Juddering wont rev under load

[tom99]

HI all

any help would be much appreciated

the other day i took my car for a drive for a couple hours all was fine just as i was near home it spluttered / hesitated under load for a split second didn't think anything of it.

then the next day I started my car drove it for 20 mins no issues, all of a sudden when the engine was under load, it hesitated / spluttered for a split second again and then carried on accelerating, then it did it again, and again, then it basically lost all power and it would barley pull away from a set of lights without revving the hell out of it, i stalled it at one set of lights and restarted it, it drove terribly after that no power and very slow and it sounds like its spluttering and missing barely able to pull 3k rpm

i then left it for 20 mins and restarted it. Drove fine and then about 10mins into the drive same problem started.

i have replaced the plugs and all 4 coil packs made no difference, the engine is a toyota 1zz, it runs a standalone ECU with no MAF or O2 sensors, has be running fine for 4 years with this set up.

I am at a total loss with this

Thanks

[Oldandslow]

tom99 said:

it runs a standalone ECU with no MAF or O2 sensors

Are you sure? There must be something, O2, air flow, air temp? The ECU needs some input to base the fuel required on.

[tom99]

Oldandslow said:

Are you sure? There must be something, O2, air flow, air temp? The ECU needs some input to base the fuel required on.

i know it has no MAF or O2 it might have something else in there but if there is i dont know what it is im afraid,

like i say its been fine for 4 years like this, now i have this issue and have no idea where to even start.

[Oldandslow]

First things I'd be looking at given you've already addressed spark is fuel starvation or a dodgy sensor. Is there any way of connecting to the ECU to see if there's an error code. ODBII, laptop?

[tom99]

Oldandslow said:

First things I'd be looking at given you've already addressed spark is fuel starvation or a dodgy sensor. Is there any way of connecting to the ECU to see if there's an error code. ODBII, laptop?

i have considered fuel issues but If it was a fuel issue would it not be present all the time? it just strange how its not consistent and strange how leaving the car for a bit then restarting it seems to cure it for a few mins

It can be plugged into a laptop and i know the ECU does log data so there should be something on it, but it requires me to have the car towed and then got to pay someone to look at it so its 200 quid before anything else so trying to avoid it if possible.

I have read that it could be a weak alternator as the EFI needs a specific voltage to operate properly. and that the alternator could still be charging the battery but not able to supply this specific voltage, if there is any substance in this i dont know?

thanks

[Oldandslow]

Yes ECU will cut out if voltage drops but you can test the voltage across the battery (should be 12.5v fully charged and not running and 14ish running if the alternator OK).

A clogged fuel filter say or tired pump will give issues where it's OK at idle but under load fuel can't get there in sufficient volume/pressure to keep engine running. After it sits and the filter lets a bit of fuel past or the pump cools down and runs better it will then be OK for a bit.

Equally sensors on their way out can work better cold or under cold engine conditions when overfuelling anyway but then run rough when hot. Does it smell fuelly like overfuelled, exhaust really black or not?

Error codes can help you figure out areas to look. I'd go over the engine, inlet and exhaust looking for sensors as possible suspects. If this is a built project, who built it and can you ask them for assistance?

[tom99]

Oldandslow said:

Yes ECU will cut out if voltage drops but you can test the voltage across the battery (should be 12.5v fully charged and not running and 14ish running if the alternator OK).

A clogged fuel filter say or tired pump will give issues where it's OK at idle but under load fuel can't get there in sufficient volume/pressure to keep engine running. After it sits and the filter lets a bit of fuel past or the pump cools down and runs better it will then be OK for a bit.

Equally sensors on their way out can work better cold or under cold engine conditions when overfuelling anyway but then run rough when hot. Does it smell fuelly like overfuelled, exhaust really black or not?

Error codes can help you figure out areas to look. I'd go over the engine, inlet and exhaust looking for sensors as possible suspects. If this is a built project, who built it and can you ask them for assistance?

Sounds like i had better start with checking voltage running and not running. and fuel filters and pumps and give the engine a once over checking sensors and connections.

it doesn't really smell of fuel but does run a bit richer than a normal car due to the tuned engine as its a long way from stock, but i wouldn't say the exhaust is really black with carbon and fuel consumption seems about right.

It is a built project and built by me, i have done everything apart from the ECU install and mapping, this set up was in a different chassis (for 4 years) which got bent at oulton park not really badly but enough, drove the car home no issues and proceed to swap everything over to the new chassis. all the sensors and wiring looms were transferred. the car drove fine for a week or so and now this.

The only thing that was kept from the new chassis was the in tank fuel pump the new chassis had done 100k so maybe could be the pump.

i have always dismissed the fuel pump as i rightly or wrongly assumed it would be a constant issue not intermittent. on start up it will run fine for a while, drive it full throttle no issue then after about 20mins splutters and then just fall on its face

thanks

Edited by tom99 on Tuesday 30th April 15:42

[tom99]

The issue has now become permanent started it from cold last night as soon as it fired up i could tell it wasnt right, tried to drive it but violently juddering and has no power.

[Heraldsteve]

I had similar symptons a few months ago and after many hours work and trying various components I discovered it was a failed catalytic converter. The inside of the cat had fallen apart and gradually blocked the exhaust almost completely. It would run for a while as some gases were escaping but it would soon choke up and would barely run and reaching even 30mph became impossible

[E-bmw]

tom99 said:

i have considered fuel issues but If it was a fuel issue would it not be present all the time? it just strange how its not consistent and strange how leaving the car for a bit then restarting it seems to cure it for a few mins

ANY electrical/electronic/electro-mechanical part in a car can exhibit an intermittent fault, there are many of these in the fuel system so your thinking isn't correct unfortunately.

As your system is distinctly non-standard I would start with finding someone/somewhere who knows the system as "local knowledge" may well be pivotal in finding the issue.

Aside of that generically you are describing a misfire so I would be looking at injectors and wiring around spark/fuel systems based on what you have done already.