JDM UZJ100 sudden performance loss - feels like driveline parasitic loss but circumstances suggest fuel (1 Viewer)

[boma23]

Hi All,

Have one of those situations with multiple leads that could be acting as red herrings...

Low mileage 1999 JDM 4.7 (130k kms). Never been less than perfect for me. Fairly recent fresh fully synth oil and NGK Iridium plugs. I live on a small Caribbean island so dealer and high-level tech diagnosis is not usually an option, with no other parts cars around and spares take me weeks to ship in at double the cost by time landed.

I only buy fuel from one garage, as the other garage on island has had repeated issues with water in tanks (killed the fuel pump in my WRX which they replaced), and they also seem to have lower octane fuel. I have set references for performance and feel, as my commute has a steep 1200ft climb which the truck will labour up in 2nd gear 2k revs 60% throttle when running healthily -100% throttle gives a lot more noise for very little gain. Otherwise if in a big hurry, physically dropping to first will allow me to accelerate hard, before hitting limiter and getting more of a run on 2nd which will then hold higher revs. Gearing on the 4 spd with 33's is less than ideal.

Two incidents happened recently that may or not be related to what feels like a 30% power loss, coupled with newly heavy shifting between 1st and 2nd, and into reverse.

1. I accidentally ran the tank dry, but coughed my way to the garage, and filled again with the "good" garage fuel, and added some good quality injector cleaner. Performance seemed unchanged - no issues at this point.

2. one tank later, I was forced to fill up at the "bad" garage, and noticed the usual slight performance drop on the hill, that happens with their lower octane.

After this "bad"/weaker tank, I ran the tank down to when the light first flickered, then filled up with good fuel again, and another splash of fuel conditioner/injector cleaner. I didn't notice immediately round town, on the flat where the truck is still perfect under light load, but my next run up the big hill saw me not able to hold 2nd gear at all even at 100% throttle, and shifting between 2nd and first is notably very lumpy. Under hard acceleration the the truck sounds really throaty like it is trying really hard, but performance is simply hugely lacking. Not wishing to push things if I am in fact running lean, I am currently going up the hill at low revs/part throttle in 1st gear at 2k revs. No check light has been seen so far.


things done so far:

- fuel filter changed to a cheap purolator which (only one available on island, but correct model specific)
- new air filter
- cleaned MAF (with proper spray)
- added a full can of Octane fuel additive to the fuel, which restored some performance, especially low down, but nowhere near all of the performance and still restricted at high revs/full load. Light load/low revs feels perfect, it's like anything over 3k revs or just 100% throttle anywhere in the rev range is still severely impeded (fuel delivery?)
- I have ran that tank down now, and am back on a "good" tank of fuel from the good garage, but symptoms are the same.
- pulled the pump from tank - tank itself looks spotless, no debris or water in fuel, and pump looks/blows clear, as does the OEM sock.
- I changed the Fuel Pump out for new one with new tank sock (better sock design than OEM); no change.
- attempted to gauge any driveline losses by pushing truck in neutral on the flat. not very scientific on 33" RTs, but seems ok.
- check brakes and driveline any noticeable excess heat after driving (binding) - seems normal.
- dumped a ton of throttle body cleaner through the intake (after the MAF)
- discovered that both valve covers were only finger-tight (there was a slight oil weep each side), so tightened them up.
- discovered that the PCV at front of engine has a very loose grommet - this doesn't look like it is new or just happened though, so do not believe to be related to my issue (also I don't believe a loose PCV valve could even cause this much bad performance though?)
- tried 2 different scan tools but OBD2 connector by gas pedal is not getting comms (they power up OK)
- removed the OBD2 end of the loom and tested continuity (all 7 pins are good); tried connecting whilst it was hanging loose and playing with the connector; both code readers still power up but fail comms (you can see them trying all the different protocols in turn).
- examined OBD2 connector pins for the scan tool end, and checked OK visually (seemed fine)

to do
- grease all driveline components / flush trans??
- I keep reading about TPS, APPS, and cam sensors as possibilities, along with cleaning throttle body?
- fix OBD2 comms

Any other suggestions? This is my daily and work truck so a huge pain, and the WRX (head gasket!) and wife's car (BMW bad electrics) are both down at minute, so this is a huge issue.

