1UZ no idle, running very rich + missfire

[Tremor]

Hello all,

I have a 1st gen 1uz I rebuilt that I recently swapped into my 1992 Toyota pickup and I am having some issues now keeping the engine running and not holding an idle. I have purchased wiring instructions from gloverman and wired it up properly and for the time being have the engine running. As far as I can tell here is everything I have checked

- verified o2 sensors are plugged in and working
-verified MAF is working
- good fuel (walbro pump hardwired for key on while testing)
- all new cap/rotors/plugs/dizzy
- all timing and tension components are correct and brand new (running just fine on the test bench)
- verified TPS position via multimeter
- checked and no codes are present, just the flashing bulb to indicate no codes found
- ECU was professionally rebuild by a UZ specialized company


The engine starts for about 2 seconds and dies immediately unless you keep your foot on the throttle, when you do force it by doing so it runs quite rough and occasionally misses. I did pull a plug today and it was very very sooted which I think may account for the misfiring? I believe with the 02s were out it went into a closed safety loop and ran rich to avoid leaning. I am going to clean the plugs today but was wondering if anyone had any idea on the no idle? really a head scratcher for me

The only things electrically aren't plugged in on the engine sensor is the EGR plug and there others that I have attached feel free to let me know if thats what I am missing. Im open to ideas because at this point im a bit more then even puzzled


is there a NSS in the trans harness that maybe I need to bridge? would a completely stuck IACV do this maybe? Do I need to adjust the throttle stop?

Thanks again,
Sam

 

[extractors]

Have you removed and cleaned the IACV ? Checked bearings etc ?

 

[Tremor]

Have you removed and cleaned the IACV ? Checked bearings etc ?

Hey there extractors, I did indeed and they seem fine no noise no issues and there is zero change between it being kinked or tested fully opened.

I did get it to display codes as I was looking at the wrong pin, I only got EGR, Sub o2's and a FP control fault (externally powered for now) which none of should be causing this severe of an issue.

Again here are the symptoms
- extremely rich run condition all of the time
- misfiring/popping under load or even idle
- 2 seconds of running and then immediately stalls out
- when holding it running it can run somewhat good at 1k rpms but after awhile it starts to slip and misfire.


I just worked through all of my wiring today following glovermans guides and short of the MREL nothing seems to be an issue, the MREL is fine and gets 12v+ when keyed on but does not stay on for 3-5 secs like its apparently suppose to but again, I have seen plenty of 1uz with this and they can still idle and never display anything as severe as this.

At this point since cap/plugs/rotors are fine my number one sneaking suspicion is a failure on one or multiple injectors to some degree or dirty beyond belief, half of them were used that I picked up from a yard and cleaned and recapped but none of them have been tested. Unless someone has other thoughts I think this is my problem since it can still run somewhat under load. Likely going to bite the bullet and buy a set of known good injectors this week unless you all have any other better ideas,

 

[extractors]

New or cleaned injectors might be worth doing either way.

Have you replaced or checked the coils ?

double checked resistance on all leads ? especially lead from coil to cap ?

How is your breather system setup ? often these are wrong causing unmetered air to enter engine ?

checked and or replaced every vac line, check for manifold leaks ?

These engines will run fine without a MAF, rich yes, and 5.5 k rev limit but do run ok for testing purposes.

I would also double check the cam timing

 

[Tremor]

New or cleaned injectors might be worth doing either way.

Have you replaced or checked the coils ?

double checked resistance on all leads ? especially lead from coil to cap ?

How is your breather system setup ? often these are wrong causing unmetered air to enter engine ?

checked and or replaced every vac line, check for manifold leaks ?

These engines will run fine without a MAF, rich yes, and 5.5 k rev limit but do run ok for testing purposes.

I would also double check the cam timing

Hey there and thanks again for your advice,

Coils are brand new, all leads are brand new and in the correct firing order, coil to cap all test good. The breather setup is the one directly from the valve cover I believe? if so I have also seen that be an issue but it is directly routed and hose clamped to the throttle body tube.

Running a pretty minimal vacuum setup short of the booster and the IACV but I believe done the correct way via glovermans video regarding vac lines, if im not using them they are rubber capped off. EGR is completely deleted via lextreme's kit. Engine was completely re built and not other vacuum is notable when tested while running.

Cam timing setting is correct including the pre tension and lineup.

The biggest note I will and neglected to stupidly is that when this engine was on the bench and wired it ran exactly like it should have not too rich not too lean and responded perfectly to throttle BUT I did have an injector fail and dump a massive amount of gas into a cylinder and actually shoot fire. When I replaced a few of the suspect injectors I replaced them with ones that were not tested and that I simply cleaned but before that were sitting on a shelf for a longggggg time so it would make sense. I ordered a set of 8 so hopefully will be able to test later this week and find out for sure, honestly I really didn't even think about how old the replacements I picked up were until today.


