hesitation - cleaned maf sensor

[jertapper]

It was hesitating like others have mentioned (from what I found in searching). So I cleaned the maf sensor and it seemed to help. It hadn't done it to me when I drove it and the wife didn't report it doing it anymore. We thought it was fixed...but it just did it again today on me. (at a very hot time of the day, if that matters...the car had only been running about 7 minutes and the ac was on full blast).

I press the pedal and the rps don't rev up...I then push further and it slowly increases a couple hundred rpm then all of a sudden when my foot gets the pedal almost to the floor the rpms shoot up.

A friend suggested I check the throttle position sensor. Does this sound like it could be the problem? Is it hard to check with a voltmeter? What voltage would I be looking for?

Any other ideas. Thanks in advance.
Modified by jertapper at 6:55 PM 8/10/2007

[yodawill2000]

Welcome to the best source of J30 support on Earth

Could be a knock sensor function.Look at the sticky on this forum about getting a code from the ECU.A Knock sensor code wont cause the Check engine light to go on.a quick Diag is to install the 1.5 megaohm resister on the Knock sensor harness.If you need help on this just reply.A bad knock sensor will act up when it gets hot.Its supposed to hit 104 here tommorrow.Arrrg.Just a fyi. the knock sensor is ignored when the Tach hits 3500 and up, At least thats what Ive read here.That would explain why the engine kicks back in when you open her up.

[jertapper]

Ok...information I left out:

-no check engine light (as others have said)

-seems to only want to do it under load (when it's doing it, if I throw it into neutral it revs as I would expect it to)

I do need some help on locating the knock sensor and what do you mean by "install the 1.5 megaohm resistor"? I might have a 1.5 megaohm resistor around but are you saying one already exists for me to use and it's just chilling in case I need it? That seems strange to me.

Ever since this started I have tried putting some fuel injector cleaner in the tank when I filled it up and also have been sure to use the highest octane whever I fill up. (Those alone didn't seem to help, but I was convinced the maf cleaning worked until today, grrrr).

I have read the sticky about the codes, downloaded it even. What are the chances that there would be a code indicating the problem and the check engine light wouldn't come on? My friend has an obd2 scanner but I haven't bothered to borrow it due to no check engine light.

So, you suspect this sensor is bad and I can do some electrical test with my multimeter and a 1.5 megaohm resistor to see? How much would a new one be? Is the install is pretty simple? How much are they?

EDIT:

SWEET SASSY

Description Year MSRP Price Core Price Your Price knock sensor, j30, q45 95-01 $168.18 $0.00 $129.50 Electrical - Powertrain control - Powertrain control - knock sensor

that sucks

I did some more searching and see that people say the knock doesn't make the check engine light come on. This is a 96 or 95 so I'll have to get a scanner and check the codes if there are any.

Apparently it is also not easy to replace. That's great news. What would be a reasonable labour charge to do the job?
Modified by jertapper at 10:40 AM 8/11/2007

[gr8scott72]

Ok...information I left out:

-no check engine light (as others have said)

-seems to only want to do it under load (when it's doing it, if I throw it into neutral it revs as I would expect it to)

Load based problems are usually MAF related.

I do need some help on locating the knock sensor and what do you mean by "install the 1.5 megaohm resistor"? I might have a 1.5 megaohm resistor around but are you saying one already exists for me to use and it's just chilling in case I need it? That seems strange to me.

No, there isn't a spare resistor just hanging out for you. lol

Ever since this started I have tried putting some fuel injector cleaner in the tank when I filled it up and also have been sure to use the highest octane whever I fill up. (Those alone didn't seem to help, but I was convinced the maf cleaning worked until today, grrrr).

I have read the sticky about the codes, downloaded it even. What are the chances that there would be a code indicating the problem and the check engine light wouldn't come on? My friend has an obd2 scanner but I haven't bothered to borrow it due to no check engine light.

There could be a stored code without a cel, yes.

So, you suspect this sensor is bad and I can do some electrical test with my multimeter and a 1.5 megaohm resistor to see? How much would a new one be? Is the install is pretty simple? How much are they?

Resistor or knock sensor? Resistors are cheap. The knock sensor, I found on ebay, brand new, for $60 and you will want to relocate it to keep from having to get to where the original is so you will want a wiring harness also. Those are about $25 from the dealership.

EDIT:

SWEET SASSY

Description Year MSRP Price Core Price Your Price knock sensor, j30, q45 95-01 $168.18 $0.00 $129.50 Electrical - Powertrain control - Powertrain control - knock sensor

that sucks

Too much, see comment above.

