Help! Corolla Misfiring! (ae92 Gt-i)

[KidKoala]

OK last night I was driving my Corolla GTi, and it started holding back... it runs a tad lumpy, and it jerks quite heavily if you try and use the power... I think it must be some sort of ignition problem, so I'm thinking change the plugs?

Any ideas as I'm going to the motorfactor soon.

[Twincam.GTi]

NGK or Nippon denso are official recomendations.

You say misfiring ...

...when you take the plugs out have a look between the spark plug 'holes' and you will see 'bung/core plugs' just check that these are not 'weeping' coolant. This can some times be a problem with the 4AGE Engine. If they are you will need to remove them with a big allen key/socket size and re seal.

Just one idea.

Another idea could be the ignition coil or lead (not a cheap item I believe)

Finally is the any oil weeping from the area of the distributor where it goes into the front of the engine? If so the distribtor seal will be wearing out (don't worry a lot do and usually will weep for another 45,000 mile). If it has gone really bad it my have sucked up oil into the distributor, to check just carefully remove the dizzy cap.

Not seen you on the site lately, glad to see you're still out there.

[KidKoala]

NGK or Nippon denso are official recomendations.

You say misfiring ...

...when you take the plugs out have a look between the spark plug 'holes' and you will see 'bung/core plugs' just check that these are not 'weeping' coolant. This can some times be a problem with the 4AGE Engine. If they are you will need to remove them with a big allen key/socket size and re seal.

Just one idea.

Another idea could be the ignition coil or lead (not a cheap item I believe)

Finally is the any oil weeping from the area of the distributor where it goes into the front of the engine? If so the distribtor seal will be wearing out (don't worry a lot do and usually will weep for another 45,000 mile). If it has gone really bad it my have sucked up oil into the distributor, to check just carefully remove the dizzy cap.

Not seen you on the site lately, glad to see you're still out there.

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Eek not sure I'm gonna get hold of NGK/Nippon equipment around here , I'll ring them and ask. Don't suppose Halfords would have them either?

What I mean by misfiring, is I'll be pulling away, and there will be almost a rhythm to the lumpyness of the acceleration, I dont know much about this stuff, don't know what it would be like firing on 3 cylinders?

It feels nasty anyway! Where are these bung/core plugs? are they underneath the spark plugs? Are they easy to re-seal etc?

I assume you are reffering to the HT leads? I believe they are fairly new.

I'll have the dizzy off and see whats in there, maybe a worn rotor arm as well?

Not had alot of time to myself recently, I'm working full time, and working the weekends doing private contracts, moving house at the end of the month and I've got no money for the deposit!!

[Twincam.GTi]

It feels nasty anyway! Where are these bung/core plugs? are they underneath the spark plugs? Are they easy to re-seal etc?

I assume you are reffering to the HT leads? I believe they are fairly new.

I'll have the dizzy off and see whats in there, maybe a worn rotor arm as well?

The core plugs will be seen as you look down above the enigne at the 4 spark plugs after removing the plastic cover (to get at the spark plugs ...I think it's that kind off cover on the later engines). Theres two 'plug' one between 1 & 2 sparkplug hole and the other between 3&4 spark plug hole. You can tell if there leaking as there will be coolant residue around the area (what happens is it leaks slight coolant onto the spark plug and causes 'tracking' thus misfiring. Having said all this it all may be bone dry ...so what i've said will not be relevant ...sorry.

Only take the cap of the dizzy off dont go taking the dizzy completely off as you will have to re-time (it ain't as easy as on old 'Min' to re time.) I've never ever known a rotor arm to need replacement. Just check no oil has got sucked up to the cap area when you take cap off. Dizzy's sucking oil up (after seal had gone)used to happen with old Mini's

One more thought when was the Fuel filter last changed? (Give system ~G a prod and ask him).

[KidKoala]

Just been out to have a look - one spark plug looked slightly discoloured, the others looked fairly normal.

Dizzy is fine.

Bit of oil round the ends of the leads where they meet the plugs - normal?

No residue around core plugs.

[andy_twincams]

for the sake of it just service it all,new cap arm leads and plugs not hard to change,i have some genuine toyota leads nearly new or some 10mm racing leads if you wanna buy em? :D

[KidKoala]

Last time I looked leads cost a fortune...