Also waiting on some replacements igniters as in my genius while testing leads near the firewall let a 12v hot wire unshielded hit the igniter body/ground point heard a good zap and now get no spark to the coils (sighhh) I will keep this updated as soon as I find out more but the more I look at injector failure symptoms it lines up the most and seems to be the key culprit.

 

[extractors]

Ok,

Start with new injectors and go from there. If haven't already replace injector plugs as well.

Maybe also bench test old injectors in the interim.

 

[gloverman]

I think your email might be one of the 75 I have to do. Sorry for the delay, Ill get onto it as soon as I can.

 

[Tremor]

Ok,

Start with new injectors and go from there. If haven't already replace injector plugs as well.

Maybe also bench test old injectors in the interim.

ITS FIXED!!!!

I replaced the injectors, charged the battery and VROOM

Truck now fires right up like its supposed to, though it pops for a little but, likely from running extremely extremely rich beforehand. Im assuming the plugs are probably extremely sooted so I will clean them up and chase it down from there. It only does this for about 10 seconds, then right after idles like a dream!

Thanks again for the help extractors and gloverman!!!!

 

[extractors]

Great news.

Ditch the old plugs just throw a new set in there. Cleaning plugs I have found very hit and miss once properly fouled.

 

[Tremor]

Well.... I spoke a little too soon.


When chasing down the misfire some bizarre things started to happen. As it was misfiring I stopped it, when to go get some gas because I thought maybe the tank was low I get back. After filling it up suddenly no spark.... hmmmm nothing has changed since then.

Pull codes and get a 14, which actually was a code I was getting on and off previously. Ignition control signal... hmmmmmm thats odd it wasnt present 15 minutes ago, So I spent all night and chased voltage through the entirety of the circuit following glovermans video

Primary and secondary coil resistance was good for both
Igniters reading 12 volts on the center pins like they should
12 volts to each coil, all connections are making contact
everything getting voltage where it should

What the f**k! Then I thought well if everything is ruled out of the equation in regards to sensors and power what could be causing this condition to pop on and off... surely not the 500$ ecu that was sold to me as a rebuilt unit by a reputable seller...... surely not....





for F*cks sake........

Stock capacitors, in there stock location with one very very clearly burned and leaking out of the bottom.

That will do it, I will keep this updated when I figure this mess out

 

[extractors]

Absolutely not surprised by this. Complete jokers. Name and shame these F..ckers !!

 

[Tremor]

Absolutely not surprised by this. Complete jokers. Name and shame these F..ckers !!

Yea very unfortunate, eBay shop by the name of pro-rebuilds pretty annoying because I directly asked if the caps were replaced and fully rebuild occurred and he acknowledged they were for every rebuild and it was fully gone through. Very surprised though honestly, he has almost a perfect rating and thousands of sales and still completely denied liability or wrongdoing.

I got very lucky and was able to borrow a ecu to test run it this weekend and the engine fired right up. It seems like it’s sorting itself out and learning but definitely doing an idle hunt but only occasionally weirdly enough (low-high-low-high idle) but the second I put on the throttle it RIPS

Misfire, trouble codes and all rough running issues are completely gone, just have some buttoning up under the hood and I should be ready to go (also an exhaust, good lord this thing is loud right out of the headers)

 

[extractors]

How does it run with AFM disconnected ?

Btw what injectors did you end up sourcing ? may be in need of a new set soon.

 

[Tremor]

How does it run with AFM disconnected ?

Btw what injectors did you end up sourcing ? may be in need of a new set soon.

Planning on testing that today, seems only on occasion for it to do. It was a little cooler out the other day and when I started it up it idled a bit higher as it is supposed to but in turn did not hunt for an idle at all. Seems like it also needs to just be driven and the engine run for it to learn a bit yet, seems to be getting smoother and smoother especially on startup, all misfiring is completely gone. I will pull the AFM plug today and see how it behaves.

Here are the injectors I sourced, I know its probably bad to get the non oems but I have a buddy with an ls400 and has run them for 2 years with zero issues and they have some good reviews. Hoping to get my oem ones rebuilt at some point just to have as backup.

Amazon.com

 

[extractors]

There's a ebay shop in the US, A $110 plus 25 ship for remanufactured and flow matched injectors. Otherwise you could have an injector specialist clean and flow test your original ones ? Aftermarket ones are probably fine as long as not running too lean.

Also make sure you have TPS set correctly per manual. Closed circuit between idle switch and ground @ .40 mm then open circuit @ .65mm. Idle won't take long to come around if TPS and IACV is working as should.

