a lean state. Im still going to check fuel pressure to see what that is.
TECH Addict
Joined: Aug 2005
Posts: 2,305
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From: Monroe,NY
Could also be a coil. Check you header temp at each cylinder and if one is a good amount cooler than the rest that would be your bad coil. I had the same problem and it ended up being #8 coil. Ran fine at full throttle but didn't at idle and part throttle. Never thru a code for me either. Might not be your problem but very easy to check.
