Car surging when idle.

[wendy616]

I have a 1995 Infiniti Q45 with around 120,000 miles. I have been having a problem with the car surging when I stop and put my foot on the brakes. It feels like when I have my foot on the brake, that someone is under the hood pressing the gas peddle. The rpm's surge when I put my foot on the brake, or even when in neutral or park. Lately it has been cutting off when I slow down to make a turn etc. I have recently changed the fuel filter, but it does not help. The car feels like it wants to take off on its own sometimes, and at other times, it seems like its not getting enough gas and cuts off. Any ideas??

[kevindanielk]

I have experienced the same problem starting earlier today. I came off the highway and before I reached the stoplight, the engine cut out. I restarted it and drove for a few blocks and realized the rpm's were erratic and it felt like it was bucking,surging and trying to stall again. It did finally stall again as I pulled into a gas station. I turned it off for a few minutes and it drove home fine. A few hours later, I went out for a drive around the neighborhood and it stalled on me a few times when turning. I checked and tightened the MAF prongs after I got home the first time, but it still happened. I can hear my fuel pump humming from inside the car. Can the pump going bad cause those symptoms I've described?

[96Qowner]

A noisy, aging fuel pump can cause the FPCU (control unit) to overheat and intermittently cutout from melting (and resolidifying) solder connections.

But your symptoms sound mostly like a bad MAF. They fail internally, as well as in the connector. Here's a recent thread about it:

zerothread/278914

[kevindanielk]

Thanks. I'm going to crack my MAF open and resolder it to be sure. Will post results when I'm done.

[cccpman]

It does indeed sound like a MAF issue. Keep us updated, there are more things you can try if it isnt

[maxnix]

A noisy, aging fuel pump can cause the FPCU (control unit) to overheat and intermittently cutout from melting (and resolidifying) solder connections.

But your symptoms sound mostly like a bad MAF. [/url]

Or maybe a dirty intake plenum, TB, Fuel filter, injectors. This post should be in IOM with a recent maintenance history and maybe some data from a power balance test so we can actually render some aid in diagnosis over the internet.

[kevindanielk]

I will also try cleaning my throttle body and plenium. I'm sorry but I don't know what a power balance is, but I would like to know. I have performed a routine maintainance on the Q a few months back. Fuel filter, plugs, air filter. I guess the carbon buildup is getting to me. Or, I'll have to pull my FPCM and check if it's melting inside.

[Q45tech]

Power balance test have been around since spark plugs and tachometers!Pull a spark plug wire to check if it makes much difference.

Nissan Consult an 20 year old device automated the process and printed out the results of sequentially killing individual cylinders and measuring the drop in idle/fast idle rpm to evaluate the power contribution of each cylinder to the overall rpm total.

Every car manufacturer has has some form of a power balance test for at least 12 years since OBD2.

[lino]

I have a 1995 Infiniti Q45 with around 120,000 miles. I have been having a problem with the car surging when I stop and put my foot on the brakes. It feels like when I have my foot on the brake, that someone is under the hood pressing the gas peddle. The rpm's surge when I put my foot on the brake, or even when in neutral or park. Lately it has been cutting off when I slow down to make a turn etc. I have recently changed the fuel filter, but it does not help. The car feels like it wants to take off on its own sometimes, and at other times, it seems like its not getting enough gas and cuts off. Any ideas??

My car just started doing something similar too. When I'm at a traffic light stopped, the car hunts for idle and and it feels sometimes like it wants to take off and it has shut off twice so far. When I accelerate, it hesitates for a second and then takes off and drives normal. The problem only happens when at idle.

[texasoil]

the surge/slump dance at idle may be a fuel injector(s) not delivering enough fuel and the IAC trying to keep the idle speed correct. A weak cylinder slumps RPM, IAC opens, more fuel-no weak cylinder-IAC closes when RPM rises too much etc.etc Been there.Run BG44 through the injectors, if still an issue, check the injector resistance (12-12.5 ohms.) If more than 14, a bottle of good single malt scotch applied liberally will postpone your sadness over pulling the plenum for removing injectors and sending to Deutsch for cleaning and testing.

[valkyie]

I am currently having the same problem with my car. I was wondering did you ever get this problem corrected?

[q45j30guy]

Check your ATF level. Mine was down 1/2 Qt, when topped off problem solved. Whole lot easier and cheaper then other possible solutions so is a great place to start.

[janc1947]

We are having a surging problem in a 2007 G35 and were told that it could be corrected if we took it in to the dealer. However, an hour after we got there , the service department said there was no fix but they did want to charge us $135 to clean something (don't recall what) We are thinking about talking to the media, this has been happening off and on ever since we got this car, if something is wrong with it, it should be covered under the warranty!

[maxnix]

First, this is the Q45 Forum. Think V8, not V6.

Second, assuming you are not the original purchaser, was this condition not present during the pre-purchase inspection byt the Infiniti technician?

I do not think you are ready for the media with no ducks, let alone oraganized ducks.

[janc1947]

Excuse me if I posted to the wrong forum, but I just found it by using a search engine. I am the original owner and the problem did not appear until we had it about six months (I called the dealer and was told that if I couldn't reproduce the problem, there was no way to fix it) It has only happend 5 or 6 times in the three years that we have had it, but it still could cause an accident and Infiniti appears to not be addressing it.