MK2 Turbo EFI system - testing using BGB

[Blue_5]

Hi all,

I know this should technically be in Electrical, but I stand more of a chance getting a response here!

OK, when checking the EFI system, the BGB says to disconnect the connectors. However, when checking the TPS and AFM, i get no readings. Looking at the diagram, they get power from B and B+ on the circuit. When the connector with these is out of the ECU, the B/B+ circuit is broken, isnt it?

So, when checking these, should the other connectors be in, so the ECU can be energised?

[JJ]

Hi Buddy....

What are you trying to achieve here ??! Problem diagnosis ?

[Blue_5]

Hi JJ,

yep, im trying to discount wiring/sensor issues. Its that non-start issue again. Im interested in the TPS sensor as well as ive lost throttle response a couple of times while driving for a couple of seconds, but the engine dosent cut, just like if you came off the throttle.

But as im reading things, the ECU sends 5v to the TPS and then reads whatever voltage is returned, and im not sure how i can read that if all ECU connectors are disconnected.

[JJ]

I'll tell you the problem right now.. its the AFM..... !!

Had the same problem on my white MR2... would run sweet, then nothing on the throttle.. would jerk about a little.... then come to an embaracing halt.... but would still run... wouldn't rev.....then come alive again... started losing my confidence in it !!

Then occasionally, would it bawls start........ crank and crank and crank.... No error codes stored either !!!

I sold it to my friend .. thought I'd recitfied it securing the pins to the AFM... became problem free.. but then reared its ugly head again. His father in law was an auto electrician.. changed the wiring to the AFM.. still the same....he stripped the AFM down and found the brush points corroded causing the problems.... never missed a beat in 2 years now !!

Do yourself a fouvour and either pick another one up or see if you can fix you're existing one.... in my eyes... anything electrically corroded is scrap....as although you may rectify the issue... the long term reliability may not be there....

Should give you confidence in the thing again !!

[Shmed]

I'm going through a similar problem identification process. I have put my car back together and started it for the first time since I bought it. Was dead chuffed when it roared into life, only to be plunged into dissappointment when it spluttered and stalled as soon as I took my foot off the gas.

Noticed that fuel was leaking from the FPR end of the fuel rail, but don't imagine that would stop it from idling. I had no error code so thread jacked someone elses thread in electrical and Toxo reccommended checking ICV and the TPS. I checked my TPS using the BGB and found that one of the figured sidn't marry up, but I checked another one I have knocking about, and the same figure didn't marry up. As they both read right on all other figures, I decided to try the car again. Now it splutters even when on the throttle and I have error code 24 - I belive this is the AFM.

Historically, what would be the best check to do on the AFM? I have read a few posts that tell you how to adjust the screw to factory settings, but other than this, what would I be looking for and would the AFM really prevent the car from idling when the car runs ok on throttle? Could a vacuum fault cause the problem? Also, my dipstick doesn't seem to stay in the engine, would this cause vacuum problems (it suggests in the BGB that it would).

Sorry for shamelessly thread jacking again, but didn't feel this warranted a new post.

[JJ]

Noticed that fuel was leaking from the FPR end of the fuel rail, but don't imagine that would stop it from idling

Has this been fixed yet ?? Any fuel pressure drop will cause issues with running..

I checked my TPS using the BGB and found that one of the figured sidn't marry up, but I checked another one I have knocking about

Remember this thing throws a error code if completely screwed or mal adjusted... so rotate it until the error code dissapears normally... this allows the ecu to see closed circuit of the map... idle map basically.

An AFM setup Shmed, you need to make sure there are no leaks anywhere between the AFm and the manifold. Plug every nozzle at the manifold if you've got any visable ones.. theres 2 at the back on the the track down that are usually missed .. check the breathers.. the idle control valve needs a line all the way to the induction pipe but after the AFM.. you'll see the nozzle take offs on the pipes between the AFM and the turbo.

I have read a few posts that tell you how to adjust the screw to factory settings

Kind of a static mixture adjustment....

If all the above is correct, theres an idle screw at the top of the throttle body, open that up... The initial stages of start are usually lumpy, but this is the learning period of the ecu.. try and leave it on idle ....adjusting the idle screw to compensate if you can....

If its just dieing soon as you come off the throttle.. theres a vac leak somewhere...

You'll be able to keep the thing running on idle if you jar the afm flap open a little... sends signals to the ecu to say thers air flow... and thus fuel is introduced to keep it going.... = vac leak is the air isn't being pulled past the AFM...

