86 RX EFI issues .

discopotato03 · Post by **discopotato03** » Sun Jan 03, 2010 10:30 pm

Hi all , my 86 RX is still having mad attacks of running very lean basically after getting to running temp and using more than about 1/3 throttle .
The ECU flashes code 35 which is an EGR issue ie short or open circuit .
The problem is getting slowly worse to the point where it bucks and kicks and can get savage driveline backlash .

I decided to look at the wiring diagrams to see what is involved in the EGR solenoids system and it gets sort of interesting .
The diagrams show that power for the EGR solenoid comes from the fuel pump relay and the computer has the earth return so it must be earth switching the solenoid .
A mechanic friend of mine reckons it could be the going on 24 year old fuel pump relay and wiring acting up when the computer goes to earth switch that solenoid . He also said check that the pumps wiring is giving it full voltage
Tomorrow I'm going to drop the computer off its mounts to get at the ignition power supply and fuel pump relays to see if there are any cheesy joints and maybe even swap in another relay for the pump .
I can't see how anything about the EGR system except the fuel pump relay could cause the engine to run suddenly so lean - like 16-18:1 AFR on my Tech Edge wide band 02 meter . My friend suspects that when the EGR switches on the pump could be getting short changed and getting voltage drop from possibly old and burnt relay contacts .

Has anyone struck fuel pump relay problems before ?

Cheers Adrian .

28/01/2010 Edit - in case you don't want to read this whole thread .
Eventually tried disconnecting the oxygen sensor , problem went away .

AndrewT · Post by **AndrewT** » Sun Jan 03, 2010 11:06 pm

Just thinking outside the box here...don't discount the fact that the problem may be completely unrelated to the EGR fault. Before dedicating all your time to resolving that code maybe check a few easier things first - double check ignition etc.

T'subaru · Post by **T'subaru** » Sun Jan 03, 2010 11:41 pm

I will be watching this with interest as my 89 rx has code 35 and same symptoms but to lesser effect after changing tps due to code 42. My main purge control solenoid is definately no good, stuck open and will not energize when jumpered. I believe this ties in with no real increase in power under turbo boost, but still have to play with vss code 33.

Checkers · Post by **Checkers** » Sun Jan 03, 2010 11:54 pm

The fuel pump in the RX gets a power and an Earth Feed from the ECU. Power comes through a relay and the earth come from the ECU.

I have no idea why they did this but it was how my 85 RX was setup and running.

If you need test bits I might be able to help you out as my RX was running sweet without any fault codes or issues when I pulled it so it would be fair to guess all its sensors etc are in good nick.

phillatdarwin · Post by **phillatdarwin** » Mon Jan 04, 2010 1:54 am

if it was me i wood be getting a can of carbe cleaner and trying to find a vacuum leak in a hose as it mite of started spletring over time that wood be y it is running so, lean.

U have to think that all the hoses are getting very old .

phantomD · Post by **phantomD** » Mon Jan 04, 2010 8:22 am

Are you sure your EGR solenoid itself is working correctly? I have a carby EA81 but my EGR valve got stuck open and caused a lot of damage to the carby and stuffed my spark plugs.

It also caused the exact same behaviour you describe - I was doing battle to get off from a stop because the car would buck around and want to stall.

discopotato03 · Post by **discopotato03** » Mon Jan 04, 2010 9:02 am

These are my thoughts so far .

The 85/86/early 87 EA82T's had a separate ignition system so I think its a case of it works or it doesn't and mine has newish cap and leads anyway .
I think if it was going to break down it would do it most of the time not just intermittently .

Most hoses of any consequence have been inspected and any doubtful ones replaced with the recently rebuilt engine .

I'm just looking at the Factory 86 WSM chapter on these cars and the wiring for the FPR goes like this .

1) Positive ignition switched power feed wire (BW) goes to the " FP.EGR relay" and the "IG power supply relay" .

2) (LB) wire goes to ECU pin 39 "FP,EGR relay"

3) (L) wire is the switched power supply to the fuel pump and also goes into the loom and passes through one of the engine loom connectors to the EGR solenoid and another which I suspect is the vapor purge solenoid .

4) (R) wire is shared by the FPR and Ign Pwr Relays and comes from the positive battery terminal .

Both of these relays are close to each other and I think mounted directly above the computer in an L Series .
They need to be seen togeter because they share two things , firstly ingition on powere supply and secondly permanent battery + supply .
All the FPR/EGR relay seems to do is power up the fuel pump and those two solenoids - EGR and I think purge . Its then up to the computer to earth switch the fuel pump (FP current control) wire (W) at ECU pin 50 .
The EGR solenoid has wire (BrR) which would be the earth return to ECU pin 23 "EGR Solenoid"
Whatever the other solenoid is gets power from the same place and its earth return to the same (-) or ground point as the ECU's controlling ground wires .

