2000 Maxima Semi-Rough Idle on Start

[brushandcr]

Hi all,

Hoping someone could make a few suggestions on things to possibily look at/try before possibly taking my 2000 Maxima SE to the mechanic (not mechanically savvy) -

For the last couple of weeks, ~10 seconds after I start the car there is a small period of rough idle. There is minor shaking, but can hear from underneath the car or coming out tailpipe some noise. I had the entire exhaust replaced with aftermarket parts about 2 years ago. After ~20 seconds everything is fine and there is no real roughness when idling at lights or issues driving - only shortly after start.

I did try once to start the car and quickly drive off and when I hit the gas it didn't go full blast, it kind of hesitated and then kicked in to normal speed.

Can anyone make a suggestion on what this coulod be and whether I should investigate myself or take to mechanic.

Thanks much in advance!

[loystock]

There are many possible reasons for your problem. Your best best is to get a free scan from Autozone and the likes to see if there are hidden fault codes.

The noise/rattle from the tail pipe is a consequence of the rough idle and may also be due to loose exhaust pipe hangers.

The problem may be due to fuel delivery (fuel pressure regulator), coolant temp sensor, IACV, MAF sensor, etc. Start with the simple one by checking the entire air intake - check/replace air filter, clean the MAF sensor and Throttle Body. Even if you are not mechanically inclined, for as long as you have 10mm socket and drive, and a screw driver, you should be able to remove the entire air intake. We can give you instructions on how to remove the air intake and clean the components, if you would like to tackle the job.

[NutriaforBreakfast]

Really wild guess here. You could check and make sure the EGR valve is not
sticking

[brushandcr]

Yes, if you could give me directions on how to clean the air intake it would be appreciated if you think I can handle. I may have to get the tools needed to do job (have screwdriver obviously).

As far as EGR valve, where is that located and how to verify if sticking?

Is there any chance it needs tune-up (if there still is such a thing), needs fuel injector cleaned, one of the engine coils is going bad or fuse is going bad? The car during this period is not violently shaking by any means; its slightly shaking, but also doesn't sound exactly 100%. I thought that the key was putting the car into drive while it was happening and not getting full power right away was key - maybe not.

If you go to Autozone, you on your own have to read the codes etc., or does someone assist?

[loystock]

Autozone or other parts store that offer free diagnostic will hook up an OBD II scanner to the DLC (Data Link Connector) in your car to check for trouble codes. They should be able to give you a printout of the trouble code(s) or you can copy them yourself.

For the air intake removal, you need a 10 mm socket and a ratchet drive or bit driver and a screw driver. Start by unlocking the clips on the air filter box (driver side, behind battery). Replace air filter if dirty. Next, disconnect the MAF sensor connector (push in the tab until it clicks to release the plug). Check the condition of the connector and receptacles and clean as required (use Contact Cleaner or CRC MAF Sensor Cleaner). Inspect condition and disconnect 3 rubber tubes (mark them or take pictures if you are not familiar). With a screw driver (or 8mm socket?), loosen the clamp to the throttle body. There could be 2 or more bolts that needs to be removed to fully release the air intake. Separate the air intake from the TB and lift it out. There is another clamp close to the MAF sensor which you could loosen to access the MAF sensor. Use CRC MAF Sensor cleaner (@ $8 from Autzone) and spray into the MAF sensor element (inside the tube). DO NOT touch the sensing element with bare hands. For the throttle body, use Carburetor Cleaner (@ $4) and a rag to clean it. Never spray directly into the TB as the cleaner can seep into the TB sensors and damage them. During re-assembly, apply Dielectric Grease (@ $10) on MAF Sensor connector to prevent oxidation/corrosion.

Per your information, the rough idling is only when the engine is cold and goes away when engine warms up. So the coils and plugs should be good. If the EGR valve is stuck open, then you will have a rough idle (too much air into combustion chamber). A vacuum leak can also cause rough idle and lousy acceleration. A sticky/dirty IACV will cause rough idling. A defective Knock Sensor will result to crappy acceleration (no effect on Idle) due to ignition timing retard. Other sensors, when erratic, could cause rough idling.

