20v 4AGE ST Misfire/miss.

SidewaysEightSix
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20v 4AGE ST Misfire/miss.

Postby SidewaysEightSix » Fri Apr 27, 2018 10:22 am

First and foremost, I did a search but couldn't find a thread of any significant help. Please read carefully as my setup is NOT stock.

Freshly rebuild ST 4AGE with approximately 500 miles on it. The engine was in fine shape but previous owner disassembled it to "inspect it before going turbo" mechanically it's bone stock with exception of a port match and a TRD head gasket for a minor compression bump. Running and tuned on 91 pump gas.

Running an AEM EMS-4 ecu, with 1ZZ(Prius) COPs driven from an AEM timing puck mounted to a custom distributor adapter, and RWD waterpump setup.

Car ran great, took it to a very reputable shop to have tuned where it did experience a COP failure on cylinder #1 on the very last pull while setting rev limiter/decel tuning. The coil was replaced and then ran perfect.

After about a 90 minute drive on the way to its first track day (after several successful short-medium length drives.) the car started to develope a misfire which proceeded to only worsen. I've since spent many hours trying to diagnose what is going on. The car starts and idles fine, and will drive fine below 3,000. When the car is still warming up it will rev all the way to its 8,000rpm rev limiter. As the car warms up the misfire gets worse leading me to believe it's either electrical/spark related or experiencing a lean condition. Additionally if I let the car sit 15-30 minutes to cool the car seems to run better for a very brief amount of time. Leading me to suspect it's a heatsoak/electrical/spark issue.

The guy that did the wiring harness has gone through it twice now, double checking all grounds and circuits with no faults found.

We have confirmed timing is dead on.

I've since replaced all 4 cops (with used ones) and no change.

I did have junk in the gas tank clogging the prescreen to the pump which was causing a slight lean condition on light loads which has since been cleaned up and has seemed to improve AFRs. (This was noticed on the same drive misfires started). AFRs seem to be fine, no difference from when it was originally tuned

I've boroscoped all 4 cylinders and see zero evidence of detonation

The fuel lines have been checked and do not seem to be clogged. Also checked the fuel filter which was dirty, but not clogged and has been replaced with no change.

Tomei fuel regulator / Gauge stays consistent at about 36psi

Plugs look fine. They are NGK BKR6EP-11 which were brand new so have no more than 500 miles on them, however did go through the whole startup/tuning process. I have new plugs ordered which will be here today, that's next on my list.

The injectors came with the engine prior to its rebuild. I'm considering sending them to get cleaned/bench flow tested.

I also slightly suspect it could be a coolant temp sensor however the AEM seems to be giving a fairly accurate temp reading (at least it seems to be logically close)

Also thinking that the Air Intake Temp sensor could be tricking the ecu.

I've read Intake side manifold leak could cause this, which makes sense as it would cause a lean condition, but as stated my AFRs look fine. Also it's fresh gaskets and vacuum lines so it's hard to believe 500 miles has done any damage to them.




Any insight is appreciated. Next on my list is to replace plugs, injectors, and the fuel pump.

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jondee86
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Re: 20v 4AGE ST Misfire/miss.

Postby jondee86 » Fri Apr 27, 2018 2:48 pm

Pretty sure you should be running BKR6EP-8 in a ST (AE101) engine. Might be
worth trying a set to see if it makes a difference.

Cheers... jondee86
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SidewaysEightSix
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Re: 20v 4AGE ST Misfire/miss.

Postby SidewaysEightSix » Fri Apr 27, 2018 3:46 pm

It's funny you recommend that as I was considering trying those! We shall see shortly!

Edit. I assume BT would also use the .8 then? Or am I mistaken? It's a friend with a BT that told me to use the 1.1's as that's what he's always used. I'd like to relay that info to him as well as know for when I get around to starting up my BT car....

Edit again. BKR6EP-8's installed. Cars only getting worse. Although now I'm seriously LEANing towards fuel. (Get it?!)

