1UZ-FE engine miss at cruising speeds

[mick08]

I got a !uz in my hilux 2wd, the conversion was done by me and has been virtually trouble free motoring for over 2yrs now, but in the last 2weeks its developed a miss, i don't know if its related but a few months ago i had just left work onto a busy road and gave it a bootfull, it launched fine but completely layed down just as it changed into second (its auto) it didn't stall but almost put me thru the windscreen it just died for a second and then was fine, fast forward to the begining of last week and it now has a miss under light load and upshifts thru the gears a bit earlier, it actually sounds louder and almost tinny or echoey as its missing and if i put my foot down harder it'll struggle thru it till eventually i'm flat to the floor and it picks up like normal and goes. i thought the easiest and cheapest thing to do was clean the AFM which i did with throttlebody cleaner spray (removed AFM) but this made it a bit worse, now when it breaks down at light throttle it sounds like i'm cycling my foot like a retard on the gas and off until i flatten it then it goes fine, my other thought was the TPS, is it possible for this to be burnt or worn in the most common place the throttle is held?? (part way open cruising) Any help would be greatly appreciated, THANX MICK...

[4age_fun]

Have you washed the engine lately? Water usually sits in the plug wells shorting the spark.
Also check your fuel pump ecu by bypassing it.
Check your spark plugs
Leads
Coil packs
Also the engine ecu caps can fail and give false readings/signals causing bad fuel economy and even hesitation under acceleration. Check and if necessary change the caps. (I did it and it improved performance and fuel economy on my car).

Hope this helps

[mick08]

No i havn't washed the engine lately, usually do tho every month or so but when i did the conversion i made sure those seals were in good order. Im not using the fuel pump ecu instead i use a tachometric relay to control it, seems quite reliable and hasn't let me down yet.The plugs are iridium jobbies and are only about 40,000ks old, i have checked them a few times over the 2yrs and they are always clean but ill check em again just in case, the leads im pretty sure are factory so could be as old as the engine 91model with about 14,2000ks total, the older 1uzs didn't have coil packs they just run 2 coils and use them like running 2 4cyl engines, im not real sure how to test them but will get that checked out, now the caps you mention in the ECU are very interesting, is it a hard job to replace, i imagine its a soldering job but have never looked inside an ECU, will i be able to tell by looking if they have failed-- thanks again for your quick reply.

[4age_fun]

Look at this thread should explain everything regarding the ecu - Soarer Central: Archive through March 01, 2010

[Cuzzo]

Chnage the plugs for some normal ones (non-platinum) and also "borrow" another AFM and try that.

I had the exact same symptoms AFTER i cleaned my AFM and it would run shithouse. You may even be able to drive it with the afm unplugged to see if this fixes it. If it does ill be looking at the AFM.

[4th surf]

I have exactly the same issue and have attacked it with the "Back to basics" approach starting with leads, plugs, clean injectors and giving the top end a bit of a clean up with some "Suby spray" which while it shut the noisey tappet on the L/H cylinder bank up did nothing for the missfire. Now this only seems to occur when the engine is at operating temp and when the ambient air temp is above 26 degrees C. No codes were firing nor was anything showing up in Data display on my scanner. I replaced the main O2 sensors when the new custom made extractors went on (bye bye engine strangling Crown logs) as one stripped the thread only to get a minor improvement. Now as luck would have it the alternator decided to die so once a new one was fitted she actually began to log a code when this issue occurred..And it is related to the air flow meter.. Intake Air Temp sensor which is part of the air flow meter. A replacement air flow meter should solve the problem

[timbosaurus]

could be completely the wrong path, but my 1G BHG had the same syptoms. Seemed to accel alright, but then when I backed off on the highway it would intermittantly misfire on 1 cyl. Thought it'd be plugs/vac leak, but nothing seemed to help. After a few bootfuls it just got worse, so checked and there are now bubbles in the coolant.

[George]

4th surf Among many other things, Air temp sensor error code may indicate wrong type of AFM sensor (what's curious is that with wrong sensor, there will be no MAF error code, only THA)

[4th surf]

could be completely the wrong path, but my 1G BHG had the same syptoms. Seemed to accel alright, but then when I backed off on the highway it would intermittantly misfire on 1 cyl. Thought it'd be plugs/vac leak, but nothing seemed to help. After a few bootfuls it just got worse, so checked and there are now bubbles in the coolant.

While this isn't the issue with mine it is still worth checking to rule it out

4th surf Among many other things, Air temp sensor error code may indicate wrong type of AFM sensor (what's curious is that with wrong sensor, there will be no MAF error code, only THA)

True but with the 1UZs they run the hot wire type (same as a 7M-GTE) in UCF10/11, UZS131/41, UZZ31/32 and later than that a Carmen Vortex leading upto the change to VVTi in '97 and mixing those two types up causes problems. Strangely enough the EFI Turbo diesels (2L-TE and 1KZ-TE) present a similar symptom when the IAT sensor is not connected

[Hack]

This

clean the AFM which i did with throttlebody cleaner spray (removed AFM) but this made it a bit worse

is bad.


Copied from somewhere - (Prob Toymods...)

I cleaned the afm or maf whatever its called on my 1uz (ls400) motor and the motor decided not to run too well, and now has the occasional misfire unless i free rev it to the redline.
I cleaned the honeycomb type stuff with carbie cleaner and the afm/maf unit with crc contact cleaner.
The motor decided not the start and idle, then after that sorting it self out it will run and drive fine untill randomly it will either stall or erratic idle

Its the same as the 7M ones and they dont like being cleaned , I learnt this many years ago the hard way and have since just wiped them .
Just get the electronics part from a 7M , they are the same.

Hack

[4th surf]

CRC now have an airflow meter cleaner but I wouldn't use it on a hot wire type which are supposed to self clean. And yes the 1U AFM is the same as the 7M one just ensure that the number on the top of the AFM matches yours. Toyota do give a different part no but it is sold as a complete assembly with the housing and that is slightly different in the bolt spacing..

One other dumb thought that just occured to me after spending the day playing with an "Old school" Toyota and of course after a beer is to check the condition of the "O" rings where the AFM goes into the housing. If there's an air leak there.... Well same symptoms as a dud AFM.. Guess I know what I'll be checking tom

[Cresleepa]

Good thinking about the o-ring, but remember it will still run (pretty well too) without the AFM....

[4th surf]

Yes and that's due to dropping back to a factory default that seems to be between a fault and "limp mode" and while they seem to run fine they drink fuel like there is no tomorrow. Just threw another AFM in so will see what happens on the way home

[4th surf]

Reporting back after fitment of another AFM..

Holy F@rking Sh!t Batman!!

I didn't know the damn thing went that well. 160 clicks in 3rd gear with 4.3 diffs and 31 inch tyres and one very embaressed HSV driver later

Anyhow no more missfire, Less fuel smell from the exhaust and in this instance it is without running the Sub O2s which does not seem to be an issue on models that run 1 Wire main O2s. Models that run 4wire mains need the subs. No codes fired and remember my engine is from a Soarer which has the highest output of the UZs.

I'm wondering if the AFM in mine was suspect from day one as all of the conversions that I do use Celsior engines so performance has been comparable. I want a dyno

[Cresleepa]

Good work!