whats wrong with my 20V?

[Sam_Q]

I put my 20V under high load and one of my extractor primary pipes cracked, as soon that happened the engine started to behave strangely. It started to idle at 2000 revs and sometimes rapidly fluctuate to 1500 revs and back up again. It has since used a considerable amount of fuel. I fixed the extractors and its still the same. I bridged my ECU and did a diagnosis and it has no fault codes so I am confused as to what is wrong. The only thing I can think of is that my idle control motor has gone haywire or my air flow meter is damaged.

Any ideas guys?

[Jorrs]

have you touched the AFM though ?

[Sam_Q]

didnt go near it, i heard they are sensative things though and I thought a small backfire that I didnt know of hit it, does bouncing off a rev limiter do that?

[Vios-GT_07]

first guess is to investigate the idle control motor and AFM first rough idle is normally associated with that... and yea if you're idling high, fuel consumption would definitely go through the roof.. (obviously )

[Hen]

I'd hazard a guess that the cracked exhaust pipe and the idling high are totally unrelated. A cracked pipe will take a while to start and progress, the idling sounded like it started suddenly. So don't get too caught up in trying to work out what would cause both.

Check the usual things, vacuum leak, idle valve, throttles closing and signalling idle properly etc...

Hen

[sideshow]

run engine and block the intake to the air flow while holding revs abit up

it should stall if it doesnt it might have an air leak

another hting to check is throttle linkages

idle motor will prob not make it idle so hi

so prob u got shit in throttles holding butterflies open or maybe something similar

[Billzilla]

whats wrong with my 20V?

It has the wrong number of inlet valves and a crappy combustion chamber.


</thread hijack>

[Sam_Q]

thanks guys, how do I check my airflow meter? or my idle control valve other than what sideshow says.

Bill: hehehe yes I know all about the how the middle intake valve is too shrouded by the outside ones and the lack of a proper squish design in this head, I still dont get why toyota made this engine. I wonder what would of happened if they introduced a 20v style intake, vvt and individual throttles on an updated 16V engine, would be a ripper I think.

[Sam_Q]

the other thing I forgot to mention is that it "pops" alot as in small backfires. This is on throttle lift off so doesnt that narrow it down to air-flow meter or the TPS?

[sideshow]

if it was runnin ok then all of a sudden fukt up
then it cant be too much wrong

air flow and stuff just dont fuk up easily

did it stuff up on a dyno or did u give it a thrashinbg for more than 5 mins

whats yr fuel pressure like

fule p[umps fuk up mopre often than air flows and things like that

tps will nt go out u8nless something else goes wrong

alot fo the time i fix probs that are not eletrically related

so at the moment try not to blame electrical shit especially when u get no codes from ecu

[Cruiser97_80]

If it's popping with throttle backed off i.e. slowing down,driving down a hill.
An exhaust leak can cause this. i.e. your cracked header pipe.

[Cruiser97_80]

With your other problem i am thinking that maybe your coolant temp sensor reading too cold. i.e. telling your ecu your engine is colder than what it really is. This would affect your idling and your fuel economy.

[Vios-GT_07]

the other thing I forgot to mention is that it "pops" alot as in small backfires. This is on throttle lift off so doesnt that narrow it down to air-flow meter or the TPS?

timing and air fuel ratio could cause this... especially when u're still in gear when this happens

plus your header cracking... while it's worth it to investigate the pipe construction and all that.. maybe it's also worth a few a little while to look at the engine, maybe it's running too lean causing header to heat up too much? could also explain the popping...?

[Sam_Q]

sideshow: I was pissed off at someone and I had some bad tyres on so I dumped the clutch and let it bounce off the 7200RPM limiter (no speed sensor hence lower rev limit). I dont know what my fuel pressure is like, any ideas?

cruiser: the pipe is fixed now but it still backfire, I was also thinking that it was the coolent temp sensor, the reason I think its quite possible is because when its cold it sits at 1000 revs and I dont hear a sudden change in the idle when its warm like usual. Now apart from changing the sensor is there anyway other way to check this? does someone have the resistance measurements for these things?

hey I just had a thought, what if the coolant temp sensor has been disconnected by accident? that might explain it. It would be stupid but convenient. If it is connected I will try shorting it out and see if it reacts. This will rule out the temp sensor real quick

sideshow: timing hasnt been changed, so unless the airflow meter is up the shit it rules it out.

[Cruiser97_80]

If you short your ecu coolant temp sensor it will should bring up fault code short to ground.
If you disconnect your sensor it should bring up fault code o/c , short to positive i would think.

[sideshow]

if its disconnected it will bring up code
if its shorted to ground it wont bring up code

but this wont make it idle over 2000

[c2888]

I'd pull every vac hose off the engine and replace it with either new new new rubber vac hose, or the older good stuff toyota use to use. Some where along the line (20v era) toyota must've changed rubber tubing supplier, or the supplier changed the rubber because it all falls apart.

It splits around the edges where it's been pushed over the nipples, it cracks around bends, and it generally just falls to bits.

I've seen a few and it seems to be a common problem, if it's idling crazy, you're definately getting more air.

Dan

[Sam_Q]

aaaah shit, theres a whole maze of rubber hoses under the throttles, and it would take atleast an hour to get the airbox and trumpets off. But if it does have a leak why would it run rich? wouldnt it be the oppersite?

[xolent]

it sounds like what i have; no o2 sensor!

reason for the back fire is because your 20valve has no o2 sensor so it's running rich atm.

[Sam_Q]

i do have one!!, its just far down thats all, it is a 3 wire so its ok. I will check that though.