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Re: 20v 4AGE ST Misfire/miss.

Postby jondee86 » Fri Apr 27, 2018 6:58 pm

Interesting. The NGK New Zealand selector recommends 8's for the AE101 and 11's
for the AE111. But when I checked on the Japan NGK selector it recommends 11's for
both ST and BT :? Only thing I can put that down to is that these engines typically run
on higher octane in Japan than we have available here, and the local recommendation
may take that into account. If there was no improvement with the 8's then gap is not
the problem.

If the engine runs fine at <3000rpm but starts to breakdown at higher rpm's getting
worse with WOT, then fuel is a likely suspect... or ignition. If your AFR's are between
12 and 13 then fuel is getting in there.

Do those Prius COP's have built-in dwell control ? I have not worked with them but if
both the COP and the ECU are both trying to control dwell it can cause a problem.

Cheers... jondee86
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SidewaysEightSix
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Re: 20v 4AGE ST Misfire/miss.

Postby SidewaysEightSix » Fri Apr 27, 2018 9:28 pm

The Prius coils are "smart coils" which have built in dwell-control. The AEM just compensates for this. It's possible you are onto something, but I'm leaning away from that conclusion for a couple reasons, but I won't write that off just yet.


My drive today experienced the worst/quickest symptoms to date. Which has changed my thought process yet again, yet brought me full circle to suspect yet again it's the fuel pump. AFRs seemed okay only at low rpm. Past 3,000 (even as low as 1,800 by the time I pulled it back into the garage) was showing a lean condition, up until the engine stumbled and missed heavily then AFRs were basically a blindfolded monkey tossing darts.

Once I got the car back I checked again for fuel pressure and noticed a significant drop in fuel rail pressure. Aside from that with the car off and the fuel circuit active you can hear how horrid the pump is beginning to sound.

I'm hesitant to say I'm confident, due to how inconsistent my symptoms have been, but I'm really back to suspecting the pump. If we take into account the car ran fine up to its initial issue, when I simultaneously noticed the pump cavitating, its possible the clogged prescreen which undoubtedly ran the pump low of fuel actually caused damage to the pump. This so far is theory, but it's making the most sense in my head.

This might be a case of a component lingering on and causing me to overthink things.

Of course, I'm still open to any suggestions, but I think next on my list is to order a new pump and do a vigorous cleaning of the tank.

I appreciate the response. At most you could be on to something. At the very least it's good to bounce knowledge off another set of ears, or in this case eyes.

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Re: 20v 4AGE ST Misfire/miss.

Postby jondee86 » Sat Apr 28, 2018 12:25 am

Ahh... if they are smart COP's and the ECU has been set to take that into account,
then you can cross that off your list. If the fuel pump is on the way out and cannot
maintain the correct rail pressure, then it will definitely cause your AFR to lean out
as the engine load rises.

Assuming that your FPR is vacuum compensated, the rail pressure should momentarily
rise when you rev the engine from idle. If it drops, then your pump has a problem. On
the road, if your AFR goes lean instead or rich when you accelerate in (say) 3rd gear
fron 2000 tp 3000 rpm, then your pump has a problem.

Bear in mind that any restriction in the fuel lines (kinked hose, flattened hard line etc)
that creates resistance to flow can cause the same symptoms as a dying pump. But if
you have changed the filter and cleaned the in-tank screen, then changing the pump
is a reasonable next move.

Cheers... jondee86
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Re: 20v 4AGE ST Misfire/miss.

Postby SidewaysEightSix » Sun Apr 29, 2018 12:14 pm

Just a follow up on those who may have similar symptoms or even those just curious. Dropped the gas tank today and I'm legitimately guessing I have over a gallon of rust mud. The pre screen is totally plugged up. Problem found!!

New pump and screen are ordered but I'm going to do a severe cleaning on the tank and attempt to get the pre screen clean enough to test drive today to verify I'm onto the right track!

