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Discussion Starter #1
Hi all
My 4.1 has been drinking fuel since I put it back on the road about a month ago. I have changed plugs, distributor cap, new front pipe and thermostat, cat isn't blocked engine light is not illuminated and it doesn't have any fault codes stored. I have cleaned the egr valve and egr vacuum filter, and fitted a new air filter. I dont think theres any vac leaks as it purring like a kitten at tickover.
It does miss and surge or kangaroo a bit if driving along steady @ 30mph through town. other than that power is normal and responsive.
last check it was doing about 80 miles to 17 litres and I have no fuel leaks as I did extensive repairs to tank and fuel lines recently. I have read the a faulty air intake temp sensor can cause over fueling problems?.
I think my next job is to take an ohms reading from the AIT and the 02 sensor on the exhaust plus wiring. Does anybody else know of any other issues?
 

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02 sensor.
 
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Discussion Starter #3
Thanks Batman
I tested it today (never really checked ohms with a multimeter before) i got a reading of 0.015 on the heater circuit iirc on the 20k setting on the multimeter, i think it was 0.001 on either the 2k setting or the 200k setting. I think from checking on the internet it should be something like 15.00 unless the decimal point is confusing me?. The AIT sensor was reading 2.53 ohms so i think its ok?
regards
kev
 

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Discussion Starter #4 (Edited)
Got the 02 sensor today, fitted and drove 20 miles, so far pleased as not as noticeable a drop in the fuel gauge. I will drive it over weekend and see how consumption is. I think I need a set of HT leads as I can feel there is still a slight miss when driving through all ranges, but feels better all round and more lively now.
 

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believe i will check my 02 as well. went from 320 mi on a full tank to 270. everything is maintained, no codes, just a high idle when cold and exhaust leak. would much rather change an 02.
 

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Discussion Starter #6 (Edited)
Hi Texan
sorry it took me to now to see this post, high idle is normal while cold but it should drop when temperature starts to rise( from what ive been told). Mine had major fuel usage 12-14 mpg(UK) after I fitted new 02 lambda sensor I am now getting 25mpg, still not happy as I know there is a miss-fire, most noticeable when sitting at 30-40 mph. Exhaust leaks will have an effect on your mpg. Just to update you and everybody else I have changed HT leads, plugs, distributor cap and rotor arm cleaned the EGR and EGR modulator and checked operation( although they were very clean to start with).
I have also replaced is the coolant temp sensor as it was showing slightly low on gauge. I am going to try a additive cleaner for injectors as I suspect either them or the throttle position sensor is the cause of the miss as no cel or fault codes stored.
Replacing AIT sensor as at this stage its the only old fuel issue related sensor left
I will update when I have it cured or go bankrupt:laugh

Just to add Texan I found very little difference in my new and old 02 sensor when testing the ohms, so figured it must have got lazy as notable difference in mpg with new one.
Hard to believe after 21 years but HT leads, distributor cap and rotor arm all original. I would bet 02 sensor is original as well judging from removing it. I suspect the HT leads were still good, stamped "sumitumo 1994"
 

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For an injector cleaner, try Wynn's Xtreme Petrol System Clean. I recently did a bit of research and unless the cleaner contains PEA, PolyEthSomething, it's a waste of money. The Wynn's and Redline's SI-1 are the only UK ones I've found so far, but probably more available.

Maybe try some super unleaded type petrol. It has more detergents for keeping your engine clean and the higher octane may help with your misfire.
 

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Discussion Starter #8
Thanks Slimjim
I am familiar with the wynns treatments, I will check for that ingredient. did you have any success with these cleaners? I see other members from across the pond talking about lucas injector cleaner and how its good about sorting out this problem, its available in the UK and Ireland as well as far as I have researched.
Find it hard to get super unleaded around here, need to talk to somebody with a super car to find out locations of pumps.
 

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Discussion Starter #9
I take it the word is polyetheramine. I see the lucas cleaner has 10-30% in it according to the data sheet
[edit] Just to add redline SL-1 has 35-50% in it, supposedly the most on the market so redline it is then.
Thanks Slimjim
 

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I haven't really noticed anything, but mine was running OK when I got it a couple of months ago. They do their job gradually, so would make it harder to tell anyway. The best price I found for the Redline SI-1 was on ebay, £14.70 delivered.
You also need to give it an 'Italian tune up', take it for a long thrash on one of your motorways, as often as you can.

