Really weird problem with an Infiniti G20..

[dj215]

Hello all, I hope you guys can enlighten me on this problem.

I'll try to be as specific as I can..

I have a 1994 AUTOMATIC Infiniti G20.

This sympton occurs RANDOMLY, no specific condition can make it appear, it is RANDOM.

The car hesistates to accelerate during 1.5k-2k RPM, not the motormounts (just changed the transmission and rear engine mount). Its rumbling as it accelerates, but once you pass 2k RPM, it is smooth again. You can easily tell the engine is louder than normal and notice when the problem is gone (problem randomly goes away), and the engine becomes smoother and quieter.

Next, this is an automatic car, during the weird problem stated above, if i try to brake.. and come to almost a complete stop (under .9k RPM) the car feels like its about to stall, it is at a complete stop, trying to jump up and down and stall, but it won't give out. (throwing it in neutral helps a BIT but does not get rid of it, throwing it in park gets rid of about 90% of the rumbling)

Things I have tried:

Checked spark plugs, looks fine, but in the first cylinder there is oil on the spark plugs, i'll get a new valve gasket and replace that.

Cleaned the Idle air control valve. Took it apart, sprayed carb cleaner.. soaked it.. wiped it, etc.

Checked the MAF sensor from the middle wire to the negative battery terminal = .12v, I will reground this so that the difference is less than .09v.

The TPS checked out to be @ .3-.4 (jumps to those two numbers, never more and never less). I know optimally it should be at .5 Volts...

Please, any ideas? let me know..

 

[Quest]

Disregarding the TPS sensor, have you performed the following:

- clean your throttle body with throttle body cleaner (NO ordinary carb cleaner plse!!!!!!)

-clean/replace your PCV valve? It's a screw-on type on the top of the valve cover and it calls for either a 17mm or 19mm box-end wrench to unscrew it.

-have you clean your MAF sensor (the filament type) with CRC MAF sensor cleaner? Again, DO NOT USE ordinary carb cleaner, brake cleaner or even throttle body cleaner. This one has to be very specific cleaner type that would remove oily films, crud and leaves no substance behind.

Reset you ECU by disconnecting your battery afterwards.

Lastly, how is your battery tested out? (load test plse, using carbon pile tester). If your battery is weak or your alternator isn't charging properly like it should, service it properly.

-the only last thing I can think of circa 1994 Nissan variants would be a bad/imtermittent ground reference due to corroded/intermittent/faulty grounding strap between the chassis and the engine block, and/or the chassis and the battery -ve post. Check and replace them if necessary (a proper reference ground is very important to EFI cars)

 

[rat]

Sounds similar to a problem we had with a Buick GS, turned out to be a touque converter control solenoid in the valve body. Don't know if Nissan/Infinity uses this same setup, but worth a check?

 

[wavinwayne]

Remove & carefully examine the air intake hose that connects to the throttle body. I had one crack on the bottom on a '90 MX-6 I once owned. The symptoms were identical to what you're experiencing. Good luck.

 

[g20ooh]

Quest covered almost all of it although on some of listed you would def. see a light/code . If you have already done that list and that didn't get it ,
I 'd be considering ( in reverse order ) ;
AUX. idle air control valve
EGR Syst .
Throttle and cruise control cables , both routing/ TB hook up and function .
Look carefully for a small tear on the " airtube " and vacuum/vacuum hose leaks .
Check vacuum hose hook ups - some might be switched around . ( On the first go around you can use the sticker on the hood ) .
How does it perform with a known to be good plug ?
No lights , no codes ?? ( Either way , this will save you a great deal of time )
( Bottom four simultaneously )

 

[g20ooh]

Sorry WW I didn't see your post .

If this is a factor ,the main thing that happens is the "leak " is opening and closing as the engine " rocks "

 

[dj215]

Wow, so many replies

Quest: I have replaced the PCV Valve a year ago, the TPS sensor was cleaned with Gank's Carb Cleaner and I have cleaned the MAF sensor with the one you've listed a while back... I will try the grounding points. thanks

rat: i'll ask my friend about this, i'm not too sure on this myself, i'll look into it. thanks.

wavinwayne: yeah i notice theres duck tape around my intake hose maybe theres a leak there, but isnt it weird for it to only mess up during 1.5-2k rpms?.. again i will check on it.. thank you

and thanks all for the input, i will try everything and let you guys know what's going on.. (not right now though, snowing

)

 

[dj215]

and g20ooh.. No lights, no codes, this seems to happen more frequently since i've gotten my car back from the shop fixing the motor mount, the thing is I did not remember whether i have ducktaped the intake hose or not.. and if i didn't then that means maybe the shop did it.. so I will double check by retaping the intake hose myself, hopefully all turns well.. this car is a soldier, it will never die on me.

 

[g20ooh]

dj215 , to avoid future unnecc. oil leaks make sure you have and follow correct proceedure/torque sequence on valvecover gasket . Many do the intuitive sequence which is why they get a leak sooner or later .
Thats great , all that stuff you 've already done and will do

, but on this car/engine ( no criticism intended here ) you will usually find its something really simple and its more efficient to approach a problem that way .
So in this case if no codes/light ( and maybe no manual ? ) airtube first , vacuum related second etc or something like that . I really enjoy the ones I have except certain aspects of service access under the hood - if you look closely you can see how much easier they are to sevice in the U.K. and Japan - believe they are .

