I have a 1999 Maxima with about 150K miles.
It's been running rough for a while. Generally, at highway speed and steady, it's fine. But when accelerating or idling, it's quite rough.

My daughter in college drives the car, so I'm not always able to directly check it.

Recently, CEL came on. The car was with a mechanic near Daughter's school and they said it indicated two coils that needed to be replaced. So $500 later and a week goes by and the problem starts up again. They said they saw multiple codes indicating specific coils.

My daughter took the car back in. They said it was a code for knock sensor, but they didn't believe it. They cleared it and they lubed the accelerator pedal and cable near the pedal. Sent it home with my daughter and she reported it was much improved.

A week later, problem is back. I had her drive the car home and sure enough it is running very badly. I checked codes and found P1320 which is a generic ignition failure. I took it to my local shop (who I trust) and they say bad ECU. I questioned justification for this diagnosis and they say the ECU is not delivering signal to coil pack to fire. They say they have seen this before.

ECU ordered from Nissan. Will arrive tomorrow. Cost will be about $1158 to replace. They say if it doesn't fix the problem, I don't pay for the ECU.


Opinions? Suggestions?

 

Get a new mechanic. Did they even suggest doing simple spark plug change? Clean the throttle body? Simple basic stuff that'll restore the car to normal. Maybe the MAF is acting up. Replace it with a used one or clean the electrical connections.

Also, you can get used OEM coils for like $30 each. Goto car-part.com
.
Before spending major funds on something, try the maintenance stuff thats related and much much less expensive, like clean the ground connections.

Dont get a new ECU. Yours is fine.

 

I should have mentioned that the first mechanic suggested spark plug replacement, but I declined because the plugs only have about 30K miles on them.

They also did what they call "3 step gum out fuel service".

This included fuel system cleaning with an additive, Induction cleaning and throttle plate cleaning. That was $80 of the $500 total.

 

OK then.

With those symptoms I would then try;

1. cleanning the MAF, or get a used MAF replacement. The MAF is just an electrical part and the only thing that wears out is the electrical connections, such as resistor etc.

2. Replace the coils with used OEM.

Also, goto autozone and have someone read the check engine codes for free then report back here.

The knock sensor doesn't cause erratic behaviour. Don't worry about it for now. You can drive the car forever with just a knock sensor code. all you lose is some performance. In fact, the knock sensor code does not make your check engine light go on. The other codes do.

 

Thanks for the advice. I have my own code reader, so I can do that. I also have a few, spare coil packs in the garage. I'll give it a try. The MAF was replaced around 2007 or 2008, but I wouldn't be too surprised if it was a low-quality after-market part.

 

Are the plugs NGKs?

 

Clean the MAF with electrical parts cleaner or get a used OEM MAF from the junkyard for like $50 from car-part.com

 

Good question. And, were the plugs platinum, or copper? Copper last 30K miles and Platinaums last 60K.

Stay away from Bosch-Plus-Anything

 

Definitely not copper. I'm pretty sure I used platinum NGK's, but would have to take one out at this point to be sure.


I found that it was too late to cancel the ECU replacement without having the mechanic eat the replacement part cost. Since I've taken my cars to these guys for about 20 years, I really don't want to leave them stuck like that. I'm going ahead with the replacement and they assure me that if it doesn't fix the problem, I won't be paying for it.

We'll see....

 

Well......keep the old ECU and sell it here in the classifieds.....you wont get even half your money back but it's something

 

yeah if it was running rough, start with a tune up and go from there.

New ECU???? Junkyard for that part all day. Ppl swap in used ECUs all the time.

 

Clearly you have a misfire.
Here's a few more tips.

1) The 99's are notorious for failing coils as they age. You have a 99....
2) The VQ engine and associated electronics don't like aftermarket coils. (P1320)
3) ECU's don't fail unless they catch fire and burn up.
4) Your mechanic should eat the ECU he ordered, it's not going to fix your issue.
5) Lubricating the gas pedal or cable only makes the pedal easier to depress. There are no electronics there, it's not drive by wire. Was the pedal hard to depress or sticking?
6) 20 years, it might be time to find another mechanic, maybe he's getting old and isn't up to date with computer controlled engines.

Suggestion:

Get a full set of used NISSAN coils, clean up the stalk and contact area on the secondary side. Install them and then come back and thank us.

 

The dealer swapped out the ECU and the engine no longer would start. I had warned him of this, but the dealer told the shop that this car should not have the security system.

So they put the old ECU back in and started off for the dealership to get the new ECU programmed.

Half-way there, the car died, would not start and had to be towed back to the shop.

They found that the flexible hose leading into catalytic converter was basically blown-out. I have photos and it's pretty clear the cat must have become completely clogged. This might have happened during the period the engine was misfiring.

Anyway, the shop replaced both cats without charging me. They finished the ECU swap and now the car is running very well again.

 

ummm, no. Dealer is an IDIOT. ALL 99 Maximas had NATS.
so they did the cats, and the ECU? You didn't have the original ECU back in after they did the cats?

YOU did NOT need a new ECU