There is also something called Sea Foam, which get good reviews. It goes into the inlet via a vacuum line and into the petrol also. Not tried it, maybe next year.

The problem is misfires could be one of several things. You've changed the most common and obvious, but then it get more difficult. Thinks like valves or seats not sealing, broken rings, clogged injector/s (which really need ultrasonic cleaning), vacuun leaks, partially blocked cat/silencer, fuel filter, petrol tank breather, all the emissions rubish and lots more
 

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Discussion Starter #11
yep heard sea foam raved about by members on the other side of the pond, is it available over here?

Fairly sure my cat isn't blocked, rav runs really sweet at tickover, haven't done a compression test but being from a mechanical background I have no reason to suspect engine hardware problems unless injectors, discovered a can of moly liquid injector cleaner lying in garage today, prob cheap crap but threw it into the tank anyways just to see.
I had the throttle body off a while back to clean it and iac valve{high tickover] i put a thin film of sealer on all seals when refitting so I don't suspect vaccum leaks but I suppose I sould test to be sure.
today I flushed the heater matrix as it was blocked, a lot of silt came out of it and was running freely but heat not much better after refill, still good heat for about 5 secs and then gets cool, new thermostat fitted a week or 2 back
 

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Yep, US forums are where I heard about the sea foam. I found some on Amazon, about £15. I like the idea of clouds of smoke coming out of the exhaust afterwards :)

Maybe it's the route to and from the heater, or the take off for the hoses to the heater? Maybe worth trying flushing the whole engine, with one of those additives chucked in too.
 

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I have recently purchased a 97 Rav 4 Auto with 4wd and the mileage is terrible.I changed the plugs,oil,wires,cap ,rotor,air filter,cleaned the throttle body,Ran Seafoam thru system and in tank and have no cheakengine lights.
Brakes all new and not rubbing or sticking.I am getting approx 16 mpg.I realize its winter but this is really bad for a 4 cylinder even with 4wd. It starts easy and idles smooth but seems pretty gutless on excelleration,really struggles.Like im draggin a trailer.Could it be the TPS is out off adjustment? Muffler has no visible holes and looks pretty solid.I guess i could do a compression test,what numbers should i see in this 2 litre motor?Thx,sorry to
jump in but its related to post above i feel.
 

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Discussion Starter #14
I am going to flush the whole cooling system Slimjim as I think somebody put the wrong version of red coolant in and its got rusty and contaminated but cant get coolant flush stuff until motor factors open on sat, never tried to flush the return pipe running back to the thermostat housing and possibly it could be blocked. Another job for sat.
 

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Discussion Starter #15
Hi moresquirt
sounds like 02 sensor as similar mpg and a bit gutless like mine although I don't know if mine gained a whole lot more power from changing 02 sensor. Mine had no cel either, also as pointed out to me it could also be a blocked cat as that would leave it gutless and drinking fuel. Your rav if you live in the states will have two 02 sensors [but I'm sure you already know that]so that makes it harder to diagnose which one or both are faulty.
You have done all the cheap replaceable stuff first as I did but first of all I would get the cat checked for blockages then the 02 sensors. I still suspect my injectors or throttle position sensor are faulty but at least I'm now getting 25mpg[UK] hope after I find last fault it will jump to around 28-30 mpg.
 

