hi guys. ive been trying to diagnose my check engine light for awhile now, and wanted some help from u guys. the car is a bone stock 2000 R. it gets a code 73 (misfire on cylinder #3) at idle. sometimes, the CEL actually flashes at idle. the idle is rough.. sometimes low, and the gas mileage on it is pretty bad. other than that, the car drives very smooth. it pulls about 18-19inch vacuum at idle... and doesnt smoke through the tailpipe

things ive checked:

- valve adjustment
- new plugs, wires, etc
- new intake manifold and throttle body gasket
- TPS voltage
- unplugged every injector and noticed a drop in idle.
- fuel pressure is around 45-50psi with vacuum line on
- compression is 210 - 210 - 180 - 210

i noticed that cylinder # 3 is a tad lower, but i felt it wasnt low enough to cause a misfire. if i unplug the battery, and reset the ecu... the code doesnt come back right away. you would need to idle it for about 15min before its back on. besides swapping the injector out with another cylinder, im not sure what other tests to try out. any help is appreciated

 

update : 1. switched injectors with another cylinder, but still throw cylinder #3 code.
2. redid the compression check and yield 200 220 190 190

not sure what to try next. maybe the primary o2 sensor?

 

Judging from your low compression numbers, I'm going to assume you have some decent miles on the motor. Which means there is probably an aftermarket distributor on there. The thing about the popular 200.00 auto parts store's distributors is most are made in Taiwan and of very poor quality. Cheap internals cause them to start acting up and failing long before an OEM unit would. When I was running these off the shelf distributors (They have a sticker that says "TD-84u or 86u" instead of the metal being stamped like an OEM unit) I was always having issues with the code for "Random misfire on all cylinders". It was like you are describing being fine at idle and fine for random amounts of time but then the CEL pops on out of nowhere. Have to reset the ECU again and again.

Some of the aftermarket units are worse than others but all I have tried only last 15-30k miles. I had one die on me at 8k. Just try borrowing a friends distributor and see if your problem goes away. Sadly, there are not many OEM units out there these days and to get one the total cost adds up to around $600.00 from the online OEM parts sites. Hope this helps.

 

thanks for your input s2kryan. my distributor DOES have alot of miles on it, but still OEM. the code 73 is specifically for cylinder #3. all the other cylinders are fine which leads me to believe the distributor is fine since I changed the Cap and Rotor already. I never did the Primary o2 test after, because after some thinking, I figured that would cause all cylinders to misfire also. I'm out of ideas on how to isolate the cylinder. I guess a leakdown is my only other option.

 

you change plugs and wires to that cylinder? should be one of your first steps. next take a vacuum gage and check manifold vacuum. a stock itr should have 23"hg of vacuum at warm idle. if you're modded up it may change but the needle will be steady. if there is any flutter you have compression leakage that's affecting the engine

generally you won't get a misfire code unless compression is WAY off, like chipped valve off