Hello guys,

Well this is my first post and I hope you can help me out here. I have done a search and I have found a few clues about my car misfiring but perhaps I need some more re-assurance that I am not looking into replacing the injectors..

Here is the scoop: I have a 1989 Maxima with 205K miles and it has been running great until about 2 weeks ago... I did a MAJOR tune up at 180K miles (TB, all wires, filters and so on)

So my car runs great when I first start the engine.. Yes it has lost some power but mainly due to its age... Then when it gets warm it starts misfiring bad really bad like if it was running in 4 or 5 cylinders...

I took the plugs out and they were all within specs except for one that was white and had the porcelain part a bit yellowish... so I installed new spark plugs last night(gapped them at 0.044)... measured resistance of wires and they all had 1.5K ohm at the most...check the ignition coil (~1.1 ohm), cleaned the cap/rotor, installed new fuel filter, air filter and nothing...

It seems to have power but I know lately it had been pinging (use 89 octane BTW)!

So the car then misfires all day long and I am afraid of causing more damage..

Could it be the injectors, the EGR, the PCV or the IACV? Remember the car runs great for the first 15 minutes in the morning and then like crap.. like if a valve gets stuck or something after the car has reached its normal temperature...

Have you guys seen this before? If so what could it be?

In advance, I wanted to thank you for your help...

Carlos

 

are you getting a check engine light? even if you aren't you may try seeing if the ecu pulls up any codes. has the o2 sensor been replaced? that's about the only thing i can think of. possibly the knock sensor since it has so many miles. only time i've had backfiring was when my plugs were fouled really bad. what kind of plugs are you using?

 

Yeh if it's pinging, it might be the Knock Sensor.

 

I am not getting any check engine light...

Yes the O2 sensor was also changed when I did my major tune up. Besides, having a bad O2 sensor will make it run rich since the ECU is not reading the right voltages therefore it goes to a default config which richens up the mixture right? This shouldn't cause the engine running as if it was running in 4 cylinders I believe.

Since it started pinging on the "crappy" gas we all get in the Republic of California I am going to check the engine timing next, but still this would cause the symptons I am describing right? It will ping yes but it shoudn't run as if it's misfiring.

How do I locate the IACV?

Thanks
Carlos

 

might be obvious, but did you change the coil?

also, I hope I don't get flamed for saying this, but try a known good MAF in it and see if that fixes it. find anyone with a 3rd gen max (the MAF is the same) and see if that fixes before you try anything else. there was just long thread about how it's not always the MAF...but this is symptoms of a faulty MAF...

 

I did not change the coil but I measured the impedance across... ~ 1 ohm (actually 1.1 ohms) which is what the manual says it should read.

If it was the MAF, then shouldn't this be always failing? As I said, early in the morning the car runs fine for about 15 minutes until it warms up I believe and then it will run like this all day. Very confused here.

I guess it's a sensor getting stuck either open or closed related to a vacuum leak perhaps?

Thanks guys... This forum is great.
Carlos

 

a symptom of a bad MAF is the car running bad once it gets warm, so it makes sense...although after it gets cold again it should run fine till it gets warm again...hmmm

 

First I recommend getting the engine warmed up and then removing a plug wire from each spark plug. If you have any bad/failing injectors or plugs this test will find it. Basically what your looking for is any cylinder that doesn't run as bad as the others with a plug wire removed. Also when U did the tuneup, was it with OEM nissan parts?

I've found out that our cars are picky about its ignition parts and OEM tend to run the best majority of the time. After that is done I suggest putting the ECU in diagnostic mode V and see if it detects in problems in real time.

 

A bad MAF would let the car run, you just can't rev it past 2400rpms (well, on the VE this is true, maybe not for the VG).

Did you try checking your ECU for any codes? Search for the forum for the process. It's been posted here before.

Edit: your CEL doesn't have to be on for your ECU to be throwing codes. I had a code 12 and a code 34 (MAFS & KS) and my CEL light wasn't on.

 

Check for a vacuum leak. A rubber hose is probably cracked someplace. You can sometimes hear a hissing sound or you can get a can of carb cleaner from the store and spray it around the engine near the hoses, TB, manifold. If you spray the leak the engine will speed up.
With a pliers pinch off the hose the goes to the brake booster. If the engine smooths out the booster is no good.
Seen this happen lots of times.

 

Guys,

This is what I discovered today:
I cleaned the IACV with carb cleaner and I went for a drive this morning... I got excellent response for about 20 minutes... then the misfiring came back.

I started forcing the EGR valve to open/close and guess what the problem went away... I drove for another 10 minutes and the car was fine...

Then the misfiring came back... and w/o turning the engine off I sprayed carb cleaner in the EGR valve opening... It kept misfiring but as I drove away the problem went away...

To make it short.. Is my EGR valve getting stuck? If the EGR doesn't open/close it lets vacuum when it's not supposed to?

Any ideas here?

Thanks
Carlos

 

Hi Pololo,

Did you ohm the coil wire. I had the same exact symptom on a `90 that I used to have. It ran great until warm....then just skipped big time when warmed up. My coil wire measured infinite, but still managed to run do to the internal arching that it did when warm.

