Massive fuel economy/performance problems

[shmoth]

So I'm new to ozhonda, I was told about this place a few days ago when asking about a problem I'm having with my car. I drive a 97 VTI-R automatic and I've been having significant fuel economy and performance problems for a few months now. I've taken the car to THREE different mechanics and none of them could fix it, nor did they even seem to have a clue what was going on. It's driving me insane that nobody can fix it, and it's costing so much for petrol.

I'm getting about 200-250km on a tank when i was getting nearly 500. The check engine light keeps coming on over about 90kph or when going up a steep hill, sometimes even just when driving normally. The car billows unburnt fuel from the exhaust at idle, sometimes nearly stalls when i stop at lights etc, and I've had a 50-75% power loss, sometimes I barely even make it up a hill. The problem is FAR worse in the middle of the day when it's hot too.

I've had the O2 sensor replaced a month ago, and had a mobile honda specialist test the O2, map, coolant temp sensors and all are apparently fine. He said it was running rich due to a 5-6ms injection pulse, and said the barometric sensor was giving a bad reading of 2.9v @100KPa and suggested i replace the ECU, which is going to be a huge pain in the ass and I'm not even convinced it will fix it.

If nobody has any ideas, could someone please point me in the direction of someone who can actually fix this BS in the Brisbane area it would be greatly appreciated. Thanks :)

[gumus89]

I cant fix your problem, but Preludeaustralia.com might.

What i'd like it know is if you have checked the check engine light codes?
To do it, you find the blue OBDII connector thing that is behind the little carpet covered cover on the drivers side footwell.

Lol, I cant be bothered explaining anymore. Join Preludepower.com, an international but american based prelude forum. This thread has step by step instructions on the CEL code retrieval and the site in general has a heap of other cool shit. There is just a lot more prelude owners over there.

http://www.preludepower.com/forums/showthread.php?t=312936

[shmoth]

I cant fix your problem, but Preludeaustralia.com might.

What i'd like it know is if you have checked the check engine light codes?
To do it, you find the blue OBDII connector thing that is behind the little carpet covered cover on the drivers side footwell.

Lol, I cant be bothered explaining anymore. Join Preludepower.com, an international but american based prelude forum. This thread has step by step instructions on the CEL code retrieval and the site in general has a heap of other cool shit. There is just a lot more prelude owners over there.

http://www.preludepower.com/forums/showthread.php?t=312936

I can't remember the code off the top of my head, but the only code it was throwing was by the O2 sensor for rich fuel.

[Phased]

How are you going with your Fuel Consumption Issue?

Don't forget... Some ECU codes may shout out "02 sensor" but the O2 sensor may be functioning properly however it's reading "out of range" due to another issue up the line.

To me it sounds like lack of ignition or fuel pressure issues. Particularly that it gets worse in hot weather... This could heat up a component in the ignition system further and increase resistance, hence causing lack of spark. It COULD be the ecu... if you can find someone off these forums... or perhaps a mechanic that has a spare P5M ECU around it would be worth doing a swap out... it will only take 30 mins tops.

Are you experiencing any other symptoms? Such has Hesitating, Surging or Bucking.

Order of Troubleshooting:
- Swap Out and Test ECU
- Check Ignition System... (Includes Sparks, Ignition Leads, Distributor Cap/Rotor, Ignition Coil, ICM (Inside Distributor) etc.
- Check Fuel Pressure/System (Particularly the Regulator)
- Did he test the TPS Sensor? Although it's unlikely, as the readout from the TPS sensor is compared against MAP readings. So it would most likely trigger a TPS ECU Code. It's still a possibility.

Also last minute thought... Did the mechanic test that the car ECU enters "Closed Loop" mode? It wouldn't make a car run that rich... but it's worth checking out.

If only you lived in Melbourne... I have all of these components spare that you could try out. :( Well except for the ECU as mine is a P5P.

[mikewl]

Hey buddy.
I had a very similar problem.
I drive a auto 98 prelude vtir.
I was getting 12-13L/100km and the car seemed weak - vtec kicks in hard though, and everytime you get above 3000rpm or 80km/h which ever comes first the check light comes on.

