MAF sensor questions for those who replaced theirs

I've been using the one that came with my 2000 prerunner when I bout it brand new 15 yrs ago-there's a cleaner you can get at auto parts stores in a spray can, I just take mine out and spray it and let it air dry and put it back in every couple of years. Had a check engine light on it once about 10 yrs ago, cleaned it, and it went away. Happens a lot if you got one of those oil soaked KN air filters, oily film gets on it. Just don't touch those little wires up inside it with any thing.

 

UPDATE:

the last cleaning where I did what you should never do (I ever so gently used a Q-tip to wipe off the sensors) removed some dirt (had some grey ash like residue on the Q-tip) and the truck is acting much better now. I did try to fill the tube so the sensors would be submerged to soak in the cleaner but it flowed into the top circuitry part so I guess I cleaned that part by accident as well lol. going to think of a way to submerge it better to give it a good overnight soak in the cleaner just to try and do the absolute best cleaning I can on it, thinking a prescription bottle would do just fine for that.

its still not quite there so I think i'll pull it again and try with some pipe cleaners to get the back side of the sensors where I couldn't reach with the Q-tip.

just to be clear what I did if anyone is thinking of trying this idea, I just barely let the Q-tip rest on the sensor with its own weight and they I carefully rolled it back and forth without pressing on it at all, just enough to barely depress the cotton on the tip and careful not to leave any cotton "hair" left behind. I plan to redo this again with the pipe cleaners, which will carefully be used in the same way to gently wipe it but not press on it.

DO NOT ATTEMP WHAT I DID unless your ready and expect to buy a new MAF sensor if you screw it up. I don't want anyone to take this idea and go break their MAF by sticking stuff in it to "give it a good cleaning" and then get mad when there truck doesn't run after.


THREAD SUMMERY:
my thoughts on my problem is that maybe in some cases like mine where the MAF sensor may never been taken out and cleaned since it was installed from the factory, maybe it had such a thick buildup of dirt on it that it needed a lot more more then just a little spray cleaner to remove the built up film of dirt covering it. after I give it another cleaning and put a few hundred miles on it i'll know for sure if the hesitation is gone.

 

added update:

ok I recleaned the MAF with those small wire type pipe cleaners and I was able to get both sides of the sensors and reach all of the sensor much better and I "think" I removed some more dirt film from it but I cant say it was a visible amount of dirt removed.

truck is idling much rougher now so im assuming its just because it is sensing the airflow better and must readjust the air fuel ratio.

I pulled the EFI relay to rest the ecm and will see how it drives after a few trips around town to let it reset but I "think" it doesn't hesitate as much as it was doing, but im not yet ready to say there is no longer any hesitation to it.

im holding off on pulling the TB to replace the TPS and IAC because I want to make sure I see the results of each repair attempt instead of doing 3 things and not knowing which one may have made things better or worse.

 

ok, final update:

hesitation is less noticeable but still there so its either the MAF sensor itself is bad or its something else like the tps doing it because its as clean as it can ever be cleaned so its definately not acting up because its dirty.

next step, weather permitting, I will be pulling the TB to replace the TPS and IAC

 

UPDATE:

ok I replaced the TPS and the IAC today and while I don't regret spending $75 doing them (the old ones were 15 years old) they made absolutely no difference at all with my idle or hesitation issues.

it still has the rough idle and the hesitation so based on that I must surmise that the rough idle is maybe related to a leak in the EGR valve and the hesitation issue is a MAF issue.

so now I will cap off the EGR to see if it helps and I guess at some point, I need to try installing a new MAF sensor but at this time the hesitation isn't a big enough issue to make me run out and spend $100 just to solve it.

im going to wait and hope I find one at the salvage yard where I can get a used one for $10

 

The 95.5 - 98 sensor was incorporated into it's own housing. the 99+ screws into the intake tube. this may have already been answered but i'm too lazy to read through all the posts.

 

I replaced my MAF today. First short test drive seems like a bit less hesitation, but there's still a little bit there. Not sure where to go next on this - like keakar, I'm running out of things to try.

 

well not exactly, there seams to be earlier ones as well as later ones that are made as a unit and don't screw in. I think it depends on the model and "where" it was made as well as the year so it does get a little fuzzy when searching for what you need.

beyond that, its one part number that is the replacement for all the first gen models that screw in

well I read there could be an ECM issue that causes rough idle and hesitation from the computer just getting old and processing the info right but who the hell can afford to go around swapping those out just to see?

 

plugs, ignition coils, plug wires, fuel injectors, fuel filter, fuel pump, bad gas, etc, etc, on and on............... there are many things that can cause hesitation, just wanted to give you another train of thought.

