missing performance

[wallzaveerz]

I'm after picking the collective brain. My 2, temperamental from day 1 is still doing my head in. I bought it two years ago as a bit of a basket case, it looks like the previous owners had suffered the usual woes and had it rebuilt but lost interest and sold it on, so I had the makings of a good car, no unusual oil consumption, pre cats already removed.   I've spent the last two years chasing gremlins and flat spots, the main cat was blocked so I had it removed, it has an injen induction kit, now a custom made stainless exhaust and no cats and still pulls like a 1litre fiesta.   It's not a constant though, it has good days and bad days, even so I would say the good days are missing some of those 140 horses by quite a margin. There are no vacuum leaks as far as I can tell, I have tried several MAFs and O2 sensors to no avail, although admittedly never brand new ones. Out of desperation and with nothing more to lose I have been tinkering with the O2 sensors and by trial and error have discovered it is happiest with the two manifold sensors unplugged and the rear one connected. It's better than its ever been in my ownership but still not right. Any ideas guys?

[Anonymous]

I think you need to plug it in and see if any codes are logged.

Infact, considering you've been unplugging sensors, best to read the codes, write them down, clear all codes and see which come back when "normal" running....and go from there

[wallzaveerz]

I've had it plugged in before, engine light was disconnected when i bought it, I went in eyes wide open, it was very cheap and i knew what I was getting.....ish.   I've bought cars needing work before, just the MR2 is a little more highly strung. Surprisingly it didn't throw tons of codes up. It was a while ago though.   My only concern is it will throw codes up due to not liking the exhaust or the lack of cats.

[Joesson]

Has the battery always been connected during your " tinkering"?
If so disconnect for a while which will reset the engine management system, when reconnected and the car driven the system will then try to adjust to suit the current status.

[Mr X]

have you got a piggyback or a replacement ecu?
I would hazard a guess to it being so far from standard in the exhaust/intake system the standard ecu is no longer up to the job. It's set-up for a standard car and it isn't any more and I don't think it will be able to adjust the fuelling enough on the standard ecu.

Lack of back pressure would be of concern to me with no cat and with no remap to compensate. Torque loss was noticeable on mine after removing pre-cats and ditching the back box to a very short one I welded up myself in 2.5" and a very short silencer. I didn't get the torque back until I got a unichip.

By unplugging the o2 sensors your forcing the car to run off a basemap only and not adjust any fuelling.

The post cat o2 sensor is looking for a difference in volts between that and the bank1&2 sensors to make sure the CAT is working.

If I were you I'd clean the MAF, ECU reset, get a compression tester (they're only cheap) and if the compression is ok, get a piggyback and map or put it more back to standard.

[wallzaveerz]

Thanks, yes cleaned the MAF and reset the ECU when i unplugged the sensors. It ran like a sick pig for ten miles, wouldn't pull more than 3000rpm and was backfiring through the air filter, then it sorted itself out and was miles better. I haven't disconnected the battery since I plugged the back sensor back in but it has made a huge difference plugging it in which is a bit confusing in itself.   Oddly I have just had the conversation with my mate about buying a mappable ECU and having it mapped to run "as is" being a cheaper option than three new O2 sensors, a new exhaust and a new cat.

[wilko59]

I removed my cat and replaced with a home made straight pipe as my cat was blocked, restored performance and improved the sound too.  No remap needed in my case, stock filter and box with a stainless m/fold.   I get an EML light on the dash though for the missing cat (I've seen a workaround on here somewhere).  I have the dashcommand app and a cheapie OBD wifi adapter that shows realtime HP output and mine appears to have nearly all the horses it came with 15 years ago.

Is there any chance you could have a loan of someone else's MAF?  I posted before about how one of the Yaris MAF's are identical and can be had much cheaper on eBay.

[wallzaveerz]

There are MAFs on ebay for 30 quid or so, wouldn't be a permanent fix but worth it to try and see if it makes any difference at all before three times that on a denso one. But as I've said previously I have tried a couple of different MAFs with no difference. Is there a possibility the VVTi is not switching properly, I can get a second hand actuator for 35 quid which might be worth a try. The thing that baffles me a bit is its intermittent, sometimes it sings happily to the red line, other days I couldn't live with an electric milk float through the gears.   If it's important it runs very lumpy, always has, to the point that with the twin exhaust fitted now I've been asked on more than one occasion if it has a subaru boxer engine fitted.

[Mr X]

take out the OCV, put 2 shielded terminals on the connector and put it back in. Then, while it's idling put 12v down the wires to the actuator. If the VVTi cam and OCV are working ok, the engine will stall! Also, make sure the OCV looks ok... I pulled one out of off my backup cylinder head and it had a crack across it!

[Mr X]

I have the dashcommand app and a cheapie OBD wifi adapter that shows realtime HP output and mine appears to have nearly all the horses it came with 15 years ago.

