Hesitation On Na

[urotsukidoji_badassdemon]

Hey guys, those of you who have change your air filters to high flows, did you have any problems with drivability? I just had my cam belt fitted, and now its like ' I don't WANT to go ' below about 2500 rpm. It's doesn't even like it when you just take it easy. Above 2500 rpm, its fine, runs just normal, so don't know if its the air filter that making it run weak at low revs. I don't have the original resonator box anymore, so can't put that back on to test it. I've put a new rotor arm and dizzy cap on too. Idea's on a postcard to....

[BLOODUK]

Tried an ecu reset? thats what i did when i changed my belts

[mikeb]

I would be surprised if a filter made that much difference.

Maybe one (or both) of the cams is a tooth out? I am only guessing, but that may cause something like the problem you are having.

Blood, why would changing the cam belt need an ECU reset?

[EarL]

I would be surprised if a filter made that much difference.

Maybe one (or both) of the cams is a tooth out? I am only guessing, but that may cause something like the problem you are having.

Blood, why would changing the cam belt need an ECU reset?

Cams???

If it was a cam a tooth out, you'd prolly be looking at bent valves! :ffs:

If you've just fitted an induction kit and haven't adjusted the fuel/air mixture, your motor will be running very weak (because of the increased air flow). Get that sorted and it'll be right as ninepance.

[mikeb]

From discussions on these forums, I thought that it was a non-interference engine. However, I have just done a google on it and there seems to be a lot of contradicting information. Anyway, one tooth wouldn't make the valves hit each other.

[urotsukidoji_badassdemon]

Well, going to TRy to book it into Toyota asap, to have the timing checked AND the air/ fuel ratio checked/adjusted. I phoned up Van Aaken Dev. earlier, and they said they don't do Jap cars, not even their Smartchips. They said Jap cars aren't even chippable neway. True or False??

[EarL]

What a load of b******s!! :ffs: If jap cars weren't chippable (if that's grammatically correct) how come the likes of Dastek and Superchips have a business?.

[midmotorsteve]

Well, going to TRy to book it into Toyota asap, to have the timing checked AND the air/ fuel ratio checked/adjusted. I phoned up Van Aaken Dev. earlier, and they said they don't do Jap cars, not even their Smartchips. They said Jap cars aren't even chippable neway. True or False??

Absolutely ===== TRUE

thats why all thats on offer are:-

MOTEC - ECU

GREDDY - PIGGYBACK

UNICHIP - PIGGYBACK

BLITZ - ECU

APEXI - ECU

SUPERCHIPS ICON - PIGGYBACK

the 'chipping' technique used on the likes of VAG group cars where they replace a chip from the board with a writable flash chip isn't used on jap cars due to the way they construct the boards. Thats why everything is a replacement ecu or a piggyback thats cut into the wiring harness.

[Bobby-H]

Hey guys, those of you who have change your air filters to high flows, did you have any problems with drivability? I just had my cam belt fitted, and now its like ' I don't WANT to go ' below about 2500 rpm. It's doesn't even like it when you just take it easy. Above 2500 rpm, its fine, runs just normal, so don't know if its the air filter that making it run weak at low revs. I don't have the original resonator box anymore, so can't put that back on to test it. I've put a new rotor arm and dizzy cap on too. Idea's on a postcard to....

I have an induction kit on my 2 and it caused no problems. If you have just had a new cam belt fitted I would say the problem is almost definately that one of the cams is a tooth out of alignment. Where did you get your cam belt changed, maybe you should take it back there and get them to sort it out.

[EarL]

:ffs: If a cam was one tooth out, it would be rough (at the very least) right through the rev range. Demon said it was ok above 2500.

[Bobby-H]

:ffs: If a cam was one tooth out, it would be rough (at the very least) right through the rev range. Demon said it was ok above 2500.

It might not be that rough, my dad had a similar problem on a car he had years ago, the car still went but not very well and that was on a car with a single cam. If just one of the cams is out it might be not be so obvious.

Ok, it might be the fuel mixture but usually the engine management system compensates for the extra air flow.