I appreciate all the help Jondee86!

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Re: 20v 4AGE ST Misfire/miss.

Postby SidewaysEightSix » Tue May 29, 2018 10:51 am

Well. Another update. Brand new fuel tank, fuel pump, and fuel filter installed. Fuel pressure is good now, however my heavy misfire remains. Car runs fine until it gets warm. Then it runs like complete crap.


To update,
I've checked Timing
I've swapped coils
I've replaced the plugs twice
Brand new fuel tank
Brand new fuel pump
Brand new fuel filter


Next is to pull the injectors to send out and also do a compression test.

This is frustrating

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jondee86
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Re: 20v 4AGE ST Misfire/miss.

Postby jondee86 » Tue May 29, 2018 3:12 pm

I have never looked at the AEM software, but there should be an enrichment
table that adds fuel when the engine is cold and fades out the extra fuel as the
water temp rises. It should be zeroed by the time the engine reaches normal
operating temp. I would expect that when your engine is fully warmed up it would
have an idle AFR in the low 14's... could be a bit higher depending on the tuner.

The fact that the engine runs fine while warming up is likely due to the richer
mixture. So a simple test would be to bump your fuel pressure up by say 2-3psi,
and see if that has any affect on the misfire situation. Setting the Master Fuel
Trim 5% higher would have much the same effect. If more fuel does not reduce/
eliminate the midfire, then you can cross lean misfire off your list.

Cheers... jondee86
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Re: 20v 4AGE ST Misfire/miss.

Postby totta crolla » Wed May 30, 2018 2:11 am

Have you done a log with the AEM and checked for timing errors ?
AEM EMS is notoriously noise sensitive and if you have used any of the original wiring from the CAS to the ecu it should be replaced. Driving ok below 3000rpm is a classic symptom.

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Re: 20v 4AGE ST Misfire/miss.

Postby SidewaysEightSix » Fri Jun 08, 2018 5:57 am

I'm not using the stock CAS, nor the stock harness, please read my first post again. I'm using a AEM Timing puck purely to reduce issues communicating with the ECU.

We have done logs and as far as the AEM is concerned, timing is fine.

I've now replaced the entire fuel system, new tank, new pump, cleaned and benchflowed the injectors which are all at 100%. I've bumped fuel pressure 4psi. AFRs are fine, and never leave a prime mixture now.

I performed a cold/dry compression test and the results are as follows
#1 180
#2 181
#3 179
#4 182

I also found a intake manifold gasket leak, this has been remedied as well.

Misfire remains. Car operates flawlessly until about 5 minutes after startup. And again. Misfires anywhere above I'm guessing 2,800-3,000rpm

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Re: 20v 4AGE ST Misfire/miss.

Postby jondee86 » Fri Jun 08, 2018 4:52 pm

If you slowly increase the engine rpm, say in 3rd gear on a level road, can you
reach high rpm with little or no misfiring ? That is, does engine load affect the
onset of misfiring ?

If it does, it would be worth trying a set of plugs one heat range colder. A cheap
set of basic NGK's would be fine... just to see if the plugs are overheating.

How does the AEM fire the COP's... sequential, wasted spark or batch ? Any chance
that the COP's are overheating ? Unlikely, but I'm just trying to think of anything
heat related that could be making a problem.

That engine is going to want some good quality gas. Depending on what you are
currently using, trying something higher octane or adding some octane booster
could be worth a crack.

Best thing is to change only one variable at a time and check for a +/- change.

Cheers... jondee86
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Re: 20v 4AGE ST Misfire/miss.

Postby SidewaysEightSix » Fri Jun 08, 2018 8:23 pm

The Cops were run as wasted spark, that was one of the first things we looked at. It's now sequential.