I did some more searching and see that people say the knock doesn't make the check engine light come on. This is a 96 or 95 so I'll have to get a scanner and check the codes if there are any.

So what is your car? A 95 or 96? The 8th character from the end on your VIN tells the year. S would be 95, T would be 96. And if it's a 95, it might be OBD1 which you can't hook up to your buddy's scanner. There is a sticky at the top of the forum to tell you how to read codes on OBD1 J30s.

Apparently it is also not easy to replace. That's great news. What would be a reasonable labour charge to do the job?

No, to replace the original knock sensor would take a huge pile of money. In fact, the dealership here said they wouldn't even do it for me. Too much time. Look into relocating the sensor instead.

But like I said, if it's a load-based problem, you probably still have a problem with your MAF.

[jertapper]

LOL, 8th char from the end is a 'V'.

And my wife has the camera that I took pictures of the MAF with (of course I didn't take them off).

Anyway, I cleaned the maf with the stuff I had laying around that I thought was good enough to clean it with. I cleaned it with this stuff:

http://www.abra-electronics.co....html

Except a spray version.

Is that not good enough? Or possibly my maf is faulty.

Maybe what I used is the reason it seemed to clear up then come back a week or so later?

I took off the air filter cover and sprayed the little tiny thing inside...it was similar to a light bulb filament. That was the maf, was it not?

I also disconnected the connector for it and sprayed in there. Now if we could get this year deal straight I'd find out if I need to get a scanner.

[gr8scott72]

LOL, 8th char from the end is a 'V'.

And my wife has the camera that I took pictures of the MAF with (of course I didn't take them off).

Anyway, I cleaned the maf with the stuff I had laying around that I thought was good enough to clean it with. I cleaned it with this stuff:

http://www.abra-electronics.co....html

Except a spray version.

Is that not good enough? Or possibly my maf is faulty.

Maybe what I used is the reason it seemed to clear up then come back a week or so later?

I took off the air filter cover and sprayed the little tiny thing inside...it was similar to a light bulb filament. That was the maf, was it not?

I also disconnected the connector for it and sprayed in there. Now if we could get this year deal straight I'd find out if I need to get a scanner.

You have a 97 (V) which is OBD2.

You might still have a bad MAF. That would be the next thing I replaced.

And yes, the MAF is just inside past the air filter.

[Pogophil]

FYI -- I also have this problem. Changed the knock sensor (I was getting a code), but the sluggishness persisted. I cleaned the MAF -- it persists. I changed the MAF to be doubly sure, still a problem.

It may be that load based problems are tied to the MAF, but I still don't get it. And, in our case, it didn't solve the problem.

I have this same problem, and it's driving my dad nuts. Hopefully we can figure this out.

[gotspeed]

Pogophil, did you replace the knock sensor in the existing spot or did you relocate it? and if u didn't relocate it did you replace the harness too. Also did you check the harness leading to the ECU? I relocated mines and my car hasn't done it since.

[Pogophil]

Had the dealer replace the knock sensor in the original location.

[gr8scott72]

Had the dealer replace the knock sensor in the original location.

What did they charge you?

[yodawill2000]

Look at his list of cars Scott

Prolly pocket change .. hehe

[jertapper]

Just got back from a few hundred mile trip. It was sluggish occasionally. If I gun it when it's being sluggish (which is usually off the line) I noticed that even if it was below 3k when I put the pedal to the floor (or near it) it the needle would jump up. I'll check the codes tomorrow and see if there are any codes stored in there. Thanks for the help thus far.

[Pogophil]

What did they charge you?

Hey Scott. They charged me $275. I had an indy quote $350.

After agreeing to the work, the dealer was pi$$ed it was such a difficult job, and took FOREVER to get it done. They claimed it was a 10 hour job for them, and should have charged me $1,000. HA!

I definitely knew I didn't want to do this one, so the $275 and $350 quotes seemed like bargains. I love working on cars, but not if it's an all-day thing, where I'm learning as I'm going.

[gotspeed]

[QUOTE=Pogophil]

After agreeing to the work, the dealer was pi$$ed it was such a difficult job, and took FOREVER to get it done. They claimed it was a 10 hour job for them, and should have charged me $1,000. HA!

