Various minor issues - Warm idle misfire, Petrol smell, slightly poorer than expected

[cered]

Having a few very small issues but it's causing me to worry so hoping to get it sorted so I can go back to enjoying my car rather than worrying about eveyr single thing...

 

#1 - Very, very minor misfire at idle when warm. Like rev counter doesnt move, engine doesn't cut out but every second say there's a hiccough and the engine faulters, can feel it when sitting inside and hear the tiny 'thump' through the exhaust. Very very very minor, like I doubt anyone else would notice it. Car's running fine, plenty of power and no noticeable difference. AS far as I can tell the msifire became apparent after replacing the spark plugs - Used BKR6EIX-11 NGK plugs which are pre-gapped

 

#2 - Petrol smell, I don't know if this is because I have a decat but there's a pretty rich petrol smell coming from the exhaust when I start the car or come to a stop and the fumes drift into the cabin (rarely) but when I get out I can smell petrol in the air. I've checked the safety warning thread and the metal brake/fuel lines under the rear sub are fine and no leaks or bad stuff. Charcoal filter is still fitted too.

 

#3 - Getting about 18mpg for gentle a-road and maybe 20% town/suburban driving. Seems other people are getting 20-22mpg for normal driving even in towns. The o2 sensor has been replaced for a new denso one, brakes aren't seized (can't hear the pads dragging on disks at low speed, but when i coast the car stops quickly below 5mph but think that's the fat tyres/weight pressing down on them).

 

Known issues that may be of interest/going to eliminate these and see where I am regarding the above niggles.

- Coolant/heater hoses at the back of the engine weep when the heating's on slightly so drains the coolant a bit.

- Front tyres are due replacing & probably need alignment

- Fuel filter needs replacing (tonight) and fuel filter (K&N) needs cleaning and oiling

 

Also what's the turbo vvti cambelt change interval times? 60months/90k miles? I think it was done two years ago at about 80k miles but not sure, one resource said it needs doing yearly or every 12,000 miles after the initial replacement

[Wez]

Low MPG, fuel smell and lumpy idle, could be running rich.

 

Do you have an AFR gauge?

[np89]

Could be a faulty water temp sensor, will cause it to overfuel all the time

[cered]

Apologies title should read "MPG slightly poor-"

 

Yeah my gut feeling tells me it's running rich even with the new o2 sensor, but no AFR sadly. What could cause it to run rich? It's had new spark plugs, new o2 sensor, serviced in September 2015 btw

 

Is there a way to diagnose it? I'm going to be draining the coolant to replace the heater hoses so worth doing the temp sensor & thermostat at the same time? (The car warms up well, hot air after 5-7mins of driving through town for example so I don't suspect the thermo is faulty but may replace to cover everything)

 

Thanks for the quick replies, very much appreciated

 

- - - Updated - - -

 

Apologies title should read "MPG slightly poor-"

 

Yeah my gut feeling tells me it's running rich even with the new o2 sensor, but no AFR sadly. What could cause it to run rich? It's had new spark plugs, new o2 sensor, serviced in September 2015 btw

 

Is there a way to diagnose it? I'm going to be draining the coolant to replace the heater hoses so worth doing the temp sensor & thermostat at the same time? (The car warms up well, hot air after 5-7mins of driving through town for example so I don't suspect the thermo is faulty but may replace to cover everything)

 

Thanks for the quick replies, very much appreciated

[Wez]

Maybe the new O2 sensor, where did you source it from and does it have same part number?

[cered]

Trying to look for a temp sensor; 89422-35010 but having no luck online. Will call Toyota and see fi they have any for less than £1,000,000 and my pet goat.

 

o2 sensor was a Denso OEM replacement one, had the exact same plug, wire length & fixings as the old one (Genuine Toyota no longer available for VVTI TT) so had to make do. Bought it in a hope to improve my MPG but it didn't do anything to improve it

 

EDIT:

 

http://www.ebay.co.uk/itm/JZA80-Supra-2JZ-GTE-Water-Temp-Sensor-ECU-2Pin-Conceptua-/150706781515

 

 

These 'racing' ones any good?

Edited May 4, 2016 by cered (see edit history)

[Sheefa]

Similar idle issue here mate.

 

Firstly, give your idle control valve a good clean out, that certainly helped mine.

 

I have an AFR gauge and it keeps switching between slightly lean and slightly rich on idle. Idle dips below 900rpm when running ECU detects running too rich and so it reduces fuelling and then when it goes too low it thinks it's lean so increases fuelling and jumps to about 1200rpm.

 

I think it's a faulty/dirty O2 sensor too but not entirely sure yet as haven't checked. Car runs wonderfully all the time except this hesitant idle.

[Dr_Doom]

What mods does the car have? Are you BPU?

I see you have a decat fitted are you still running stock boost? You might be better with grade 7 spark plugs instead of 6.

[cered]

Similar idle issue here mate.

 

Firstly, give your idle control valve a good clean out, that certainly helped mine.

 

I have an AFR gauge and it keeps switching between slightly lean and slightly rich on idle. Idle dips below 900rpm when running ECU detects running too rich and so it reduces fuelling and then when it goes too low it thinks it's lean so increases fuelling and jumps to about 1200rpm.

 

I think it's a faulty/dirty O2 sensor too but not entirely sure yet as haven't checked. Car runs wonderfully all the time except this hesitant idle.

