Intermittent power loss, 1kz-te

Hi,
Got a strange power loss occasionally while on a light throttle and wondering if my diagnosis is correct.
When driving around 80 - 100kph and on a light throttle, I get a very very occasional surge/loss of power. Bit of black smoke on start up from cold, clear when warm, occasional black under load but not excessive or noticeable.

Feels like a stutter, air/fuel blockage, but I've run a tank cleaner/injector cleaner for quite a while, changed the fuel filter, checked the air filter and cleaned it out a couple of times but its in ok condition generally.

Had a good look over the engine and can't see any leaks or faults (owned it for six years so know it well).
Only thing that I did spot was the intake manifold needs a clean judging from the outside seeping a bit of oil so am thinking its a blocked intake manifold from the egr valve. Being an ex forestry van, its spent a fair bit of time idling and while its got 380k on the clock, its got an almost full service history by Toyota. Its not a service item so wouldn't have been done according to Toyota.

Can't think what else it could be besides a blocked injector, but my mechanic doesn't think its that at all - recons most diesel places pull them and clean them too easily and not to waste my money going that way. Did run the tank low a few times, but same mechanic says he's never done a tank filter in a Hiace and wasn't sure it would be that either (tried running it full, half or near empty tank, with no difference).

Short of going to an expensive diesel specialist, I think its a blocked intake manifold, and reckon its time to remove the egr from the system to prevent it happening again in the future. Being in NZ with plenty of Hiaces about, I like to fix things myself so unless anybody has some other ideas, its out with the seats tomorrow!
Cheers

If it's a fuel blockage it affects full power far more than part power.
I had a blocked tank filter from the diesel bug and it really showed on power

IIRC the EGR closes at idle so idling for a long time won't bung it up. The inlet manifolds do get well clogged anyway though.

Could also be ECU caps starting to leak, not sure if 1991 models are affected as much as the mid 1990s.

Ah, cheers for that reply, power is down for sure. Figured black smoke was overfuelling due to lack of air, thought the EGR worked at low revs rather than high? Its a 1998 but don't know if that makes any difference. ECU caps, this is new to me, capacitor I take it? Anything else I can check for this fault, really don't want to do the intake if its not that, but know it needs doing anyway.
Only does it occasionally rather than every day, just don't want problems down the line as maintenance is key to long life.

Search for ECU or capacitors.
I did a thread here:
https://hiace-super-custom.forumotion.com/t3391-ecu-capacitors

I thought the EGR worked at middle revs only, it would mess up a nice idle. It does clog up the inlet manifold though.

Did u resolve the issue ? I’m in nz having the same issue ,, Boggs down at 3000rpm and gotta feather it to 100kmph , I can’t tell what’s up cause some days it’s mint next day or when I stop and then turn key to go again it’s a pig , annoying me

Hi there fellow Kiwi.
First check would be the ECU as @GPW said since this is a known issue. Take it out, remove the cover and look for any corrosion damage around the round capacitors. If you find any get that attended to before you start chasing other potential issues as unless the caps have already been done they will give trouble soon even if they're not the cause of the current issue.

Thanks mate I’ll be checking that right now , have been checking all back lines and everything looks normal , drove today ,70km one way ran like a dream , turned it off for 20 mins jumped back in and shame loss of power again , half throttle I can get it to 100 , if I plant foot if just sort of does nothing and slows down

Checked ecu , all clean and clear , blew fuel lines , all good , pulled tank out , drained , cleaned pick up filter , new fresh diesel , started up .... no change , thinking primer pump leaking into the
Fuel filter , or injection pump , I’ve checked everything else

When you plant your foot down and it does nothing is there any black smoke?
If not it sounds like a fuel restriction.

If the new primer-pump and fuel filter don't do the trick then: There is a TPS (Throttle Position Sensor) on the 1kz as it's essentially a throttled engine that tells the ECU to add more fuel, rather than a regular old diesel that just injects more fuel when you press the accelerator (that's connected to the fuel pump).

The TPS is tucked on the 'difficult to access' side of the throttle body but could possibly be tested for smooth action with a multimeter without taking it out.

Hi did you find the answer to your power loss I had same problem (3ltr 1kzte ) found the turbo pressure sensor pipe and filter from inlet manifold to sensor was bunged up cleaned it and poked out spigot in manifold improved performance immediately. All the gunge comes from the egr valve .