I'm going to replace the spark plugs but i cant get into town until this afternoon

[KidKoala]

Changed all the spark plugs and it was running fine again, took it for a blat up a dual carridgeway and was fine. Then coming back down the carridgeway it started to do it again, and gradually got back to how it was before i changed the plugs!! :/

Whats next? Leads? or is that oil on the leads a problem?

[KidKoala]

Another point, note that I did not set the plug gaps with feeler gauges, maybe these don't need the gap setting? I don't have feeler gauges anyhow, but if I need them I will buy some.

[Twincam.GTi]

This oil on the leads ...where is it coming from?

Plugs do need to be gapped, setting is in owners handbook..... what make of plug did you buy (please don't say 'Equium' which are french or Bosch which are German, nether of which seam to run well in a Toyota!)?

[KidKoala]

NGK plugs. so it could just be the plug gaps?

[Unity Jon]

dont agree with the 'bosch' theory, i can still run a 15sec quarter on my Bosch super 4's ??

Kid Koala (isnt he a late 80's rapper ?) you may have to check your dizzy cap for very small hairline crack, which when cold will be ok but when it warms up will open very silghtly causing odd problems like you have described.

Oil around the plug leads could be nothing more than spillage from the oil filler that has run into the chambers. I wouldnt worry too much about coolant or water running down the leads into the plug holes as the plugs make an airtight seal against the block, if they didnt imagine trying to get your air/fuel mixture right LOL...

If there was a lot of liquid then a short could occur, but i doubt you'd be running with 2cm of liquid down each lug hole ;)

Does the car tick over 'lumpy' ? if it does use some plastic pliers to pull one plug lead at a time whilst its ticking over, if you pull one of and it makes no difference to the tick over thats your dodgy plug/lead.

P.S clean your airfilter before you do anything more, you'd be suprised what that will cure with a 4age !!

[L4AGZE]

When you say one of the plugs was discoloured did it look as though it was burnt and do you mean the top of the plug where the HT lead connects?

If it is that it will mean a new set of HT leads more than likely. I had a smiliar problem and a new set of HT leads sorted it. managed to pick them up for about £50, not bad for an ADL part!

If you bought NGK plugs did you get the right ones? The code can be found in the owners handbook, if so the gap should'nt need adjusting.

[KidKoala]

KidKoala a late 80's rapper? Not quite.. KidKoala is a turntablist, born in Canada and currently resides in North America... on the Ninja tune label. He's the crazy man who makes a whole live show out of scratching with about 6 decks.

I removed the dizzy cap and did have a good look, it looks very new and didn't look damaged at all.

I assumed a bit of oil around the leads was no big deal being so close to the oil filler cap. There wasn't a hughe pool of it, far from it infact.

It does sound a little lumpy at tickover at times, but this problem seems to be slightly erratic.

Can someone please confirm that the plugs do need to be gapped on the later non TVIS 4AGE lump? I've never had to set plug gaps before, so don't know how it's done, however i didn't see any adjuster on these plugs, only a washer. I could well be wrong though ;)

Also, System~G, when you read this could you let me know what leads you used? If they are Halfords items I will replace them with Toyota items.

[System~G]

I have only just read this post. And have not read all the replies.

Almost a year ago I had a similar misfiring thing with the car. I change all the electrical components (plugs, dizzy, rotor - the lot). Hesitation still occured.

We eventually tracked it down to a dodgy connection to the Map sensor. Check this. I replaced a contact on the connector - it may have worked loose.

Also around this time (trying to find and solve the problem) I noticed some oil around the leads near to where they meet the plugs. No.1 plug was drenched in oil. I cleaned removed the plug cover and cleaned out the area an also tried as best I could to get as much oil out the plug hole itself. If toppingup oil and it spills - it has a tendency to go under the plug cover, but the rubber seals on the leads should keep the oil out. I kept my eye on the plugs to make sure no oil was getting back in their and it seemed to keep clean.

HTH

Conrad, you're welcome to contact me directly for concerns like this, I know the history of the car very well. Also any niggles I had with the GTi were documented in some way or other on this forum B)

[KidKoala]

I have only just read this post. And have not read all the replies.

Almost a year ago I had a similar misfiring thing with the car. I change all the electrical components (plugs, dizzy, rotor - the lot). Hesitation still occured.

