webby293

Hilux Acceleration Hesitation

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Hi guys, new here.

I have a 1999 hilux xtra cab rwd, RZN154R engine is 3RZ-FE (2.7L Multi point EFI) that i bought second hand about 1 month ago, and it has acceleration hesitaion which is starting to annoy me, especially when driving round canberra where i need to accelerate quick. in any of the gears, even first, when i bought my foot right down it just sounds like its going to stall, similar to a badly tuned whipper snipper that burs when the throttle is opened. Then at around 20-30km in first it will just suddenly take off as the revs very slowly build up to that point (not sure what the rpm is as it doesnt have a tacho). It sounds like it is lean from the injectors not compensating for the wide open throttle.

This is what i have done to try and solve the problem.

Cleaned air filter, changed oil and oil filter, changed spark plugs, and cleaned the throttle body, i have also ran it on a tank of v-power 98 mixed with Nulon total fuel system cleaner, on the free way for 4hrs, helped a bit, but got worse a couple of weeks after treatment.

I would normally ask at work as i am a 1st yr apprentice mechanic but the work is flat out there and haven't had time to ask yet.

Help is much appreciated

Thanks

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Just a thought but it could be your valve timing. If you ask at work you should be able to confirm easy enough.

Hope this helps.

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I had my ute checked out today, i asked them to check the timing and because its DIS i can't check the timing with a timing light (according to the mechanic) and apparently because its all computer controlled it should never change unless the ECU stuffs up which i do not believe it is, but he told me to clean out the throttle body, which i did today and it didnt help, he said he will scan it next week because it has OBD2. Does anyone know what else i can try.

Thanks

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Sorry I should have been more specific. I was suggesting it could be VALVE timing not IGNITION SPARK timing. This would require testing the TDC position and then making sure the valves start opening etc at the correct degrees. I have seen valve timing cause lag once when I changed the timing chain on a ute I owned.

The other thing to keep in mind is that a small engine doesn't generate much torque until the revs are up.

I would ask the mechanic if they have the gear to test valve timing.

Cheers

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Ah ok, valve timing, got it. I don't know if this will contribute to the problem or is the cause, but the previuos owner must have removed the EGR valve and all related vacuum hoses, and plugged it all up, is the beneficial in the sence that it doesnt circulate exhaust, or does it confuse the ECU if it has been suddenly removed?

Thanx for your recommendations

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Hi guys, new here.

I have a 1999 hilux xtra cab rwd, RZN154R engine is 3RZ-FE (2.7L Multi point EFI) that i bought second hand about 1 month ago, and it has acceleration hesitaion which is starting to annoy me, especially when driving round canberra where i need to accelerate quick. in any of the gears, even first, when i bought my foot right down it just sounds like its going to stall, similar to a badly tuned whipper snipper that burs when the throttle is opened. Then at around 20-30km in first it will just suddenly take off as the revs very slowly build up to that point (not sure what the rpm is as it doesnt have a tacho). It sounds like it is lean from the injectors not compensating for the wide open throttle.

This is what i have done to try and solve the problem.

Cleaned air filter, changed oil and oil filter, changed spark plugs, and cleaned the throttle body, i have also ran it on a tank of v-power 98 mixed with Nulon total fuel system cleaner, on the free way for 4hrs, helped a bit, but got worse a couple of weeks after treatment.

I would normally ask at work as i am a 1st yr apprentice mechanic but the work is flat out there and haven't had time to ask yet.

Help is much appreciated

Thanks

not familiar with this model, but if it has a air flow meter, check it. check h/t leads if it has them or does it have coil packs, how many k's has it done

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the car has done 194 thou, it has an airflow sensor, i believe it works fine, it has 2 ignition coil packs, and how can I check the TPS? Also if the sensors are all fine, whats your opinion on fuel additives?

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(from memory) tps should show different resistance when throttle closed, to just slightly open. I believe on the commodores it was something like enough throttle to hold it at 2000 revs in neutral when warm, so just barely open.

Fuel additives- I use one religiously, because i know it does what its supposed to. But I have no idea whether other commercial additives work. That is, if your injectors are blocked or have a poor spray pattern, which should be noticeable with a poor idle, poor fuel economy and even a miss when accelerating (as opposed to a lag)

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I have good news if the problem is caused by dirty fuel injectors, at CIT (Canberra Tech) they have an injector cleaning/ testing machine, the ultrasonic type and they are happy for me to bring in my injectors and test and clean them, for free. Problem is, they don't allow me to take off the injectors at CIT so i have to do it at home and use public transport to get there and back, but i guess the end results would be worth it.

I will also check the resistance of the TPS, and post in the results of the resistance.

Edited by webby293

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I have tested the TPS, and here is the results,

CLOSED: 2.792K Ohm

Open about 5mm from idle screw: 2.68K Ohm

Approx Half open: 1.8K Ohm

OPEN: 0.815K Ohm

There are also no sensor fault codes when i bridge the wires to activate the OBD to get the engine light to flash codes, and the code it flashed was everything ok, but its nowhere near as thorough as using a scan tool, which is what im hopefully doing tomorrow

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I cleaned the trhottle body and top half of the intake manifold - the plenom side, and it has helped a bit but still has the problem, i am going to see if i can make a tempory swap of the MAF and see if that solves the problem, if it does, i'll be buying one from Frank's parts for $110 second hand with warranty.

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Couple of guys at work checked it out, they removed the floor mat and said it was fine. But i disagree it still doesnt sound right to me-when i first bought it and it didnt have floor mats, a mechanic with over 40yrs experience looked at it and said it has hesitation.