Thanks for all and any help/suggestions!

Dom

 

[boma23]

Hi All,

Have one of those situations with multiple leads that could be acting as red herrings...

Low mileage 1999 JDM 4.7 (130k kms). Never been less than perfect for me. Fairly recent fresh fully synth oil and NGK Iridium plugs. I live on a small Caribbean island so dealer and high-level tech diagnosis is not usually an option, with no other parts cars around and spares take me weeks to ship in at double the cost by time landed.

I only buy fuel from one garage, as the other garage on island has had repeated issues with water in tanks (killed the fuel pump in my WRX which they replaced), and they also seem to have lower octane fuel. I have set references for performance and feel, as my commute has a steep 1200ft climb which the truck will labour up in 2nd gear 2k revs 60% throttle when running healthily -100% throttle gives a lot more noise for very little gain. Otherwise if in a big hurry, physically dropping to first will allow me to accelerate hard, before hitting limiter and getting more of a run on 2nd which will then hold higher revs. Gearing on the 4 spd with 33's is less than ideal.

Two incidents happened recently that may or not be related to what feels like a 30% power loss, coupled with newly heavy shifting between 1st and 2nd, and into reverse.

1. I accidentally ran the tank dry, but coughed my way to the garage, and filled again with the "good" garage fuel, and added some good quality injector cleaner. Performance seemed unchanged - no issues at this point.

2. one tank later, I was forced to fill up at the "bad" garage, and noticed the usual slight performance drop on the hill, that happens with their lower octane.

After this "bad"/weaker tank, I ran the tank down to when the light first flickered, then filled up with good fuel again, and another splash of fuel conditioner/injector cleaner. I didn't notice immediately round town, on the flat where the truck is still perfect under light load, but my next run up the big hill saw me not able to hold 2nd gear at all even at 100% throttle, and shifting between 2nd and first is notably very lumpy. Under hard acceleration the the truck sounds really throaty like it is trying really hard, but performance is simply hugely lacking. Not wishing to push things if I am in fact running lean, I am currently going up the hill at low revs/part throttle in 1st gear at 2k revs. No check light has been seen so far.

things done so far:

- fuel filter changed to a cheap purolator which (only one available on island, but correct model specific)
- new air filter
- cleaned MAF (with proper spray)
- added a full can of Octane fuel additive to the fuel, which restored some performance, especially low down, but nowhere near all of the performance and still restricted at high revs/full load. Light load/low revs feels perfect, it's like anything over 3k revs is still severely impeded (fuel delivery?)
- I have ran that tank down now, and am back on a "good" tank of fuel from the good garage, but symptoms are the same.
- pulled the pump from tank - tank itself looks spotless, no debris or water in fuel, and pump looks/blows clear, as does the OEM sock.
- attempted to gauge any driveline losses by pushing truck in neutral on the flat. not very scientific on 33" RTs, but seems ok.
- check brakes and driveline any noticeable excess heat after driving (binding) - seems normal.
- tried 2 different scan tools but OBD2 connector by gas pedal is not getting comms.

to do
- fit new fuel pump that just arrived
- work out where the OBD2 fuse is and check that, along with remove the OBD2 plug and check pins. I want to see if any lean codes or other errors.
- grease all driveline components
- I keep reading about TPS, APPS, and cam sensors as possibilities, along with cleaning throttle body?

Any other suggestions? This is my daily and work truck so a huge pain, and the WRX (head gasket!) and wife's car (BMW bad electrics) are both down at minute, so this is a huge issue.

Thanks for all and any help/suggestions!

Dom

edit - OBD2 has power (so not the fuse), just no comms....