I got a mate to do a 2 pin check using a paper clip - should be able to google that. Turns out my knock sensor wasn't working.
So I called up Honda to ask for a new knock sensor - got quoted $265 and there was only one in Australia, so I decided to take my one out and operate on it.
Took it out and pretty much there was only two thin wires connecting the base to the plug inside and one of the wires had broke off somehow. I wasn't going to pay $265 so I soldered it myself =D D.I.Y.!!. Then I put it back into the car and let vtec rip on the highway; the light stayed off and disappeared - been awhile now and it's still hasn't appear. I've been keep and eye on the fuel comsuption and it has gonna down to around 9L/100km which is normal I guess.
-Definitely try it - few hours work.
Hope this helps - rep me.

[Phased]

Although this is a possibility. As far as I know he mentioned he did an ECU check and the only code it threw was Oxy Sensor (Too Rich). In most cases the Knock Sensor will trigger the relevant Error Code to the knock Sensor... If your handy though, it's definitely worth a shot.

[shmoth]

Just a quick reply to update for anyone else who might have these problems in the future. It turns out that the "new" O2 sensor that my first mechanic fitted was faulty, and he had no idea what the code even meant, he was just speaking out of his ass. So i had a new O2 sensor fitted last week by a dealership and it fixed the fuel economy problem straight away, but not the smoke, low power or check engine light. The problem was that the O2 sensor is only a symptom of the other issues, or possibly just a co-incidence. As i was driving it the other day it started to overheat quite badly, i had to turn the heater on just to get it home. I cracked open the radiator to find out that it was nearly empty, with no signs of leaking anywhere...

So after 5 different mechanics, including the biggest honda dealership in QLD, looking at my car and NONE of them being able to work out the problem, it took a mate of mine from work 5 minutes to find out what the issue was and i'm in the process of getting it fixed now. He enlightened me of the fact that the smoke was actually white, and there was also coolant dripping from the exhaust... White smoke and coolant coming out of the exhaust, combined with oil and coolant loss with no actual leaks whatsoever and a massive loss of power apparently equals a blown head gasket and subsequently water-filled cylinders...

About 4 months ago the bottom radiator hose blew and the car overheated really badly as i was on the highway and had nowhere to turn off straight away. The hose was fixed, but the check engine light and issues started soon after, i just forgot about it because it was so easy to fix. It turns it overheated so badly the head gasket busted, and has been slowly getting worse and worse over the past few months. Because of how expensive head gaskets are to replace, and the fact that my transmission is surging between gears and neutraling out when it goes into reverse, I'm just going to scrap the engine and get a JDM one with about 100k on the clock put in it, $1100 for the engine, maybe a grand for labour.

What a complete mess this whole process was, if anyone wants a list of the terrible mechanics i took it to in Brisbane just ask me. I just don't understand how all of these mechanics could have missed such a blatantly obvious, MASSIVE problem with the engine. Thanks for the advice given in the thread, i would have definitely used it if i did actually have a mystery problem in my car, rather than a series of unbelievebly bad mechanics.

[Phased]

It's great you got it sorted out!

In regards to mechanics. As soon as I heard about the loss of power and white smoke/coolant. It straight away clicks head gasket, especially when you mentioned it overheated one time. I mean with us over the internet (without the history and seeing the smoke) we couldn't of drawn that conclusion. However a mechanic should have.... quite easily. Some of them just don't want the business/headaches.

To be honest, I have a mechanic (I rarely go to him as I D.I.Y) however I asked him to trouble shoot a slight part-throttle hesitation issues and he said either Coil Pack or Distributor, I suggested the Oxy Sensor, he said definitely not.

In the meantime I replaced... all of the ignition system, all fluids, cleaned and tested sensors and replaced a few of them... you don't even want to know the list! haha.

Turns out... It was the oxy sensor & partially the TPS being calibrated incorrectly (was removed by previous owner for some stupid reason). Now this guy is easily the best mechanic I've dealt with(mainly works on Race Boats/everyday cars.) However... some things... just slip there minds. Especially when you don't drive it, know all the symptoms and are unaware of the history. If a mechanic knew about your overheating issues, even a 1st/2nd year apprentice would of said your headgasket. Being a mechanic can be painstakingly difficult, time consuming and often results in more error than "trial", lol.

At least you worked it out in the end though! xD

Also you will find it wouldn't of been coincidental. The leaking/'blown" headgasket would of most likely caused the failing oxy sensor. As when you're engine burns coolant; it releases chemicals that will destroy an oxy sensor, not to mention the burning of water itself, lol. This and the fact the chemicals and unburnt fuel from misfiring would also give out a rich reading!