[BNE] Loss of power with smallport

[timbo]

Car - ae86 JDM

motor - 4AGE smallport

use - daily soon track

problem - lack of power

occurs/started when - see below

personal situation -frustrated!

I got my car back from the mechanics today where it has been for almost a week sorting out a cracked intake manifold, various other vac leaks and a dodgy wire for the TPS. The week before that Johno (Juturna) and myself (mainly johno!) replaced the timing belt so timing is set correctly.

So there are now NO vac leaks on the intake manifold what-so-ever and I have a brand new TPS and plug that both work and have been set correctly. The car idles at 900rpm when warm and drives quite well, however it has an odd exhaust note and lacks decent power with WOT from about 3500rpm onwards. It can reach redline but really struggles to get there. With the dizzy set at proper idle timing the motor runs smooth but driveability is some what limited. If you advance the ignition timing it improves a little but doesn't solve the problem and I assume advancing the shit out of the motor isn't a good thing. I have had a previous problem similar to this that was timing related but ATM I do not understand as everything has been set correctly (TDC and dizzy shaft etc). The biggest difference to myself is the exhuast tone, to describe it would be like an airing flapping like raspberries with your lips (please, no sexual jokes, not in the mood!), which sounded like when the motor was retarded.

Just to point out, at idle if you rev the engine it advances as it should.

Please ae86dc smallport boffins, guide me with you eternal wisdom!

[blair]

Done a compression test at all man?

Has it ever been better than where it is now? i.e. before you did the timing belt etc..

[timbo]

it has definitely been better before, beats corolla sportivos etc!

well it began just before we did the timing belt. i assumed that it had stretched and simply gone out of time. i think the biggest issue was the various vac leaks as the car was not drivable at all but is capable now. have not done a compression test but the motor was hard to crank to tdc which i thought would indicate good compression.

[timbo]

i found this quite interesting:

http://forums.club4ag.com/zerothread?id=64090

however the problem is not tvis as it is a smallport. i think this is going to be a timing issue, does anyone think it is possible that the crank marking for TDC is somehow not actually TDC?

[Anthony]

incorrect igniter maybe? Is the engine management setup all AE92 or bits from here and there?

[timbo]

it has a bigport loom, dizzy, coil, ignitor, water setup etc. but the car has run perfectly in the past with the exact same setup. do you think it is possible that the engine is not getting enough spark?

[Faceplant456]

it has a bigport loom, dizzy, coil, ignitor, water setup etc. but the car has run perfectly in the past with the exact same setup. do you think it is possible that the engine is not getting enough spark?

yank out the coil to dizzy HT lead at the dizzy side and crank it while someone holds it near a earthed metal on the car ... you can get a good idea of how your spark is like that... my one like that was about 8mm jump which i thinks is massive but it depends on the car ... i would say take your plugs out and check them ... they might be clogged up with crap or they might just be crap ... also check what type of plugs they are ... as the small port is supposed to run with platinum plugs ...
then while they are out do a compression test ...

[.ady]

i had a similar problem with mine, turns out it was my injectors, the plugs werent connected properly and it lacked so much power.

[ke70dave]

giving the funny exhaust note, and the fact that it has started around doing the timing belt, id say you are out a tooth or 2 on the belt. worth checking anyway.

and also you say that the ignition timing has to be really advanced, id say there is something funky with your timing in general.

[timbo]

faceplant, plugs are NGK platinums but i haven't checked them since the problem started so its on the to-do list. is a compression test fairly cheap? i understand there isn't alor involved but i don't have a gauge.

ady, will check injector plugs and run a multimeter on them just to be safe.

dave, it happened before we replaced the timing belt thus we replaced the belt thinking that it was the problem. i thought it was timing related but this afternoon i went back and re-checked everything and can confirm that it is all how it should be, 10degrees bridged, cam markings line up, belt not loose etc.

it is really beginning to bug me... to me the exhaust note just spells out retarded but for the life of me can't work out how it could be. many thanks for the input so far guys and keep it coming!

