Slowey23

As the title states my 92 4runner 3vze wont rev past 1500 it cuts till it back below 1500 then revs up again over and over, its either in limp home mode or the fuel cut off is engaged but it wont give ma any codes, if i start disconnecting things it will flash those codes but once cleared still wont run over 1500 and wont give me any codes. If I disconnect the TPS nothing changes but it also wont give a code for that circuit, I have checked connections for distributor, tps, o2, airflow and cant get it sorted.
Its setup on dual fuel and will run on LPG but when it runs on LPG its drives ok but is laking some power almost like the timing isn't advancing, not sure if limp home locks the timing at a set value or this is the source of my problem, this has been an intermitted problem for some time but now it seems permanent so I hope someone on here can help me out.
Thanks Shaun

SPARKS89

iTrader: (1)

I don't know for sure about the 3vze, but I know on the 22re when you unplug the TPS and nothing changes that's a dead giveaway that the TPS is bad.

Gamefreakgc

I know nothing about LPG fuel vehicles but pulled this off wikipedia:

"Not all automobile engines are suitable for use with LPG as a fuel. LPG provides less upper cylinder lubrication than petrol or diesel, so LPG-fueled engines are more prone to valve wear if they are not suitably modified."

I've never heard of cutting out that bad over 1500 RPM. I've also never heard of a Toyota running on LPG. I hope others can chime in since there could be a host of issues wrong. I'm concerned about your valves, they could be burnt and/or stuck open. Or it could be fuel buildup or lack of pressure when reaching higher RPM's.

JohnnyCanuck

I ran propane for 25 years on my '90 GMC, I used stellite valves and seats, I learned the hard way when I burnt my oe heads up. A lot of the new engines have hardened valves and seats but I'll bet these older Toyota's are just standard.

Gamefreakgc

Yeah, these trucks are known to burn valves if left out of adjustment for long periods of time. I doubt the valves themselves are anything out of the ordinary.

Marc

Are you checking for stored codes by shorting the diagnostic connector?

Slowey23

Ill look into the TPS, but I had it unplugged some time ago accidently and the engine ran fine but did give a code for it back then.
Im pulling the codes by jumping the TE1 & E1 termials, I'm confident that its an electrical issue as when I switch to LPG the engine run almost perfect as I mentioned above, if it was a valve issue it would affect both fuels.
I have read something about this engine having a fuel cut as a safety feature but cant remember any details, if someone could fill me in that would be great

Slowey23

just in case anyone else has this sort of issue, mine ended up being the engine coolant temp sensor

Gamefreakgc

I've known that ECT sensors cause a host of wacky issues but this one takes the cake