Hope you've followed that !

Also, my dipstick doesn't seem to stay in the engine

What d'you mean ?? it blows out ??!! Theres a breather at the other end of the cam cover ( gearbox side )... that needs to vent to atmosphere at least or if its blumbed into the pre-turbo induction pipe.... If you havent vented this, the engine will be creating positive crank gas pressure and it'll blow at the weakest joint ( dip stick ! )

[Shmed]

Cheers for the response JJ. I haven't 'fixed' the fuel leak problem so to speak, though it seems to have gone away. Obviously I'm not going to leave it at that, but I want to try and get the car idling before I take it apart again.

I haven't had an error code relating to the TPS, I just thought it would be a good thing to test on the basis that the car wouldn't idle.

I will have a closer look at all the vacuum connectors to make sure there are no leaks. I have noticed the vacuum hoses on the back of the inlet manifold (one of them is blocked off with a screw so I'm not sure where that should go). I think the vacuum line I have connected to the ICV is attached to the rocker cover, is that wrong (I will check later if that is actually the case)?

So jsut to clarify, if I test the car with the AFM flap slightly open, and the car idles, then the problem is a vacuum leak?

The dipstick jsut doesn't seem to stay in the hole. The dipstick doesn't pop out when the engine is running, it simply won't plug the hole when pushed in. It's almost like the dipstick is too long for the hole.

[JJ]

The dipstick just doesn't seem to stay in the hole. The dipstick doesn't pop out when the engine is running, it simply won't plug the hole when pushed in. It's almost like the dipstick is too long for the hole.

Too long... okay... there maybe a mismatch in parts here... the Celica GT4 dipstick and tube is different to the MR2.. The MR2's is longer.. but if you've a dipstick from a celica... then you'll get a mismatch...

Check to see the tube is actually going into the block as well.. sometimes on fitment, can stick it into a bolt hole instead of the actual dipstick hole !

MR2 dipstick and tube is around £20 if I remember !

So just to clarify, if I test the car with the AFM flap slightly open, and the car idles, then the problem is a vacuum leak?

Yip !! You can remove it altogether from the intake hose or leave it in situ... as long as you open the flap a little, it'll fuel accordingly... Remember its the AFM's flap position that dictates the fuel calculation not the flow through a sensor ( position of the flap indicates the voltages 0-5 to the ecu )... you open the flap more, the ECU responds with more fuel ( chugging / black / enrichment out the exhaust )

Where the sensor differs from the map sensor driven ecus, the AFM setup reads 5v to 0v's.... ( 0v being full load ) map is 0v to 5v ( 5 being full load )... hence why people have to be soo very careful fitting fitting fuel computers to the earlier models... the thing reads backwards... anyway.. thats another topic !

It explains why when you rev it.. it'll run.... but on idle wont...= air leak

Nozzles at the rear of the manifold is normally plugged on MR2s.... Unless boost controllers / boost gauges have been fitted previously !!

[Shmed]

I had wondered if I might've got the wrong hole, but the dipstick does go most of the way in, even though the thing seems to kink up on it's way in. Should the oil tube protrude from the engine block?

Cheers for the tipso n the AFM, I will test that later

I know the car did have a boost controller before I got it, but it doesn't any more.

Going back to the fuel leak, I didn't replace the 'O' ring on the FPR when I put it back together, but I thought I had tightened the nut enough. In your experience, do you find the 'o' ring should be changed every time? and is there a way to tighten the FPR nut without taking any coolant pipes off?

Cheers

[Shmed]

I think the vacuum line I have connected to the ICV is attached to the rocker cover, is that wrong (I will check later if that is actually the case)?

Oh, and is this right?

[Shmed]

D'oh, what a tw t!!!!

Just had a look on the ToyoDIY parts pages and have noticed there should be a tube for the dipstick. It seems that the guy who had the car before me decided that it was surplus to requirements!!

Looks like it's back to Mr T for some more bits. Am I right in thinking that the oil dipstick needs to make a seal to airtight the vacuum? Could this be the problem?

[JJ]

I think the vacuum line I have connected to the ICV is attached to the rocker cover, is that wrong (I will check later if that is actually the case)?

Oh, and is this right?

ICV under the throttle body has a port towards the passenger side.. this needs to goto the induction pipe after the AFM but before the turbo - if you've got the original pipes, you should see a take off for this - next to the dump valve dump tube.....

