Hey guys,got a new project and having a few problems getting my bigport 4age to run properly in my ae86. MAP sensor'd

cars undrivable at the moment, if i give the throttle a real quick hit and bring it up to say 2500rpm it misses and backfires and carrys on, if i move the throttle slowly to 2500 not a problem at all

idles like crap (see vid)


What ive tried;


Have statically timed (everything lines up, cam timing etc)

timing is at 10BTDC with diagnose bridged (timing is pretty erratic, 10degrees for 2-3 seconds then jumps to 15 then back to 10 etc etc..)

compression check 140-145 on all 4 cylinders

checked vac hoses

TPS adjusted and in range

Cleaned iscv/throttle body new gaskets everywhere
new dizzy cap
new plugs
new leads
all sparkplugs are sparking


Any ideas?

brandnew plugs, ran for 5mins

SPARKPLUG CYLINDER ONE



SPARKPLUG CYLINDER 2,3 &4



also a video of how its idling, it will idle like this and eventually stall out on its own....

Looks like a lot of fuel on that plug. Bad injector on #4 cylinder, replace it, [try to clean, search injector cleaning] If you want to confirm, swap the injector to another cylinder and re-check the plug condition in that cylinder. You need to lube the O-rings on the injector before installation. Dave W

Fuel or maybe even oil. Try to figure out what is on that plug and why it's there. Could it be oil from the spark plug well getting on it as you pull it out?

This is where the FSM will be your best friend.
Go to the FI section and start going through all the related troubleshooting and diagnostics. It will be faster and more efficient than any advise you will find here. Once you go through all the related tests and if you don't find anything suspicion report your results here and we can try to figure out where to go next.

Sorry for the late reply, have been busy at work.

Took injecters out and cleaned. cleaned plugs and no more black plug on cylinder one so that problem is fixed. altho seems to have not helped it running like crap still. im seriously at a loss to what it is...

also set idle again and tried another TPS but hasnt changed a thing still the exact problem i was having before, misses, idles crap, no power etc..

went thru the book and did all the tests to check coil/ignitor etc etc etc all were within spec

any idea where to go now?

I have the same issue you are having .. if the car is missfiring when cold like that it can be a stuck open fifth injector ,a bad vane air flow meter , temp sensor anything that affects fuel mixture on all cylinders , bad fuel pressure regulator .. i checked all the things u did too im just left with that so i understand what ur going through

Sent from my SGH-M919 using Tapatalk

smackdownz wrote:timing is at 10BTDC with diagnose bridged (timing is pretty erratic, 10degrees
for 2-3 seconds then jumps to 15 then back to 10 etc etc..)

When setting the ignition timing you need to be sure that the engine actually goes
into diagnostic mode when you jump the plug. If the timing does not drop back by
5 degrees or so when you jump the plug (and the rpm's drop enough for you to notice
that they drop) then the engine did not go into diagnostic mode.

Here isa bit of reading
http://club4ag.com/forums/viewtopic.php?f=9&t=11359&p=75364&hilit=diagnostic%3Bmode%3Bconditions#p75364

If you set the timing to 10 deg BTDC and the engine was not in diagnostic mode,
then what you actually have is timing retarded 5-6 deg. Might be worth checking.

Cheers... jondee86

yeah its getting pretty annoying whitecomet10 lol

cars definitely going into diagnose mode when bridged out, set timing at 10btdc and if un-bridged goes to 16ish.

Looking at you vid I would say the engine is running out of gas. Hooking a
fuel pressure test gauge up to it would be the best way to check, but clamping
the fuel return hose shut while it is idling might give you a clue.

I'm guessing that when you try to drive the car, as soon as you let the clutch
out and apply some load to the engine, it just bogs and dies. Dies faster if
you give it more gas ?

Cheers... jondee86

Interesting, it sure does.. What does clamping the return show? Just gives me more fuel in the rail. Will check fuel situation and let you know

EFI engines need pressure and flow in the fuel rail. If the pump is failing or
the filter is blocked, the fuel pressure will be low. Low pressure means that
less fuel gets injected as the ECU has no way of knowing the pressure is less
than design. Clamping the return hose will raise the rail pressure with a
healthy pump, and probably will raise it a bit even with a dying pump.

If the engine runs better with the line clamped, that is a sure sign that either
the pump or filter is bad. A bad fuel pressure regulator could cause low rail
pressure, but they are pretty reliable critters, and the FPR would be at the
bottom of my list of suspects.

If you can, try winding the clamp closed with the engine running so you can
observe any changes.

Cheers... jondee86

Hmm alrighty, started it up sounds like crap lol gave it a few revs and let it warm up for a min or so, clamped the return line and no so much difference in the idle but when i went to rev it, its a million times worse lol as soon as i open the throttle it just wants to stall up, doesn't rev at all etc

How did it rev when the line was not clamped ?

Did it blow smoke or stink of fuel when the line was clamped ?

Cheers... jondee86

really wouldnt rev at all, id try open the throttle and its like it was taking a massive gulp of air and nothing happened just choked spluttered and carried on, didnt blow any smoke that i noticed, no smell of fuel either.

have a fuel pressure gauge now, i will hook up to the coldstart injector port on the rail and see what pressure im getting there.

Yeah... definitely sounds like your fuel pressure is down. If the pump
is struggling to deliver, clamping the line might have made it struggle
even more. A healthy pump would have raised the rail pressure and put
more fuel into the engine... yours didn't.

Cheers... jondee86

Alrighty i dropped the tank to check the fuel pump, turns out it has a walbro gss 341 pump. Had a look at thr little rubber hose that is connected to the pump in the tank and there was a massive split in the hose, so thats where i was losing all my pressure.

But new problem i bolted it all back together the walbro pumps a wopping 255lph and gave me almost 60psi at the rail. I think the pump pumps to much and the regulator cant handle it. Blackens the plugs instantly lol so external regulator will go on to get me by for now and see how that goes...