Engine running issues

Grommit327 · Apr 22, 2010

'96 toyota tacoma 3.4 V6 with about 180k on it completely stock motor. Been having some issues for awhile and threw a P0171 code which is lean condition. I pulled the MAF and cleaned it. After that it would start and idle roughly at 500rpm and if you applied any throttle it would die. I pulled the ground on the battery to reset the computer and now it will start and rev up to about 1500rpm like a normal cold start and then start sputtering and dies within about 5-10 seconds. So far it hasn't thrown any more codes. Also lots of backfiring if you try to give it throttle.

Thanks for any insight
Joe

rubikong1 · Apr 23, 2010

Well I would guess that the lean code would be derived from the O2 sensor and not the MAF, but you could check the plugs for indication of it really running lean and, if they are fine, then change the sensor? Was it running fine lately, or sitting in the sun, with old gas? Generally you would notice a fuel filter over a period of time and not all at once but might as well put it on the list anyway if not already done, with 180k.

zukkev · Apr 23, 2010

A dirty MAF WILL cause a Po171 lean code...When you cleaned the throttle body and MAF, what did you use to clean the MAF with Joe??? And sis you get the MAF plugged back in?

zukkev · Apr 23, 2010

Also what issues were you having prior to cleaning the MAF, just the lean code??? OR was it running poorly??? I'd be leaning toward a damaged MAF for your immediate concerns with the start/stall condition after cleaning...

Damnyankee · Apr 23, 2010

O2 sensor, MAF or vaccum leak.

Vaccum leak can be a vaccum line, or head gasket.. or or or..

rubikong1 · Apr 23, 2010

Found some info

So knowing all of this what should we check when we have those pesky rich or lean codes? The most common issues for lean codes are:

1. Vacuum leaks - check for failed or loose vacuum lines, leaking intake gaskets, intake air tubes loose or any other source of un-metered air leaks (leaks after the Mass Air Flow Sensor)
2. Restricted fuel filter or bent/pinched fuel system lines
3. Incorrect input from other sensors, such as the Mass Air Flow Sensor, which may not always drop a separate code
4. Engine misfire

Grommit327 · Apr 23, 2010

Alright total history. Truck has been sitting for about a year and a half with only occasional starts and short drives. Took it out the other weekend for a drive to my friends house and it ran great all night. Drove it the next day and after a quick stop it wouldn't start again. Finally got it started but it took several minutes of feathering the throttle before I could get it limped to my friends house. I changed the coolant temp sensor since I knew it was faulty already but it didn't help. Checked plugs and they looked a little lean/white but not terrible. I bought a scanner and pulled the codes and came up with the P0171 and a P0115(which was the temp sensor I replaced). Cleared the codes and pulled the MAF/intake tube/throttle body off and cleaned it all. The MAF was just sprayed out with MAF cleaner. After that it would only idle at 500rpm and wouldn't allow any throttle to be applied.

Changed fuel filter just for shits and giggles last night but same thing now starts easy idles up to 1500rpm then dies after 5 seconds. Won't throw any codes but guessing that's because it isn't running long enough.

I did do a scan on the O2 sensors but I don't know how to interpret the data I am looking at to see if they are both working or not

Sorry for the long story but thanks for the help this thing is making me tear my hair out

Rix · Apr 23, 2010

maf sensor and o2 sensor
and get some good gas in it, a bottle of fuel drier wouldnt hurt
make sure you havent had rodents chewing on vacuum lines.

Grommit327 · Apr 23, 2010

Rix said:
maf sensor and o2 sensor
and get some good gas in it, a bottle of fuel drier wouldnt hurt
make sure you havent had rodents chewing on vacuum lines.

It should have good gas since it barely had any in the tank while it was sitting and I just filled it up last weekend. Going to pull the O2 sensors tonight and put a dmm on them and see if either is bad. Is there a way to test if the MAF is bad?

deerlick · Apr 23, 2010

normally on these motors with your code and symptoms you will find a bad MAF causing your problem.

Grommit327 · Apr 23, 2010

If'n one didn't go with a new Toyota MAF what's a good brand of a reman? A-1 Cardone, Beck/Arnley and Standard Motor Products are three that I see listed for about half of what a new OEM one costs. Really don't want to pay $600 for a new one :eeek:

Rix · Apr 24, 2010

check your fresh air ports on the o2 sensor, clean the MAF sensor with non clorinated brake clean, that's about it.
If something with the o2 sensor was wrong that was going to show on a DMM, you'd probably see a code for it.
The sensor can be sluggish and cause lean, but still be within "normal" parameters, but you have to watch fuel trims or o2 sensor voltages (VF and ox or ox1 in the diag box) to tell that.
Could also have injectors starting to spray poorly.
As for aftermarket MAF sensors.... I can't recommenda good one beside OEM.

zukkev · Apr 24, 2010

Grommit327 said:
If'n one didn't go with a new Toyota MAF what's a good brand of a reman? A-1 Cardone, Beck/Arnley and Standard Motor Products are three that I see listed for about half of what a new OEM one costs. Really don't want to pay $600 for a new one :eeek:

Beck/Arnley's not a bad brand...Not sure if they offer it, but Altrom supplies many of the OEM import parts...at a MUCH lower price (Our local NAPA sells Altrom):awesomework:....

Grommit327 · May 6, 2010

Finally got around to changing the MAF and no dice. Starts fine idles up smooth then dies. Every so often it will hit 100-200 rpms and chug back up to 1200 then die. Any feathering of the throttle just kills it. Won't throw any codes. Any ideas where I should look next?

zukkev · May 6, 2010

Check the TPS to make sure it is working properly....I've got a 22re pickup that someone had put the tps on incorrectly....Oh and I also had to replace the main relay as it was bad....

Rix · May 6, 2010

Clean the IAC valve with some carb clean or the like.
See if it helps.
Besides that, I'd have to see it.

Grommit327 · May 7, 2010

Rix said:
Clean the IAC valve with some carb clean or the like.
See if it helps.
Besides that, I'd have to see it.

I will check the IAC tonight to see if it's working. Never even heard of it before you mentioned it and I looked it up (engine newbie). Any chance the fuel pump could be cutting out after it starts? It's almost like it loses fuel pressure after it fires

zukkev · May 7, 2010

Grommit327 said:
I will check the IAC tonight to see if it's working. Never even heard of it before you mentioned it and I looked it up (engine newbie). Any chance the fuel pump could be cutting out after it starts? It's almost like it loses fuel pressure after it fires

Very well could be...go after the EFI main relay...test it to make sure that it's working....