Q45 idling problem sometimes????

[miata007]

Hello,

I have just joined the forum and hope to get some help on my 1997 Q45 I recently purchased. The car has gotten about 120k and has been dealer serviced since new. After I bought the car, I realized that it's got an idling problem, not sure if it is major or minor. When the car is in idle, the tach. meter shows around 700 rpm and it fluctuate +/-50 rpm at times (at times). The symptom is consistant so doesn't matter if the car is warmed up or not. If put in drive while the car is not moving or come to a stop, the engine dips all the way to 500 rpm and back to 700rpm (also happens sometimes). It feels like the car is about to stall when that happens but has never stalled. Driving on freeway speed, nothing is noticeable. It is very smooth and powerful when I floored the gas. But at speed from maybe 25 mph to 45, I can feel the engine rmp fluctuation is still there. Does anyone have any clue what is wrong with this car?

Talking to several Q45 owners, they have mentioned about the air flow sensor. This part is $300 to $350, I want to confirm if it is really the cause before I change it. Another thing that come across my mind is the injectors? or the coils? I am currently waiting for the service record from the dealer the car had serviced at. It's my fault to not check that before buying this car. Hope you guys can help. Does anyone have any recommendation for a good mechanic or shop(non Infiniti dealer) around the Sacramento area?

007

[3Q Jay]

welcome to THE home of Q45.

there have been a LOT of recent posts on MAFs, so do some reading.

you say the car only idles at 700 on a cold start??

my fy33 o-ccasionally has a low idle and surge when warm start, oscillations damp out after about 10 seconds.g50 does this sometimes too. if only when around ~650 [warm idle], then I'd say IACV/AAC--whatever you want to call it.

but the fluctuation at mid rpm sounds more like a MAF--you could try taking it out and douching it first --do a search on MAF cleaning.if that doesn;t do it, I'd go to general intake cleaning next, before dropping bux on a new MAF.

[miata007]

Thank you for the reply. I did an extensive search on idling problems, coils, injectors, and MAF on this forum and some other forums already. From talking to the Infiniti person at the dealership the car was serviced at, I believe the person said the MAF was replaced last year and the problem didn't go away. I am still waiting for the complete 10 pagesservice record by mail. Also, the person at Infiniti mentioned suggesting of replacing all 8 coils. That's already more than $1000 in parts then add in labor. I really try to stay away from that since it the most expensive options other than replacing all 8 injectors.

I will do some testing this weekend such as listening to the fuel pump, replace the fuel filter, and clean the MAF or check it's connection. By the way, is there a FSM for the 97Q. Most of the postings and materials are for the 1st generation Q. Is the 97 similiar enough to so I can use the same techniques/tips to work on my car?

007

[elwesso]

Welcome to NICO

I agree with Jay. Clean the MAF and its connector and see what it does. Otherwise id clean the IAC and see what that does. also clean the TB

The IAC works by opening and closing a valve a number of times to maintain the idle speed. If it sticks it can cause the problems you said. Its not like other things where it stays open a little, it just turns on and off to maintain things.. take it off and clean it....

I dont think your problem is with injectors or coils...

[maxnix]

Hey, welcome over to where the real Q45 knowledge is, Miata007! (He's a refugee from that Far Away Board)

As I posted over there, intake path clenliness is what is important after all filters are renewed. Mileage? Ever done a rail flush or used BG44K? Quite oftern the IAC valve is misadjusted to compensate for far a badly behaving dirty intake path, which leads to further problems.

[3Q Jay]

Hey, welcome over to where the real Q45 knowledge is, Miata007! (He's a refugee from that Far Away Board)

yah, i knew the name looked familiar-- i never go over there anymore!!

007, you can 'buy' the manual online as a download for $20. i think it's nissan-techinfo.com

tip: download the '98 front suspension, not the '97 they have in the library as it is wrong.

