Hey All,

I have a '96 auto Maxima. When the car is cold it runs great. No issues at all. Car starts up all the time no issues. When the car gets to operating temperature and maybe 10 minutes after that, the car starts to hesitate horribly! It does it at idle and ALL RPM ranges. The car idles where it should, but will stutter at idle.

Any ideas? I can't think of what would be causing the car to run so bad only when warmed up. Also, when it does this it won't stop. It's continuous and consistent it's not like it comes and goes.

I've had this issue for a while and have troubleshooted it a few times but couldn't figure it out. Looking for suggestions.

Thanks!

 

easiest place to start is pull one of the spark plugs and see what it looks like. also try cleaning the MAF, 2 easiest starting points

 

spark plugs are fine(something I checked in the past), maf is good afaik. Why would the maf start acting up only when heating up?

More I think about it and read, the more I think it's a clogged cat. I do get a code for the rear O2 sensor every now and then.

 

Its one of your coils.....finding which one is the hard part. Best bet is to buy a bunch of used OEM coils from the junkyard. Replace 1 and drive around. Keep doing that until the problem goes away. Testing the coil with a multi meter wont help, unless you can test a hot coil. That could be rather difficult

As for your O2s, replace only the primaries...even if the code is for one of the secondaries. This assumes you've never replaced them before.

 

It's definitely one of the coil packs. Get the engine hot so it's miss firing the pull the plug off rack coil one at a time. When you get to the coil that's acting up, there won't be any change in the roughness.

 

Well, 2 people who are confident it's a coil pack. I'll start there.

I did multimeter them in the past, but if one of them is acting up only when heated up, then I wouldn't have noticed.

Is this a common symptom of one that fails? Why would the whole engine hesitate if only 1 cylinder is not firing? Almost seems like everything cuts out for a split second. What is it about the engine heating up that causes the pack to go crazy? It's designed to take a lot of heat.

This is frustrating as if it's an electrical part that's malfunctioning when heated up it could literally be anything. Why not the injectors? What is it about the coil packs that malfunction when heated vs some other component?

 

The ignition coil is like a portable box of lightning. After some time, especially given that it's sitting inside a hot cylinder head, the 'box' can no longer keep all that lightning in check and going to the spark plug where it should. Fuel injectors at least have a cool liquid (the fuel) to keep its temperature down. Besides, your symptoms are classic failed ignition symptoms.

 

I hooked up my consult cable and noticed tha car is basically overheating.

Anyone know what operating temps you all are seeing on your cars?

I know the fans seem to be coming on @ 203 or so. My car will run upwards of 210 while the car is moving which makes no damn sense. I think the heat is the main issue. If I can fix that I think my hesitation issues will go away or diminish greatly.

I also turned each cylinder off one by one and didn't notice a single one which made the hesitation go away which means it's an engine-wide issue or more than one cylinder is having this issue.

Also from consult, I'm confident it's not the MAF or TPS because I didn't see them 'jump' when I got the hesitation.

I'm gonna figure out the temp issue and go from there. Probably the thermostat, but if that doesn't fix it then I'm guessing the cat is the main issue of all my problems. All the symptoms line up.

New thoughts?

 

I would think a clogged cat would make it run bad cold or hot?

If it's running this way only when its at operating temperature, I would say look at sensors that only function when at operating temp. The oxygen sensor readings are only used once the car reaches operating temperature. You also have a code for bad o2 sensor. I'd start there. I believe you can test it by unplugging the o2 sensor, then running the car. It should use pre-programmed fuel/air ratios with the sensor unplugged and it should run better, if the sensor is in fact faulty.

A bad knock sensor can also cause it to run like crap/cause hesitation when accelerating when warm as it affects your timing.

Overheating issues? Hopefully not a bad head gasket (which would contribute to killing your o2 sensor)?

 

You can download the FSM from here;

http://boredmder.com/FSMs/Nissan/Maxima/

Still think its a coil. If its the cat, you would less likely get a misfire, and more a loss of power.

Strongly doubt the thermostat as well. I belive that its designed to fail open as opposed to fail closed. So a failing thermostat would have the engine run too cold or take too long to warm up, not overheat.

 

I'd guess a bad knock sensor, which would lead to limp mode, would make the car run super slow, but shouldn't make it hesitate as it basically would retard timing.

In regards to the cat causing issues with the car cold/hot -- I think the cat is the reason for the heat, which is causing the hesitation. So yes, the cat is clogged when cold, but due to it being clogged, it causes the car to heat up and then that's when the car hesitates. Cat causes hesitation through overheating, not directly.

I don't get any white smoke nor great loss of coolant so I'm ruling out head gasket.

Coil pack causing the car to overheat? explain. Also, I've had thermostats go bad and trust me, they can basically just not open so thinking they can't fail closed must be some sort of myth.

 

A bad KS doesn't cause that drastic a performance hit. The ECU just uses a program which assumes 87 octane, even if you have 93 octane in your tank. I had a bad KS in mine for like a year.....you can drive your car forever with a bad KS......you just wont get the maximum power out of your car.
Actually you said overheat. I'm just saying that the bad coilpack is causing your hesitation.

It makes sense to re-engineer a relatively simple device, especially when its failure could cause extremely expensive engine damage. Warped heads on this car is essentially a new motor diagnosis. It's way too expensive to rebuild a DOHC, timing chained V6 motor. I think most modern car thermostats automatically fail open by design.

 

Sounds to me more like a MAF or IAT sensor. You said it seems like everything cuts out for a second, which leads me to think MAF more than coil packs. Bad coil packs cause hesitation, but more like a stutter, and a bad MAF will cause more of a bucking like hesitation. Just my two cents if you want more input.

 

I checked MAF voltage in Consult and it didn't move wildly or out of spec when the car would hesitate which makes me assume it's not the MAF. Also, afaik, at least on my 200sx, the IAT is only for diagnosis and doesn't actually actively make changes to the ECU, but maybe it's different on the Maxima.

::EDIT:: In the FSM for the IAT it states: "This sensor is not directly used to control the engine system. It is used only for onboard diagnosis". OK, so like my 200sx.

I'm leaving all options open, but I'm more concerned about the overheating currently. I need to figure that out first and if I still notice hesitation after I fix the overheating I'll dive more into other stuff. I'm pretty confident, however, that the overheating is directly related to the car hesitating.

 

I had a thermostat failed closed on my Max not too long ago. I think they get corroded around the valve part and that causes it to stick.

 

Bad coolant temp sensor causing a lean or over rich condition and telling you your overheating when your not?

Bad ks will not cause a miss or hesitation. You will just loose some power and fuel economy.

When unplugging coils, your not looking for one to smooth things out. Your looking for the fi e that make it worse and the one that makes no difference.

 

Surprised it took 16 posts for someone to say ECTS. Check that with a multimeter, it's really easy to do. Follow the procedure in the FSM.