Offroad-Express

Have brought a Surf with a 1uz in it which runs fine 95% of the time. The other 5% it will go into a "limp home"ish mode where it uses bucket loads of gas and won't idle and wont rev over around 4 grand (engine gets louder but power curve dives down) sounds as if its overfueling. Nothing triggers this one day it will be running fine, next day will be shit then fine again, happens off cold as well as off hot just seems to occur randomly. Have checked ecu caps, changed ecu temperature sensor, cleaned AFM and all sensor plugs but still seems to be happening. Also getting around 17L/100km on the open road but 14L/100km offroad which seems abit strange. Wonder if anyone has had this problem before or if any of the 1UZ pros out there know how to fix it?

few things to check, not a toyota guy but have had same issues with nissan engines.

firstly is it a serises one or two 1uz... ...1uzfe?

the difference being vvti/quad cam

Knock sensors.
02 sensors...(are they even still there)

there are some 1uz's with a cold start injector under the upper inlet manifold.if equipped)


could be faulty ecu temp sender

also if it is chucking in fuel the ecu will be thinking one of two things...

it has picked up a knock and so retards the timing and increases the fuel.

or it thinks it is too hot and will do the same.

IF it was a major sensor it will just shut down, since it is in limp mode i doubt it will be either of

crank angle sensor(theres two of them one on each head), AFM, ignition module, injector circut

The ecu temp sender is the biggy. it rely's on this for two major caluculations and that is injector modulation and ignition timing.

also from memory if your 1uz has 3 temp senders the one with the black plug could be faulty.

but if it hasn't it could be the o2 sensors, there are two kinds of 1uz-fe o2 sensors. The heated four wire kind, and the older two wire kind. Of course you find the older two wire kind on the older engines, pre 1991 (yes there are older 1uz's). The four wire kind have a powered heater in them to get them into a operational range and keep them there. The heating system has to be hooked up for the o2's to work. You do want the o2's working. The are not wide band sensors, just the on/off type. The wide band sensors tell you how much oxygen is left in the exhaust gases, factory sensors do not, they just say to the ecu something like ‘o2 found = add more gas next cycle’ and ‘no o2 = use less gas next time’.

Shes one of the older non-vvti ones. Replaced what I believed to be the ecu temp sensor last weekend (3 senders: One small one wire, looks like its for the gauge, one large red plug and one large green plug (replaced green one)) and its still the same. Next on the list was the O2 sensors they are the single wire type. Is there a cheap aftermarket type that can replace these with?

Green sensor is temp for ecu so u got right sensor. I had same problem with mine doing funny things and it ended up being spark plugs. I thought it was worse than just spark plugs but it fixed. 1uz are never good on petrol in surfs especially if running big tires and factory ecu.

You will likely find the single wire sensor matches up to wide variety of like aged toyotas, at with a lot of the other sensors.
toyodiy.com/parts is gold for this purpose, plug in the vehicle that the engine came from to find the O2 sensor part number, then go back to the main page and go to 'search by part number' and paste the number in you just looked up, it will bring back every vehicle and models that that particular part was used on.
Green should've been the ECU temp sensor, on my one the other larger plug is brown, that is the cold start injector timer

useless_surf wrote:Shes one of the older non-vvti ones. Replaced what I believed to be the ecu temp sensor last weekend (3 senders: One small one wire, looks like its for the gauge, one large red plug and one large green plug (replaced green one)) and its still the same. Next on the list was the O2 sensors they are the single wire type. Is there a cheap aftermarket type that can replace these with?

unplug the red one and go for a drive. leave it unplugged till the morning and then start it. if its hard to start plug it back in, if it fires up okay i suspect you may have a 1uz with the 1000cc cold start injector. unplugging it will circumvent the flooding issue but this is only the symptom not the cause.

If this is the case you may need to get the sensor with the red plug looked at as above it could be faulty

Is it bringing up a check light? Have u checked the fault codes?

Sounds like dodgy wiring.. not wired correctly..

bridge T1 and E1( diagnostic plug) with a hair clip then count the number of times the light blinks( tester with light) when you earth and attach to W port in the diagnostic plug.. if there is no terminal in the plug then you have to find it on the ecu.. Also if there is no power on B+ in the plug then it's wired wrong.. plain and simple..

Check you knock sensors, ive had issues with a set that caused a intermittent fault that kept putting truck in limp mode like what your experiencing, or start looking for a broken wire in the loom, heard from a few people lately that have been having issues with the 20year+ old wiring breaking causing random faults...........

Had a wee look at the loom last night, apparently twisting and taping wires together is an appropriate way of wiring up an engine these days. Looks like a weekend of soldering wires ahead of me Hopefully this fixes my problem

well, that will help a lot.. but still check the wiring that it goes where it suppose to go to.. otherwise your essentially doing the same and the result will be the same.. no go..

useless_surf wrote:Had a wee look at the loom last night, apparently twisting and taping wires together is an appropriate way of wiring up an engine these days. Looks like a weekend of soldering wires ahead of me Hopefully this fixes my problem

Eeek, gotta love cleaning up someone elses mess
Not sure why people bother if they cant do it at least halfway properly. I crimped and soldered all the ECU connections on mine although its not a V8. Still had a problem, ripped all the engine bay loom apart again, to find when the previous owner had unplugged the loom they must've pulled the injector plugs off by the wires, and one had popped the pins out the back of the plug, but of course with the waterproof boot you couldnt really tell, and test probes were going in far enough to touch the end of the pins so everything appeared fine DOH, live and learn.

As mentioned could be knock, O2, temp, or cold start sensors, or a loose/crap connection or something else entirely but gives you some places to start looking. If your cold start timer is stuffed or wired wrong the injector maybe staying open all the time or flicking on and off when driving, it should only run when cranking and under a certain temp. Mine is rigged to a manually switched relay off the starter wire since the timer was buggered, works fine this way just not automatic like it should be

Yea got my crown ecu pinout and pretty much going over the whole loom making sure it's correct. Also on my way to have a look at plugs and leads my cambelt just happened to be stopped on a spot revealing a huge chunk missing out of the cambelt. The deeper I dig the worse she gets . Next truck will be built from scratch at least then you know everything is done properly.