I've been trying (off an on) to track down the source of a bad miss for a couple of months. It started right after a timing belt change.

Symptoms: Runs fine (normal) when engine is cold. After engine is hot, sometimes immediately, sometime after several minutes, a bad miss starts (sounds like a lawnmower!). RPM range is normal, but there is a definate loss of power (I'd say 25-30% loss). I can usually make it start missing if the engine is hot and I accelerate with wide open throttle. After that, the miss won't go away until the engine cools. It is reluctant to start when hot, but has never not restarted.

I performed a tune up, plugs, wires, cap, rotor this past summer. A mechanic friend put some sort of analyzer on one plug wire that gave a display of the plug firing pattern and said it (firing pattern) looks fine so I'm largely ruling out the electrical side. I have replace the fuel filter and run injector cleaner through the system and 1 vacuum line. No change. I don't thinks it's injectors since it is so temperature dependant. I checked ECU and replaced Ox Sensor and Engine Coolant temp Sensor (had a code 13 and 33). After that it runs a little better cold, but no change when hot. Rechecked ECU - no errors.

I am at my witts end with this. I am leaning to a sensor since it is so temp dependant, but which ones should I start with? Or could this be somthing else entirely? Someone help!

 

Hmm, after timing belt change eh? Who changed the timing belt and did they make sure timing was adjusted afterward? I believe timing can cause your problem.

 

I trust the guy who changed the timing belt (brother-in-law/professional mechanic). We changed the belt together so I know it was done right and yes, we adujsted the timing after it was compelted.

After some time in the engine bay today, I think it may be injectors. The car has over 300K on it for reference. I believe the injectors are the original. Wiggling the wire at the fuel injectors would frequently make a noticable difference in the engines smoothness at idle. There was some minor green corosion on the injectors and plugs I could reach, so I cleaned them (vinegar) and blew them out to dry. I also Ohmed 2 of the injectors so far and am getting very inconsistant results. Shouldn't these be around 10 Ohms for a 90SE VG30 (per the other threads I've found)? #6 was either reading infinite or 12 Ohms depending on which direction/how hard i pushed against the contacts. #4 was pretty consistantly around 53 Ohms. I also checked the voltage at the leads and they all were 12V, so I think the wiring is OK.

After cleaning the 5 connectors I could access, it smoothed out a little, but fiddling with the connectors still gives mixed results. Is simply checking resistance a sure-fire check for a bad injector?

I suspect as the engine heats up, the resistance in the injectors is going up. Is this likely?

For my 81 Z I know someone made a better aftermarket connector that was less prone to breaking than stock. Is there such a replacement connector for the VG injectors?

Thanks.

 

3rd gen maxima injectors should be 10-14 ohms no more, no less. So that 53 ohm injector is most likely the one causing the problem. All others should measure 10-14 ohms if not then they're bad

ColombianMax

 

temperature actually will cause your injectors to work intermittently. especially what you're describing (works on cold start then goes out). 89-92 injectors will get that green corrosion making resistance checks inaccurate. scrape em to get an true reading. But before that, start the car, wait till it starts missing, then pull your spark plug wires one at a time and find out which injector(s) aren't spraying. it could be corrosion but if you just clean the terminals, there's a good chance it won't make a bit of difference, although you did say wiggling the harness helped, so you can try if you want, just don't be surprised if you have to take the plenum off again to replace the injector(s).