High idle, bad power delivery

[Matasb]

Hi guys,

Just bought an MR-2 Roadster with a bag of problems. Or just one problem, but a big one, I believe. We can't identify the source of it though...
Here is the case.

When the car is started, idle keeps at 1800-2000 rpm. The engine reaction to the accelerator is kinda laggy. If I put my foot down (WOT) on idle, the engine revs up till about 3000 rpm, stops for a millisecond, revs little more, stops again, and it keeps going this way. When the engine warmed up, the engine drops to about 1100-1200 rpm but still suffers when pushed.
There is a little white smoke from the exhaust pipe. Maybe it's condensation? (the car wasn't running properly for some time... Obviously, because the engine was struggling to rev, according to the ex-owner)

- We tried to change the whole throttle body with things around it (throttle position sensor, etc) - no results. Even though, mechanic told me that diagnostics showed strange throttle position. Something like 15 percent at idle and ~70 (or 80, can't remember) percent at WOT.
- The diagnostics showed decent MAF data (well, that's what the mechanic said). Disconnected MAF instantly affected engine behavior, so it seems that it's working fine.
- We tried changing the fuel (the car was not used properly for a few months, I believe).
- Spark plugs seems in OK condition.
- Engine check shows both primary (pre-cat) lambdas, but since I owned one MR-2 Roadster before, it had same problem, but there was no such drama. Idle was unaffected.

What else should we check? The hesitation of the engine to rev reminds me of a problem of a fuel pump. But I can't see how that could affect a relatively high idle...
Is there a possibility (in theory) that timing chain could have jumped a tooth or a few?

I will try to capture the whole thing on a video, that would be helpful for you guys to understand/see the problem. But maybe you will be able to recommend me some advice already.

[JoeCool]

- We tried to change the whole throttle body with things around it (throttle position sensor, etc) - no results. Even though, mechanic told me that diagnostics showed strange throttle position. Something like 15 percent at idle and ~70 (or 80, can't remember) percent at WOT.

Can't help beyond this, but I believe these cars show those numbers for normal throttle behaviour. I know mine only reports 78% throttle at max throttle.

[Carolyn]

A couple of thoughts:  Just 'cos a MAF is working, it doesn't mean it's working 'fine'.  It sound like an intermittent sensor problem.  Intermittent problems are usually down to a dodgy wiring connection.  I'd go round all the sensors, disconnect and spray both sides of each connector, blow out with air, spray again (with contact cleaner).  Check all the earths that go from the wiring to the engine (especially the crankshaft sensor, a common cause of strange revving behaviour).  Make sure there are no air leaks on the input side.  Clean the Idle Air control and make sure it's moving freely.
Going to have to be a systematic ruling out as you go.

[m1tch]

What are the fuel trims like - and the 02 sensor voltages - I found mine had issues with hunting idle until the engine relearnt the fueling after the O2 sensors warmed up and the fuel trims were adjusted - pull the ECU fuse and leave it out for 20 minutes and put it back in then report back.

[Matasb]

Thanks for the replies, guys. I talked with specialist again, he confirmed, that there were no anomalies in the diagnostics (regardless O2 sensors). The idle seems to be OK now.

Here are the links to the videos, if they help.
Cold engine, full throttle (my foot was planted down, but look at the reaction of the engine).
 m https://youtu.be/AqEZrO_BJBo m

Here the engine is warmed up, revs much better, but it seems it still struggles in the low-end range (till 2k rpm or so...). The car is running "normally" from 4k rpm.
 m https://youtu.be/X1s4bhYAFm8 m

Sorry for my humble english  s:) s:)

[jonbill]

I think air leak after the throttle - air leaks are more noticeable cold and at low rpm (because the extra air is a small % of the overall air)
I think live monitoring of o2 and fuel trim data will be very helpful - not the same as diagnostic report of whether there are any errors stored.