Strange 20V Silvertop Misfire - FIXED!

[nmcgowan]

I took the ECU circuit board entirely out of the casing so I could tilt it on an angle to see under the caps, even with a really bright torch I cannot see any sign of leaking capacitors on my original ECU, I did find a leaky capacitor on the other ECU I got from Pickapart as stated earlier. Im not unsoldering every capacitor to see if its leaking, I may aswell just replace it with a Link and be done with it, which Im happy to do if I can have it confirmed without doubt that its the ECU. Are there any tests to prove the ECU is functioning correctly?

Tried new plugs, no difference.

I've got FXGT_Race coming over tomorrow to cast his eye over things, if he can't throw any new light on it I've got a mobile mechanic coming out next week.

One way or another I'll find out what it is and post up the results.

[BZR4AGE]

I have the same issue.

I've changed knock sensor, oxy sensor, plugs, coils, leads, nothing helps!

I am now running a Link G4 also, and it still happens randomly - not as often as before though.

The only thing I haven't tried is a ignitor. Have one coming my way soon so I will also update if I have any luck.

[rollaholic]

16v 4ages have been known to flog out the keyway on the crank sprocket which can cause some issues, though it sounds to me more like a proper misfire than lack of timing. i tried all kinds of things to sort that one out, just about impossible to see without taking the crank sprocket off.

glenn / ezy10s is fairly switched on with toyota stuff and does some mobile tuning etc, i dunno if he comes on here much anymore but you will find him on garage dori if you are still looking for someone to check it out.

[fxgt race]

Couldn't get the old girl to rev, checked the timing and its ok,Put it to tdc and all the timing marks on the cam wheels and crank sprocket line up,we did a flow check on the pump but not pressure check across the rail, It just won't rev, I wouldnt call it a mis fire as much as its like the engine is so retarded it just won't rev,it bangs and pops out the airflow meter, its got me a little stumped at the moment.

[85AW20v]

Make sure you've got the right timing marks lined up as there are a couple of sets on the 20v that you can mix up. When its at TDC there should be an elongated dimple visible in the inlet camshaft when looking into the oil filler hole lining up with the metal bit that half covers the filler hole. If it's there, then check that the other timing marks line up, with the front top cover removed. There are 2 marks opposite each other where the cam wheels are closest together as well as the marks at about 1 o'clock and 11 o'clock that line up with the marks on the head.

[rollaholic]

yeah when i experienced the cam sprocket problem on the 16v all the timing marks liend up okay. it wasnt till you took the sprocket off that you could see the damage, which was allowing it to shift while the engine was running.

[nmcgowan]

So was the damage on the inside of the actual sprocket closest to the crank, the one with the actual timing mark on it? If so then thats suck because we pulled the alternator belt and large pulley off the other day to check the timing but didnt take the inner sprocket right off.

I found this thread by googling "4age backfire through intake"
http://forums.club4ag.com/zerothread?id=40032&page=1

It talks about checking the STA signal at the ECU to ensure there is voltage while the car is cranking. Well I checked and it definitely gets voltage while cranking, about 9volts. Maybe its supposed to be 12v but the earth I had was probably a bit sh1te as I was in a hurry. I'll check tomorrow night to see if the voltage drops off after it fires up as its too late to do it tonight. Also checked the started relay and that works fine.

Has anyone dealt with Tama Autos out west? would they be a good bet to be able to troubleshoot something like this? I might be able to borrow a trailer to get the car out there if required.

[fxgt race]

the car starts and idles perfectly so the timing can't be out that far by using the wrong timing marks. Neil a guy had a similar problem and a baffle had came lose in the exhaust and blocked it, check the flow, worth a shot.I brought my volt meter over the other day to check the volts but we didnt quite get there.

[rollaholic]

tama autos are good guys, they will sort it for ya just means you have to pay someone else to do it, heh

and yes, the damage was on the actual timing belt sprocket around the keyway. i re-read my earlier post and realised it says cam, but its actually the crank sprocket im talking about. i did the same as you - checked it about 45 times then finally decided i would just set it up from scratch. the car idled fine too

all that being said i've never heard of a 20v with this problem

also the car would rev too, was just very sluggish at low rpm (and high rpm, was just less noticeable)

it sounds to me like an AFM problem, but you already replaced that yes?