It just seems like a bit of a co-incidence that the problem occured after the cam belt change.

[mikeb]

A miss timed cam is likely to have a much bigger effect at the bottom end than mid to top end (just like the problem badassdemon described). It's just like when you put a 'hotter' cam in an engine, and the bottom end gets 'lumpy'.

As for the air filter, at low engine speeds the difference in flow between a stock filter and an aftermarket one would be almost non existent. The only way the filter change could have caused this problem is by the consequential effect of messing up the tuned length of the induction system. Personally, I think this is pretty unlikely because the changes are upstream of the throttle body.

[dawolf]

Try checking your spark plugs are all okay. On my old GTI one spark plug wasn't firing properly coz it was loose. Tightened it back in again and voila it ran great again and I regained some lost power. Worth a check.

[Razor_Rage]

i recently had my cambelt changed and let me tell you.

the car ran like **** through the whole rev range, so the cambelt aint any tooths out.

and to whoever said the valves would be bent, they are not, because if you get the cambelt just 1 or 2 tooths wrong it just has the timing wrong. got the timings adjusted and it ran like normal again.

but to me it doesn't sound like the timings are off on your car mate. if they were you would notice hesitation through the whole rev range.

do you have an AFM on your car? did you have that put in again after getting an open air filter?

my bet is on the spark plugs aswell, my 2 was hesitating a bit on lower revs, and noticed it wasn't toyota's platinum plugs in it, changed the plugs and got a major difference in responsiveness in low revs.

[urotsukidoji_badassdemon]

The plugs are only 4 months old, with less than 1k miles on them. I have thought about checking thme again tho, cos all of them got pulled out when the Daig tech ame to see why it wasn't starting(found the cambelt had gone) to do a compression test. But would un tight plugs cause the engine to hesitate ONLY up to 2500 rpm? But be fine upwards of it? Its sorta erm...hesitates for a cpl of secs, to just above 2k rpm, then suddenly, it surges as it gets to 2500. Turbo lag on an NA?? Hmmm. My cars a 91 Rev 1, so doesn't have an AFM. Unloaded(idling) she revs up as normal, but when in 1st, to go, its like its taking a breath before going!?!?! Will have a check of the plugs again 2mro, if it isn't chucking it down.

[kalmr2]

when i put the induction kit on mine after i first got the car it started spluttering and holding back up until 2500rpm............then everything was fine after 2500rpm

i even used to get flames :) :) :) :)

after spending an absolute fortune at the local Garage (is actually called The Garage) i found the problem myself.......

i needed a new sensor (can't remember the name of it) on the underside of the exhaust (apparently a common problem as most dealers keep them in stock!)

took me about an hour to fit it and everything has been fine since :)

just an idea worth checking ;)

[midmotorsteve]

when i put the induction kit on mine after i first got the car it started spluttering and holding back up until 2500rpm............then everything was fine after 2500rpm

i even used to get flames :) :) :) :)

after spending an absolute fortune at the local Garage (is actually called The Garage) i found the problem myself.......

i needed a new sensor (can't remember the name of it) on the underside of the exhaust (apparently a common problem as most dealers keep them in stock!)

took me about an hour to fit it and everything has been fine since :)

just an idea worth checking ;)

lambda sensor, detects oxygen in the exhaust gases, its what the ecu uses to determine fueling, hense if its knackered flames are a side effect :)

[System~G]

Also check your MAP sensor (dunno if this is also refered to a lambda) and connector that goes into it.

I had really bad hesitation on my corolla which was the fault of the MAP sensor connector... cheap and easy to fix

[urotsukidoji_badassdemon]

Erm, I don't have a standard exhaust on my car. All its got is the manifold and the pipe which comes down vertically from the manifold, then it's got like a T piece to an exhaust box either side. Would this sensor be located at the end of the manifold or down pipe then? I have just come back from the cinema, which takes me along a nice long stretch. The car seemed to struggle to get over 80. SO definitely something IS amiss here. Also, I've noticed the engine note changes at different revs at high speed in 5th gear. Could this all be down to cams being out of timing? Or this sensor I am supposed tohave? My car is a 91 UK NA. Hasn't got a cat on it either. Is it safe to drive it like this btw? I don't want to go up the road and then BANG. Or hear SCREECH as something jams up in the engine!!