 

well on mine I replaced:

full set of spark plugs
full set of spark plug wires
TPS
IAC
fuel filter
full set of injectors

plus I cleaned EGR valve with no result and I cleaned MAF 6 times (it cant possibly be any cleaner)

and I still have the hesitation on soft acceleration but when given more pedal (like you have some place to go) it responds normally without hesitation.

my only thought left was to replace the MAF just for the hell of it, but now that MrRiverMan has tried this with no result im in no hurry to drop $100 on a OEM Toyota one for my truck.

I rule out the fuel pump, bad gas, and coils because these would not work fine any other time except for one specific throttle position or rpm range, if they were bad, then they would be causing trouble at other times as well.

 

Yes, I have replaced plugs, wires, distributor (no coils on mine), injectors, fuel filter, checked fuel pressure (45 PSI at idle), changed gas, etc. etc. on and on. Also blocked off the EGR for a bit, cleaned it, checked for vacuum leaks, replaced the cat, cleaned the throttle body, replaced the IAC, replaced the upstream o2 sensor, adjusted the valves.

Next I'm going to disconnect the exhaust behind the cat to see if my muffler is clogged up. Not sure where to go after that except a compression test.

 

im actually getting to the point of looking at how I might throw all this computer crap in the garbage and getting an intake and carburetor from an 80's yota and be done with it

 

I would love that-I started driving in the 70's and all my early vehicles were 1960's models-my first car a 1965 Dodge Dart. I understand those engines-I'm also an A&P mechanic (aircraft), and small airplane piston engines are so damn reliable with points, plugs and a magneto it's a shame we can't have them in our cars now. But the emissions laws are the reason for all the computer crap-and with the huge back pressure from the catalytic converter on the exhaust systems, it's amazing cars have any power at all. My 2000 pre-runner is a second vehicle now, bought it brand new, and it has served me well, got me through some rough financial times when I had to neglect maintenance. It's a project for me now, my every day ride is a little 2014 Mazda 3-gets 36 mpg. I can't bear to part with my Taco- got the TRD super charger installed by the dealer, and they gave me my original intake, which I want to put back on-no more premium gas - and I badly need new shocks and struts, way past due for timing belt and water pump which I'm going to pay to have done, I'm getting to old and my back is out to do the work myself. And in another 5 yrs or so, it will be a classic!.....ok I'm rambling, sorry.

 

I was having what sounds like a similar issue with my 98 2.4L 2wd. I just replaced the pre-cat 02 sensor this weekend and there is a noticeable improvement in acceleration and performance. I'm hoping that my MPGs will improve, too. There's still a slight dead spot where upon light acceleration it looses a little momentum when the engine isn't warmed up. I'm not too worried about it, as it's definitely performing better now with the new O2 sensor.

Have you been getting any codes throughout all this trouble?

Do you have an automatic tranny? I've wondered sometimes if this hesitation stems from it, because my engine doesn't seem to sputter or anything when I feel this slight hesitation, but seeing that you have basically the same truck as me, I think I know exactly the issue you're experiencing. I've does a trans fluid change recently with no effect.

 

auto tranny but MrRiverMan has the same issue with his 96 2.7L manual, so if you are referring to those who blame it on the tranny, I have seen a few suggestions guessing its maybe torque converter related but that assumption doesn't hold water since manual trannys do it too.

on mine its mainly noticed when it is warmed up but then when its still cold its idling at 1200 rpm so im sure its still there but its just being masked by the higher rpms.

I have never had a CEL code for anything, it runs good otherwise and gets the listed gas mileages 19/23 so no signs of something wrong but it idles like its running on 3 cylinders.

I cant see where it would hurt to replace the upstream o2 sensor since I don't know how old it is, so I wouldn't be opposed to replacing it but it it wasn't working right I would expect to see a CEL but it could be dirty and I don't know how many miles are on it or if its original.

 

Well, FWIW we drive basically the same truck and your hesitation issue sounds very similar to what I was experiencing (not the idle issue, though) and my truck is running like a champ since I replace the 02 sensor. I had a P0420 code though, so....yeah

 

well the idle is aggravating but I can learn to live with as I have so far, but the hesitation issue is not normal and says there is a problem that NEEDS to be fixed.

I will be watching for and buying when I find, not just a good deal, but a great deal on a denso o2 sensor

 

Update: did this today, didn't help. Sure was noisy, though.

I'm going to replace the vacuum modulator for the EGR tomorrow. It's pretty much shot. Short of that causing a miracle cure, I'm on to the compression test next.

I guess if the compression checks out, I'll once again change the wires (38k miles old), plugs (20k), distributor cap (38k), and rotor (38k).

If none of that works, it'll be time to shop for en ECU. Unless someone has other ideas for me?

 

well im not sure, but I have heard reflashing or reprogramming the ECM is whats needed to "renew" the software so its working right again so it may not need to be replaced but then I just don't know if this is really true or not.

my truck has started running worse since the last MAF cleaning and TPS and IAC replacements after running much better at first.

it now stumbles at idle and seams to almost want to die when stopped at traffic lights then picks up again and idles ok but still roughly.

 

Brake booster is faulty.