I have been curious if it's a low octane issue. But again the car was tuned and running on pump gas fine

I did some digging and I found a issue that at least in theory answers every question. The custom distributor adapter (for lack of a better name) that drives the AEM timing puck is taking in oil. It's actually making its way all the way into the timing puck itself.

My theory is, oil is filling the bottom side of the puck and getting the internal trigger wheels "wet". This explains why it starts and runs fine for a short period. Once the engine warms up, the oil is being pushed through the bearings and causing the Hall effect sensors to miss some counts. The computer doesn't show bad timing but I think it's trying to compensate. This also explains why it won't hot start now. And it explains why a 20 minute wait remedies the symptoms for a breif while.


It's all theory. But this is going to be the next step. For now I'm attempting to drain it to see if I get a difference in performance. It's also possible I've already destroyed the puck

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Re: 20v 4AGE ST Misfire/miss.

Postby jondee86 » Sat Jun 09, 2018 2:51 pm

Just googled to see what was inside that "puck" and it uses optical sensors.
So if you have oil getting flung around inside you probably have your answer.
A bit of printed circuit board cleaner spray should clean that up OK.

Cheers... jondee86
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Re: 20v 4AGE ST Misfire/miss.

Postby Sprite » Wed Jun 13, 2018 7:30 pm

Might be a bad Igniter. I believe it may change the dwell times at around 3k rpm right where you are seeing the miss- had a similar issue with a Mitsubishi igniter once. $30 used ones on eBay. 89621-12050
Rick

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Re: 20v 4AGE ST Misfire/miss.

Postby SidewaysEightSix » Tue Jul 03, 2018 12:00 pm

Sprite/Rick. No offense, I appreciate all input, But you didn't read my post/thread. If you did you'd see that I'm using COP setup and have tried swapping coils more than once with no change.

Jondee86. Yes. You are right. Unfortunately the puck is bolted together using three small Phillips screws that have undoubtedly been set with some kind of threadlocker. Meaning I've had no success in cracking it open. My buddy has a tool for high torque screws so I'll try that soon to crack it open and clean it


However, I have an update. I pulled my custom adapter out and added a shaft seal in between the two shaft bearings. While I did this I left the puck on a tray, harness down, and got about 1.5 teaspoons of oil out of the puck by it draining through the harness slot over the course of a little over a week. I reinstalled every thing yesterday and the car was back to full power and no misfires what-so-ever even after 15 minutes. I parked it before I pushed my luck. So it was definitely a timing issue due to the optical sensors being confused from the oil. The remaining question is, was it oil volume? Or oil pressure? (Inside the puck)


I need to do some more testing, but so far, I think I'm finally on the correct track. The good news is I found other potentially bad issues before they became catastrophic.

I'm going to have to re-tune the car however because the fuel system is back to 100%. Fuel pressure is roughly 4 psi higher than originally tuned, and the injectors are on average firing 14% more fuel.


Huge shoutout to everyone that posted, even if the suggestions turned out to be inconsistent with the issues... it's always good to bounce logic off a few other minds. I'll keep you all posted!

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Re: 20v 4AGE ST Misfire/miss.

Postby jondee86 » Tue Jul 03, 2018 5:47 pm

SidewaysEightSix wrote:The remaining question is, was it oil volume? Or oil pressure? (Inside the puck)

Optical sensors can be affected by anything that obstructs light getting from the emitter
to the receiver. So dust, condensed moisture, carbon, insects or oil getting in the wrong
place will eventually cause a problem. That is why the puck will be pretty well sealed up.
However, there should not be anything inside the puck that would be affected by pressure.

SidewaysEightSix wrote:I'm going to have to re-tune the car however because the fuel system is back to 100%.
Fuel pressure is roughly 4 psi higher than originally tuned, and the injectors are on average
firing 14% more fuel.

You might save yourself some work if your ECU has a Master Fuel Trim. If you set that to
trim 14% it should have the desired effect until you have some other reason for doing a full
re-tune of your fuel map.

Cheers... jondee86
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