Page 4: Return to the 'Max Power' era

[willswitchengage]

A smidge over three years ago I bought a 1991 Toyota Corolla E90 with the 2E (1.3) engine. It's been fantastic(ish).

 

It had about 16K on the clock when I bought it, and it barely got home. It had a remarkable fully stamped service history book but this didn't detract from the fact that the seller (son of the deceased owner) had 'forgotten' the latest service note that said the engine was rough and hesitating - it had only driven to the MOT centre in about ten years. I drove it home cold as the thermostat had seized open. The car had almost zero acceleration - put your foot down and the engine would stall. However, I quickly discovered that if driven at over 2500 rpm it would work fine as this is the speed at which the second venturi would open on the carb (it's the Toyota (Aisin?) K-type). I replace the thermostat, distributor and spark plugs when I got home, slowly put through the carb a couple of bottles of REDEX and the problem persists to this day, despite having put about another 15K on the car now.

 

Symptoms:

 

+ The engine runs perfectly when cold and the autochoke is (presumably) engaged. It accelerates well at low RPMs and the loud pedal is nice and twitchy like it should be.

+ When at operating temperature the engine hesitates under 2500 rpm. You need to feather the accelerator. Put your foot down and nothing really happens. Rev the engine and the revs don't drop until a couple of seconds after you let go of the pedal, and the revs generally drop very slowly when driving. Makes gear changes tricky!

+ When at operating temperature the engine behaves normally above 2500 rpm. When accelerating through the revs you can really feel a turbo like WHOOSH at the transition and the power picks up. Max acceleration at high revs still feels a little slow for a 75hp car that weighs <1000 kg but that's always difficult to determine.

 

Thoughts:

 

+ Weak coil? The behaviour of my 2CV improved markedly when I replaced that on mine, and that had similar symptoms but also had hot start issues which sort of gave the game away. This may also explain why replacing the diz and plugs made an improvement.

+ Restricted primary jet? Would explain why the primary hesitates but not the secondary, and also why the car functions fine when cold as the choke enriches the mixture and negates the effect of a restricted fuel flow.

 

...but that's just my guesswork. Any more intelligent answers would be much appreciated.  

[DSdriver]

I'd strip down the carby - can you get a service kit for it?

[forddeliveryboy]

Remove and clean the primary jet and check the operation of an accelerator pump.

 

I'm guessing you've already done the usual checks for inlet manifold air leaks, including the carb mounting?

[mercrocker]

This sounds exactly like the symptoms on my VW T25 (two-stage Pooburg on the inevitable boxer petrol engine).   It was virtually undriveable unless you tap-danced the pedals.   I tried a few carb cleaning sessions and so on but ended up sending it away to a specialist.  It has been excellent ever since although still retains an irritating flat spot which I think VW put there themselves.... 

 

I wonder if the low mileage/useage and inevitable periods of inactivity have caused some kind of fuel varnishing?

 

Basically, can you find a suitable specialist via forums etc for the Keihin - maybe a bike lad somewhere?  

[red5]

Accelerator pump weak or non existent. Have a peer down primary Venturi and open throttle-quickly, not gently. Should be a decent squirt evident.

[willswitchengage]

Incidentally I have just gone out to change the spark plugs. No difference made but the old ones that I removed were a little blacker than Haynes says they should be - although the electrodes themselves match the 'good condition' photo. Nice little V-notch dug into the graphite.

 

More evidence... CO and HC readings from my past few MOTs:

 

CO:

0.174

0.194

0.182

0.39

 

HC:

133

143

110

174

 

The last (and oldest) reading was taken on a different machine which may explain the jump in CO. These abnormally high or low, or telling me something?

[pshome]

Way to lean... 1.5% CO is what you want. Sure you have no air leak somehwere?

Turn that idle mixture screw up. Revs will go up. Keep going until max speed, then 1/2 turn back.

Now adjust idle speed screw to get revs to normal.