All the IG power supply relay appears to do is power up the ECU (WB) wire to ECU pin 50 "IG power supply" .

I have a few things to check here but I suspect the problem is FPR related or possibly the controlling ground for the computer .
My mechanic friend tells me that most problems are related to poor connections/connectors and relays or earths . A hot side short circuit usually means blown fuses or smoking burning somewhere in the wiring .

Possibly the easiest thing to check is the the FPR - and its connector for signs of heat/bad joints .
If I knew where the computers "controlling ground" wires earthed to the body that'd be the next thing to check .

Ideas ?

Cheers A .

discopotato03 · Post by **discopotato03** » Mon Jan 04, 2010 11:44 am

Just from a little more reading the 4 plug ECU cars are totally different , factory WSM shows that EGR wiring goes nowhere near the FPR .

Also engine earth points are different on Spider manifoild cars so have to treat it like a 3 plug Spider car ...

A .

steptoe · Post by **steptoe** » Mon Jan 04, 2010 2:10 pm

Disco, Disco, Disco....when are you gonna get yourself, beg, borrow or steal a vacuum gauge. This time I reckon you NEED one to tinker with to help sort your problem or suspicion of EGR. If you do what I did to get a feel for how and when thew EGR works or should work you will develo a better understanding of it and or the ECU's control or lack off control of EGR.

I got a vacuum gauge to watch as I drive.
T piece in another 4mm vacuum line from the EGR valves vacuum and ran it through to cabin and hooked up a spare EGR valve. My little finger is small enough to stick into EGR frame to feel diaphragm move at same time active EGR is. Held finger there as I drive to get a feel for how and when it operates in relation to vacuum reading and loud pedal feel.

It may just help as you watch your lean out gauge, or get the bad feel of the engine, it may not.

From memory, the fuel pump relay is the same as all those other round relays same part number. I found mine directly above ECU with another relay on a bracket. Also same as found in lots of Mitsubishis.

steptoe · Post by **steptoe** » Mon Jan 04, 2010 2:20 pm

WARNING HERE:

I suspect the trouble codes are not the same between 3 plug and 4 plug ECUs

T'subaru Mark mentions code 42 and tps in same sentence with his 89RX. Code 42 in 3 plugger is fuel injector code. Code 35 may be common for both as EGR solenoid switch. And code 33 is coolant thermosensor on 3 plug. T's mentions VSS for code 33, whereas 31 is speed sensor in 3 plug.

steptoe · Post by **steptoe** » Mon Jan 04, 2010 2:25 pm

Also, on fuel pump. Wjen my original was on its death bed I would prime it by hooking up a SLA battery directly to its connecter at the pump, and tap it with a hammer to get it rattling away and car started. No harm in hooking up power to fuel pump directly for observation diagnostics surely? The plug is round two pin much like if not same as the indicator connectors frrom a donor wreck ?

steptoe · Post by **steptoe** » Mon Jan 04, 2010 2:27 pm

Also, fuel pump pressure gauged T'eed into line after fuel filter and taped on windscreen and took for a zip up the road, saw pressure drop right off as power did. New pump fixed that litle chapter of grief.i

steptoe · Post by **steptoe** » Mon Jan 04, 2010 2:37 pm

Adrian, you say at running temp - the EGR is not supposed to operate until a certain temp ...found it ...carby in Sweden and Switzerland 35 deg C before it will work. Australian turbo it is not until 75 deg C, (what temp thermostat you got?

) the solenoid valve bleeds air off to the air intake boot. Speed sensor is also supposed to shut EGR off above 45 kph. Mine runs all temps all speeds from 0 to 10inHgo

2-1 p 16 fig 22

Maybe divert the bleeder fromn the solenoid to inside the cabin to monitor youself asit bleeds off?

additional note on the Tridon thermostats. They have a 2.5degC tolerance plus / minus

steptoe · Post by **steptoe** » Mon Jan 04, 2010 2:50 pm

6-3 p20 has common grounding locations depicted (roughly)r

T'subaru · Post by **T'subaru** » Tue Jan 05, 2010 12:13 am

steptoe wrote:WARNING HERE:

I suspect the trouble codes are not the same between 3 plug and 4 plug ECUs

T'subaru Mark mentions code 42 and tps in same sentence with his 89RX. Code 42 in 3 plugger is fuel injector code. Code 35 may be common for both as EGR solenoid switch. And code 33 is coolant thermosensor on 3 plug. T's mentions VSS for code 33, whereas 31 is speed sensor in 3 plug.

