bcaslow

My son drives a '91 4Runner, V6 4WD w/ 5-speed. It has almost 200k miles; we bought it at an auction as a fixer upper, but now am wondering if it's worth it.

The problem: he was drivig home from school, and it started chugging, barely running, then died. By the time I got there he had pushed it off the road. It started, idled fine, rev'd ok, then went to this chugging -- acting like it was starved for fuel. I changed the fuel filter: same problem.

Had it towed home, checked it over, started up and ran fine; rev'd real high and good for about 15 seconds, then same as before. After the initial start up, once it starts chugging, when you rev it you have to play with it and when the throttle body is open wide it is just sucking air from teh sound and actions. And yes, it has plenty of gas in the tank. the initial start up is so normal it's what leads me away from thinking it is with fuel pump, etc.

Checking thru the forums I don't know if it is the Vane Air Flow Meter (as it doesn't sound as if it has a MAF sensor) or something else. I saw one post where they said they tested according to Chilton's manual, but I don't have any such documentation -- not to mention others said to throw that book out!

So, if the MAF / Vane Air Flow Meter can be tested with an ohm meter, or if anyone else has suggestions (other than taking it to a shop. With so many miles, all the rust, and the fact we're 25+ miles from any shop and would have to pay $$$ for towing) it would be most appreciated.

thook

Hi and welcome..

This is the online factory service manual...
http://personal.utulsa.edu/~nathan-b...fsm/index.html
Testing the VAF meter...
http://personal.utulsa.edu/~nathan-b...92volumeai.pdf

Has the check engine light come on? Jump the terminals at the diagnostic box and see if there are any codes.....
http://www.off-road.com/toyota/tech/codes/index.html

hosh

http://personal.utulsa.edu/~nathan-buchanan/93fsm/

engine 3VZ-E MFI system-VAF meter

This is the FSM. It will be good for your year. Volume Airflow Meter is the mass air flow meter. Just another way of doing it.

Check that your truck has had the head gasket recall. Local toyota dealer can tell you if you give them the vin number.

Welcome YT

hosh

thook beat me

thook

That's me....lightening fingers. Now, if my brain will just catch up.

bcaslow

Hey! Thanks for the great -- and fast -- replies! I did some checking and not much more I can say so far: the check engine light had not come on to my knowledge (I asked my son, he said "If it did I didn't notice it..."). It wasn't on when I got behind the wheel. I went to check the codes: all I got was the check light flashing constantly -- no codes. According to the manual, that means no malfunction.

My ohm meter starts at one and goes up by one digit to 6, then 8, 10 and up to 100 and then just before infinity it has 1k. The instructions for testing the Volume Air Flow meter for the various temps were 10-20k, 4-7k, 2-3k, 0.9 ? 1.3 k and 0.4?0.7k. My readings started at 6 (not 6000) and went down to only about 5 when heat was increased. This was between terminals THA ? E2. The test between VS ? e2 and VC ? e2 seemed fine, so I don't know if I just don't have the correct ohm meter, or if the VAF is bad.

Final note: after doing the tests above, the engine started and died right off. Did this a few times; I couldn't even rev it like I could before. Then after a few times it refused to start. I don;t have a meter for the fuel pressure, but there is definitely pressure on the lines.

Any additional feedback would be most appreciated! This site is great!!


Bill

thook

I'm not sure on your readings, but you may need a meter with a broader range. I ran into that when testing my VAF and TPS. All I had was a little one like yours, but a digital multimeter from Lowe's made it easier and diagnosiing more accurate.

This site might help you out more:
http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml

You might check out the rest of his site, as well. Lots of good info and tricks, particularly on using a meter for testing these EFI components.

bcaslow

Yep... reading another part of the online book said you need to use a voltmeter with high impedance (110k ohm / volt) so I'll need to get one before re-testing. Once that's done, I'll post again.

Thanks!

bcaslow

Thanks again for the posts and great sources of info. Just to let anyone interested know, I bought a new volt/ohm meter and ran the tests as outlined in the online manuals. Vane flow meter checked out OK, so I dug deeper. Ran all the tests I could for the ECM (there's a couple where the engine is to be running); again, everything passed. So I asked myself "Self, are you sure it ain't the fuel pump?"

I disconnected the fuel line at the filter (as I had just replaced it) and hooked up a hose to a gallon jug. Turned on the ignition and... a trickle, at best. Just enough to build some pressure. So, five hours later and $160 poorer (pump, strainer and fuel cap -- my son left it on the wheel when filling up and forgot it, and promptly ran over it...*sigh*) and it's a runnin' again. Seriously debating putting the money into rebuilding the engine as the body has so much cancer....but I do like this vehicle. More fun than our newer Explorer, and with a new power plant, I bet better power/performance/economy, too.


thanks again!

hosh

glad you came to the yota family. you'll have fun for many years.

ej1bullet

thanks man i was lookn for that!