Surges Whie Idling and Cruising
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Joined: Nov 2002
Posts: 149
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From: Ft Worth, TX
Car: 91 Z28 with 64,000 miles
Engine: 350 TPI
Transmission: 700R4
Surges Whie Idling and Cruising
I have been hunting this problem for quite a while now. I bought the car about three years ago and it has never idled right. The hunt caused other problems this week described in this thread:
https://www.thirdgen.org/forums/tech...dle-after.html
It idles normally until closed loop operation. Then it will intermittently start to surge at idle and while at cruising speeds. It has only died a couple times in the past year and that only happened when I turned the AC on. Doesn't do it everytime I turn it on, just happened a couple times. I haven't lost any power that I can tell but the fuel mileage is only about 13-14mpg in the city. Mileage is worse than it used to be but not by much. Just passed California smog yesterday with these values:
At 15 MPH and 1352 RPM:
Measured
%CO2 Measured 11.5
%O2 Measured 5.1
HC Measured 30 Max Allowed 108
CO (%) Measured .04 Max Allowed .71
NO Measured 238 Max Allowed 767
At 25 MPH and 1298 RPM:
Measured Max Allowed
%CO2 Measured 11.5
%O2 Measured 4.8
HC Measured 30 Max Allowed 83
CO (%) Measured .09 Max Allowed .58
NO Measured 199 Max Allowed 706
In the last two days, I have cleaned the IAC and throttle body (they were REALLY bad), set minimum air, set TPS to .54 volts (it travels smoothly to 4.08 volts), replaced all vacuum lines, replaced the O2 and MAP sensors, and checked the fuel pressure (42.5 psi). I have not pulled the EGR valve, but I can hear the bellows in it when I apply a vacuum and release it.
About a year ago, I thought it was an ignition miss, so I installed an MSD 6A box, MSD coil, Taylor wires and did the normal spark plugs, cap and rotor and fuel filter. Only put about 3,000 miles on it since then (it spent most of the time at the body shop getting paint and body work).
When cleaning the IAC, I noticed pitting on the pintle. How tolerant is the pintle seating area?
The engine, other than the ignition described above and in my sig, is stock. Still has all the smog equipment installed and the car only has 54,000 miles (Hawaii car originally). I am forgetting something. I'll post updates as I continue.
Mike
https://www.thirdgen.org/forums/tech...dle-after.html
It idles normally until closed loop operation. Then it will intermittently start to surge at idle and while at cruising speeds. It has only died a couple times in the past year and that only happened when I turned the AC on. Doesn't do it everytime I turn it on, just happened a couple times. I haven't lost any power that I can tell but the fuel mileage is only about 13-14mpg in the city. Mileage is worse than it used to be but not by much. Just passed California smog yesterday with these values:
At 15 MPH and 1352 RPM:
Measured
%CO2 Measured 11.5
%O2 Measured 5.1
HC Measured 30 Max Allowed 108
CO (%) Measured .04 Max Allowed .71
NO Measured 238 Max Allowed 767
At 25 MPH and 1298 RPM:
Measured Max Allowed
%CO2 Measured 11.5
%O2 Measured 4.8
HC Measured 30 Max Allowed 83
CO (%) Measured .09 Max Allowed .58
NO Measured 199 Max Allowed 706
In the last two days, I have cleaned the IAC and throttle body (they were REALLY bad), set minimum air, set TPS to .54 volts (it travels smoothly to 4.08 volts), replaced all vacuum lines, replaced the O2 and MAP sensors, and checked the fuel pressure (42.5 psi). I have not pulled the EGR valve, but I can hear the bellows in it when I apply a vacuum and release it.
About a year ago, I thought it was an ignition miss, so I installed an MSD 6A box, MSD coil, Taylor wires and did the normal spark plugs, cap and rotor and fuel filter. Only put about 3,000 miles on it since then (it spent most of the time at the body shop getting paint and body work).
When cleaning the IAC, I noticed pitting on the pintle. How tolerant is the pintle seating area?
The engine, other than the ignition described above and in my sig, is stock. Still has all the smog equipment installed and the car only has 54,000 miles (Hawaii car originally). I am forgetting something. I'll post updates as I continue.
Mike
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