Yes they are different. My vss (33) failed the slow rolling voltage test ( wsm says to replace ecu) but I havn't had time to pull instrument cluster and test further. btw, new purge control sol ( egr as I have no egr valve as such ) is only 176.00

discopotato03 · Post by **discopotato03** » Tue Jan 05, 2010 2:57 pm

Slightly comical at this end .

My car has an EGR valve plumbed in and sealing exhaust wise and a matching solenoid . For some strange reason the vac lines desolve in use and the whole system is a thoughtie so to speak . Nuff of that .

My sole interest is in fixing this mad mode it goes into and the only reason I'm looking at EGR wiring , wiring alone , is that this is the code the computers light flashes every time it does the stupid mode thing .

The EGR's wiring only makes me suspicious because it gets its power feed from the fuel pump relay just as the fuel pump does .
Since the said valve doesn't do anything you can rule that out .
If the EGR solenoid/wiring was working as it should it would keep the electrical system happy .
If electrical gremlins at the fuel pump relay were doing silly things then a lazy pump can make the fuel pressure drop and the engine run lean . Pump is a 12 month old Bosch VLT one .

The relays above the computer should be the ignition power supply and
fuel pump ones . I think most of those cylindrical relays are the same , the four up and behind the fuse box are .

I'm going to ask my mechanic friend to attack all the earthing points we can find and I'll swap in different relays to see if the current FPR one is dieing .
I only have section 2-7 (Fuel Injection System) of the 86 L Series factory WSM . The one I bought a while back is the 87+ Factory WSM but it covers later 4 plug cars only . If I drive a couple of hours from home I can access a complete Factory 86 WSM because the people who rebuilt my engine have them .

So any earthing points between the engine and body need to be inspected and made as new , and the engine loom ones made as good as possible .
I only had a cursory glance at my spider manifold yesterday and could only see one small earth wire attached to the back of it . Surely there should be others , must check fusable links too .

Can anyone post a pic or link of the 86 L common ground points ?

I think when the Vipec computer goes in I'll need fresh power feeds earths and relays and probably new fuel pump wiring as well .

Cheers A .

steptoe · Post by **steptoe** » Tue Jan 05, 2010 4:33 pm

EGR solenoid valve plugged into loom or not? If it is plugged in and there is a "stick to open" or "stick to shut" fault present within the solenoid....

PM sent

discopotato03 · Post by **discopotato03** » Wed Jan 06, 2010 11:29 am

Thanks Steptoe , yes the 87 WSM shows quite a few ground or earthing points to check - and yes there only appears to be the one on the inlet manifold .

1) Dr side strut tower .
2) Two near where fan motor and thermo switch wiring exits the loom across front of car .
3) One to the left of the battery .
4) One on front of pass side strut tower - I think .
5) Three under rear of drivers seat .

Later , cheers A .

Gannon · Post by **Gannon** » Wed Jan 06, 2010 3:42 pm

Im gonna go out on a limb here, is you car going lean because of all the air it is now ingesting, but the factory tune cant keep up. I read on another site that the early toyota efi systems with a flap style air flow meter is good at reading air flow at low to medium speeds, but as soon as you go WOT, the ecu ignores the AFM and relies on pre programmed maps instead

Could Subaru have done the same?

discopotato03 · Post by **discopotato03** » Wed Jan 06, 2010 7:59 pm

We got a chance to have a look around the engine bay body and engine grounds and they're actually not too bad for a 24 and a bit yr old dame .

I removed the computers three mounting nuts and dropped it down so I could get at the Computers ignition supply and FP relays . They actually sit on top of the ECU's mounting frame in clips .
Me thinks bugger that and now have them draped down over the front of the black box where I can git at them easily .
They actually run quite warm bordering on hot so I fitted a pair I had off a later cars loom - newer .
I got my mechanic mate to pull one apart just to check out its guts . The power contacts were not real good so you can't just assume these things are .
Another curious thing is that the "coil" side has a resister across it so probably can't replace them with your usual 30 or 40a Bosch relay and base . I think they do relays with resistors but need to price the OE relays first .
My friend tells me later Mazdas and Toyotas use them too so maybe not too dear . Anyone know for sure ?

Lastly I replaced the EGR solenoid with another I had just to see if it made a difference .

I think the ultimate plan would be to fit the Vipec computer and new relays somewhere on the pass side so the eventual changeover can be reasonably seamless . It could all be put in place just waiting to be connected to the engine and relay power supplies . The std gear could stay where it is just disconnected at the fuse box and engine loom connectors .

Any heads up on those std relays , cheers A .

BTW Gannon , no it acts up at low speeds and revs when it plays up .
I noticed the microswitch doesn't always release on the throttle pedal so must look at that too .

Cheers A .