Hey guys. Found the sight through a google search for my problem and was glad to see yall actually at least try to help.
I have a 99 tacoma 4x4 3.4DOHC with auto trans. Truck has been great until recently and I have done all I know and some I didn't.
I have a horrible stumble in the mid throttle range. Idles great and easy up to speed seems fine. trying to accelerate to pass or get out in traffic is a no go. Seems like it has no gas. Coded lean condition bank 1.
Work so far: seafoam through gas tank, new plugs and wires, new fuel filter, new precat O2 sensor, new fuel pump, cleaned MAF, removed and cleaned T/B, replaced PCV valve, and replaced air filter. No help at all. The kicker here is that with the air filter (old or new) the truck runs like a scalded dog!! I am lost and dont know what to do now. Any help or suggestions would be very much appreciated.
Is it still giving the lean condition code or did something you did clear that up?
If you're still getting the code you should look into fuel delivery problems - bad injectors maybe?
Thanks for the response Gameboy. Still same lean condition code but in the time between the original post and now I have (using poor man stethascope) listened around the engine for vacuum "hissing". I did find a hose from under the throttle body that some noise was coming from so I disconnected and hard plugged it. Initially (within 1/4 mile or so) didnt see a difference but suddenly the truck began to run better. I came back and put the line back on with a clamp and the problem is all but gone. I still hear the hiss but much less now so I believe the line is cracked and will be replaced. Hopefully this will end my problem but time will tell. I will update this thread as soon as I know so nobody else spends 350 bones and countless hours of head scratching unless they have to. Again, thanks for the response.
BTW, My scanner is with my friend until 430 ish this evening so code clearing/ reading is just a guess at the moment. And I just noticed in my original post that I said with air filter. Actually it should have said with air filter removed engine ran like a scalded dog. Sorry for that important mistake.
Okay I spoke too soon. Problem still there just not as noticeable. My MAF is reading in the 35 range which doesnt even come close to what I am seeing on a buddys V6 in his solara. Even at 2500 rpms he is only getting to around 16-18. Is there a way to test the MAF sens? Can anybody give me a typical OBD reading for a 3.4 Toyota engine at idle and/or "at speed"? I dont want to throw another hundred at it just to see. Thanks in advance for your help.
You could try this testing procedure for the MAF sensor:
http://easyautodiagnostics.com/testing_maf_sensor/maf_sensor_testing_1.php
Maybe this will help with the MAF OBD readings (PDF):
home.comcast.net/~dntsdad//MAF%20malfunction.pdf
^Link is troublesome due to double-forward-slash, try copying that into your browser's address bar
TomHolley wrote:
replaced air filter. No help at all. The kicker here is that with the air filter (old or new) the truck runs like a scalded dog!!
I don't understand this. Do you have some sort of cone type filter on the thing, and it works ok with the stock airbox?
Thank you again. I will try this procedure as soon as I can and get back to yall with results.
Well I'm back!!! Tacoma still stumbling and getting lean code. In the process of troubleshooting the problem with the truck I noticed a cracked radiator. Truck ran better when water was topped off so I felt it important to replace this before going forward which I have done. MAF numbers seem to be in line (OBD wise) with specs when idling and easy on the pedal on the road. I am still getting high numbers though when driving and getting after it!! Is this normal? Also, the short and long trims go to 19.5 and stop when trying to accelerate hard. I am still leaning toward a bad MAF sensor but want to be sure before spending another hundred only to find out mine wasnt bad and I still heave the same problem. Any help and/or suggestions with this would be appreciated.
If you have a pin hole in a fuel line, it will run fine at idle but will start sucking air once you start moving and burning more fuel. I had one that was on top of the line and so small that gas didn't even drip, though the line was wet on the outside.
Thanks for the reply Woody. I can see how that could happen. I have been all over the engine while running, looking for vacuum leaks, and havent had even a slight sniff of gas or seen wetness on fuel lines.
Did you follow the whole procedure from that document I linked to?
home.comcast.net/~dntsdad//MAF%20malfunction.pdf
It looks like you might have the "E3 circuit open" problem.
I've a 98 T100, so we've likely the same engine. While I did not have your specific symptoms, I've had some similar troubles.
In observing my various vacuum lines, I could see that many of them were fractured where they mounted, and were capable of minor leaking.
I took an hour or two, pulled all the lines off, shrinkwrapped the ends to tighen them back up, and reinstalled. Things were much improved.
The hard to use link Gameboy gave you is to a section of the factory service manual. The factory service manual has superb diagnostic steps for the various components in your car. If you don't have the factory service manual, get it. It really helps.
Years ago I had a similar situation with my 99 4runner. First I replaced the O2 sensor, which didn't fix it. I finally replaced the MAF sensor after cleaning it didn't work. It wasn't too expensive, because it was just an insert into the housing.
In reply to GameboyRMH:
Gameboy I did not. I did go to the first link in the post but found that to be for a three wire MAF which didn't match mine. I thought the "copy and paste" link was to the same place since you said the link was difficult ...... After reading the pdf in reference I'm not seeing any of the conditions it says for maf malfunction and I am not getting the P0100 code either. At idle the OBD is reading between 4 and 12. Could it be that its is reading therefore not throwing the code, but not getting the right numbers due to a bad sensor?
In reply to spitfirebill:
Spitfirebill, Did the MAF replacement solve your problem or just make it a little better?
Update: After looking at the schematic of the MAF sensor in the pdf from Gameboy I realized/ found out there were contacts I couldn't see or clean with it on the truck. I removed it and did a thorough job cleaning it with some MAF cleaner and reinstalled it. Test drive followed and I believe the problem is solved. I will know for sure in the morning when I drive it from dead cold and will let yall know. Thanks again for all the suggestions.
So after a few weeks of running the truck, it seems that the problem is gone. Runs great with no stumbling or missing at all. No check engine light or pending codes either. Note to self and anybody else with sporatic engine trouble; remove the MAF sensor for a good cleaning first. Could save hundreds of dollars and alot of headaches. Thanks again guys. Yall've been a great help.