[tommotech]

Way to lean... 1.5% CO is what you want. Sure you have no air leak somehwere?Turn that idle mixture screw up. Revs will go up. Keep going until max speed, then 1/2 turn back.Now adjust idle speed screw to get revs to normal.

The HC readings don't suggest an air leak but O2 and CO2 reading would confirm. The CO is way too thin and the mixture needs to be richer for sure. If the carb is clean great but if you're struggling to get it any richer check the float level setting.

[forddeliveryboy]

I've seen plenty of pre-cat carb engined cars with CO below 0.5 which drive fine (if not as well as they could), suggesting non-functioning accelerator pump or partially-blocked primary jet, if there's no air leak downwind of the carburettor.

[willswitchengage]

Question two in the EARLY LEARNING CENTRE

 

What would happen if I just unwound the dashpot screw a few turns so it wouldn't hold the throttle on so much on deceleration? The previous three carb cars I've had (and my old motorbike) didn't have the dashpot hold and were nice and snappy.

[tooSavvy]

.... Ohhh! OAP grade Toyyo speak!!

 

Mine (1.6) has a fluffy 'ramp up' of revs - from idle

 

I have recently been 'dumped' at lights because the engine simply fluffed to a standstill (sounding like it was drowning in fuel.. but probably too weak?)

 

The car goes like a rocket [hoon mode lite] so is fuelling well in the sloshing it back range.

 

Starts OK at 0/-1deg (as lately) and is strong when on choke.

 

Spose the 'knob twiddle' tweaking will show some improvement.

 

CarbClinics were everywhere b.i.t.d.

 

 

TS

[forddeliveryboy]

Question two in the EARLY LEARNING CENTRE

 

What would happen if I just unwound the dashpot screw a few turns so it wouldn't hold the throttle on so much on deceleration? The previous three carb cars I've had (and my old motorbike) didn't have the dashpot hold and were nice and snappy.

You'll make more pollution so more kids will have breathing problems. But the car will drive better.

 

Your choice, but bear in mind there was less childhood asthma when we burnt coal so much everything turned black, but didn't spray pesticides and eat processed food.

[Station]

i had the same troubles with the Justy (the one I bought off you incidentally). I could not get it to run properly, and couldn't find anyone to fix it, and the more I faffed about with it, the worse it got. It was drivable until I put Redex in the tank. I checked everything.

I'd honestly find a carb rebuild place and send it off.

[Guest Hooli]

Rip the carb apart, it'll be blocked somewhere. Take loads of pics as you go & keep the bits from each venturi together so you don't mix jets etc up.

[xtriple]

Carbs are nice, simple things that logic and common sense still work on, not like this new fangled injection tosh that makes sense only to the man who made it and God almighty... when it goes wrong that is! Find a biker locally with a Honda 900 Fireblade and ask him nicely to strip and clean the carb for you. As he will have been doing the same to his Hondas 4 carbs after every winter since time began, your carb will be a piece of light relief for the poor bugger

[mat_the_cat]

+ The engine runs perfectly when cold and the autochoke is (presumably) engaged. It accelerates well at low RPMs and the loud pedal is nice and twitchy like it should be.

+ When at operating temperature the engine hesitates under 2500 rpm. You need to feather the accelerator. Put your foot down and nothing really happens.  Rev the engine and the revs don't drop until a couple of seconds after you let go of the pedal, and the revs generally drop very slowly when driving.

 

Don't discount the fact that you may have more than one problem, or things may have been tweaked to try and compensate for the problem. But for this

 

"Rev the engine and the revs don't drop until a couple of seconds after you let go of the pedal"

 

I can think of no other explanation than an air leak. If you think about it, your foot is off the pedal, the throttle butterfly is closed so the engine needs air to keep revving. Things are OK when the cold start enrichment is supplying extra fuel to go with the extra air, or when the second choke kicks in to suddenly bring the mixture closer towards optimum. So I would really try and check for air leaks first, before spending money/time elsewhere.

[HillmanImp]

i had the same troubles with the Justy (the one I bought off you incidentally). I could not get it to run properly, and couldn't find anyone to fix it, and the more I faffed about with it, the worse it got. It was drivable until I put Redex in the tank. I checked everything.