 

[boma23]

edit - OBD2 has power (so not the fuse), just no comms....

last night I did following (first post edited to reflect)

- I changed the Fuel Pump; no change.
- dumped a ton of throttle body cleaner through the intake (after the MAF)
- discovered that both valve covers were only finger-tight (there was a slight oil weep each side), so tightened them up.
- discovered that the PCV at front of engine has a very loose grommet - this doesn't look like it is new or just happened though, so do not believe to be related to my issue (also I don't believe a loose PCV valve could even cause this much bad performance though?)
- removed the OBD2 end of the loom and tested continuity (all 7 pins are good); tried connecting whilst it was hanging loose and playing with the connector; both code readers still power up but fail comms (you can see them trying all the different protocols in turn).
- examined OBD2 connector pins for the scan tool end, and checked OK visually (seemed fine)


Power-wise, it feels like the car is bogging anytime more than light throttle is applied, e.g. on any incline, despite hearing the engine note change as it should under heavy load / full throttle. Snorkel seems to be sucking vast amounts of air when free-revved so assuming air flow is good esp. with new filter.

So the only causes I can still think of are:
1. over fuelling under load (bogging)
2. under fuelling under load (scared I'm running lean!)
3. parasitic loss somewhere in transmission when under load in drive only? Is it worth a transmission flush (prob due for maintenance anyway)

The shifting issue when labouring/bogged under acceleration is really worrying me, and so bad i can't help wonder if I'm being mislead by all the fuelling issues, and that I've got an issue in the transmission?

I'm also now considering 02 sensor and knock sensor, but could either of them do what is being described? Coupled with the really noticeably worse bangs in shifting?


Without OBD2 or even a standard check light, this is killing me! Any further ideas on getting that working would be amazing. Might I need a special code reader programming for an early JDM OBD2?

 

[boma23]

it's quiet on here.... please don't tell me all the IH8mud LC experts have now moved to crappy FB groups as well!

 

[jLB]

One suggestion/observation, I’d suspect that a JDM model of that vintage may not be ODB2 compliant, and may be M-OBD instead. You may want to search the forum for “M-ODB” for other (non-US) owners solutions for compatible readers.

 

[boma23]

Thank you! you were on the right track there!

Managed to get hold of another more expensive code reader (tablet PC type thing), and this was able to read VIN, identify model and region from the VIN, and then give me the codes I need! Not heard of JDM stuff needing different OBD readers before and I've had a few imports, all of which worked with current readers!

so to the codes >>

P1135 Bank1 O2 sensor heater circuit failure
P1155 Bank2 O2 sensor heater circuit failure

so reading this up, and considering i've got 2 codes for both 02 sensors appearing at same time, and coupled with the bad shifting, it looks like I may have a failing ECM / ECU!! So all the fuelling stuff was indeed a bit of a red herring...

I'm going to replace both upstream 02 sensors with OEM Denso regardless, as I've no idea when they were last done, and I can do that within the week. I've read of problems installing Bosch or other non-Denso OEM.

I will also pull the ECM and replace all capacitors as a start. I had to do this on my JDM KZN130 at a fairly similar age, so not a surprise with a JDM Toyota of this generation. Hopefully, the replacement caps will solve me the pain and expense of trying to source and swap in a new JDM ECU entirely.


Copying the linked material to this thread for future reference:

***********************************

What Causes Toyota Code P1135 / P1155 ?

The majority of the time, the P1135 / 1155 code initiates from these causes:

• Faulty air/fuel ratio sensor in bank 1, sensor 1
• Air/fuel sensor harness for bank 1, sensor 1 has a short or isn't properly connected
• Air/fuel sensor for bank 1, sensor 1 has a poor electrical connection
• ECM is faulty

The first step in diagnosis is visually checking the wiring for the harness to make sure no wires are damaged. Next, check the connections to make sure nothing has pulled loose. From there, replacement of the sensor is your best bet; a bad sensor is almost always the cause of this code and is a very common occurrence. The air/fuel sensors are made to be replaced; their position on your Toyota makes them vulnerable to heat damage; they may also be damaged from coming in contact with certain things like antifreeze/coolant. Most are made to only last 50,000 miles without damage from outside factors. These sensors are also commonly called "oxygen sensors" or "o2 sensors".

The most uncommon problem associated with this code is a faulty ECM; however, if you've addressed the other causes and the light remains on, it is possible that your EMC is problematic. Other symptoms of a bad ECM include a car that won't start, poor performance, an unexplained drop in efficiency, problems in shifting with an automatic transmission, and jerking and stalling with manual transmission.

For a comprehensive list of trouble codes, check out this article on the Toyota Parts Center Blog."

