stocko 4age playing up!

[ke70dave]

hey folks, got a tech Q for you 4age junkies.

ok the setup

-"Jap spec" 16v 4age (as far as i know)
-jap ecu (definately)
-rwd loom
-head reco few months back with new head gasket of course
-new gaskets everywhere
-bp ulimate fuel run all the time
-base timing set to around 15-20 degrees before tdc, doesnt ping
-fuel system is just an external fuel pump under the back of the car.

ok the symptoms.

engine seems to bog down and die, if the throttle is opened quickly. if i build up the acceleration relatively slowly (ie not instantly) the engine picks up well . but if i "snap open" the throttle under any circumstance the engine will cough and splutter for a bit and then sort it self out and continue reving well. the coughing and spluttering is sort of "power surges" it is really quite violent . it is especially apparent when changing gears quickly while accelerating fast. ie...rev out first gear, off throttle change gear, and back to 100% throttle it will cough and splutter violently for a few secs then keep going.

note the engine starts perfectly fine, and drives great all the time, except for the circumstances listed.

my initial thought is that the spark is breaking down, the spark plugs are prolly 3 months old and were pretty good condition last time i checked (few weeks back). The spark plug leads are new, not sure on the coil, but i guess that is fine.

also note i am unsure when this problem started as since ive had the engine in my car i haven't really driven it that hard all that often, its only that ive started becoming more confident with my driving with it that ive noticed this problem. i do know that it hasn't always done it though.

so if any one has any ideas that would be great! my understanding is that i should be able to stomp on the throttle at any time (within reason) and the ecu should sort things out for me....

[Robo86]

mmm my problem was kiiiinda similar. it turned out to be a clogged fuel pump, threw in a 7mgte one and i havnt had a problem since, just something to keep in mind maybe?

[ke70dave]

hmmm interesting

i have been suspicious of my fuel pump since i got it (unknown history, which yes i know is a dodgy thing to do)

i have a 8mm line and a surge tank to put in....im sure it would improve the situation. but there are plenty of guys running just a dodgyvl pump and they seem to run ok.

thanks for the reply though mate!

[KE70]

I have the same problem but its not my fuel pump as it measures ~40psi upto the rail.

Let us know if you work it out.

[Nikkojoe]

I would check all earths, paying great attention to the engine loom earth bolted to the inlet manifold. Check ecu codes for errors.

[slydar]

its unlikely to be the pump.

you need to put some effort into sorting out a way to read the fault codes, thats my main advise.

the fuel line size is fine. 1/4" is big enough. checking the earths is a good idea. the main one on the engine loom is usually bolted to the intake manifold behind the fuel rail.

[LittleRedSpirit]

As Ive said many times, take it to my mechanic.

You will waste your life playing with something like this.:oh:

[ke70dave]

As Ive said many times, take it to my mechanic.

You will waste your life playing with something like this.:oh:

haha good luck getting me to take something to a mechanic!! (assuming its mine!!)

right ive had a bit of a play this arvo

pulled out the spark plugs and found them to be a tad white on the tips, which from my understanding is a bit lean or possibly a bit of detonation?

anyway checked the timing again, found it to be a bit too advanced (around 22 before tdc) so i knocked it back to around 15 deg tdc.

i also found my tps a bit lose which could do annoying things, so i put that back to where it idled the best (could hear the idle switch kicking in) at around 1000rpm constant.

checked the earths and they are all nice and tight, specially that one you guys are talking about on the intake. all nice and schmick.

gonna go for test drive in a bit (parked in....) so hopefully ive made some improvements

quick question, do 4ages have any sort of automatic cut out if it senses something "bad"? like the "boost cut" on turbo cars? i didnt think so since it doesnt have a knock sensor, but you never know.....

next step is to get my check engine light working and start checking some codes! but its a bit dark for that now...

[hachi_dk]

did u take it round the block :D

[Nikkojoe]

When I meant check earths, I actually meant check if the wiring on them is still good. Best to check all the sensor earths (ie TPS, MAP, etc) which are denoted by a brown wire. These wires run to that earth connection on the inlet manifold (engine ecu/loom earth). Make sure they all earth out to the engine/car body, even when giving the loom wriggle near the earth mounting point.

Failing every other test (even fault code), unplug the tps and take the car for a drive. If its fixed, you probably have a problem with the tps and/or wiring to the tps.