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Couple of guys at work checked it out, they removed the floor mat and said it was fine. But i disagree it still doesnt sound right to me-when i first bought it and it didnt have floor mats, a mechanic with over 40yrs experience looked at it and said it has hesitation.

did you get the air mass sensor tested

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No they didnt test it, because they said it was fine, but i have cleaned it and seen no improvement, i have also checked the resistance of it and it checked out at the right ohms according to my service manual. tomorrow i will ask a guy at tech who has the 3RZ-FE in his car, if i can swapp the MAF and go for a drive to see if it improves, if not and he's car goes fine then i think we can rule out the MAF. Also i forgot to mention this earlier, when i changed the spark plugs, i looked down into the pistons, all of them has a dark brown rly rough surface on them, like a very course sand paper, the intake manifold and throttle valve was full of carbon build up.

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My money is on the Throttle Position Sensor.

+1, I would also do a check of all vacuum hoses, particularly where the EGR was removed, to make sure there are no leaks.

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No they didnt test it, because they said it was fine, but i have cleaned it and seen no improvement, i have also checked the resistance of it and it checked out at the right ohms according to my service manual. tomorrow i will ask a guy at tech who has the 3RZ-FE in his car, if i can swapp the MAF and go for a drive to see if it improves, if not and he's car goes fine then i think we can rule out the MAF. Also i forgot to mention this earlier, when i changed the spark plugs, i looked down into the pistons, all of them has a dark brown rly rough surface on them, like a very course sand paper, the intake manifold and throttle valve was full of carbon build up.

did you get your injectors cleaned - follow that up

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The MAF can now be ruled out as i swapped it over and it didnt help and his car worked fine.

Im going to try and get the injectors cleaned this wedsneday at CIT.

In the mean time im going to rule out if the clutch is slipping, I was talking to a guy at tech and he said his car had a similar problem, and it was the clutch, at his work they said the clutch was stuffed but adjusted it anyway and it accelerated fine afterwoulds. But mines hydaulic so im going to change/bleed the system to see if the problem lyes withing the clutch, it does seem to crunch sometimes when the clutch is fully pressed and the car is at a complete stand still, i will also do some prelim checks specified in the service manual.

Also im thinking of running a can of upper cylinder cleaner through the engine to help get rid of the carbon build up around the valves and on top of the piston before the injectors get cleaned, what is your opinions on that stuff, i can get a can of Wynn's Upper Cylinder Cleaner for $12.

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Hello,

Ive got the same problem with my Hilux 2.7 2003.

Its only done around 80,000kms and ive had it since around 45,000kms. Its always had this problem where it takes off fine and as the revs build it kind of hits a flat spot, then what feels like 1 to 3 seconds it takes off, sort of like hitting a power band on a two stroke motorbike.

Ive tried many things that have been listed previously on this topic but nothing has worked.

How did this end up for you WEBBY, did you get it sorted or does anyone have a suggestion??

Cheers

Edited by HARDWAY

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FYI

I have a 2001 hilux 4WD 3RZ-FE with same problem. Vehicle been running on LPG for 60K with no problems except valve recesion of 6thou every 10k. Rebuilt cyl head 5k ago. This is normal as the intake seats and valves are of poor quality. No problem just need to be able to grind your own shims to be cost effective. Vehicle pulls much better on LPG rather than ULP. This should not be the case as there is more energy in ULP per intake stroke. I have put in a Jaycar air fuel mixture kit mainly for tuning the LPG as my system has mods and the factory system is open loop so no reporting back to ECU regarding exhaust conditions as factory system does not have any oxcygen sensors fitted. Vehicle runs very lean on ULP regadless of throtle position. No problem with the Mass Air Flow meter, which is also combines the air intake temp sensor. this tests OK. No fault codes displayed when pins 4 and 13 on the DLC3 are shorted (once ECU has been reset with removal of EFI fuse or battery isolation and vehicle driven through usual driving cycles).

I will check again the Throtle Position Sensor output as I don't have the option of part swaping. Must admit that this is frustrating so any feed back welcome. Vehicle runs very well on LPG so problem is not related to timing / spark etc. Currently playing with the factory variable resistor settings which is wired in with the TPS sensor. Have checked variable resistor and all seems to test ok. I agree with past comments that the power when running ULP seemed to be like hiting band in a two stroke. This used to occure once you got up to 3500rpm. I have tried OBD scan tools but system is M-OBD so no go. Short out pins 4 and 13 does the job. Can email cheat sheet if interested.

Any ideas?

Just joined up so still working out how to change my profile, system won't let me , must be doing something wrong.

Cheers Bloke

Edited by Bloke

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Hi,

I also have a 2001 hilux doing ths same thing, it has done 100,000 and i have done most of the things mentioned.

Looking at the Forum it appears to be a common problem, has anyone got any ideas to fix it

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How did you go with this issue webby ?.

topgun i think is on the right track. what brand of airflow sensor have you got on it. if it is a hitachi and non removeable this wont help. there is a removeable sensor fitted to 3rz and 5vz (prado hilux)

toyota gave a dealer service hint back in 2002 that the sensor should be cleaned periodically. co spray or even shellite. if you can remove it from the air box with 2 screws its the correct brand one.

i have had a hilux and a prado (vzj95) have similar issues and even an echo. the prado surged and if you pushed it it would backfire. swapped out the sensor from anopther vehicle and it made a huge difference.

see how you go..

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Hi Guys - I'm new here and came looking for a solution to this problem too.

I may have a partial answer for some of you. I have a Hilux 2.7 2008 and about a year ago it lost power barely able to get up a small hill, it has happened on 3 occasions since then.

It is the same problem each time and it is to do with the air intake control?? I take it back to my mechanic and he fixes it in 15 mins and off I go again. I was hoping for a permanent solution or advice on how to fix this myself.

Hope this helps.

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