1998 QX4 won't start AGAIN, please help.

[landa220]

Hopefully this isn't going to be too long of an explanation, but our 1998 Infiniti QX4 isn't starting again. The car has 192K miles, but engine has approx 90K and ran fine for the year we've had it.

It ran fine until recently it simply would not start. It would crank but not catch and start. The only available mechanic in small town where it broke down noticed the distributor was cracked and could see "arching" inside.

They replaced plugs, coils, distributor, spark plug wires, changed oil. Car started but was not running right. They presumed the timing was off a bit so they changed timing belt which was due to be changed $oon (soon).

After doing that twice because it was off by a "tooth" after first install, it ran fine. For about a week that is.

There was an increasingly rough idle and a "miss" in it. We had codes for 2 oxygen sensors being bad which have basically been bad for a few months with no apparent complications. But now the idle got so bad that eventually the car would not start.

Now that the car is back home, we were able to take it to the Infiniti dealership to solve the problem. They said the work done before was not done right and re-did the timing belt work.

It started and ran fine...for about a week. Idle was getting rougher and rougher and would shut down at stop-lights.

Returned to the dealership who said the plugs that the initial repair shop installed were wrong and replaced them. The car ran fine...for about a week. Same issues. Now again it won't start at all.

Please let me know what I can look at myself to try to at least get it started so I can sell it. It's not worth much, but worth nothing at all if it isn't running. Otherwise it's a great car to beat around in and still looks fine. It runs great with the exception of at idle.

I can't understand what is changing or deteriorating over a week each time to make it idle terribly until it shuts down and won't start.

Thanks for any direction you can provide to at least get it started so I can try to get it to someone else or fix this myself.

[Slumpert]

My frist thought is the computer needs that time to switch to closed loop mode.
If your O2 senors are bad or there is one of the dozen issues casuing the alert can certainly result in your symptoms

[landa220]

My frist thought is the computer needs that time to switch to closed loop mode.
If your O2 senors are bad or there is one of the dozen issues casuing the alert can certainly result in your symptoms

Thanks for the response Slumpert. I think that will be the main thing I'll correct are the two bad sensors. Thanks for the confirmation that this COULD be a cause.

Also, what is "closed loop mode"? Is there a way to revert it?

Thanks again.

[Towncivilian]

If you post your current engine codes, we can find out which sensors are bad. If they're just the rear oxygen sensors, they would not cause starting issues because their only purpose is to monitor efficiency of the catalytic converter.

Closed loop mode is desirable; this is what the engine runs as at operating temperature. When first cold started (and in certain other conditions), the engine runs in open loop. If you wish to learn more about open and closed loop, see page EC-20 of the factory service manual.

[landa220]

Since the car won't start, I cannot get the car to the nearest auto service center for a code. HOWEVER, the previous codes that have been active for about a year are as follows.

P0131
P0151

Can anyone confirm which sensors these relate to? I'll start by replacing them.

Thanks again to everyone for your help. This is truly the best forum for troubleshooting issues and sharing results.

[Towncivilian]

Those are both of the front oxygen sensors. You can try to follow the diagnostic procedure as best you can that's described starting on page EC-169 of the factory service manual, but more than likely it's the oxygen sensors themselves that need replacement.

Advance Auto Parts has the upstream left and upstream right Bosch direct-fit oxygen sensors (Bosch is the original manufacturer for the sensors on our vehicles) for $101.48 before tax if you order online using discount code TRT41 and pick-up in store. You may need to call the store to check for availability or have them order the part to your store. If you'd rather not go through all that hassle, RockAuto has the same sensors for about $114.50 including shipping after entering discount code 6892D28E6E22 into the "How Did You Hear About Us?" box in the shopping cart.

[landa220]

That is excellent Towncivilian, Thank you. That's a great price as well. I remember that we should use the Bosch as they are OEM on these cars.

I should have the money to change them next week so that's what I'll do.

I truly think in spite of the chronic issues with the idle, it has to be something simple. Why it progressively gets worse over a weeks time is beyond me, but changing these sensors will at least resolve one huge potential problem.

I believe I should check the spark plugs to see if they are fouled due to it probably burning rich even though they are only about a week old. What do you think? Let me know if there is anything else I might check as well.