20v 4AGE ST Misfire/miss.

SidewaysEightSix
Posts: 6
Joined: Fri Jan 11, 2013 9:59 am

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.

Disable adblock

This site is supported by ads and donations.
If you see this text you are blocking our ads.
Please consider a Donation to support the site.


User avatar
jondee86
Moderator
Posts: 2225
Joined: Fri Jan 11, 2013 10:21 pm
Location: Wellington, New Zealand

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
Give a person a fish, they eat for a day. Suggest they search before posting, and they learn a skill for a lifetime.

SidewaysEightSix
Posts: 6
Joined: Fri Jan 11, 2013 9:59 am

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?!)

User avatar
jondee86
Moderator
Posts: 2225
Joined: Fri Jan 11, 2013 10:21 pm
Location: Wellington, New Zealand

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
Give a person a fish, they eat for a day. Suggest they search before posting, and they learn a skill for a lifetime.

Disable adblock

This site is supported by ads and donations.
If you see this text you are blocking our ads.
Please consider a Donation to support the site.


SidewaysEightSix
Posts: 6
Joined: Fri Jan 11, 2013 9:59 am

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.

User avatar
jondee86
Moderator
Posts: 2225
Joined: Fri Jan 11, 2013 10:21 pm
Location: Wellington, New Zealand

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
Give a person a fish, they eat for a day. Suggest they search before posting, and they learn a skill for a lifetime.

SidewaysEightSix
Posts: 6
Joined: Fri Jan 11, 2013 9:59 am

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!

Disable adblock

This site is supported by ads and donations.
If you see this text you are blocking our ads.
Please consider a Donation to support the site.



Return to “TECH: 4A-GE ENGINE”

Who is online

Users browsing this forum: No registered users and 2 guests