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.

[ke70dave]

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

[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.