Possible vacuum and exhaust leak on a 1993 Q45

[Infinitiguy19]

Ok I know I have made a lot of topics, thought I may not have said very directly. But after getting a long overdue and very deserved break I got a chance to hook up the laptop consult and run some tests. I cleared the "self lean" from the ECU then started the car up, The car still had a stumble in fact it was greater this time than before cleaning the self learn. But the RPM's were lower so according to the FSM (Service Manual) I have a intake leak.

Now I would like to know what the most common place an intake leak could arise from (Wish hose specifically)?

What are other ways of finding the exact location of this leak?

I believe this may attribute to the "ticking noise" in some way. Don't ask how because its a crazy theory.

I was also told by a trusted shop (Lou's Custom Exhaust) that I have an exhaust leak. He said it was in the exact opposite location of my last exhaust leak , So I am unsure if he is saying that because he needs the money or is totally honest. And I say trusted shop because the previous owner of the shop was known thought New England.

But again are there any other ways of finding an exhaust leak?

I DON't WANT to Seafoam!

And I would like to say after reading most of my previous posts: THANK YOU all for your help. I know I wasn't the brightest bulb on the tree (to put it nicely). I would like to thank you all for not giving up on me despite my absolute retarded posts. I can hardly believe I posted some of the stuff, and whats shocking is that some of my previous posts are being repeated by new members.

[maxnix]

You live forever on the internet.

The exhaust guy should be able to demonstrate the leak location with the car running on the lift.

For vacuum leaks, read about leak detector smoke machines. It is either a hose that you thought you replaced correctly or a hose you should have replaced. Or a gasket on the intake. j

[Skibane]

This will probably seem crude by Infiniti standards, but the shadetree mechanic's customary technique for finding vacuum leaks is to spray some WD-40 on the most likely source of the leak while the engine is idling, listening for a change in idle speed immediately after spraying. The WD-40 temporarily plugs the leak, smoothing out the engine for a fraction of a second. If no change in idle is noticed, move on to the next most likely culprit and repeat.

(NOTE: WD-40 is flammable, so take care to avoid spraying it on hot exhaust manifolds).

[Infinitiguy19]

The exhaust guy should be able to demonstrate the leak location with the car running on the lift.

He showed me 4 feet away where it was for "Saftey reasons"

For vacuum leaks, read about leak detector smoke machines. It is either a hose that you thought you replaced correctly or a hose you should have replaced. Or a gasket on the intake. j

All hoses should have been replaced in 2005 when the new injectors, rails and harness was done. I even have some extra hoses and as far as I can tell none are vacuum hoses. The secondary throttlebody gasket was recently replaced allong with the spark plugs. The main TB Gasket is been on since 2005.

I saw as the mechanic was doing the plugs the the two front cylinders has some oil on the coil packs. While thats not good for them (Because there 90 rubber) can that cause a stuble problem?

This will probably seem crude by Infiniti standards, but the shadetree mechanic's customary technique for finding vacuum leaks is to spray some WD-40 on the most likely source of the leak while the engine is idling, listening for a change in idle speed immediately after spraying. The WD-40 temporarily plugs the leak, smoothing out the engine for a fraction of a second. If no change in idle is noticed, move on to the next most likely culprit and repeat.

(NOTE: WD-40 is flammable, so take care to avoid spraying it on hot exhaust manifolds).

I did think of this, but I was hoping for a possibly safer way to find the problem.

I do wonder if Berner (Unknown007) has checked and made sure all of his vacuum hoses because we both share the same problem I think.

[Q45tech]

Find and borrow an UltraSonic Leak Detector which translates the impossible to hear sounds and blocks out all the sounds you can normally hear with ears. Human hearings stops ~~ 15k whereas leaks make ultrasonics >20k and 40-55 KHz is ideal to listen for leakshttp://www.uesystems.com/why_u...n.asphttp://u ... p_9000.asp

EBAY has 16 items at present "ultrasonic detector"Be sure you understand what you are buying as the best units are just hetrodyne and don't need a transmitter. A 40Khz sound becomes a 5 kHz sound so you can hear 35.1> 50KHz.

Used by world class techs to locate wind noise inside car at speed from deformed rubber seals, windshield, you name it................you can zero in to 1/4" of location THEN FIX IT.

[Skibane]

Quote »Quote, originally posted by Skibane »This will probably seem crude by Infiniti standards, but the shadetree mechanic's customary technique for finding vacuum leaks is to spray some WD-40 on the most likely source of the leak while the engine is idling, listening for a change in idle speed immediately after spraying. The WD-40 temporarily plugs the leak, smoothing out the engine for a fraction of a second. If no change in idle is noticed, move on to the next most likely culprit and repeat.

(NOTE: WD-40 is flammable, so take care to avoid spraying it on hot exhaust manifolds).

I did think of this, but I was hoping for a possibly safer way to find the problem.[/quote]It's not a particularly hazardous technique - much less so than replacing your fuel filter or fuel pump, for example. WD-40 isn't nearly as flammable as gasoline. Do it outdoors, keep a garden hose or fire extinguisher nearby, and you'll be fine.

[Infinitiguy19]

OK I just want to add, that I checked the injectors when they were cold (Sitting for 5+ hours in 70* weather) and I checked them while they were hot and only #4 OHMed .3 OHM's higher than the others. Which means that they are due for some redline S1. Or if I feel up to it a BG fuel rail flush.

And seeing as how the Injectors are fine, the plugs were recently done and the MAF sensor works as it should according to the laptop consult and the TPS is at .42 volts (I will pull out the multimeter on this mother and get it to .44 volts since it summer (And coolant has less chance getting colder than in winter temps.).

And I also read in Kiven422 post* that with the MAF sensor unplugged the car should still idle fine in Park or Neutral and that's just not the case here, once the MAF is unplugged the engine shuts off. So is his post correct or not?

I also got a new battery (Costco Battery) 6-8 months ago but I think its kinda weak despite no crazy sound system or electrical doodads everywhere, So I will be getting a new one but I doubt that will do anything. Once I get a new battery I will load test it and see if it passes.

And the motor and transmission mounts are not due yet I think I have 20K+ till there due last time I checked.

I will try pinching the blow by hose as shown in the service manual to add further proof of intake leak. But I think I might go buy a smoke machine at I Party for $60 because that's seems like a sure fire way of finding this damn leak. And because no one around me (Car part stores) have anything but today is Monday so I will be calling some shops in the morning to see if I can find this bugger and get this problem out of the way.

So this leaves the Intake leak through process of elimination. My question was not directly answered:

Are there any intake hoses that could be possibly suspects so I can narrow my search down?

I can't wait to get back my car to a point where is was so quiet I once tried to start it while it was running, It will be a true sleeper.

C'mon plenum pulling people.

*zerothread?id=323719
Modified by Paul Wall at 2:04 AM 7/6/2009

[Infinitiguy19]

No Vacuum leak found after tee-ing in a vacuum pressure gauge. After doing so I got a reading of 20-21 Inches of Mercury.