Strange misfire and smoke.

[Jack1998]

Evening all, 

Hoping the forum can come to my aid again as everyone was really helpful last time. 

 

Having a strange issue with my car. It started after a very spirited drive, first time I've really opened the taps on full boost since owning the car. 

Since doing that, whenever I start the car it begins with misfire, idles like a bridgeported rotary engine, very lumpy. This doesn't matter if it's cold or hot or if I've just turned it off and popped in the shop. This is almost always followed by no power and it stumbles up the rev range, if I baby the throttle and get it over 3,000 rpm it will clear and it will run absolutely perfect for the remainder of my journey. So far I have no smoke. 

Once I've gone through the above it will then proceed to smoke at me but only during certain conditions. It will smoke if I have a long period of decelerating, plumes of grey smoke come out the back. Or long periods of driving at low rpm, say 6th at 40mph, once I pull up I will be overtaken by a cloud of grey. On boost I get nothing, if I drive everywhere holding my gears I get nothing. The smoke will sometimes have a blue tinge to it but the car doesn't use any oil!

So far I've done a compression test which netted an almost perfect 180psi across all 6, a leak down test at 50psi which netted a perfect score across all 6. 

6 new NGK BKR8EIX,

6 new OEM coilpacks, 

Unwrapped all the coilpack loom and checked for breakages

Coolant is spot on, done a sniff test and no headgasket issues. 

I've had the car running and sprayed brake clean over everything to try and find a vaccum leak but the revs never rise. 

Pulled the crank sensor and cleaned 

Pulled TPS and cleaned 

Fuel filter replaced. 

When I pulled the plugs the other day to read them they are running hot, so would indicate to me lack of fuel. 

Im a mechanic by trade and feel bloody well defeated at this point. If anyone has any ideas or has had a similar problem before I start blindly replacing parts that would be greatly appreciated. 

My next thoughts are fuel pump, pulling injectors and flow testing, checking injector wire continuity. Turbos are in the back of my mind too but there is no smoke on start or on boost, or on overrun after boost. 

 

Thanks, 

Jack. 

[Swampy442]

Id say turbo oil seals for the smoke, when its hot let it idle for a while, if it smokes then thats the answer. Also pull the error codes, thats the first thing to do before spending a ton of money on parts, take it the coil clips are OK?

Edited May 15, 2023 by Swampy442 (see edit history)

[Jack1998]

 

50 minutes ago, Swampy442 said:

Id say turbo oil seals for the smoke, when its hot let it idle for a while, if it smokes then thats the answer. Also pull the error codes, thats the first thing to do before spending a ton of money on parts, take it the coil clips are OK?

Left it to tick over after a good run for about 30 minutes the other day, not a whiff of smoke. Certainly an odd one! It has got that smell that burns your nose, smells very much like unburnt fuel. 

Coil clips all look in very good order, I haven't tested them for continuity so possibly the next step. 

I have noticed on my boost guage my negative vaccum sits at about 360mmHg, which seems a bit on the low side Possibly worth borrowing a smoke tester also. 

[Swampy442]

What car is it first off

 

[Jack1998]

32 minutes ago, Swampy442 said:

What car is it first off

 

Sorry i should have put that to start with. 

Supra MK4, TT6, still got the factory twins

[Scooter]

 

This bit is a wierd?

"This is almost always followed by no power and it stumbles up the rev range, if I baby the throttle and get it over 3,000 rpm it will clear and it will run absolutely perfect for the remainder of my journey."

Are you saying it runs totally fine in all conditions after this or just when kept over 3000rpm?

[Jack1998]

3 hours ago, Scooter said:

 

This bit is a wierd?

"This is almost always followed by no power and it stumbles up the rev range, if I baby the throttle and get it over 3,000 rpm it will clear and it will run absolutely perfect for the remainder of my journey."

Are you saying it runs totally fine in all conditions after this or just when kept over 3000rpm?

Yep totally fine in all conditions after this. It's like taking it above 3,000rpm clears whatever sulk it's having. 

 

[Swampy442]

Is it UK see, J spec, any mods, and add on electronics etc

[Jack1998]

2 hours ago, Swampy442 said:

Is it UK see, J spec, any mods, and add on electronics etc

J spec, just basic bpu mods, walbro pump, fmic and piping, induction kit, restrictor plate, FCD, boost controller 

[Swampy442]

FCD set correctly? Its not outside the realms of possibility that the ECU is shot, thats becoming more common.