We eventually tracked it down to a dodgy connection to the Map sensor. Check this. I replaced a contact on the connector - it may have worked loose.

Also around this time (trying to find and solve the problem) I noticed some oil around the leads near to where they meet the plugs. No.1 plug was drenched in oil. I cleaned removed the plug cover and cleaned out the area an also tried as best I could to get as much oil out the plug hole itself. If toppingup oil and it spills - it has a tendency to go under the plug cover, but the rubber seals on the leads should keep the oil out. I kept my eye on the plugs to make sure no oil was getting back in their and it seemed to keep clean.

HTH

Conrad, you're welcome to contact me directly for concerns like this, I know the history of the car very well. Also any niggles I had with the GTi were documented in some way or other on this forum B)

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Interesting point about the MAP sensor, is that all documented in the Haynes Manual, or can you give me some instruction on what to look for, and where it is in the engine bay, as I'm new to toyota engines and don't know my way around the block at all.

Could I ask what leads you put on the car? If they aren't toyota leads I think I'll replace them, as this is most likely the cause of the problem as far as I can see.

Thanks - I did however lose your mobile number, my phone cocked up and I had to replace it, and I have a new number myself now!! I knew that you'd see my post and reply here at some point anyway :)

[KidKoala]

Goodness me! Just spoke to Toyota in Bath. HT leads are £91.28 a set!!! and I doubt that includes VAT!

Lets hope its not the leads, I have to tax the car at the end of the month!

[ae111sr]

Goodness me! Just spoke to Toyota in Bath. HT leads are £91.28 a set!!! and I doubt that includes VAT!

Lets hope its not the leads, I have to tax the car at the end of the month!

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A set of 8mm Magnecor leads from Fensport would cost you around £50 -£60

[KidKoala]

And these would be as good as toyota items?

[KidKoala]

Just rang fensport, £57.95 + VAT for Magnecore 5mm leads.

Apparently it is 5mm leads on this engine.

[Twincam.GTi]

Unity Jon Posted Today, 09:41 AM

I wouldnt worry too much about coolant or water running down the leads into the plug holes as the plugs make an airtight seal against the block, if they didnt imagine trying to get your air/fuel mixture right LOL...

I'm sorry to say you are wrong! Coolant (leaking from say a core plug) around the leads and in spark plug holes does cause a problem i.e tracking ...how do I know... because I had this precise problem in 1996 on my GTi and it was the core plugs weeping and it shorted a plug out (and in turn 'blew it) when traveling through France and Belgium. Thankfully I had a spare plug, didn't think much of it at time, changed it and carried on; a month later it happened again. After this further investigation descovered one slightly weeping core plug.

As in Kid Koala's case my asumption was wrong (sorry) but was only trying to help from symptons described which appeared the same as a past problem of mine.

Mr Unity Jon I would appreciate less of the demeaning statements although I realise you do have great 'technical Knowledge' (Your 'Lowrider' construction proves this of which I have great admiration.).

Thank you.

[System~G]

I can't remember the make of leads. They weren't original Toyota parts though, but are OEM equivalent sourced through Halfords. Being new last october, Idoubt very much they will need changing already. They were also correct for the car.

Magnecors are meant to be very good though

As far as I can remember, the map sensor is mounted on the bulkhead just to the left of centre. You should see some black PVC tape around it or the cables. It should also be shown in the Haynes manual I sent you.

Plugs should have a either a 0.8mm or 1mm gap can't remember which. If you bought the correct plugs, they *should* be pre-set. You will need a gap checker/adjuster thingy available for less than £2 from most decent motorfactors.

Before making the same mistake I did by spending loads of money on new leads and other ignition components, check the MAP sensor.

HTH

[KidKoala]

Cool, I'll take a look at the MAP sensor tonight, and take a photo of it.

I did buy the correct plugs, they are the right NGK plugs for the later 4AGE engine, so its not the plug gaps at fault. I put in exactly the same sort of plug that I removed.

If the MAP sensor isn't at fault then I think the leads are the most likely culprit.

[KidKoala]

All sorted - It was the MAP sensor.

The wire needed re-stripping, and i stripped enough off to fold it over a couple of times to make a decent connection, then taped it all up.

Running sweet again :)

[Twincam.GTi]

Kidkoala & System~G

This is useful to know, learnt something today, maybe of benefit to me in future.