The engine misses slightly in the morning when it's humid outside.
When it's raining and the car is idling, the RPMs will suddenly drop, and then usually drop a few more times and stall. The RPM drop happens in drive and neutral, but has only stalled while in drive.

I've had the car hold the RPMs at 4K at WOT a few times, and most of the time there's a noticeable loss of power.

Videos of the RPMs dropping:
http://www.youtube.com/watch?v=1BXH-u7pF-s
http://www.youtube.com/watch?v=AgVyimsJdtw

Video of exhaust when it's missing slightly:
http://www.youtube.com/watch?v=wS_gUMww7J4

I've noticed that the miss stopped when I unplugged the MAF sensor, but returned when I plugged it back in while the car was running. Replacing the sensor didn't seem to fix it though.


Parts I've replaced since the miss started:
TPS
MAF
plugs
plug wires
cap and rotor


Thanks,
Gus

 

It's possible the maf you replaced it with is also bad. you are pearl93ve's cousin right? Get together with him and swap his maf if you can.

It may also be a bad/dirty iacv/acc unit.

 

When I unplug the MAF on my VG it shuts the car off.

 

Sorry, I meant I unplugged the MAF while the car was off, and then started it.

Greeny: I have another MAF as well.
I'm wondering if the ECU ignores other sensors if the MAF is unplugged, possibly a sensor that's causing the problem.

 

That is normal, a good maf will shut the car off when unplugged.

 

Well, if the idle/dying issue is solved by unplugging the maf, then it is most likely the culprit. when my maf went out on the ve, i would stumble/die at idle, until i unplugged it, replaced the maf with a good used one, problem solved.

 

did u check ur coolant temperature sensor and its harness? that causes misfire through exhaust too....

 

He got both MAF's from Goon, still misses when the car is cold. We replaced the CTS as well Burhan. Gus, when was the last time you checked ohms on the injectors? Did you ever end up checking the one's under the IM?

 

how about fuel filter...did u change that too? if havnt been changed since 15000km....if u did then did u check ur fuel pressure with gauge if u did then did u check ur timing? and check ur fuel injectors as well....try these things i m sure its one of these.....if not then we will go after other things.... ( u can check ur compression pressure too if u can )

edit: and see if u can start the car with accelerator fully depressed...( it shouldn't start )

 

I doubt it's injectors. Happens when the car is wet, so I'm thinking electrical. And whatever it is, it manages to stall the car.

I did have an instance where cylinder #4 wasn't firing, but I put some Lucas cleaner stuff in the fuel tank and that stopped mostly. After that it would miss immediately after starting, and to stop the miss all I had to do was get on the throttle a bit.

I do have a fuel injector wire that's only covered by duct tape. Would one injector be enough to stall the car though?

The missing only happens noticeably when the car is wet, or it's raining out, regardless of how warm the engine is.

oh yeah, would a bad air filter let enough moisture through to affect the MAF? It's routed into the bumper by the way.

 

Please just do us all a favor and test each injector. I had a missfire on one cylinder went to replace it and 4 tested bad. These injectors are prone to go bad. When they fail it is usually intermittent. Sometimes your car runs good, sometimes not. At least check them all to cancel a big thing off the checklist. Also when you pull the plugs check the plug itself for corrosion and clean the contacts on the injectors. It is normal to see green residue on them.

May want to watch my video on vg misfire in stickies for other ideas if its not injectors.

 

Replace the fuel filter too... would rule out a possible culprit if it doesn't end up being what's wrong.

 

i've been having this same problem for the past 4 1/2 years and can't seem to find the damn problem as well. i replaced spark plugs, wires, cap and rotor, fuel filter, checked fuel pressure and it was fine, cleaned all injectors with battery acid to remove the green corrosion, cleaned all connectors with contact cleaner and i just recently found out that one of my injectors is pulsating faster than the rest??? does that mean that injector is going bad? i changed the MAF and it still did the same. it only does this when its humid or when its raining. when its nice and dry out it doesn't do it but lately it will even do it when dry as well but once in a blue moon. i am getting really aggrevated with this problem. im going to have to replace all injectors and injector harness's and see what else happens, i will also replace my CTS and O2 sensor since i had faults for those 2 awhile back.