None of it explains the smoking though, engines dont smoke intermittently, they either do or they dont

[Jack1998]

10 hours ago, Swampy442 said:

FCD set correctly? Its not outside the realms of possibility that the ECU is shot, thats becoming more common.

None of it explains the smoking though, engines dont smoke intermittently, they either do or they dont

FCD is set about 7.5, seems to work well. 

ECU is another thought, I do have a spare link g4x with a basemap on which Im going to throw in and see what that nets me. 

The smoke is grey, so I'm assuming fuel, but with it happening only on low rev overrun it's a bit of a mystery. Only other idea I had was a slightly blocked oil pickup strainer in the sump. 

[Jack1998]

I have also noticed I'm getting up to temperature a lot faster and my fan kicks in more than usual (electric one), possibly coolant temp sensor confusing the engine

[Mike2JZ]

Electric stock fan is controlled by a temp switch at bottom of the rad so works independently to ECU, so likely you are getting very warm in the rad if you get that to come on (98C+)

id put the HKS FCD back to 12 and lower the boost for a test. See if issue still relevant like that. 
 

had a similar issue to this once with a stock ECU, used to run like shit for 30seconds after starting, smoking etc then cleared up

[Jack1998]

12 minutes ago, Mike2JZ said:

Electric stock fan is controlled by a temp switch at bottom of the rad so works independently to ECU, so likely you are getting very warm in the rad if you get that to come on (98C+)

id put the HKS FCD back to 12 and lower the boost for a test. See if issue still relevant like that. 
 

had a similar issue to this once with a stock ECU, used to run like shit for 30seconds after starting, smoking etc then cleared up

Just had a quick play with the FCD, only turned it down to 8 as it fixed the problem on a friend's car the other day! 

I could actively hear the idle changing as I switched the dial, changed it to 10 and seems to be idling about 900, still wobbles a little on idle but nothing out of the ordinary for a modified decat I wouldn't think. 

[Jack1998]

Just eyeing the oil as well, smells very much like fuel on the disptick, I wonder If the FCD playing funny buggers has caused overfueling resulting in fuel contaminated oil. Would explain the smoke if the oil has been thinned. 

Just waiting on it to cool down for 20 minutes, fingers crossed setting 10 does the job, still boosts fine, to 1.2 bar. 

[Jack1998]

No joy with FCD, unplugged it altogether and wired the ECU back to standard but still no go!

[tomgeer]

Can you borrow an igniter from someone? They are known to cause issues sometimes.

 

[Mike2JZ]

Typically with HKS FCD, settings lower than 12 will make the engine run leaner as the load signal (MAP) gets skewed more the lower the setting is. This skewed load signal has a knock on affect on fueling/ignition/idle and a few other bits and pieces. A setting of around 9 is generally in the right area, but to be honest unless you are monitoring AFR/Knock and power output it can be hard to dial in the HKS FCD settings, as there are variances on how each 2JZ runs even from the factory which has a knock on affect on what the HKS FCD will do. 

From factory 2JZ runs quite rich on boost (~10AFR), said that If you are running rich enough to cause smoke come out the exhaust, then I'd imagine this will be why your oil smells of fuel. There is a number of different things that could be causing this, but my approach to diagnosing anything on a stock ECU car is to first start with the ECU. In their old age these ECU's can do funny things and you can chase your tail sometimes trying to approach the problem from the wrong end. Normally I change ECU, if issue is still prevalent then I dive into further diagnostics for whatever system could be at fault.

 

[Scooter]

Jack1998 where are you based? I have a test ECU (it works perfectly apart from not allowing 4th gear on an Auto)

You could also get a Chris Wilson FCD as they are I think more reliable/non adjustable.

[Jack1998]

Fixed! 

 

Appreciate all the responses, the problem ended up being the upper o2 sensor causing the missfire. This was shoving loads of fuel in at idle, which was going straight past the pistons into the sump diluting the fuel causing the smoke on overrun as it was pulling the diluted oil past the rings. New sensor, replaced the oil and it's a very happy car again. The oil I took out stunk of fuel! 

[Swampy442]

Nice fix and thanks for the update