Around the throttle body, there should be a little nozzle from the cam cover pointing up, this should be directed to a small nozzle in the manifold.

Theres also a right angled nozzle ( 14mm if I recall ) from the passenger side of the cam cover... this also needs to goto the same pipe as mentioned, or vented to atmosphere !

Dont forget, there should be a line from the FPR to the manifold too as this will alter its fueling on boosted conditions..

there should be a tube for the dipstick. It seems that the guy who had the car before me decided that it was surplus to requirements!!

Crikey.. get this sorted first.. you might not have enough oil in it !!

Am I right in thinking that the oil dipstick needs to make a seal to airtight the vacuum?

Not strickly to run.. bit like the PCV line I've mentioned ( 14mm right angle from the cam cover ) .. its not directly part of the induction.... you'll need to make a tight seal when it comes on boost though...as all the oil in the sump will blow out of it under PCV charge.

[Shmed]

Crikey.. get this sorted first.. you might not have enough oil in it !!

Have ordered the parts from Mr T, will be arriving tomorrow. I know there is enough oil though as I changed it and poured 4.5 litres in.

I'll have a check of all of the pipes, I know most of them are connected right. I have a small K&N filter which I think was connected by the guy who used to have the car, can I connect this to the PCV hose instead of routing it back into the air intake? And what benefit does it have?

[JJ]

I have a small K&N filter which I think was connected by the guy who used to have the car, can I connect this to the PCV hose instead of routing it back into the air intake? And what benefit does it have?

Yes you can fit that to the PCV vent .. the benefits to routing it back to the intake is simple.. the vacuum the turbocharger creates allows the vent not to just blow off, but the gas being pulled through and burned off through the intake reduces oil leaks as you're creating a vacuum on the internal areas.. ( big problem with Supras blowing the front crankshaft oil seal )

Drawbacks... pipes can get messy, intake pipes can get covered in oil with high boosting... the turbo can actually pull particles of oil out of the PCV.... hence induction / intercooler pipes get a little messy !

You'll be a master of this soon with all the head scratching you've done over the past few weeks... well done for getting it running

[Shmed]

Cheers, I'm quietly chuffed with myself for getting it going. I used to be fairly well clued up on cars, but took a long break to focus on the career. Never really dealt with turbo's much so have had to do loads of research. Every time I feel I've got a handle on what I'm doing, something else crops up. I reckon someone at work will cotton on that I'm doing very little work soon

So what's the benefit of venting the crankcase pressure to air? I'm running the car fairly standard now, so don't know if there is much point in modifying stuff like that.

Cheers for all the help by the way

[JJ]

So what's the benefit of venting the crankcase pressure to air? I'm running the car fairly standard now, so don't know if there is much point in modifying stuff like that.

Clean pipes - if you're not introducing an oil vapour cocktail into the intake, technically... the engine isn't as prone to detonation ....

The vent has hot air coming out of it, so you're sucking it through... intercooler has to do more work....

I've still connected mine up as my sump is weaping a little on boost.. seems there must have been a little grease on the surface when I sealed it !!

Cheers for all the help by the way

No probs, thats what this forums all about... !

[Blue_5]

Hi JJ,

S'possible. I removed and cleaned the AFM a while back, I had a dodgy AFM problem before on my GT4 so wanted to clean it up. The ECU light thing is the main 'clue' so its possible the AFM may be shorting out the ECU. Ill pop the top off tomorrow and just doubel check theres no corrosion (theres none at the connector end).

Cars running now, fine as you like. I just don't like the thought of the cars new owner having a problem with it.

[Shmed]

Hey, stop hijacking my thread......

[Blue_5]

GTFO my internets!

[Shmed]

JJ,

I have propped the AFM open, and now the car starts and idles (though it is basically just revving between 1 & 2k RPM). I guess that means I have a vacuum leak then.

As this is the first time the car has idled, I noticed that there seems to be smoke coming around the turbo flange which I guess is exhaust gas. Generally, would you always change the gaskets between the turbo and the manifold (i didn't bother)?

I only had 5 minutes to look at it tonight, but will have a closer look tomorrow. As far as I can tell, all of the vacuum hoses are properly connected, the FPR is connected to the inlet, the stock boost gauge sensor is connected to the inlet and there is a pipe connecting from the passenger side of the inlet which runs to the BOV. The cam cover nipple connects to the small 90 degree pipe out the bottom of the throttle body and that is it. Is the VSV on the same vacuum circuit?