[nmcgowan]

Mups, Yeak I'll check but how do you really know if a baffles come loose other than disconnecting the exhaust? (I'll get the earmuffs!)

Yeah I bought a 2nd hand AFM and it didnt help. I might just for arguments sake try it again anyway.

Well I phoned the guys at Tama today and you're right they are nice guys who seem to know what theyre talking about. Only problem is that he's about as stumped as we are, he would have gone to all the things we've already tried. What he did suggest was:

Sounds like timing or overfuelling if its backfiring/popping out of the intake and bogging down with throttle.

1) Check the timing again after checking that bottom sprocket for any damage.
2) Check dizzie rotor is in the right way (I think this is keyed to stop that isnt it?)
3) Swap the TPS
4) Swap fuel pump and fuel filters
5) Get the guy who wired the car up to come back and check to see if there is a wiring fault somewhere.
The guy at Tama said it would be easier for the sparky who wired it years ago and whos done several of these conversions to come back and look over all the wiring again rather than paying them to reverse engineer everything and start from scratch on the troubleshooting front. So MAX props to Tama Autos for being honest and upfront rather than just taking the job on knowing they would chew up the hours on a diagnosis. If I get stuck after Steve the sparky has looked at it then its going there and I'll be happy to pay them.

The saga continues.....

Mups, You left your screwdriver and pry bay here...I'll swap them for that pulley remover, timing light and a frosty beer eh!

If it stops pouring with rain I'll open the garage door, fire the car up and record the noise it makes, maybe that will help with understanding what its doing.

[Flannelman]

help or not, perhaps the distributor is the issue?

under the rotor is the sensor that tells the computer where the engine is in its rotating cycle. if this is faulty or sad wiring to/from this then it may be your problem

[rollaholic]

what is the exhaust like?

have seen a car or two with a $&#$% CAT behave in a similar fashion, in fact if you held your hand over the intake pipe you could feel air being pushed back out it haha

but never seen a regular muffler do that

[nmcgowan]

Looks like its a dodgy fuel pump. We pressure tested it last night and the readings suggest that the pump is knackered. It was basically all over the place before settling at a solid 10psi....not ideal!

So I'll drop the tank out, replace the pump and filter and confirm that thats what it was.

Thanks everyone for their help to date.

[rollaholic]

you have to drop the tank to get the pump out?

[Crampy]

you have to drop the tank to get the pump out?

Last I looked you just need to remove the pump upwards with the rear seats removed.

[rollaholic]

yeah thats what i was getting at

[nmcgowan]

Well there are no rear seats as its stripped and caged so that would be IDEAL if I dont have to drop it out but I was told by Steve (the mechanic and 4AGE guru) and FXGT Race that Id need to cut a hole in the floor and then patch it up or drop the tank out - FXGT Race would know he's done it plenty of times. This is one time I hope they are wrong!

As for a fuel pump upgrade at the same time...any thoughts? Do I really need to get a 255lph Walbro (or similar) I'll never get close to maxing that out so it seems like overkill. Is there a bolt in upgrade from another toyota that will fit? Supra maybe, surely that must have a beefier fuel pump? but will it fit?

[xsspeed]

I think for the ae82 that the bit that you can remove with the seats out is only the fuel level device, and the pump is actually further back.

from toyodiy

I think the level unit is the on the left in this pic and the pump in the inset pic goes into the right hand hole.
Hope that makes sense.

[nmcgowan]

Yeah that looks about right to me from memory so I will have to drop the tank out. At least Steve wired the pump relay so that when I turn the car on it will pump continuously so should make draining it quicker and easier. Now I just have to run my Evo dry so I can pump the fuel into that, Im not wasting a totally full tank of 98, thats liquid gold!!!

[Crampy]

The motor is stock pretty much isn't it? So, no real need to get a super flash thing. Maybe a 20V one will fit (unsure).