Engine Performance problem
1991 Infiniti G20 4 cyl Two Wheel Drive Automatic 160000 miles
The engine on my 91 G20 Infiniti with automatic transmission with 160.000 miles has been running rough and missing inconsistanly. I replaced the plugs, spark plug wires, distributor cap, rotor, fuel filter, and PCV valve. The plugs were worn but not fouled. I then turned the ECU to diagnostic mode with no response from the LED lights or the Check Engine light. This blew the 75a fusible link which cause most of the electrical components not to work. I replaced the fusible link. The car started and ran for a trip around the block before the engine stalled and would not start. There was also a strong smell of fuel from the exhaust with liquid coming from the exhaust. All 4 plugs were fouled. I put in the old plugs and the same thing happened, it ran for a trip around the block, stalled and would not start. The plugs were fouled again. I checked the coil and power transistor and both tested fine. Also the fuel pressure was good. Not sure which direction to go in next or how it should be checked.
I would suggest checking the fuel injectors first. Seems they are leaking and causing excessive fuel to be delivered to the cylinders causing the fouling and gas smell.
Remove the fuel rail and injectors.
Make sure injectors are securely attached to fuel rail without the injector wires attached.
Turn ignition On and OFf a few times slowly and watch if the injectors are leaking fuel. If yes, the injectors are bad.
December, 8, 2008 AT 6:01 AM
I'll check the fuel injectors but the part I don't understand is when I took out the plugs, before doing the self diagnosis on the computer, they were all normal. What would cause all 4 fuel injectors to leak at the same time or how could all 4 go bad at once?
December, 8, 2008 AT 7:33 AM
There are 2 possibilities that I can think of.
1. When engine stalled, continous cranking without it firing up would result in flooding. If that is the case, the sparks might be too weak to fire up. Check if the sparks are bright blue, if they are orange, it could be due to a weak coil.
2. The PCM is faulty resulting in no control over the injectors.
3. Fuel pressure is too high resulting in the leakages.
Now that you mention it, I would suggest testing the sparks first. Does drying up the plugs eneble you to start immediately or do you have to wait before you can start?
December, 9, 2008 AT 6:36 AM
When I dry the plugs, I can drive for 2 minutes before it stalls and won't restart. If I wait 5-10 minutes it will restart and idle, but the engine dies if I go beyond an idle.
The fuel pressure tested at 40 psi. The service manual says approx 36 psi and turning the key off then ON will be about 43 psi.
I tested the coils and power transistor using a meter and they tested good.
This weekend I have time to check the spark and for leaky injectors.
December, 10, 2008 AT 4:54 PM
Not wanting to step on KHLow2008's toes, he's heading in the right direction, but could the diaphram in the fuel pressure regulator be popped and dumping raw fuel down the vacuum hose? This is an old GM trick. Just a thought.
December, 17, 2008 AT 10:28 PM
The spark was bright blue.
No leaks from the fuel injectors with the rail off.
Fuel pressure only 4 psi higher than it should be.
The hose attached to the fuel pressure regulator was dry.
I try the self diagnostic mode again (the first time I thought it blew a 75a fuse but perhaps something else cause that?) And it gave " 13" - Engine temperature sensor circuit. Would a bad engine temperature sensor cause spark plug fouling? If not, any other suggestions?
Also, this car will overheat on hot days when the car is not in motion. Would the bad sensor also be the cause here?
December, 18, 2008 AT 8:39 AM
Yes, a faulty ECT can cause starting and engine running problems. It gives false signals to the PCM so the fuel metering is inaccurate.
Overheating when not moving would be a different problem. Possible causes are
1. Radiator or cooling fans, either one could be faulty or weak resulting in insufficient cooling.
2. Insufficient coolant in system. A slight shortage of coolant would cause the overheating.