Is there any chance you could have a loan of someone else's MAF?  I posted before about how one of the Yaris MAF's are identical and can be had much cheaper on eBay.

you know apps are never accurate! They use weight, speed and time. Having a rather large lunch, 1/2 a tank of fuel and leaving your wallet at home will throw it out! It's nice to play with though  s;) s;)

Cheat and put your vehicle weight in as 3000 kg!   s:lol: :lol: s:lol:

[wallzaveerz]

It will completely cut out?   I've heard about this simple check before but was told to listen for the engine note changing, not for it stalling, although I guess that is a bit more definitive!! Oh well, it's a nice day, I've nothing else to do, i'll go and have a try with that.   Thanks all.

[Mr X]

It will completely cut out?   I've heard about this simple check before but was told to listen for the engine note changing, not for it stalling, although I guess that is a bit more definitive!! Oh well, it's a nice day, I've nothing else to do, i'll go and have a try with that.   Thanks all.

Or run like a bag of c$£p! It will be noticeable as the timing will be wrong for that rpm

[wallzaveerz]

That's interesting, if I had to describe how it runs at present, very lumpy and burbly and extremely lethargic I would say the timing was out. Didn't think it could be the case on a modern, standard engine though. Is there any way it could be put back together after a rebuild with the cams operating the opposite way to how they should?

[Joesson]

In the past I have had problems with other cars relating to the  timing of the cams, in a vw beetle the timing gear wheel broke its fixings to the cam shaft.
On a Ford Escort the timing belt lost some teeth.
On a Fiat 1500 the timing chain slipped.
These situations all gave a similar scenario to the cams being in the wrong positions.
In each case the engine would not start.
In the first case a replacement engine, in the second case new valves ( very lucky with that as the belt went on start up).
In the last case a new chain and sprockets fixed it.
In my experience if the cams are misaligned you have a problem, just the size of the problem varies from car to car, but I am pretty sure you would not be driving it around so you can take that off your list of possible causes for the lack of performance.

[wallzaveerz]

Right, few hours spent with a mate with a code reader.   Had the following codes stored P0135, P0141, P0155 and P1346. Also had the P0135 and P0155 logged as "pending" faults.   Given that two of my three O2 sensors are unplugged nothing too unexpected with most of these. The P1346 is a bigger cause for concern. However we cleared the codes let it idle for ten minutes and checked again for new codes, none logged!   So took it out for a ten minute blast, still no new codes!   My mate is under the impression it is making far far too much noise through the intake side of things too, it is incredibly loud. Very odd, and starting to sound very expensive!

[Anonymous]

So are your sensors plugged back in now ?

[wallzaveerz]

No, I think they are toast too, it runs better with them disconnected at present. It's looking increasingly like the major problem is a cam timing issue going off how the car feels and that P1346 code.

[mrzwei]

If you think it's timing have you ruled out a faulty cam position sensor? Had this on my old Z3 and it ran fine on start up and then like a bag of nails on re-start. It did store a code though. Crank position sensor is a more remote possibility because you are more likely to get stalls and poor starting.

[wallzaveerz]

If you Google that fault code one of the results links to a thread on here. Someone who had the same code was basically told by Toyota they weren't sure what was wrong.   How do I go about ruling out the cam position sensor and crank sensor without changing them? Is it possible to get the cam timing wrong on the 1zz and have it still run without damage to the engine?

[mrzwei]

You can test them but you need to be good with auto-electronics, use of a multi-meter etc. There are clips on youtube
With the cam sensor you are likely to get rough running and poor performance. With the crank sensor it will be poor starting and stalling, usually at tickover.

If the timing is just one cog out either way then the engine will probably run without damage but poorly. If it sometimes runs really well then this is unlikely to be the issue.

[wallzaveerz]

Thanks for this, right I can rule out the crank sensor then, it starts fine and has never stalled, I have most definitely got rough running and poor performance, I plugged the two O2 sensors back in before to go and pick my missus up from work, ran terribly again, unplugged them again before driving home and much much better again. Although it has good days and bad days I'm guessing it's never completely right but have never had a healthy one to compare it to, all I know is it doesn't feel how I'd expect a flyweight 140bhp to feel, and my mates Mk1 MX5 makes it look silly. But yes i would assume if the cam timing was off it wouldn't be intermittent. Just plugged it back in after the last run, it's thrown two new codes up now P0100 and P0110 which seem to relate to intake pressure or temperature looking on Google. Grrrrrrr

[Ardent]

Wallz

you have pm

[JoeCool]

Sounds like cam timing or phasing to me. It's probably been rebuilt wrong.

[wallzaveerz]

Ardent thanks, received and read and can now eliminate those two codes, realised now that's my fault, since clearing the first lot of codes I started the car again and unplugged the MAF while it was running to see if it cut out, it did so the MAF is working and I'm guessing me unplugging it generated those codes.   Joe Cool, I'm not a total novice, i'm an old school diesel fitter so engines I can do, i've leaned towards the cam timing being wrong from the start, it's the VVTi thing I get a bit lost with, I fully understand that the cams could be timed up wrong and only a strip down will cure this but how can they be phased incorrectly? And although I suspect I'm clutching at straws now is there a possibility it COULD still be the OCV playing up?

[Anonymous]

Are your O2 sensors knackered? I'd be cautious about running it without them plugged in long term. If they are knackered, the first thing I'd do is replace them before trying to fault find any further