 

Yeah will clean out the TB and ICV when i get my K&N filter service kit, hopefully that improves things. I dunno if its the VVTI but my car idles at about 500rpm according to the clocks, maybe 900rpm when it firsts starts but then settles to 400-500pm but its smooth, doesnt strike me as the idle speed being too low. Will get a pic to show what i mean tomorrow. Certainly a frustrating thing, trying to find a tiny fault that could e on of 30 things -_-

 

What mods does the car have? Are you BPU?

I see you have a decat fitted are you still running stock boost? You might be better with grade 7 spark plugs instead of 6.

 

Yeah BPu with walbro fuel pump, decat, whifbitz full exhaust, K&N panel filter, NGK iridium plugs (BKR6EIX-11) but no boost controller or FCD so all standard boost wise. what's the part number for grade 7 NGKs?

Edited May 4, 2016 by cered (see edit history)

[Dr_Doom]

Yeah BPu with walbro fuel pump, decat, whifbitz full exhaust, K&N panel filter, NGK iridium plugs (BKR6EIX-11) but no boost controller or FCD so all standard boost wise. what's the part number for grade 7 NGKs?

 

That could be your idling issue. It's BKR7EIX. See here - http://www.mkivsupra.net/vbb/showthread.php?41927-FAQ-Spark-plugs

 

I used to have the same issue years ago when BPU and increasing the plug gap a tiny bit fixed this (obviously you can't do this with iridiums)

 

Also, while you're fault finding, have you checked to see if there are any fault codes stored on the ECU? It's easy enough to do with a paper clip;

 

http://www.mkivsupra.net/vbb/showthread.php?35920-How-To-Check-the-diagnostics-codes

 

Once you've done that, it might be worth resetting the ECU. When you start the car afterwards, the ECU self learns for around 10-15mins (just leave it idling, don't drive it). It'd be interesting to see if that makes any difference to your idle problem.

 

Check for error codes first as resetting the ECU will wipe any stored codes

[Dr_Doom]

Also, have you replaced 1 cat or both of them? There are two on the supra.

 

If you've only replaced 1 then this is still likely to have raised the boost, just not enough to see boost cut/fuel cut. This only kicks in at over 1bar. Stock is 0.8.

[cered]

Double decat as far as i can tell, two stainlesss piece where the cats should be. it does cut out at about 100mph at full throttle but sometimes at say 70-80 in manual mode

Edited May 4, 2016 by cered (see edit history)

[Dr_Doom]

If it's double decat then you must also have a restrictor ring fitted to prevent your turbos from over boosting and blowing up. The cutting out you mention is almost certainly boost cut which the ECU triggers at over 1 bar. Restrictor rings are usually set at around 1 bar although this changes depending on the car/mods.

 

Have a read of this (appologies if you already have ) http://www.mkivsupra.net/vbb/showthread.php?94705-BPU-(Basic-Performance-Upgrade) Especially the Jspec part as that explains the restrictor ring etc.

 

Either way you should definitely see a benefit swapping to grade 7 plugs.

Edited May 4, 2016 by Dr_Doom (see edit history)

[cered]

Aha, yeah I think there is a restriction ring on the exhaust - The car was sorted by whifbitz so should have it in place, would the fuel cut be a lot more frequent if it was straying over 1-1.2bar more often? I only get it once or maybe twice on a hard bit of accelerating (say 50-110mph on autobahn when overtaking)

 

Yeah I think I'll get more suitable plugs, the ones in there have a 1.1mm gap, suitable for TT BPU according to the FAQ but will get some 0.9mm ones

[Dr_Doom]

I might be wrong but I think that if you hit fuel cut it stores as error code 34 on the ECU?

 

According to the manual it's triggered every time you're holding over 1 bar for more than 2 seconds.

 

http://www.mkivsupra.net/vbb/attachment.php?attachmentid=13922&d=1112558346

 

You would definitely notice this when overtaking. Also, it would happen more on a cold day/night where boost would be naturally higher.

 

 

In terms of the spark plugs. I think it's more the heat rating of it than the gap. You're practically full BPU.

 

I'm not technically minded enough to know whether using a grade 6 instead of 7 would cause you to run rich and have lower MPG but there are plenty of people on here that will know

 

I'd add a boost gauge to your shopping list as well as a great safety precaution if nothing else

Edited May 4, 2016 by Dr_Doom (see edit history)

[cered]

God knows, but that does make sense, for example say I put my foot down at 60, and climb up to 90-100 about halfway through the rev range maybe where the turbos change over the fuel will cut very briefly and continue accelerating. Seems to happen regardless of temperature, winter or hot days like today. I'll text the previous owner and confirm if it has a restrictor ring in place

 

And yep, defo, going to get a manual boost controller & a basic but functional gauge to keep an eye on things for the sake of turbo longevity. Thanks for your help with this, hope to get an update after fitting & cleaning a few bits

[cered]

Water temp sensor in, the fuel guage doesn't seem to move while im driving anymore (noticeably) and the engine seems to be a LOT cooler after a long drive... looking positive so far

[cered]

Update:

 

"That's why she 'spittin"

 

Car's struggling a bit under heavy pedalling, particularly after second turbo. Seems to misfire causing a lot of popping and banging. Buying Grade 7 plugs and will update.

[Burna]

Update:

 

"That's why she 'spittin"

 

Car's struggling a bit under heavy pedalling, particularly after second turbo. Seems to misfire causing a lot of popping and banging. Buying Grade 7 plugs and will update.

 

I'd say coil packs, had to change mine recently.