 

How exactly would the fuel filter be affected by moisture?

Tested out the injectors
#4, the one that wasn't firing for a while, ohms from 5-54.
The one I replaced recently was 12ohms
One was 5ohm, another 24 ohms, and another was 11ohms.
There's one under the manifold that I can't reach.

But how would this explain only moisture causing the car to go insane?


edit: any ideas on a bad filter letting too much moisture in, or is this not really possible?

 

Replace all your old injectors before any other parts. them #'s are waay out of spec

 

Ok here's the deal. Suck it up and take that intake manifold off. Its not that hard. Just disconnect hoses, EGR, throttle cable etc. Once you have the IM off then you have direct access to injectors. It is likely your fluctuating reading is due to corrosion and or bad angle to test. With all injectors exposed clean and test again and you will get more accurate readings. Mine all read between 12.3-12.6. No reading or anything over 14 is no good.

 

right...dats wat i was gonna say too...

 

When distr ground is semi-lost, campos signal becomes warped. ---> misfire. Easy test is to add new gnd - when the problem is on, see below. If lost gnd is the problem, adding new will be an instantaneous fix.

All groundings should be cleaned - and NOT with acid. That creates myriad problems... As said above, injectors have specs for a reason.

see http://www.cardomain.com/ride/748507/10

 

Distributor bolt has some weird white crud around it, and the cap is cracked...?


Is that black rectangular box the original ground?
That one was loose for a while, had to fix it.

 

We assumed you had a good cap and rotor per your first post. Looks like you may have tightened the cap too much and it cracked if that white line by the bolt is the crack. So I would do the ground thing get another cap and still check your injectors.

 

Engine would have to be wet to test the ground wire.
Are our engines safe to spray down with a water hose?

Checked injectors by the way, 3 bad. But that's another problem altogether seeing that if I unplug the MAF when it's missing the car runs fine.

 

Try to get focused pics ... FROM inside - the problems [if] are 90% inside. Cracks often cant be seen w/o magnifier lens, bright light, practiced eye. If any doubt, swap (as many as needed) until you get a good one.

No need for water though electrons love skating on it...

All starts from checking charge voltage at batt, ECU....

 

i got 4 good injectors that fit a 93/94 if you want them. i'd send the whole rail of 6 and just mark the bad 2 so you don't use them by mistake

 

okay, turns out the cap is fine.
No cracks on the inside.

Is the intake manifold, top left (two bolt holes there, one with a ground and one is empty) a good place for a permanent ground?

Also, for some reason when I'm going at a constant speed, the RPMs will just jump up around 200RPMs and then drop again. Could this be the crankshaft position sensor as well?

 

well... RPM on an a/t isn't fixed to your speed like it is on m/t.... so there are some RPM variations you'll see as you get on and off the gas, up or down hills, etc, even in the same gear. variation can be as much as 500rpm from coasting to accelerating, in any given gear at any given speed. so you say constant speed..... but are you sure your throttle position is constant? perhaps lockup is kicking on and off erroneously?

 

yeah, throttle is constant. I also have instances where the transmission will randomly downshift into 3rd. I think it's a bad mount though, since it happens a lot on banked turns.

 

that's weird.... i've never heard of mounts causing a tranny to downshift unnecessarily. perhaps your TPS is messed up a little bit? perhaps your throttle cable isn't mounted properly and is getting jarred by bumps?

 

replace bad fuel injectors before you go any further

 

+1 +1 +1 !!!!!!????

Are you still getting these ohm #'s on the injectors?????

If you are sure of the #'s REPLACE THE INJECTORS!!

 

free fix

 

GND: Any place that is constantly and well connected, healthy way, into battery negative, suits the electrons. You decide how well it fits your purposes. Just make sure the connection route exists today and in the future...