 

[jLB]

The most uncommon problem associated with this code is a faulty ECM; however, if you've addressed the other causes and the light remains on, it is possible that your EMC is problematic.

You seem to be glossing over this part, and jumping directly to “bad ECM”. I’d replace the sensors, and check the wiring, before I started soldering on the ECM/ECU…

 

[jLB]

Not heard of JDM stuff needing different OBD readers before and I've had a few imports, all of which worked with current readers!

OBD2 was a US mandate ~1996 model year, non-US market models/drivetrains can be a mixed bag from the late 90s to mid 00s

 

[boma23]

You seem to be glossing over this part, and jumping directly to “bad ECM”. I’d replace the sensors, and check the wiring, before I started soldering on the ECM/ECU…

No, not at all - I said I would replace the 02 sensors regardless as a 50k service part (no idea how old they are) and they are already ordered. But the bit that mentions jerky shifting coupled with 02 codes specifically references a bad ECM.

I have already opened the ECU - it looks factory-spotless-clean TBH. Very few caps (only 5) and a lot more ICs than the older KZN ECU, so am also thinking that if it is bad I will have to bite the bullet and order a new one as it looks far less DIY repairable, much smaller tracks and a much more modern board.

But I'll be ordering the caps straight away, so that once I've fitted the 02 sensors, if they don't fix it, then I'll already have them in hand by then. And then soldering the caps is a last ditch before ordering new ECU.

 

[boma23]

Still waiting for the 02 sensors and caps to arrive.....

But I've made a weird discovery since clearing the error codes - the performance is 95% back - as long as I use DRIVE and don't try to hold gears with the auto selector!!

Sounds weird I know - but on the same long climbs if I just leave in D and floor it I am now getting up fine (performance is still a TINY bit down) - pulling back into 2 immediately sees it lose power, and it regains it soon as pushed back into D!!

Anyone heard of this? I'm still replacing the 02 sensors regardless when they get here, and now will add a trans flush to the "may as well" list of things to try. But this is really odd.

Clunky shift is still there, and economy down around 15% per tank (normal tank 260km now 220kms - it's steep round here!).

 

[boma23]

Well.... wow is all I can say. 2 new inner tie rods and and the sensors went on at the weekend.

The 2 new 02 sensors were obviously well overdue! Motor feels stronger than ever (sounds harder too!), and the clunky shifting in forward gears has gone, along with the drop in power when holding 2nd. I didn't know that 02 sensors going bad could so heavily affect shifting. It still feels clunky into reverse, but as all the other bad symptoms have gone, I'm not sure if I just didn't notice that before...

I've just filled up, and tomorrow I do the usual commute over the hill, so coupled with next week when I see my MPG after a tank I'll know if the 02 sensors were really the cause of all. Never heard of 2 going bad like this at the same time before, unless there was something really crappy in that bad fuel tank.

 

[boma23]

Bit of a follow up for those that may read this in future. BTW it's an A442F transmission.

Initial rejoicing above was too soon:
- 02 sensors did indeed fix all engine performance, and in that sense truck is good again, when in D.
- Shifting is still overly jerky (less so than before, but still more than usual), unless waiting an extended time between D/N/R, and still lumpy between 1/2/D. RPMs appear normal and quickly drop to idle (i.e. i don't think its due to revs staying high and being slow to drop)

This is the weird bit:
- on my "test" steady state steep 2nd gear climb on my commute, a flat wide open throttle barely gets any further performance than 2/3rd throttle, with the engine just using torque at lower revs, although it does sound louder. If sudden additional acceleration is needed, then a hard kickdown/manual shift to 1st is required.
- on this same stretch of climb, switching from D (where trans is actually in 2nd) to 2 will result in a noticeable drop in power & deceleration - but the transmission does not physically shift when this happens! Shifting back from 2 to D restores performance, all the time whilst the transmission has stayed physically in 2 all along.

I've just bought 17 litres of Maxlife to fully lush, given how hard this transmission works, but I'm not convinced given the above, that the issue is not ECU/electronic.... all otrher ideas appreciated at this stage. Even looking at second-hand ECUs to ship in and test-swap (not cheap!).