Again, due to numerous possibilities as to what is causing your rough idling, get a free scan first, check the condition of the air intake and look for obvious sign of leak. Clean intake components as required. Refer to the link below for access to the FSM (Factory Service Manual). You can read the various chapters but pay close attention to EC (Engine Control), EL (Electrical System) and MA (Maintenance).

http://www.nicoclub.com/FSM/maxima/2000/fwd.pdf

[NutriaforBreakfast]

Go to the ec.pdf section to see where the IACV is on page 20
I couldnt find the EGR valve

[brushandcr]

Thanks for the info; will check it out on Friday/Saturday.

Not sure if this is related at all, but over the last few weeks I have also noticed a "rattling"/"knocking" when accelarating from what seems underneath front driver's side. I have been mixing regular and high grade as I can't afford the premium these days; not sure if its related or something completely different - but wanted thoughts as well on it. Is it possible all of this is related to something breaking/wearing on exhaust?

[loystock]

It could be the exhaust pipe or the engine mount - you have to check them yourself or your trusted mechanic.

Get an OBD II scan ASAP.

Premium fuel is recommended in the Maxima for optimum performance but is not required. For as long as you use Tier 1 gas, regular or not, it should not be a problem as the Knock Sensor-ECM combination can detect 'knocking' and adjust ignition timing as required. I hope nobody 'cheated' the ECM by installing a 550K resistor in place of the Knock Sensor. In that case, the engine may be knocking but the ECM will never know about it, hence the possibility of destroying the engine.

[brushandcr]

Sorry for the late reply, but came down ill and had more urgent things to deal with.

In any case, I had a friend's friend (previous mechanic) who happened to be local and lent me a hand with the intake and he thought that it it looked fine. I then went to Autozone and there were no codes pulled up on the computer.

Additional information:
- I had the car idle for 5 days and when I went to start it up, it did start and was a little rough and then stalled. I waited 20 seconds and started it back up and it hummed a couple of different tunes and then was ok
- When it starts up, you hear a specific hum and the rpm sits at ~.4 then when it gets to the 2nd type of hum it jumps a bit as soon as it gets to the 2nd hum to ~.6 then slowly goes up to ~.8 and then goes to 3rd hum type (could be back to 1st tye of hum) at that point the car is ready to go (~a total of 20 seconds before driveable). If you go to drive and hit the gas during this period the car feels like its stuck in the mud and then when it hits the 3rd hum you have a jolt of the car (literally) and then have full power
- May be a tiny bit rougher idling in the colder weather (now that it is getting colder) and worried it may start stalling at lights when the temperature really drops but hard to tell if this will occur or just on start up only

I guess I could go back to Autozone and re-test, but may have to bite the bullet and take to a mechanic. Any other ideas?

Q's:
- Is there such thing as a tune up that is needed? (73K miles)
- Could it be any type of belt? I had 60K service and said belts looked good and I haven't checked them very well.

Thanks again for the help. I obviously don't want to do more damage by driving but don't want to be told by mechanic it is one thing and spend hundreds of dollars and doesn't fix the problem. I've gone to them a number of times and are ok, but did tell me I needed an expensive part most likely due to error and has never come back. Therefore, want to research as much as possible myself before biting the bullet but don't want to damage engine, etc. as I was hoping to hold onto it a couple more years as mileage is pretty low (but still a 10 year old car).

Thanks.

[brushandcr]

I figured I would give an update since it could help someone out in the future.

I brought the car to the local mechanic and the code they finally pulled up was it was running lean on both banks. They tried cleaning the throttle body, but did not fix the issue. They figured it was the MAF sensor and after replacing with Nissan MAF sensor and reprogramming, the stat up is much better (no audible sounds like the car wants to stall). The car also seems better when just driving normally as well.

The part was $113 and the labor/programming was $100.

[loystock]

Great! And the MAF replacement cost is reasonable.That's why I insisted on getting a scan so the problem can be isolated. Symptoms may be the same but the root cause may be different.