[miata007]

Thanks guys! I am glad we have already met before. Hope I didn't burn any bridges with you guys back then. I bought a techron fuel cleaner today and plan to put it in when filling up this weekend. I remember somewhere in the owner's manual that specifically not to use any fuel injector cleaner. Is that a concern?

007

[maxnix]

Techron is Barbie grade, BG44K is GI Joe grade.

Both are fine, but many others are not.

[miata007]

Finally got a chance to type now. On Friday I received the history report of my car. It shows all the maintainance have been done at a couple of Infiniti dealership. The most common problem of the cars were rotors need to be turn a few times. The customer mentioned several times regarding to this idle problem. Here's a brief history

108k 5/28/04Idle doesn't feel right. Found code P01110 INT/V TIM SOL & KNOCK SENSOR CODES. REPLACED LEFT SIDE INTAKE SOLENOID. Advice to replaced to knock sensor but owner declined repair.

110k 6/23/04Multi point inspection. Code still showed need to replace knock sensors. Declined repair.

105k serviceCustermer complains about same idling problem. Found alphas(???) low.No repair made.

110k 7/10/04Check engine lite on. Confirmed P0301 cyl 1 misfire code. Alphas low. Clean leaves from MAF.

115k 10/11/04112,500 mile service

117k 11/19/04Replace MAF at customer request. Note codes for knock sensors present. Customer declined repair.Fuel injection flush service done at customer request. Please have Mike road test veh...Engine stumbles to almost a stall at stops and surges when..unable to duplicate surging and stalls. Lack of power due to knock sensor codes customer declined repair.

118k 12/06/04Owner states idling problem acting up again. Scan test were not able to confirm misfire.Owner states going up hills requrires almost flooring gas. previous mention of know sensor but pls check

*tech remarks **duplicated a cylinder misfire during road tests. miss is so intermittent that sacn tests are not detecting misfire. based on past experiences, suspect prolem is caused by ignition coils. recommended replace all 8 coils and spark plugs. estimated $2200. Owner declined repair.

120k 2/7/05112,500 mi service

121k 2/17/05brake serviceCustomer reports engine stumbles at times while driving and feels like it might stall. Check and advise road tested and and verifed concern one time for a second then tested several components to determine mass air flow meter.Reroad tested vehicle several more times but could not duplicate concern.

---------------------------------------------------------Over the weekend, I checked the fluids. Took out the air filter and inspect the MAF connector. The filter seems to be ok so I tapped it to the floor to get some dirt out. While the engine is running, I removed the MAF connector. The engine die right away like me shutting off the ignition with key. I read somewhere in this forum saying when the MAF connector is removed, the engine should continue on running????? Is this right or the MAF is bad again. It was replaced November last year. From reading the history, it looks like the problem seems to improve somewhat with the MAF replaced. But record shows the problem hasn't gone away this year. Can you guys give me more advice? Thank you!

007

[miata007]

My problem has not gone away yet. Can somebody give me some help base on the service record before this message. The record shows engine misfired and suggest to replace knock sensors, spark plugs, and coils. So far I have listened to teh fuel pump and seems very quiet. I inspect the MAF connector and seems good. I assume the MAF is good since it was replace new last year. I haven't clean the TB yet.

What does a knock sensor do and how does it affect the engine operation?

Thanks for you guys help!!!

007

[99q45t_vl]

I would replace the plugs and the knock sensors, along with the wire harness. Have the injectors cleaned with BG44, and make sure the throttle body is clean as well. Don't forget about replacing the PCV valves too.

[3Q Jay]

bad ks won't cause the rough idle. will affect your mid rpm power band.

when you pull the plugs [at 120k, you may find your on the originals....] look carefully for any differences. if you see on with more deposits than the others, that could have the marginal coil. not saying your coils are bad, just that the plugs will bear witness marks of what is going on for that cylinder.

[redmanfx]

The TP sensor will cause rough idle as well, mine did when it went bad. It will also throw a code. Joe has them for around 125.00

red