Some say electric motors work w/o GROUND. They may be right, dont u still believe em...

Yes its true, it works : http://www.cardomain.com/ride/748507/10




Semi dead injectors suddenly reporting to duty will cause fluctuations. The fluctuating oxygen content caused by erratic injection also causes ECU to adjust erratically. "I got it right" -she would say when asked....

Stop the analysis-paraysis -loop, get on the injector swap work...

 

okay, added the extra distributor ground, sealed the stock one properly. Rained last night, started this morning, and it stalled.

Any other suggestions?

 

Yeah, i suggest you start reading the posts in this thread...

this one--> http://forums.maxima.org/6672325-post15.html

this one--> http://forums.maxima.org/6680762-post28.html

and this one--> http://forums.maxima.org/6680833-post29.html

your own post--> http://forums.maxima.org/6672201-post14.html

Once again, if you are you sure about the injector ohm #'s,(if not sure, retest) if you positive of the said injector ohm #'s then you need to replace the bad injectors, period

 

If injectors fail, groundings never help. List of suggestions above, reread...

"#4, the one that wasn't firing for a while, ohms from 5-54.
The one I replaced recently was 12ohms
One was 5ohm, another 24 ohms, and another was 11ohms."

Your injectors are a heap of crap = lucky man to get it runnin...

 

Yeah, 3+ Injectors not in the right OHM can't be good. Are you saying the car has ran flawlessly the past few days when it hasn't been raining though? No Morning trouble at all? This happens ONLY when it rains outside or it's a very dewy morning? Either way, I think if it's something strong enough to actually stall out your engine, it's not going to be a sensor. It's your car struggling to stay running with uneven or possibly even no gas being injected.

Also guys, when I sold my parts car to my neighbor he swapped out the engine that was in it and gave me his old 97k mile engine. He said he couldn't get it to stay running because either- A. The headgasket is bad, or B. The head is cracked. That being said, the only thing to symbolize that was the water coming out of the exhaust, but the engine didn't overheat and there was no white/black/blue smoke coming from the exhaust.

Later I come to find out that only ONE of the six injectors ohms out to a correct number. He's an old school backyard mechanic that works on 80's chevy pickups and stuff so he knows more about carbs and stuff and didn't even really know about injectors when I was telling him to check them before he replaced the engine but I don't think he ever did. I've heard the engine running and it has absolutely no VTC clack and was running fairly smoothly.

I guess the only real way to tell would be to tear the engine down to the head and replace gaskets or check to see if it really is cracked..... then build the rest of the engine up from there (If it isn't cracked that is) I guess my question is do you think the injectors could be suspect for the entirety of problems that engine was having?

 

yea, 5 bad out of 6 is more than enough reason to cause a motor to fall flat on its face. It will run on 3 cylinders... it will hate you forever, but it will still run. but try spinning however-heavy of a rotating assembly on only 1 properly functional cylinder (and 5 randomly functional cylinders).... let alone moving the car.

when i went down to Goon's place, i was on 5 cylinders (one injector's coil broke entirely.. NO continuity)... and it ran HORRIBLE. I can't imagine running on more than 1 bad cylinder....

 

Yeah, of course. I don't think any of them have completely broken coils, just think they were continually going out and coming back meaning it would be unknown how the car would drive other than it not being good.

 

It ONLY happens when the car is wet, meaning it's really really moist out in the morning, or it just rained. Cold or hot engine doesn't matter.

Also, with the MAF unplugged it doesn't stall. Plug it back in, and it acts up. Wouldn't this have to be a sensor? The ECU ignores certain sensors if one fails, correct?

 

I know for a fact the ECU doesn't do this with the MAF and ECTS on a 2 mode system. Greeny and I tested that theory a while back and it interprets all other sensors fine. Have you tried both MAF's that Goon gave you? Regardless I think this is all gonna tie to the injectors.

 

i'm done here..