[Faceplant456]

you would probably be looking at about $20 plus labor for a compression test ... if you were located near me i would just borrow the tester from work and do it for free... but sadly your not .

but as a guess i would say it could take about 30-40 min to get the compression test all done and then the plugs put back in ... so your gonna be looking at about $60+ for the test ... it just depends on how fast and good the mechanic you take it to is ... and if they charge the same rate that we do which is $80PH .

[timbo]

well i might see if i can borrow some equipment of a certain apprentice i know...

[Faceplant456]

sounds like a good plan ... its good when you know people in the trade ... but its even better when your in the trade ... like me :D

[hao.]

I have a compression tester here man. come over one arvo and we'll do a comp test.

[timbo]

fuck yeah, hao to the rescue again! weekend, maybe saturday? still gotta fit those lines, damn cars!

[hao.]

yeah man, call me or something on saturday..I'll just be at home working on the datsun. :)

[Nikkojoe]

I had a similar intermitant problem once on my first bigport. Turned out to be bad earth on the engine loom to the manifold (but a bad engine earth would cause the same issue). It would run fine, then randomly struggle to rev out (sounding really retarded, poping intake too).

I initially thought it was the AIT (air intake temp) sensor and when i replaced it all was good, but it was only because i had jiggled the earth connection to the intake manifold near by.

[ke70dave]

something i just thought of..what about blocked exhaust? Do you have a catalytic converter?maybe its collapsed?would explain both the power loss and funky exhaust noise.

[timbo]

okies, just visited the wise hao and performed a compression test. 225psi on all 4 cylinders. fkn high and fkn consistent.

dave, yes i have a cat but the whole exhaust was brand new only a few months ago... are you suggesting a drive whilst only running extractors?:cool:

hao and myself had a discussion on smallport timing so i think i might investigate the possibilities of timing issues re crank marking etc.

[blair]

225?? what the

[hao.]

That's what I thought....but the compression tester was brand new, could've been faulty though. I dunno, I've never heard of any 4AGE's having that high a compression before. :S

[70XIN]

225 sounds pretty healthy for a smallport :)

And just agreeing with others here; kinda sounds like you're off by a tooth on the timing, which would also affect what you *think* is the correct Ignition timing. it's probably ACTUALLY running retarded/advanced as all fark.

[timbo]

well i do think it is a timing issue, but all markings line up meaning that somehow the markings are incorrect...

[Nikkojoe]

if timing was out, you would notice your compression results would change and not be AS consistent (though it really depends on how far out it is).

[timbo]

well it certainly has got me stumped... hao recommended a workshop so i will probably give them a call tomorrow and sort something out.

[Faceplant456]

hey man i took my 86 for a drive the other day after playing around with my dizzy and it was really crap untill it got up in the RPM play with the dizzy timing. i had mine running good before i played with it. it sounds really similar to your issues ...

also normal compression for a smallport is about 195 on average give or take 15.

[Nikkojoe]

a bigport in very good nick will get you 180-190 (smallport 4agze is similar, but more 170-180)

a smallport in very good nick will get you 200-220

[timbo]

well i guess a have a very good condition motor that isn't running right! anymore thoughts on things to check guys?

[70XIN]

Clogged fuel filter and/or stuffed fuel pump?

Robo's car had sorta similar symptoms. Fine up to about ~4k rpms, then laboured REALLY badly trying to get above that.

[timbo]

i wouldn't mind doing a fuel pressure test to be sure, anyone got a gauge?

[.ady]

each compression tester is dfiferent.....i got a reading of 250 across all fours on 1 and 195 across all fours with another....as long as there consistent i guess its alright? number isnt really an issue

[Faceplant456]

i have the toyota 4A-GE repair manual from toyota. 195 is average across all cylinders for a small port.

ill have a look in the book and see if that can help diagnose the issue your having ... this book was what helped me work out my auxiliary air valve was fucked.

[Marco]

tim my man. we have a fuel pressure gauge at work. i can hit the bossco up to borrow it next weekend if you not sorted by then. shame you haven't got all this shit sorted yet:(

[ke70dave]

hey man ive got a fuel pressure guage but its kinda mounted in my car....

i bought one from autogay for about $30 or so. (pluss a few bucks for fittings)

if you get desperate you can come round and we can temporarilly mount it in your car, but its sorta part of my fuel system.