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91 Nissan Pickup - Post-squirrel-in-air filter issues

Hi all -
After something got into my truck’s air filter and nested in there, I drove it around for a few weeks. I didn’t realize anything was wrong until the truck started having trouble accelerating. When I finally got to the mechanic, he took out the acorns in the filter but warned that he didn’t know how bad the damage would be unless he took some things apart. He ended up putting the mostly eaten old air filter back and disconnecting the fuel-air connector because the car was driving slightly better that way and I drove the truck home but after a few days of limping around, the truck started accelerating without my putting my foot on the gas and having trouble braking.
Anyone have any idea what it could mean? If I got a new air filter, reconnected the fuel-air, and ran the truck for a while, is there any chance of it recovering or is it too far gone…? I haven’t taken it to anyone else because the mechanic said it was probably not worth even a diagnostic (the truck is old). But it’s never given me any problems before the squirrel.
Any advice would be helpful. Thanks!


I’m sorry, but I don’t know what this “fuel-air” is supposed to be

Can you describe it, or post a picture

You’re using incorrect, or at best incomplete, terminology

I suspect, whatever you disconnected, caused the powertrain control module to use default values instead

Putting the destroyed air filter back was not a good idea. Now any debris has a better path into the engine . . .

Accelerating on its own and trouble braking sounds like you may have a problem with the idle air control system.

Just because the truck is old doesn’t really mean it’s not worth a proper diagnosis and repair. A competent mechanic could probably do a proper diagnosis in a fairly short amount of time, considering you know it’s rodent related damage

Is the truck a rust bucket which has been poorly maintained, and nothing works properly?

Please don’t take offense to me posing the question

But if the answer is yes, then you have to also take that into account

If you sucked a piece of Acorn or Air Filter you might get lucky and find it in the throttle body butterfly…prying it open…and increasing idle and producing acceleration…you need to LOOK

I would also agree with DB4690 he makes excellent points here…

I am also having a little trouble with your terminology…we are gearheads here and things have proper names but I digress… Im thinking your Air connection comment means you didnt hook up the hose from the throttle body to the air filter box? If so you dont have your MAF in the loop anymore and also…throws my debris in the throttle body theory a bit…but since you did run it without knowing what kind of debris you sucked in…it still holds water in my mind

Trouble braking would come from the fact that this vehicle surely sat a while…I deduce this from the fact that a critter made base camp in the filter box…they dont do that on daily drivers. SO…how long did she sit for? Months? Yrs? Your brake rotors are surely rusted…and may not clean up sometimes they do…sometimes they dont…depends on the severity of the rust on the rotors.

Check for debris lodged in the throttle body…something might be propping that open and you need to hook up the MAF if not already done.


I would consider getting another mechanic. I would not have put the old damaged air filter back in. These are pretty cheap and easy to replace. Putting the damaged one back in allowed debris to work its way down the intake jamming things up.

Thanks everyone so far for your imput. Sorry I don’t have the exact terminology. I think what the mechanic did was unplug the MAF.
The truck hadn’t been sitting for too too long - only a couple months, and I ran it every once in a while during that time.
Yes, the truck is rusty for sure and doesn’t have a ton of time left. But, the truck has been maintained well by myself and probably even better by the previous owner who owned it the longest. Like I said, I have not had any real issues with it other than typical maintenance.
There’s a ton of debris in the throttle body and I’m wondering if it’s safe to use a vacuum to suck it out. Or, what’s the best way to clean it as an amateur…?
And, after cleaning that, get a new filter, reconnect the MAF, run it and see what happens?
Thanks, again. This is really helpful. I love my truck and would love a little more time with it.


Thanks for the update

When the mechanic unplugged the MAF sensor, the control module was forced to use default values

As for the throttle body, use carb cleaner or throttle body cleaner to clean it. A spray can is only a few bucks. Spray the carb cleaner on a clean rag, and use that to clean the throttle body.

Replace that engine air filter and plug the MAF sensor back in. It might take a few miles of driving for the control module to figure out what’s going on

Another idea . . . after replacing the filter, cleaning the throttle body, etc. unplug the battery negative cable, and leave it unplugged for several minutes, before starting the engine up again.

also replace any obviously broken vacuum hoses/lines and air intake tubing, which may have been damaged by the rodent

It sounds like there ar shreds of debris past the air filter, Not sure wht to do.

What’s the problem?

Remove the air intake tube. Clean and/or replace, as needed

If in doubt, remove the throttle body for a proper cleaning. And then you can inspect if anything got past the butterfly

Do the best you can

There are two tube to the air filter, one is the air horn that goes from the top of the radiator to the filter and the other is the make up hose for the PCV system. There is a two wire harness that connects to the bottom of the air filter box but I don’t remember what the sensor is, but it is not the MAF.