I am hesitant about non infiniti mechanics working on my car especially with something so labor intensive, and like you said they didnt know it was that much work involved, i'd make sure they put the car back together correctly. I would also check the harness and make sure that its not the old one that they left on there. You are suppose to change the harness as well as the sensor. also check the wire leading back to the computer

[gr8scott72]

I would also check the harness and make sure that its not the old one that they left on there. You are suppose to change the harness as well as the sensor.

You don't need a new harness. The only reason you use a new harness is when you relocate the knock sensor and you need a new one then because you can't get to the original knock senson to unplug it and reuse that harness.

[Pogophil]

The KS code is gone, so for me that isn't my problem (any more, anyway).

[Q45tech]

Always test idle, cruise, and WOT fuel pressure as a pump slow down can drop pressure to point where acceleration is more than just sluggish.

Won't throw any codes that would indicate the problem other than wating adaptive learn trim at WOT..............or O2 voltage [lean when it should be rich].

[jertapper]

Checked the code....was hoping for MAF....but I don't have very good luck.

P0325 :-(

knock sensor code. Of course.

[jertapper]

Always test idle, cruise, and WOT fuel pressure as a pump slow down can drop pressure to point where acceleration is more than just sluggish.

Won't throw any codes that would indicate the problem other than wating adaptive learn trim at WOT..............or O2 voltage [lean when it should be rich].

These things you mention, would any of those problems actually cause that code and the knock sensor actually be functioning properly?

[Pogophil]

These things you mention, would any of those problems actually cause that code and the knock sensor actually be functioning properly?

If you got that code, it's because you have a bad knock sensor. As a result, the ECU is retarding the engine timing, robbing power. You need to fix it if you want any hope of solving your problem.

Unfortunately, even if you replace the knock sensor, there's a chance the problem will persist (as it did in my case).

Good luck.

[Pogophil]

Just a fyi. the knock sensor is ignored when the Tach hits 3500 and up, At least thats what Ive read here.That would explain why the engine kicks back in when you open her up.

Yoda, I'll have to respectfully disagree with that comment. The ECU would retard timing regardless of the rpms if the knock count is high enough. (I've actually seen this happen while datalogging my Stealth.)

It wouldn't make sense for the ECU to disregard knock above 3500 rpms -- high rpm's are the most dangerous place to be getting knock. The KS is there to save your engine in the event you get dangerous knock, by retarding spark timing. This prevents detonation (aka engine knock). Engine knock is very hard on the rod bearings -- spun bearings (from excessive knock) often mean a damaged engine -- that means you'll eventually need a new engine if high knock persists.

Unfortunately, I know all of the above from personal experience.

Now that I think about it -- given that, even in sluggish J30's, the power usually comes on after 3000 rpms, it may not be the knock sensor that's the problem. It seems like a bad knock sensor would consistently retard timing, consistently robbing power across the rev band. The problem as described by most J30 owners doesn't fit that description (i.e., the power loss is typically evident only up to 2500-3000 rpms).

Thoughts/reactions?

[yodawill2000]

As i mentioned I heard the 3500 thing from someone here.Im by no means a Infiniti tech

[jertapper]

I'm about ready to purchase a knock sensor off ebay and do the relocation deal. Anyone have a recommended seller for me to use?

Thanks for all the help guys. After this I plan to do the shocks/struts.

[jertapper]

Got the knock sensor.

The dealer wants to charge me 45 bucks for the harness though.

[jertapper]

Ends up the dealer says they can't get the wire harness now and that it's been discontinued. LOL

Just my luck. I guess I'll have to try the scrap yards. Anyone have any ideas?

Edit: Anyone think that the harness from a 1990-96 300zx would work? http://www.courtesyparts.com/M..._Code=

I'm pretty sure the knock end would be right. I'd be willing to rig up the other end if I had to...even solder it. Since I'm relocating it, it won't be hard to undo right from the sensor.

[gr8scott72]

I'm pretty sure the knock end would be right. I'd be willing to rig up the other end if I had to...even solder it. Since I'm relocating it, it won't be hard to undo right from the sensor.

What do you mean "undo right from the sensor"? Undo from the original sensor? If so, then you don't need to get a new harness. The only reason to get a new harness is because you can't get the old one off.

[jertapper]

What I would do is cut the current wires about half way to the sensor...then solder them to a harness for another car...say a 300 zx and cut that one half way to the sensor to get the half that is still connected to the knock i'm not going to remove.

I just need to get a harness for the knock first...for any car that uses the same sensor.
Modified by jertapper at 10:03 AM 9/20/2007