1FZ Petrol Issue

[Simmo88]

Hi guys,

I have an 80 on gas, and a few months back I started having some real issues with my petrol side. Basically, it really lacks power (can't maintain 100 on the highway) and has a very rough idle. It bounces around a few hundred revs, and at times stalls. When you start putting your foot down, it feels sort of restricted. The revs stumble around and it just feels like its trying to take off, but it cant. Somethings stopping it.

If for example I try and take off from the lights (Its an auto btw) it really has trouble doing it. Same thing for ANY incline. it wil eventually get there, but I mean slow ( although one day I ran out of gas on a slight hill, and I could not take off on the hill. I had to roll back down to the flat, stitch back to gas and do a u turn on fumes.) If you floor it it just stumbles, and if u back your foot off a bit, it just doesn't have any power to move. the revs just die.

Weirdly, if you can wind it out (I mean wind it out) to 3200 rpm, it will take off with a surge of power, but it is still less than when on gas. In the past, it has always had much more power on petrol. After the surge, seems to keep power, but you can still feel it strugling. And it is not practical to drive around at over 4000rpm every where.

Another thing I have noticed is when the petrol tank gets emptier, it runs worse, to the point where it will not drive at all. I have had it down to the fuel light, and basically it idles really bad, and if u put it in drive, it will pretty much hunt (car starts bunny hopping) until it stalls.

After refilling the tank, it began to run better over time - not straight away, i had to run it in abit. The same thing happened at the snow last year, with a full tank i was able to keep myself out of trouble, but its not really drivable though. And it seems to have gotten worse over time.

So, any ideas? Its abit of a hard thing to describe.

I assume fuel system, because as soon as you switch it back to gas, its perfect, no problems at all. i am looking at maybe fuel pressure issues, maybe from pump or filters? I don't really know much about the fuel side, as it's usually only my back up.

Id rather have abit of a play for myself before dropping it off at Toyota, because its my daily drive to worlk and my only car.

[oldmate]

I'd be looking at the fuel pump and relay. There is a low/high pressure for low/high rpms. Sounds like it's working fine in the high rpms.

[flyology]

When was the last time you replaced the fuel filter? might be blocked or collapsed.....

[Newbs-IIA]

When was the last time you replaced the fuel filter? might be blocked or collapsed.....

especailly if you infrequently use petrol and the fuel in the tank goes stagnant

How often would you say that you go through a 90L tank of petrol? (assuming you still have the factory main tank)

[Simmo88]

I have really only done 2 tanks of 90L since I have had the car about 18 months now, but partly due to it not working well. Last time it was at the mechanics, he said the filter was clogged with mud, and replaced it. when it started happening, i thought filter too. I though maybe the tank much be full of sludge, so that when it was getting low, it was sucking it all up. But I have since drained the tank, and it seemed fine. The current tank of fuel was only put in a week ago (from empty).

Is there an easy way to bypass the filter to see if its the issue? On the old diesel I was told you can just put a bypass hose in to check, I assume you cant do this with the high pressures on the petrol. It's located under the intake manifold isn't it?

Can you tell me more about the relays? Location, function etc.

[Ruffy]

I'd be checking fuel pressure because it's easy altghough it doesn't sound like a fuel pump issue.
Sounds like you may have a faulty Air flow meter.
Even a slight backfire on gas can damage the AFM but they will fail just because they can..

[flyology]

I would not by pass the filter, if there is crud and stuff in the tank/fuel lines all you will do is let it through to your injectors.....

See if the filter is clogged first, then if so, unplug the line, blow it out backwards, then flush it out. Make sure there is no crap in the tank, and try it again with a new filter.....

[Simmo88]

Gee I really hope its not the AFM, I just replaced that last year at 600 for a swap over. I'm pretty sure its not the air flow meter - i could be wrong, but I have found if it does't work, then the motor shuts off. how easy is it to check fuel pressure?

[v8zuki]

change the pump if the filter was clogged then its a fair chance that thepump will be sad
do it in this order
fuel filter again
pump and another filer
injectors after the others have been done
my brothers 80 did the same thing he overhauled the fuel system and all good went better than it ever did
theb his air flow meter died lotsa fun trying to find one of them
but they can be rebuilt if its the early alloy one
if its the plastic afm you shouldnt have any probs as they rarely givs dramas

[Simmo88]

Yeah I know all about chasing AFMs. I will give the new filter ago, and see what happens. If no good, I'll look at pump. Anyone know what a new pump is worth? Can they be cleaned out or anything?

[Simmo88]

I changed the fuel filter this morning. Seemed a little better, but in no way fixed. what's next pump?

[petes 80]

Hey mate,

I had similar issues with my 94 1fz. I replaced the Air flow meter and the oxygen sensor and the Throttle position switch, it is now a rocket again. Have you had the computer plugged in to it yet to see if there are any error codes? I had mine checked and thats were i found out i had faulty components.

Just a thought because it isn't always fuel that causes these problems

Cheers Pete

[Simmo88]

I have not had a computer plugged in. I checked the fault codes a while ago (after it started happening) but nothing was coming up. Initially I suspected oxygen sensor, but not too sure. As I said, I have replaced the AFM in the last 12 months, and the lpg NEVER backfires, so it should be fine.