I’ll check that now

Blew through both of them no blockage at all , so this is how I fix it... I start up and warm up all good when I leave the driveway and there isn’t the power there that should be I bump it into neutral, turn key off and roll down the road and flick the key to star again and flick back into drive and most of the time after a few of those it comes right then usually it’s ok for the rest of the day

Thats wierd but so many variables to work 100% for full power (my latest was air in fuel from vac gauge fitted to monitor filter blockage I run on 50% vedg oil)easy fix, before that it was the said pressure switch and before that the dreaded ECU caps. Ahh the joys of running old vans but all in all they do go on for ever, I read with interest the horror stories of modern cars that break down (and they do) costing the owners a fortune to recover and pay the main dealers another fortune to fix, example Audi with a inertia fuel cut off switch under the passenger seat cost him thousands for a tow and garage charges before eventually fixed and that was a new car not covered under warranty.

Well update , limp mode , went to work did a quick job all good. Then came home and went to go out again and whammo limo mode , no check engine lights no nothing , and no power , won’t rev past like 1000 and been to diesel mechanic and they got no idea so it’s off to the doarkys Monday , geez I hope they fix this as it’s my work van and need it everyday , other wise it will be for sale as is ,

Nzcustom wrote:

Well update , limp mode , went to work did a quick job all good.  Then came home and went to go out again and whammo limo mode , no check engine lights no nothing , and no power , won’t rev past like 1000 and been to diesel mechanic and they got no idea so it’s off to the doarkys Monday , geez I hope they fix this as it’s my work van and need it everyday , other wise it will be for sale as is ,

Are you sure the ECU is good? I know you checked for leaky capacitors but that may not be the end of the story, and intermittent faults are often electrical. If there's any way you can borrow one and try swapping (both ways- make sure yours is OK in the other van), it would probably be worth it to at least eliminate that variable... (If you've already done that then I'm stumped).

Cheers,
W.

As stated some of the ECU caps can have subtle invisible faults.

The other side is that an input signal can tell a good ECU to go into limp mode - such as overheating etc so you may want to check all the sensors and wires+plugs that go to them are Ok.

Also the ECU has an ODBII port to tell you what is wrong, if the ECU is fine then ask it what the problem is: even if it means getting a Toyota garage to plug it in...

I’ve got it at the auto sparkys today , they can test and fix ecu onsite which is good , I told him to check absolutely everything , he is very good I’ll post an update soon as I know

We have it fixed !!! Ok so after all that it turns out it was the diesel pump . Got a second ha d one for $350 and needed a new spill control valve which we salvaged off the old one and done back to full power better than when I bought it !! Back to loving my van again , way too low and bouncy but I had to lower it for work , I lift a heavy carpet cleaner machine in and out all day ,

Great news!
The pump has a number of resistors and sensors - I wonder if it was a failure there rather than a mechanical issue - the random element of limp-home cutting in seems to rule out simple wear.

I had every electrical thing on it checked , and everything was fine , even on the old pump all resistors and things like that we’re giving the right readings. I think it was more that the only thing left was the pump itself as there were no other options

Spooky. Glad its all sorted, the Hiace always reminds me of ScoobyDoo when I'm in it LOL.

Sooooo , I ended up getting it fixed was a crappy diesel pump $1500 nzd later all sorted and running great , then it started to over heat ....a lot .... it broke my heart but I sold it , out so much time and money into it , but I still made $2500 profit which was awesome . Same day I find a one owner 4wd Toyota granvia , immaculate condition, $3500 , so I buy it and it’s great ....until .... any kind of u turn omg omg , the absolute worst turning circle I’ve ever had , I couldn’t turn around in one go on a very wide go ,,,,, then the diesel it would use holy heck !!! Was making me broke running that thing ..... so I sold that quick smart . Same price I bought it for then then then .... I find the absolute model is always been chasing for the same price $3500
93 super custom limited in white / gold , lowered , rims , tints , the works , and it runs fabulous!!!! I think I’m just gonna sit on this one , done some good kms though , 404,000 km but I take that as a good thing really , been well serviced and it’s not a bloody lemon !!! Yay back to a super custom I’m so dam happy