1988 yota

i have a few questions, im new to the yota world, just picked up a 88 yota. it has 107k miles on it with a new head, because my friend overheated it and warped the head.

well to cut to the chase, i have 2 small issues. 1 is that in the middle of the rpm band when its colder out, itll randomly bog out. but if im barely touching the gas its fine, or if i put it to the floor it doesnt bog.

im wondering how to test the mass air flow meter, or is there a way to get rid of it completely? or could is be that my truck is running to cold? because the temp gauge shows that the needle is 25% of the way up the gauge, its not right in the middle where it should be.

so im wondering if the colder engine is causing the issue because the choke wants to stay on? or would the mass air flow meter be causing an issue?

1988 yota

also sometimes it will have a rolling idle. and i have an electric fan, and when it has the rolling idle, if i turn my fan on, itll idle smoothly

1988 yota

it has new fuel filter, plugs, wires, air filter. i just dont want to throw parts at it, id rather diag it and replace the part/parts it needs

quiggs12

You may have air in your coolant system. Try burping it? Park it on an incline so the engine is higher than bed. Take the cap off your radiator and let the truck run long enough to open up the thermostat and cycle coolant through the engine removing the air.

Do you have an CEL codes being displayed?

1988 yota

I had a couple come on for a few sec, i have no cat on the truck. but nothing for the past few days.

TrikeKid

Check the codes, they'll be stored even if the light isn't on constantly. I would also check the operation of your EGR valve, sticky EGR can cause lots of driveability problems.

OBD0/OBD1 don't monitor catalyst efficiency so it won't kick the light on for that.



There are two ways to get rid of the MAF... run on propane, or run a carburetor.

1988 yota

what would happen if i just took the mass air flow meter out and put a pipe to the throttle body? because the meter is just like another throttle body before the throttle body isnt it?

combatcarl

No. The VAFM is an integral part of the engine management system. It will not run without it. Check codes. Google, its gonna be your best friend. Sounds like you may have several issues. Vacuum leak, TPS issues, etc, etc. But that's what the OBD1 system is for...it does the preliminary diagnosis part for you.

Sent from my LG-P505 using YotaTech

SPARKS89

iTrader: (1)

I'm leaning towards an issue with the TPS on this one. You said it won't bogg down if you're light on the throttle or if you floor it. You might have a ' dead spot' in your TPS. Check your sensor and make sure it's still within spec.

quiggs12

Try unplugging your o2 sensor and see if you have the same bogging issue... You may have an issue with it even if you're not getting a code.

SPARKS89

iTrader: (1)

Any updates?

Snortin Nortin

I'm having a stuter too these voulume air flow meters are kinda funny like that I've had 5 vehicles with them! they have that sweet spot and that bad spot no matter if its working fine or not lol!

1988 yota

my timing was off by 13 degrees. i timed it, runs a whole lot better. but now i still have the sweeping idle when i press on the brakes. it doesnt bog down as much, the only time it will now is when the engine is cold and its in cold weather.

as for the CEL codes, they are; 25, 26, and 41. does anyone have code list so i can look them up?

i also fixed a couple vacuum lines. i hooked up a vacuum gauge and it seems to hold a vacuum and the gauge holds steady.

1988 yota

and my uncle is a mechanic, and without doing any tests he is leaning towards the TPS as well. one of these days when i have free time, ill do a test on the TPS and the MAFM. what are correct specs they are supposed to be at?

Dirt Driver

41 is a TPS signal (open circuit or short) code and the other two are for air-fuel ratio too lean and too rich, so something going on with the O2 sensor.

There's a downloadable service manual out there if you look for it.

donomite49

download your FSM while you still can.
http://web.archive.org/web/201101022...ttora.com/FSM/