[Razor_Rage]

when my timings was wrong my 2 was struggling to go anywhere, but i do remember something about when my mates Audi's Lambda sensor was broken the car acted funny above 60mph.

don't know if this applies to The MR2 but i would suspect so, but the lambda didn't cause hesitation on low revs for him.

could it be that your cylinder head isn't completely tight, need to change the bit between cylinder head and block, could be that it gets a wee bit of air in which would cause this hesitation phenomenon aswell.

could be a combination of errors to.

add: if the timings are out don't drive too much with the car!

[mikeb]

A 91 UK car is pre cat legislation, and I would be sursprised if they made any MR2s without a cat but with a lambda sensor. So, I don't think you have a lambda sensor to worry about. If you do have one it is a pretty obvious thing to find as there will be be electrical wiring onto it. They are usually on the downpipe just after the manifold, as they need to be hot to work.

I don't know how difficult it is to work on an MR2 engine, but I suspect it is a pain judging by the engine location. A simple (but not totally conclusive) way to check your cam belt would be to remove the plastic cam belt cover at the top of the engine. If you can't undo the whole thing you might be able to get the top couple of screws out and bend the plastic far enough to see inside. The cam pulleys will have a notch/mark on them and they should both line up i.e. when one points straight up the other one should also point straight up. If you can't see the marks then you will need to crank the engine briefly until it stops in the right place (unplug the HT leads so it doesn't start). If you don't want to do this yourself, take the car back to whoever changed the belt and ask them to recheck the timing.

Even ff they do line up, then it is still possible that they are both out of time relative to the crank, but if this was the case I think the engine would unlikely run at all, or at best be totally undrivable (one tooth on the crank pully = 2 teeth on the cam pulleys).

Razor, which pulley was out in your case: Inlet, exhaust, crank, and which way was it out, advanced or retarded? There are 6 combinations of being 'one tooth out' and they will likely cause different effects (all will run rough in some way though).

[urotsukidoji_badassdemon]

Well, I did notice that when the belt was done, there were silver paint marks on the cam pulleys to mark 'up' I spose for the previous mech, and my mech said the paints marks weren't very old, as with old paint, it would have faded some, but these were quite recent. So I don't know what may have caused the belt to go, there was like only 1/3 of the belt left intact. But I got the whole kit, belt and 2 wheels. How can you tell the crank pulley is where it's sposed to be tho? Is there a notch or something on it to like centre it up to the cams? Also, the pin which holds the cam pulley from spinning, one of them, the 1 to the rear of the car, what ever that does, ex or in, had snapped too. He sawed off a screw to replace it for the time being, so will have to go Toyota 2mro to order one up. Does ne1 here have a ported head for sale by any chance?? And cams too.

[mikeb]

The pulleys usually have a notch cast into them rather than just painted on. The crank pulley should point straight up or straight down (alternately, due to 2:1 ratio) whenever the cam pulleys are lined up with their marks. However, you can't see the crank pulley without removing the alternator and pas drive pulleys from the crank. But you can also use the timing mark of the outer most pulley instead. Rotate, the crank until the notch on this pulley is at 0 degrees (the plastic lower cam belt cover should have 0 to 10 degrees indicated). At 0 the cam pulleys should both point straight up.

3s-ge cam pulleys should have 3 or 5 holes for the knock pin. The kock pin should also be in the straight up position when all the marks line up.

It's a bit worrying that a knock pin was broken, I don't know what could of caused that (possibly the pulley retaining bolt not being tight?). The exhaust cam is the side of the head where the exhaust connects and the inlet cam on the side where the inlet manifold connects.

According to my manual:

"If the timing belt broke during engine operation, the belt may have been contaminated or over tightened."

"If the belt teeth are cracked or pulled off, the distributor, water pump, oil pump, or camshafts may have seized."