so sick of crappy idle issues

[Chriskaw440]

Ugh...so flippin sick and tired of dealing with erratic high and stumbling idle issues that my '90 SE does whenever it feels like it. Replaced everything over the last year or so and still wants to jump up to between 1000 and 2000 rpms when idling and its a rough stumbling idle....eventually (and sometimes not....) dropping back down to normal range and very smooth. Then it can start going wacko anytime it's taken out of gear or sitting at a stop light even with clutch in and in gear. TPS replaced, IAC replaced, all new vacuum lines, new spark plugs, new lifters and intake manifold/plenum gaskets, new fuel injector o-rings, etc etc. Cleaned the MAF (gently) and K&N cone air filter is pristine. Maybe it's a vacuum leak but damned if I can find it.

 

For the most part it runs great when under load.....but cripes this idle crap is making want to either just shoot it with one of my .12 gauges or just sell it off for whatever I can get for it and move on to another vehicle.

 

I've had people/mechanics tell me it's a bad neutral switch , and I've had people/mechanics tell me it doesn't have one because it's a manual tranny....

 

love my truck but dang lol.

[ejin4499]

Ugh...so flippin sick and tired of dealing with erratic high and stumbling idle issues that my '90 SE does whenever it feels like it. Replaced everything over the last year or so and still wants to jump up to between 1000 and 2000 rpms when idling and its a rough stumbling idle....eventually (and sometimes not....) dropping back down to normal range and very smooth. Then it can start going wacko anytime it's taken out of gear or sitting at a stop light even with clutch in and in gear. TPS replaced, IAC replaced, all new vacuum lines, new spark plugs, new lifters and intake manifold/plenum gaskets, new fuel injector o-rings, etc etc. Cleaned the MAF (gently) and K&N cone air filter is pristine. Maybe it's a vacuum leak but damned if I can find it.

 

For the most part it runs great when under load.....but cripes this idle crap is making want to either just shoot it with one of my .12 gauges or just sell it off for whatever I can get for it and move on to another vehicle.

 

I've had people/mechanics tell me it's a bad neutral switch , and I've had people/mechanics tell me it doesn't have one because it's a manual tranny....

 

love my truck but dang lol.

Dude I have the exact same problem. Other than the intake filter is yours stock? Does yours go nuts while its in first with your foot off the gas like your rolling through a parking lot? Have you swapped out your o2 sensor? Tried unplugging mine and it didn't do anything different.

I've done the auto to manual swap and swapped in a vg33 block and heads with thorley headers. Maybe we can at least figure out one of our trucks problems.

I've opened up my idle screw on the manifold and that so far has helped a little. Namely when its starts stumbling it doesn't do it as hard.

[Slartibartfast]

Well, don't shoot it, somebody tried that with my project car and it didn't help much.

 

I've heard you can find a vacuum leak with WD40 or something, spray it on joints etc and it'll suck it in and cough or something when you find the bad spot.

 

I'd expect a vacuum leak to be pretty consistent though... have you checked your grounds? Is the computer throwing any codes?

[sewebster]

You could try disconnecting the AAC valve (it's the valve in the idle control body that the ECU uses to control the air going in and therefore idle speed). WIth it disconnected the idle should drop to 700 RPM. With it unplugged the ECU will be unable to use any strange sensor information to adjust the idle speed. If the idle is unstable with it unplugged you know you are looking at a certain set of issues. If the idle is good with it unplugged, then you know that the ECU is messing this up, either because it is bad, or because it is being fed bad information by a sensor (e.g. crank angle sensor).

 

You can unplug the AAC valve at the valve itself, which is inconvenient because it's under the plenum, or at the connection on top of the passenger valve cover. It should be the only connector with only two wires there.

[Cuong Nguyen]

Is the ECU throwing any codes?

 

possible things to check as well:

 

EGR functioning?

PCV valve good?

brake booster check valve good?