The MAF plugs into the side of the throttle body. The throttle body sits on top of the intake manifold like a carburetor so airflow is downward. The air filter sits on top of the throttle body so the whole thing looks like an old school carburetor setup, but it is a multiport fuel injection system.

I am going to guess eliyellow only asked for a diagnostic and did not pay for any of the mechanics services, or paid very little and that was why the air filter was not replaced. That was a mistake. Now the intake manifold and throttle body will need to be removed and cleaned out, and the MAF cleaned or replaced. The OEM MAF is no longer available and was $400-500 when last available. There are Chinese made replacements on Amazon and eBay for $20-60 each, but the reviews have them working only about half the time. 50/50 chance but at those prices, buy two. The one I bought worked for me, lucky I guess.

Edit: while you have the intake manifold off, replace the PCV valve. Its about the only chance you’ll have to replace it. Nissan had a very talented difficulty enhancement engineer locate the position for it.

Yes. It was the MAF that he unplugged. It’s exactly what you described, Keith.

Is it okay to use a vacuum to try to clean out the throttle manifold to clean larger debris before using the cleaner…?

You will still have to remove the throttle body in order to get a vacuum cleaner wand down into the manifold. If the stuff that is in the manifold is mostly soft material, it may not do any damage if it just passes through the engine, so you could try to just vacuum the throttle body. Be sure to open the throttle.

You should still pull out the MAF because some debris could get stuck in the tube that feeds the MAF. The MAF is very fragile, not from shock but if debris was to hit one of the sensors in it, it could damage the sensor. While you have it out, you can dip the sensor end into a cup of rubbing alcohol to clean the sensors. You probably can’t vacuum the tube for the sensor as it is too small, but you could blow it out with a spray carb cleaner, with the MAF out. If you spray carb cleaner down the tube with the MAF cleaner in place, it could damage it.

I would remove the throttle body just to check the underside of it.

I mean throttle body

Yes you can vacuum the throttle body, but I still recommend that you remove it.

Yikes. Is that something I can do myself fairly easily?

No, unless you have the tools and for example could easily do something like replacing a water pump and brake pads and rotors and calipers. Removing the throttle body requires an experienced diy’er usually. Shop mechanics do it all the time, so your local shop would be the place to go.

I guess the first mechanic figured the truck was an old one, on its last legs, and a few more acorns down the throttle body wouldn’t affect much. But most reputable shops would have recommended the car not be driven or even engine started until a replacement air filter was in place in that situation. Driving away in that condition just makes a bad problem worse.

The idle speed issue is probably related to disconnecting the MAF, but you may also have an air leak somewhere allowing air into the engine. All the air is supposed to come in via the throttle body. Air coming in elsewhere will cause the rpm to increase, sometimes unexpectedly.

BTW, it couldn’t be that old of a truck if it has an MAF!

Heres an old trick I use for similar instances… Shop Vac…end of hose for vacuum… TAPE a piece of stiff wall plastic tubing…whichever diameter you want into the mouth of the vac tube…and tape off the remaining open space that will leak vacuum… Now you now have suction at the end of a small tube that fits almost anywhere…in plug holes…down Throttle bodies…etc… It may not suck large things thru but it will bring them back to your hand. Duct Tape, Shop Vac, and that white semi clear plastic tubing…works like a charm my man…

I would see what I could see first…I mean its not as though you sucked in a bunch of steel BB’s…your debris if any could be harmless. But see if you can mitigate prior…because that is the time to so so and that time is now. You should be able to unbolt the TB from the intake and then have a nice 2 or 3 inch hole to go into with the modified vacuum hose I mentioned…sometimes you can unbolt it…sometimes not.

You should be OK without a semi major teardown. Use a piece of that white firm plastic tubing…pick an appropriate diameter…ive used some pretty small tubing and the vac before with fine results…use what diameter you want…Home Depot and Lowes carry this firm plastic tubing…Go to town with it


FYI Blackbird, it has 4 one inch diameter ports under the throttle body, kinda looks like a mini 4 barrel manifold.

Oh yeah…I remember that one Keith…you are correct. But why not unbolt the throttle body and go to vacuum town? Just use the narrow tubing in the normal shop vac hose… Or hell remove the manifold if the fear of debris is so great? Either way…again not like it inhaled steel BB’s or anything


Agree, but my biggest concern would be something that gets stuck in the valve and keeps it from fully closing. I don’t think that nuts and paper will hurt the engine if it passes through, its not passing thru that is a concern. If you vacuum the ports, I’d suggest that the crank gets turned a full rotation and then vac again. That gives him a shot at getting each intake valve when open to clean the faces of anything stuck there.

I cant argue with you there man. I thought the same thing…yes wedging a valve open isnt that tough to do…hell even paper can do THAT… So yes you are on the right page brother.

In addition to vacuuming out the intake…once youre done that…send it down the plug holes as well…just for fun.