I'd honestly find a carb rebuild place and send it off.

 

Could you not just use a local motorbike garage? They will be good with carbs still won't they?

[Station]

I tried two local ones, but they just couldn't be arsed.

[Uncle Jimmy]

Bring it to my house, I have an old bloke who will swear it into submission. Otherwise, yes, sounds like the idle jet is constricted in some way. I doubt it's a vacuum leak, it would have to be considerable to cause that kind of hesitation.

It's not the coil though dwell angle and advance could well be wrong.

[Des]

With a warm engine, uncover the carb, rev the knackers off and stuff a big handful of rag down its gullet like you're choking a traffic warden, pull out just before it dies and repeat, like you'd do with a traffic warden, you might get lucky. Or wind the mixture screw out a half turn.

[Junkman]

Alternatively, it could be a knackered accelerator pump.

[Guest Hooli]

Carbs are nice, simple things that logic and common sense still work on, not like this new fangled injection tosh that makes sense only to the man who made it and God almighty... when it goes wrong that is! Find a biker locally with a Honda 900 Fireblade and ask him nicely to strip and clean the carb for you. As he will have been doing the same to his Hondas 4 carbs after every winter since time began, your carb will be a piece of light relief for the poor bugger

 

Injection is just as easy once you get your head around it. It's doing the same job after all, just in a different way.

[AMC Rebel]

With a warm engine, uncover the carb, rev the knackers off and stuff a big handful of rag down its gullet like you're choking a traffic warden, pull out just before it dies and repeat, like you'd do with a traffic warden, you might get lucky. Or wind the mixture screw out a half turn.

 

I feel compelled to mention that last time I tried this, a massive sheet of flame shot out and I nearly had a cow - you may fare better however, and it was a long time ago.

[barefoot]

 I nearly had a cow

 

 

WT actual F?

[forddeliveryboy]

Have you checked the accelerator pump?

[AMC Rebel]

WT actual F?

 

I got the expression from Bart Simpson (along with "underachiever and proud")

 

Per Urban Dictionary -

 

As in when a person will be extremely upset, angry, or suprised about something

Bob: Hey, did you hear about how Fred's house got bulldozed over while he was on vacation?

 

Joe: Yeah, he's going to have a cow when he finds out!

 

 

[tooSavvy]

^^ any post with the 'three fingered guy' in it is a winnah 4 me

 

... my current spell of 'introspection' is likely going to throw up a great deal of Quality Time.... for carb tinkering

 

 

TS

[willswitchengage]

This is fun. After being stood for three weeks outside this was the first morning the car has, er, not started. It was bloody cold though - the car was bathed in ice and it took a lot longer than usual to warm up.

 

Correction: did ultimately start, but only after maybe two minutes of intermittent cranking (fortunately the previous owner installed an oversize Bosch superbattery) and experimenting with a variety of right pedal positions (usually a single pump and start with no accelerator breathes it into life). Ultimately started with my right foot mashed to the floor for ten seconds as it gurgled to a stable speed. Drove fine. Annoyed.

[xtriple]

Where do you live? If local to Torquay I would be happy to look at it for you though you may end up doing most of the actual work (cripple is a good excuse for laziness!) or if further afield, I'm sure there is someone near you who can rave the carb off in seconds (sledgehammer takes the least time).

 

It seems obvious to me it is a carb related problem, spray carb cleaner round the base of the carb (watch out for flames   ) and see if the speed picks up = air leak. Take off air filter box/whatever, and with engine NOT running, press accelerator on the carb sharply while observing down te throat of the carb you should see a jet of neat fuel from some little jet/pipe near the top of the carb = accelerator pump is working. Personally, I think it's a blocked pilot jet caused by lack of use, it's unlikely to clear without violent use as described above or by taking it apart and inspecting/prodding with relevant tool.

[somewhatfoolish]

Short of removing the carb and lobbing it in the nearest skip, getting the thing a nice bath in an ultrasound jacuzzi wouldn't hurt.