Good contacts and ground on MAF sensor?

Power steering pressure sensor connected and not damaged?

O2 sensor functioning and wires not melted on exhaust pipe?

[msavides]

I had been going through the exact same thing.

 

I believe we have even collaborated on a few ideas.

 

Well what has finally fixed it was. I purchased the factory Maf Ground harness repair. Ever since then my truck has not acted up once, it has been over a year and a half.

 

It costs about $30 If I remember correctly.

 

 

I had tried cleaning the ground connectors, replaced all injectors, replaced AAC, TPS, All Vaccuum lines, O2 sensor, Plugs, Plug Wires, Coil, ECU And IAC. Nothing fixed it.

 

Now that I think about it I am kinda pissed that it was the ground all along.

 

Mark

[Chriskaw440]

Thanks for all the suggestions....I will probably NOT shoot it since with my luck, the shot guy bb's would ricochet off the plenum and hit my neighbors cats or something......

 

O2 sensor was replaced also....and I did the unplugging and plugging back in while running and it made no difference so I ruled that out. (also made sure I routed the wires away from exhaust pipes!)

 

ECU codes flash all normal (gotta love the old school red and green flashing lights....)

 

When I disconnect the MAF sensor with the engine running...it dies immediately.

 

Replaced ignition coil also with no improvement.

 

done seafoam and pcv and replaced the brake booster vacuum line when I did the Knock sensor replacement project a while back.

 

I've sealed the dry rot cracks I found in the air intake tube with silicone also.

 

But yeah when it is NOT acting up idle-wise, it runs great and idles as well as a truck with 257,000 miles would be expected to. (has a sputter ever now and then...no big deal...it is old....)

 

sometimes when driving along at a slow speed I can feel the truck surge forward and if I take it out of gear...there goes the crazy idle again...(it started going wacky while driving along..)

 

I've tried adjusting the idle speed slightly and it will still go nuts like before.

 

And yes...rolling through the parking lot at wal mart can be annoying at times as that seems to be when it wants to go screwy just when I am waiting for people to cross in front of me at the crosswalk...vvrrrrrRRRRRROOOOOOMMMMMM

 

"Its not me people...my engine is possessed!" lol.

 

I have seen where some have problems with the MAF wiring or connector....where might I find one of these repair kits or replacement things? How can I check mine...just grab it and wiggle it around to see if it causes any hiccups?

that connector does seem to sit right against the underside of the hood from what I remember...

 

I have never thought about the power steering pressure sensor but it is connected and I did replace the high pressure line about 2 years ago after it developed a pinhole leak...I will check to make sure it is still connected and such.

 

This will give me something to do this coming weekend along with replacing the serpentine belt tensioner on my stepsons girlfriends ugly blue 99 ford escort

 

thanks for the suggestions! -Chris

[adamzan]

Shoot the escort to release your anger lol.

 

The maf repair harness can be found at nissan, there is a thread here somewhere in this section with the part number also.

[msavides]

I got my MAF harness through Rob. Just call him and tell him what you need He will look it up.

 

Grabbing it and wiggleing it around will not help. The issue is intermittent. I tried to use volt meters to check for ground and it was all ok. I think the intermittent ground puts the ecu in a weird state and it takes the ecu a while to recover from it. This was a really weird problem and sometimes it would go weeks without acting up then just when I am about to pronounce it fixed it comes back. I have pronounced this fixed several times and it has not come back. I hope this fixes your problem as well.

 

PART NUMBER: 24079-40F00

ENGINE SUB HARNESS

$19.83 (NISSAN LIST $32.50)

 

Make sure to mention you are a NPORA member!

 

WWW.FACTORYNISSANPARTS.COM

phone 1-866-742-0297

 

 

Rob Lacy

Parts Department

1-866-742-0297

1-214-491-6565

Edited August 10, 2011 by msavides

[Chriskaw440]

Thanks for the info! I will get in touch with them about the part on pay day.