 

[g20ooh]

Quote:

---

and g20ooh.. No lights, no codes, this seems to happen more frequently since i've gotten my car back from the shop fixing the motor mount, the thing is I did not remember whether i have ducktaped the intake hose or not.. and if i didn't then that means maybe the shop did it.. so I will double check by retaping the intake hose myself, hopefully all turns well.. this car is a soldier, it will never die on me.

---

Well there you go .
We just crossed our posts - I'm doing so much of that here I'm becoming cross eyed

.


I " think " you have the problem in hand - never seen the " duct tape solution " hold for very long on this install .
Unfortunately , the used ones are pretty much the same way and a new OEM one at this point is not cheap , but at some point , you are going to want to replace it - they only get worse with time .
If you do try to find a used one , regardless of year , look for one of two donors . A really old high miler that may have been already replaced , or a MT equiped car .
The reason for the MT is as follows ;
four engine/trans mounts instead of three , and the additional mount is solid so the air tube gets " worked " a little less . Your go /nogo on a used one is usually determined by whether or not your careful inspection reveals an old/tired /thin crumbly area in one of the " accordion valley sections " - just look at yours , it is almost always the same location .
( MTs failure areas are located in one of two spots , one almost same , one different . I think this depends on how serviced and/or driven ) .
Post if your buzz doesn't go away when you settle the motor down .
I like them enough that I just snagged another one about a year ago . Can't kill them unless you beat'em about the head and neck with a very big stick .They are amazingly forgiving of abuse , and I do mean the whole car .

 

[dj215]

thanks for really taking the time and trying to help me out i'll give it a whirl on Sunday! thanks!

 

[g20ooh]

dj215,
You betcha

You want to know the funny part ? Depending on if/which mounts are allowed to go all the way bad and how the engine " settles and cocks " you can actually end up with less " airtube tug effect " going forward . Go figure .
Most of the time its exactly opposite . In fact , loose mounts really tear up the tube and are the bigger part of the story

They really have never sold many of them relative to the G20 population and that plus the fact its one of the stouter ones out there helps make them expensive .
Good to hear all of this thread of yours might help .
Keep us abreast of how it goes .

One other thing , maybe helpful until Sunday .
Sometimes you can get a useful improvement in how a " cut " tube performs by rehanging it nice and relaxed between the airfilter box and the TB . IF it is really AFU , " push " both ends a little bit off their correct position towards the cut . Its also worth a pause at neutral when going from Park to D or R esp. when cold . Minimising rapid throttle movement both up and down helps as well .

 

[dj215]

alright, well i made sure to tape up the intake tube tightly and alot! The reason why I try one thing at a time is to try to figure out what the problem is, now I just need to drive a lot and see if the sympton shows up again because again, it is completely random, and I do not know how to replicate the problem

hope this works.

 

[g20ooh]

One at a time is a real good method .

When I posted bottom four simultaneously I should have written that differently , maybe something like bottom four rapid fire , or bottom four quickly in a row
I was trying to indicate relative weight/what I would consider , so if that came off as must do these four ..... my apologies for not making a clearer post .

Well , back to your G ! If the tape is holding and its running right , then as far as the original problem goes you are probably done !
I say that because of not only your tape fix , but also because you replaced two of the three motor mounts . So on the issue of the airtube , Its likely you have dealt with both the cause and effect .

As to that randomness thing , if the airtube leak was the sole source of the running problem , it does have a consistent explanation .

Your three mounts are all liquid filled and are relatively soft ( keep in mind all rubber mounts allow a certain amount of movement - they have to , to do part of their job ) , so in normal operation there is a certain amount of pushing and pulling on that tube as the engine moves around .

What happens when your tube has a leak is that essentially the tear is opening and closing as the engine rocks fore and aft .
There are many factors that cause a forward or rear movement of the engine , so , it can appear random from the driver's seat .
Easiest way to see how this works is to watch your engine while somebody applies throttle up and down and then watch while they ( at idle ) go from D to R and back .
Now , what I really wanted to ask , is hows it running now ?
" sounds like its good to go "

 

[dj215]

Your posts are really imformative, I appreciate you taking your time to help me out. So far so good! I will drive this car all week to see if it comes up again. I will keep this updated if anything occurs.. Also I do plan on regrounding the MAF today, as that helps with smoothness and I doubt that causes the problem I have been encountering

thanks again

 

[g20ooh]

 

[dj215]

Ah, so the problem persists, when it happens, it is not as rough as usual. People tell me to take it to the shop and get it diagnose but I feel this car is a soldier and I don't have the extra money to spend at the shop.. Maybe I should try new spark plugs, I don't know anymore at this point.

 

[rshaw125]

From just reading your original post it does sound like something to do with the torque converter.

 

[dj215]

Wouldn't a torque converter throw off a CEL? Oh yeah, just to mention, I have a bad knock sensor, but I don't think that should cause this problem..

 

[g20ooh]

This is the problem with not being there ......
Well no biggie .
Lets start here .
1 ) Still no codes or MIL/CEL ?
2 ) How large is the the tear ? ( No amount of tape is going to work once the tear is big enough - appearances can be deceiving on this )
3 ) How is the problem different running wise , now ----compared to prevous ?
4 ) Have you had a chance to check vacuum hoses for correct routing and condition ? ( start by egr valve - airtube - fuel filter area first )
5 )Is everything else that hooks up to the air tube in good order ?
Don't get discouraged , so far , you still have a very high probability it is something very simple and cheap
6 ) After you taped the tube did it however briefly , run all the way right at all ?
7 ) Have you cleaned the throttlebody ?

Lets stick to one at a time and knock down the easy ones first .