 

[Tremor]

There's a ebay shop in the US, A $110 plus 25 ship for remanufactured and flow matched injectors. Otherwise you could have an injector specialist clean and flow test your original ones ? Aftermarket ones are probably fine as long as not running too lean.

Also make sure you have TPS set correctly per manual. Closed circuit between idle switch and ground @ .40 mm then open circuit @ .65mm. Idle won't take long to come around if TPS and IACV is working as should.

Yep, setup TPS using the multimeter and verified set position using a feeler guage. Its giving the correct indication at least electronically that it is engaging and I popped it off and can physically turn the spring with no issue.

Switched back to my old ECU before sending it out today, its somewhat intresting. It will run perfectly fine and idle and rev fine but then all the sudden it will immediately pull the "I cant idle" bit and idle super super low, in the 300 rpm range then 5 minutes later instantly die for the next 5-10 restarts. It runs just fine now (no code 14) but for the life of it no matter what I unplug, replug it will only stay on with my foot on the throttle and presents
no codes other then the usual EGR and sub 02's.

ECU is getting shipped out to Texas today to a rebuilder to hopefully end this nightmare (after I paid $500 for a "rebuilt" unit) and to actually get it properly capped, traced and tested, even if something else is wrong man its hard to troubleshoot without a known good ecu. I will keep the forum updated.

 

[extractors]

Yeah agree, sort ECU first. I have a few ecu's so easy to swap for testing.

In the interim also check. Water temp sender underneath top right coil, cam and crank sensors, check resistance and continuity back to ecu.

 

[Tremor]

Yeah agree, sort ECU first. I have a few ecu's so easy to swap for testing.

In the interim also check. Water temp sender underneath top right coil, cam and crank sensors, check resistance and continuity back to ecu.

Might have a lead here when I was doing some chasing around this morning

earlier when it was idling "ok" without any real issues I had tested the TPS sensor with the feeler guage and a test light to rule that out as a possibility. Well, after it started doing its no idle cycle I probed the TPS before I sent the ECU out and there was no movement on the red/ground wire (the one that illuminates when you operate the throttle) I can fully squeeze the throttle with key on and absolutely no light when applying voltage to that wire.
Again, per usual no codes present other then the typical egr, sub 02's etc
My question is now what in the hell would causes interment TPS communication issues, Per the book I thought the ECU was supposed to go into protection mode and cut the 12v to the injectors when it did not detect communication with the TPS and a few other sensors?
My leading theory is somehow somewhere the wiring for the TPS is messed up (again though, intermittently like this for wiring issues in my history is unlikely) OR both ECU's are completely stuffed and failing to send the correct TPS communication signals?

working on probing out the crank sensor, cam sensors, knock sensors and the temp sensor today.

 

[Tremor]

Might have a lead here when I was doing some chasing around this morning

earlier when it was idling "ok" without any real issues I had tested the TPS sensor with the feeler guage and a test light to rule that out as a possibility. Well, after it started doing its no idle cycle I probed the TPS before I sent the ECU out and there was no movement on the red/ground wire (the one that illuminates when you operate the throttle) I can fully squeeze the throttle with key on and absolutely no light when applying voltage to that wire.
Again, per usual no codes present other then the typical egr, sub 02's etc
My question is now what in the hell would causes interment TPS communication issues, Per the book I thought the ECU was supposed to go into protection mode and cut the 12v to the injectors when it did not detect communication with the TPS and a few other sensors?
My leading theory is somehow somewhere the wiring for the TPS is messed up (again though, intermittently like this for wiring issues in my history is unlikely) OR both ECU's are completely stuffed and failing to send the correct TPS communication signals?

working on probing out the crank sensor, cam sensors, knock sensors and the temp sensor today.

Just re tested the TPS on this ecu while I was bored, again displayed the same symptoms so could deffintely be 2 bad ECU's but

Following Gloveman's vid I pinned 12v with my test light from the batter positive with my key in the on position, when I pin the RED wire, next to the brown wire like he says to instead of it being a ground and flipping the light on with 12v it is active as a positive wire and has 12 volts

Here are the rest of the readings

Blue-5v
Yellow-1.86 volts
Red- 11.6 Volts
Brown- Ground

To my understanding this TPS wire should read at 0.5 volts, right ?

Is this another ECU related thing, who knows... really really weird regardless though.

 

[Tremor]

SORTED!!

Though it tested fine the IACV bearing was completely seized, you couldn’t turn it even by hand.

I had a spare that was a little better, still doesn’t spin freely but still way better.

Swapped it in and sure enough it idles again, definitely not good or smooth but idle has indeed returned.

after I can figure out which bearings I will go ahead and buy some to swap in so it’s properly rebuilt but it was definitely the key issue.