 

But yeah, sometimes it will go a few days and idle fine...and somedays, like a couple days ago....man, it was just non-stop wanting to idle-up crazy on it's on every time I came to a stop light. Of course, after a few moments it would settle down to normal if you waited long enough.

 

I'd like to shoot the Escort...man it is one ugly car...and smurf color faded-blue.

[msavides]

I actually had a check engine light come on, however it was a leaking injector code that did not get added to federal ecu until 93-95 California ecu have this in 1990 - on. So I Imagine the intermittent ground when it acts up the Maf senses incorrectly and causes the ecu to trigger the injectors to add too much fuel, And that continues for a while until the ground is restored intermittently and the excess fuel burns off. So wiggling the connector would not fix it fast enough to diagnose.

 

I only drove my truck on the weekends so that is why I say it was fine for a week. If i drove it everyday I think I would have the same frequency of the problem showing itself.

 

I really hope this fixes your problem. I banged my head against the wall for 3 years until I finally replaced the harness. I knew about the ground issues But figured since I had tested the ground wire and cleaned it that it could not be it. Another theory is that it is not so much a bad ground but maybe a problem with the common ground with other components creating some kind of interference that is affecting the ecu's reading of the MAF. Sounds far fetched to me. The ground harness adds a second ground to the harness and does not just replace the current ground. So perhaps adding diversity to the ground reducing interference.

 

I can sit here a spout all kinds of theories but in the end successfully remedying the problem is the most important thing.

 

Someone here may know more about the electrical system grounds and its effect on sensors and the ecu.

 

Mark

Edited August 10, 2011 by msavides

[adamzan]

Since for some reason that part number is not available to the Canadian dealers (I even had the guy look through all the parts lists and we couldn't find it) for some stupid reason, I fixed it myself. I took the connector and wire off of my parts truck and spliced it onto mine (the wires had come out of the connector) while doing this I soldered an extra ground wire into the harness and attached it to that ground that is on the rad support, it goes directly to the alternator. I have not had this waving idle/stalling/running rich MAF BS ever since.

[msavides]

Since for some reason that part number is not available to the Canadian dealers (I even had the guy look through all the parts lists and we couldn't find it) for some stupid reason, I fixed it myself. I took the connector and wire off of my parts truck and spliced it onto mine (the wires had come out of the connector) while doing this I soldered an extra ground wire into the harness and attached it to that ground that is on the rad support, it goes directly to the alternator. I have not had this waving idle/stalling/running rich MAF BS ever since.

 

 

I agree It is real simple to make something similar. As a matter a fact probably more reliable than the piggyback connector. However I decided to just but the harness since it comes with a new plug that goes on the MAF then the old plug plugs into it. Since I did not know where the problem lied.

 

still not sure

[Chriskaw440]

Update: I was looking at my MAF sensor connection and noticed that the area just before the connector on the wires had been electrical taped all up like crazy and far as I know it must have been like that since I have

owned the truck. So being curious, I peeled off the electrical tape and found this braided wire sticking out and going nowhere...as if it was pulled out from the connector and rest of the wires, and then taped over with

electrical tape. Does this sound weird to you folks?? Any ideas/suggestions? I will try to post a pic here also of it. thanks, Chris

 

 

Edited August 11, 2011 by Chriskaw440

[msavides]

Update: I was looking at my MAF sensor connection and noticed that the area just before the connector on the wires had been electrical taped all up like crazy and far as I know it must have been like that since I have

owned the truck. So being curious, I peeled off the electrical tape and found this braided wire sticking out and going nowhere...as if it was pulled out from the connector and rest of the wires, and then taped over with

electrical tape. Does this sound weird to you folks?? Any ideas/suggestions? I will try to post a pic here also of it. thanks, Chris

 

 

 

 

Seems awfully fishy to me. Perhaps this is your problem. Or a makeshift fix from a previous owner gone wrong. I never messed with mine so I am not sure if that is stock or not. Since all I did was install the factory retrofit harness.