 

Maybe it could possibly be too much water in the gasoline, since you were stating that you get crappy gas in cali, Here in Florida you have to stay away from some gas stations, the gasoline is horrible

 

Guys...

Update: Yes I did measure the ignition coil as I stated previously (~ 1.1 ohm) which is within range.

Definitely it could be crappy gas...

Now the "funny" thing is that now it happens only when you first turn the engine on for about 5 minutes and then the problem goes away...

Last night I filled it up with 89 and I poured an injector cleaner. I also retarded the timing to about 13-14 degress... no more pinging.

It seems as if the car is going back to normal... but I am still concerned about the EGR valve. When the misfiring was happening today while I had the hood open I "played" with the EGR valve and the problem went away... so this got me thinking...

This car has been great trouble free for about 7 years since I bought it... but I guess it's time to move on to something else. Don't want to keep spending time and money on a car that I won't even get $1K for.

Any ideas?
Carlos

 

EGR valves can get carboned up and not close. This will cause a rough idle and poor gas mileage. They can be cleaned.

 

Hello,

I don't have major gas consumption nor poor idle. This thing is really getting old. Now it happens when cold....

However when I really press the throttle hard, I get rid of the misfiring at around 5K RPM and then it's fine again...

Anybody has had similar issues here?

Do I need to open the EGR valve to clean.. Can it be opened up anyway? How do you clean it?

Thanks
Carlos

 

Best way I found to clean the EGR is to remove it and glass bead blast it.
Have you tried to pull a code from the computer??? Might tell you something.

 

i just plugged mine. i hate emissions control bs. helps being in a non testing state though.

 

How is plugging the EGR working???? I would think you would be getting worse gas mileage and maybe pinging .
The computer is made to work with the EGR, but if you could adjust the fuel curve it seems like it would work better than with a EGR.

 

it seems to be running just fine.

 

If your egr sticks open, the car will run bad. So take it off and try to clean it with some carb cleaner. If it still gets stuck, you might have to replace it. Shouldn't be too much. Fix this first. Then see what happens.

 

Update,

This is what I have discovered. After cleaning everything this is what I found:

The car runs perfect when you first start it up in the morning... Actually the car will run fine all day long as long as you don't turn it off...

The problem happens if you turn it off for more than 10 minutes.... Then the car will run like crap all day long.. misfiring like crazy... It'll still have some power but it's like if there was a plug missing.

What gives???

I can't have the %$# car ON all day long right? ... I am getting very frustrated now.

Anybody has any ideas?

Thanks
Carlos

 

If the injectors are original and with ~200k miles on them, then there is definitly one or more that are bad. You can atleast check the resistance on the injectors, it should be between 11 and 14 ohms. But remember they can still be plugged or leaking.

 

VG injectors go bad?
Never seen that happen before.
YEAH RIGHT! they were a shatiss design from the get go so much so that nissan did a recall on some.

 

Well,

If indeed were the injectors, then wouldn't this be happening ALL the time? As I mentioned, I could have the car running all day long and I will have no issue here.

It happens only if I turn the car off for a few minutes after the morning drive.

Could it be the eng temperature sensor? BTW I also removed the spark plug wires while the car was running and misfiring, one by one, and it didn't have any effect on this. The misfiring was a different noise unlike the sound of a missing wire.

It must be a vacuum leak once the car gest hot...

Any other ideas?

Carlos

 

Hi Pololo,

Just to chime back into this thread, I just searched through it, and correct me if I'm wrong, but - have you checked for any codes that may be set. And have you checked the ECU while in closed loop mode - while it's running bad so that you can find out what is going on?

 

Cleaning the EGR Valve

http://www.geocities.com/cbmaxima/maxima/egr/egr.html

I am going to need to do this too. Although, it is really cold outside today.

 

Is this just a sound you hear, or is the engine running rough?????
If it's just noise and the engine is not rough, you need to check the exaust manifold studs.

 

Guys,

Thanks for all the replies...

The car is definitely not running properly, even the idle sometimes is poor so I don't think it could be the exhaust manifolds studs.

The engine light never comes ON and now the problem comes and goes all the time...

Sometmes I feel its shaking/vibration mode so I go WOT and later the problem goes away... Very very inconsistent...

How do you check for the ECU codes? Any writeup on this? I bet it's gonna tell me that everything is OK. :(

I will clean teh EGR valve... It sounds like a hissss... misfiring... It doesn't sound like spark plug misfing...

Tx,
Carlos

 

Sounds like an intake manifold leak or a vacuum leak somewhere.

 

For the ECU, check the FAQ's at the top of this forum or a haynes/chiltons manual. They will tell you what the codes mean and how to do it. Basically you just turn a screw on the side of the ECU, and a light will flash. Also, I would replace all of the vacuum lines around the engine, even if they dont look cracked. Chances are they are worn out.

 

Nismo87se's got the diagnosis procedure pegged. Doesn't this sound like a classic case of a partially plugged fuel injector(s)? Doesn't the 'white' procelain on one spark plug tell use that?????

My 90SE has injector problems and has a lot of the symptoms he's describing - just not as bad. Mine runs great full throttle; it's part throttle that mine symptoms show up.