1987 Accord LXi. Car has the 2.0L FI engine with 170K miles. Compression is 170 PSI on each cylinder. Idle when cold is irregular. Once started the RPM hits 1500 slowly dropping to 1000 (over about 10 sec) then drops to 100 and almost dies. The RPM then rebounds back to 1000 and continues hunting for about 1 minute. The idle is still rough until the car is warm and seems rough (vibration) 80% of time at operating temp. while in drive. I have checked for external vacuum leaks, cleaned the IAC and EGR. I have new wires, plugs etc…Over the past year I have replaced fuel injectors, fuel filter, fuel pump and tank. I have the service manual and have measured the coolant and intake temp. sensors that send a signal to the ECU. They seem to be close to the temp/resistance curves in the book. I checked the fuel injector ballast resistors that should be 5-7 Ohms and are measured 12 Ohms. I don’t think these are the problem even if slightly out of spec.. Last weekend I disassembled the distributor to check if oil was obstructing the ‘Cyl’ and ‘TDC’ pick-ups for the crank sensor. They seemed clean. My feeling is a missing/false signal is being sent to the ECU and causing the hunting condition. A mechanic said look for vacuum leaks and question the valve springs and valves. Also there are NO codes set.
Any suggestions?

 

Update: I have replaced the PCV valve and cleaned the ports and hose. It seems to idle better when warm. But, I still have the minute or so cold idle problem. I have cleaned the IACV and tried to isolate it from the problem but to no avail.
More suggestions?


Modified by Dad1999 at 3:51 AM 9/6/2006


Modified by Dad1999 at 3:57 AM 9/6/2006

 

Update: I just cleaned what looks like an idle bleed screw on the front end of the throttle body. The 1/4" diameter needle and seat were covered with black deposits. I brushed the bore along with carb cleaner then blew it clean with compressed air. The car idle better at operating temp. but still has a high idle 2000 at first start(car is overnight cold) for15-20sec then drops to 50 and dies. I am debating removing the throttle body for better cleaning.
More suggestions?