[ke70dave]

yer im starting to think its tps

just took it for a test drive, its a bit of an improvement but problem is still there.

starting to think its tps, but ive replaced that recently, maybe i got unlucky twice...though before with the old broken tps it would hardly run with it plugged in.

i got a nice backfire of unburnt fuel with one of my "testing procedures" this evening as well. took off form the lights in first and just held it at 3000 revs for a second or 2, then hammered it...and a nice boom through the exhaust. it was awesome...in a not really that awesome kinda way.

will unplug the tps and try again tomorrow!

[Javal]

Is it actually Misfiring or just bogging down?

[ke70dave]

im not sure hey

sometimes i think it is misfiring (the backfire incident)

other times it feels like it hesitates for a second then gets up and goes

and other times it carrys on violently for a few secs and then gets up and goes

about the best description i can give over the internets im sorry

[Javal]

im not sure hey

sometimes i think it is misfiring (the backfire incident)

other times it feels like it hesitates for a second then gets up and goes

and other times it carrys on violently for a few secs and then gets up and goes

about the best description i can give over the internets im sorry

It does sound a lot like an ignition related misfire.

Replace spark plugs to start. See if it helps.

Then check you have a strong spark off the coil:
-If yes, check resistance in your spark plug leads. If it's high, replace them
-If no, replace your coil. Also, check all wires and grounds around the coil.

Also, change your fuel filter. Shit's like $7. Just so you can forget about it for a while, and rule it being blocked out.

[Matt-AE86]

I use to have a simular issue when my TPS plug would come off, sometimes it would come off and be ok, but I would notice something is wrong. Pull over, TEE PEE ESS.

But that said I would do the following

Try to check Engine codes
Check TPS Resistance.
Adjust TPS
Replace TPS
Check Fuel Pressure
Replace Fuel Pressure
Check grounding (not only the wire to the manifold, check battery negative to body, engine to body and so on)

[xero]

have you checked the distributor cap? this sounds likes you have oil there from a leaking dizzy....

[Javal]

have you checked the distributor cap? this sounds likes you have oil there from a leaking dizzy....

Not this.

[ke70dave]

Not this.

yer gonna have to agree with you on that one

the fact that it only stuffs up like 1% of the time suggests everything is "almost' perfect....i would expect it to be pretty nasty if there was oil inside my dizzy.

right now onto your list mr javal!

trying to avoid buying things randomly as money is a precious comodity.

yesterday i gave the plugs a decent scratch up and clean with some carby cleaner so i dare say they are as good as new now (only 2months old anyway, prolly only 2000km)

i currently dont have a fuel filter installed (yep dodgy too, but you get that), i have a brand new one ready to go in, so currently there is no restriction from a blocked filter.

its jsut occured to me that the spark plug lead from the dizzy to coil isnt brand new like the others, so that might be a problem i guess, will get the multi meter onto it this arvo.

oh and matt-86, how do i "Replace Fuel Pressure" hehe. ill head down to repco maybe they have canned fuel pressure for me:P

i know what you mean though, i dont have access to a fuel pressure guage, might be able to get something...

[Javal]

yer gonna have to agree with you on that one

the fact that it only stuffs up like 1% of the time suggests everything is "almost' perfect....i would expect it to be pretty nasty if there was oil inside my dizzy.

right now onto your list mr javal!

trying to avoid buying things randomly as money is a precious comodity.

yesterday i gave the plugs a decent scratch up and clean with some carby cleaner so i dare say they are as good as new now (only 2months old anyway, prolly only 2000km)

i currently dont have a fuel filter installed (yep dodgy too, but you get that), i have a brand new one ready to go in, so currently there is no restriction from a blocked filter.

its jsut occured to me that the spark plug lead from the dizzy to coil isnt brand new like the others, so that might be a problem i guess, will get the multi meter onto it this arvo.

oh and matt-86, how do i "Replace Fuel Pressure" hehe. ill head down to repco maybe they have canned fuel pressure for me:P

i know what you mean though, i dont have access to a fuel pressure guage, might be able to get something...

Cool beans. The coil-distributor lead could be a cause of it. Shell out on a new rotor button if you can, and then you never worry about it again.

[ke70dave]

thought id let you know how this panned out.

i tried a different map and tps and it didnt change anything.

but i noticed it was getting quite rich as well.

did the ecu codes trick, and it threw up the "water temp sensor" code

$41 later for a new water temp sensor, and its running great. better than it ever has!