 

 

I think you may have stumbled on your problem. I would check to see if that wire is indeed going to ground with a volt meter.

 

Mark

[Chriskaw440]

Seems awfully fishy to me. Perhaps this is your problem. Or a makeshift fix from a previous owner gone wrong. I never messed with mine so I am not sure if that is stock or not. Since all I did was install the factory retrofit harness.

 

 

I think you may have stumbled on your problem. I would check to see if that wire is indeed going to ground with a volt meter.

 

Mark

 

 

yeah its just doesnt seem 'stock' to me.....just another one of the 'weird' things I have discovered over the years that previous owner(s) have done.

 

When I did my knock sensor job...I found a bottle cleaner brush (wire brush about the size of a test tube bottle...hence the name...) shoved inside one of the valve cover oil breather lines/pipes.

I was wondering...wtf is this doing in there? with the handle broken off too. Duh. I guess someone was attempting to 'clean out the lines', broke the handle off it...and just left it in there.

 

-Chris

[Alkorahil]

Fromthe picture, it looks kinda like it has been cut and a new connector spliced on to me.

[Chriskaw440]

Fromthe picture, it looks kinda like it has been cut and a new connector spliced on to me.

 

 

Im going to gently cut into the harness/sheath to see how the insides look and maybe figure out why this one braided wire was yanked out and none of the others. the connector and sheath around the wires looks

all original/factory to me. I will get a better photo posted later when I have time....I thought my digital camera was on macro...

[Chriskaw440]

...aren't ground wires usually 'braided' wires?

[ejin4499]

yeah its just doesnt seem 'stock' to me.....just another one of the 'weird' things I have discovered over the years that previous owner(s) have done.

 

When I did my knock sensor job...I found a bottle cleaner brush (wire brush about the size of a test tube bottle...hence the name...) shoved inside one of the valve cover oil breather lines/pipes.

I was wondering...wtf is this doing in there? with the handle broken off too. Duh. I guess someone was attempting to 'clean out the lines', broke the handle off it...and just left it in there.

 

-Chris

I think that actualy comes stock. I think IIRC that its supposed to act as a catch for oil droplets from your PCV system. I may be wrong on that though

[Chriskaw440]

well it's not in there now! lol and "oops" if its suppose be.

[JamesRich]

The braided wire is a shielding for two of the sensor wires. It is grounded at the ECM but doesn't connect to anything at the sensor. The injectors and several other sensors have this shielding to protect them from electrical interference from other fields around them. If you look in the FSM for 94 on page EF & EC 10 you can see the shielding is around two of the wires and connects to the ECM on terminal 39.

James

[Chriskaw440]

The braided wire is a shielding for two of the sensor wires. It is grounded at the ECM but doesn't connect to anything at the sensor. The injectors and several other sensors have this shielding to protect them from electrical interference from other fields around them. If you look in the FSM for 94 on page EF & EC 10 you can see the shielding is around two of the wires and connects to the ECM on terminal 39.

James

 

ahhh learn something new everyday. This is why I asked first before ripping things apart lol. Gotta admit though...it looks odd but then again, we're talking technology from 1990.

 

after reconnecting the harness to the sensor and driving it around this morning it didn't act up at all....but I am sure it will eventually, but still makes me believe more and more

that this is where the wacky idle problem is coming from. The connector doesn't even really attach very tightly to the sensor anymore...kind of a loose fitting.

[msavides]

There was a thread (I think on here) that detailed retentioning the connectors for better contact. My connectors did not have a speck of corrosion on them and a retentioning the connectors did not help my problem.

[ejin4499]

so I soldered a secondary ground line to my maf connector (till I can get a new connector with good wires) and the problem is about 90% gone. I still have a minor wobble in my idle every couple seconds or so. Just wanted to throw that in there. Made a huge difference for me. Thanks