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Gunner, at approx what rpm range are you getting the misfire?
I have done everything you mention and more and still have it, engine is good and strong otherwise and if driven carefully I can see low 30's mpg, more like 25 otherwise, it's been like this for at least 15,000 miles, when not misfiring it runs perfectly, 100% reliable too.
Only two things not changed are the TPS as when tested on my multimeter it seems fine but I may yet swap it out anyway and the cam sensor as I can't see it having any effect,
Ive done a lot of work elsewhere on the car but to the engine (and not all to cure the misfire but to maintain it too) I have changed the coolant and stat, replaced and added extra heavy duty earth straps to motor, new belts, new fuel and air filters - naturally, injectors flow tested perfectly, (previously I had used Lucas and STP cleaner in fuel, one if not both must have worked, they were like new), new injector seals, new Crank Position sensor, new coils, Denso leads/wires, change over the ECU for another used one, surely can't have the same problem..., new MAP sensor, NGK plugs, new knock sensor, new IAT sensor, new ECT sensor, new cam (timing) belt and water pump, oil pump seals etc just for good measure, new inlet manifold gasket (reports say they can fail and leak air in - weakening the mixture, it misfires the same with or without EGR but it's a little better without it, PCV is clear and working fine, TB is clean, likewise the IAC, new 02, I have run Seafoam to clean out carbon and also used it in oil to remove any sludge, works well (buy on eBay 2 for £20), also used water injection, piston crowns were gleaming!, there's probably a whole lot more I have forgotten about, been at this for five years now ....only telling you all this in case your misfire is at the same rpm range as mine (and a few others on here) 1900 - 2500 rpm in most gears but it's less noticeable in fifth.
Let us know if you do the TPS, if I run with mine unplugged it's rough at idle but not a lot different after, regards adjusting it, I'd certainly listen to any suggestions....
Overall I would say mine runs lean, a higher fuel consumption comes through having to use a heavy foot to get through the misfire range.
Hope this helps you and let us know how you get on, happy new year everyone!
 

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Hi Gunner,Thx for reply.I am going to do a compression test on engine and see what numbers i get first before going further as i have no history on car and dont know if oil changes were done ect.If that cheaks out good then will dig deeper into 02 sensors and Cat blocked ect. I would also like to check my TPS and see if in range,can u advise how to do this and what the specs should be.I have a multimeter.Motoe does not miss and idles smooth,just sucks fuel like crazy. Last tank i went 365 kilometers on 47 litres off gas,I realize its winter but thats really terrible mileage.
 

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Hey Gunner,just noticed your from Ireland.I am in Ontario,Canada but was born in Belfast,Ireland and lived in Glengormley till i was about 10 years old.Im 53 now but want to go back for a holiday with the family for a visit hopefully within the next few years.What year is your Rav. Mine has only 165000 kilometers (100000 miles) and 02,s look original and as you mentioned in your posts they were in range but when u changed them your mileage returned.Was it the front or rear 02 sensor that was bad or did u just replace both.Also how do u test Cat,i thought that if the cat was bad,clogged ect it would throw a check engine light.
 

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Discussion Starter #19
Hi moresquirt your a local then :thumbs_up: My rav is 94 and has iirc about 99000 on the clock, my rav has only one 02 sensor just in front of the cat underneath the drivers floor, I believe US and Canada has 2 sensors like the dash 2 ravs over here to meet the higher emissions standards. Apparently the cat doesn't always throw on a cel over here but not sure about your model as they were obd2 protocol but simplest way is to start her up and reach underneath and feel if the exhaust gets warm nearly as quick behind the cat as it does in front of it also if the fumes coming out of the tailpipe are warm. If you suspect it is clogged (not sure if your 02 sensor is screwed into the cat or in front of it like mine) I have read that you can take it off and drive the rav to see if theres any difference in the power as gasses will escape before the cat.
Probably best to get the cat checked first then replace both sensors if you cant figure out which one is at fault(no codes). Have you checked to see if there is any codes stored as there could be more faulty items than what we have talked about.
I picked up a denso 02 sensor(had to be jointed to the old plug) for £35 on ebay, the local motor factors were asking £120 for one I it wasn't denso
 

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Discussion Starter #20
Hi Gunner,Thx for reply.I am going to do a compression test on engine and see what numbers i get first before going further as i have no history on car and dont know if oil changes were done ect.If that cheaks out good then will dig deeper into 02 sensors and Cat blocked ect. I would also like to check my TPS and see if in range,can u advise how to do this and what the specs should be.I have a multimeter.Motoe does not miss and idles smooth,just sucks fuel like crazy. Last tank i went 365 kilometers on 47 litres off gas,I realize its winter but thats really terrible mileage.
I suspect my tps might be faulty but I haven't checked it yet and like yourself I'm not sure how to at the minute. I did read on the forum here that a scope is best but I don't have access to one nor never used one either.
My rav is like yours it ticks over lovely but it does miss slightly while driving.
Best to have a search on the forum here as regards to testing the tps, I will probably have to do the same if I don't get the miss sorted. A new tps is about £60 this side of the pond so its the most expensive part to date if I replaced it
 
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