Low (ish) idle when warm.

[Snowcat]

Hi,

My 2004 192 runs fine, starts hot & cold and pulls like a train but since owning it the hot idle seems a little low and drops markedly lower when the A/C is switched on. It never stalls but there is a slight vibration being caused by the lowish tickover (new engine mounts were fitted upon purchase) although some owners on other forums have the same problem and say it`s just a foible of some early 8`s. There are no other problems with the engine.

The car has had plugs, coils, leads, new air filter, the MAF sensor cleaned and been checked for induction leaks but the isssue remains which leads to the request for any info`. One thing to note that after recently removing and cleaning the throttle body (whilst checking/cleaning the solonoids on the UIM) the tickover was slightly lower still upon restart/use. I`ve also performed all the resets on the ECU, NVRAM & ESS and checked for any engine codes. The car is also Decat.

Is this slight issue something I just need to live with or are there any other areas which could be checked ?

Many thanks.

[Conan]

Hi,
It actually sounds normal
If the tickover goes below 800 then it might pay to alter the tickover.
it does run quicker when cold and drops hot or when the air con is engaged
Regards
Pete

[Snowcat]

Thanks Pete, How do I alter the tickover ?

Further info` which might help ; The tickover when hot is probably slightly below 800rpm ie the tacho` needle sits on the white line below the 1000rpm white indicator mark. When I`m coasting upto traffic lights etc and the clutch is depressed the needle sits on the 1000rpm line and will do so while ever the car is in motion but once stopped the tickover remains at 1000rpm for a couple of seconds then drops to the low idle.

Like I say it`s probably just something to get used to and as I never use A/C it`s not a major issue.

[qwakers]

tbh that sounds normal to me. if it doesnt stall, i wouldn't worry.

you can get the idle raised (and a load of other useful changes) by getting a mini-map. Ryan Rotary Performace do a remote service.

worth doing a full map imho, but a mini is worthwhile too.

[warpc0il]

You need to run the a/c at least once a month otherwise the seals can dry out and leak plus the magnetic drive clutch for the compressor needs to be excerised.

Speaking of which, this clutch is controlled by the PCM and if it's not operating as freely as it should then this can cause a lumpy/slow tick over.

Hot idle should be about 800 rpm, with a charged battery.

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[350matt]

there's no adjuster screw or anything like that the only way to adjust the idle speed correctly is with an ECU reprogramming tool like mazda edit or versatune

however with the AC on and in hot traffic the car should idle around 850- 900rpm

I'd say to 1st try letting the ECU do a -relearn so clean the ESS / crank sensor of any debris
then with ignition on but engine off then press the brake pedal rapidly 20 times in succession and the oil pressure needle should sweep right to left

then start the engine from cold and let it warm up without touching the throttle pedal until its fully warm

[Snowcat]

Thanks for the responses.

Next time I drive the car I`ll excercise the A/C as when It has been engaged (to check it`s still ice cool) the revs dropped to around 500rpm at a guess so maybe a partially seized compressor clutch mechanism could be the cause.

The ESS/Crank sensor will be cleaned to remove that as a possible cause, but if there was a problem with this sensor wouldn`t the ECU throw a code ?

With previously owned piston engined cars they usually benefitted from a bottle of Injector cleaner which seemed to smooth out any idle issues, but is this a safe option with a Rotary ? And if so what brands are recommended ?

[Snowcat]

Cataclean is safe enough for a rotary.

This gives the injectors a flush, loosens carbon inside and helps the cat - hence the name.

Add entire bottle to less than a quarter tank, drive hard for 20 miles and then top-up the tank.

A couple of tankfulls of Shell V-Power would also help. The extra octane isn't necessary but the additives help.

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[Snowcat]

Thanks for the recommendation that Cataclean is safe for a rotary engine so collected a bottle today from a local Motor Factors while attempting to buy a set of 8 replacement front disc pad anti-rattle clips needed for a brake overhaul as my car only has 3 on each side . Needless to say they didn`t have any and was met with the usual blank stare whenever asking for RX8 parts and have ordered a set online.

Since owning the car it`s always been run on Esso Superplus Unleaded so after the Cataclean treatment has done its stuff I`ll fill it up with Shell V-Power just to be belt and braces.

Once the a/c has been excercised, the ESS cleaned & reset and the fuel system flushed I`ll report the results.

[Snowcat]

Hi again,

On the "lowish idle" I`ve not used the Cataclean yet as the fuel tank is still showing nearly 3/4 full but while cleaning the ESS I also loosened the ac belt and checked that the compressor and idler wheel are all running freely, so will report back when the fuel treatment has been tried (the car is only used for fun on weekends etc).

BUT on another subject when the car was started the CEL stayed on and so plugged in my code reader and found P0410 which relates to the secondary air pump that injects air into the cat` upon start up (the car is running a Toyosport decat). Once the code was cleared it didn`t return on warm starts but only after being left overnight. I`ve checked all the vacuum pipes, cleaned all electrical connections inc` the earth tab,removed & cleaned the 60amp fuse, applied 12vDC to the air pump to confirm it works and rechecked the connections for continuity. Ive also read there is a relay in the air pump circuit and it should be at the front of the under bonnet fusebox but can`t seem to locate it on my 2004 192.

I understand the secondary air pump is serving no purpose on my decat car and could be removed but presumably the po410 code would remain which although nothing of concern the CEL would remain and annoy.

The fault code returns when started from cold although the car runs perfectly. Anything else I should look for ?

[Phil Bate]

It will light the CEL every second time it tries to run the pump and can't see a change in mixture at the front O2 sensor. Can you hear the pump actually running on cold start? It should be noticeable, and provide a huge woosh of air if you disconnect the rubber hose from it.

Even with a decat the car should be able to see the pumps effects and not light the CEL when working properly. If you want to disable and remove it altogether there are a few CEL codes that can be disabled so the light doesn't bother you.

[WildMan10]

The SAI pump just dumps air into the cat to get it up to temp from cold a little quicker in order to make the Euro 4 assessors happy. Removing it will throw up 2 fault codes. You will need a remap to block them, particularly when putting the cat back for an MOT when the only affect will be a little more driving beforehand to get the cat glowing.

[Snowcat]

Started the car from cold this morning and no P0410 code came up . Since the last update I`ve used Servisol Electrical cleaner on every multiplug under the bonnet inc` fuseboard, all earthing points and also pulled & refitteded all the relays too. So the problem seemed to have been caused by high resistance/open circuit connection/s somewhere in the under bonnet electrical system which due to the high temperatures the wiring etc has to endure is unsuprising.

Some months ago the intermittent operation of the power steering was rectified by cleaning the electrical connectors under the water expansion tank, it seems that a good blast of electrical cleaner and filing the numerous earthing ring points back to shiny metal works wonders and as my car`s nearly 16 years old a little maintenance is to be expected.

As the car has now got around 1/4 tank remaining the Cataclean has now been added and driven hard for 20 miles, and will be filled up with Shell V-Power next time. Interestingly the CEL illuminated with a P0420 code after adding the Cataclean but will hopefully not return after its run through the fuel system. The car is Decat and occasionally shows P0420 code, but only twice in the last 1000 miles.

[warpc0il]

Probably too warm this morning for even a "cold" start to trigger the SAS.

You'll know if it is running as it sounds like a vacuum cleaner (if the motor's okay) or a jet turbine (if the bearings are worn) for about 30 seconds after the start.

[Snowcat]

To confirm the air pump was running on start up I held a hand against it while turning the ignition key with the other, it does sound vacuum cleaner like. Hopefully the problem is now sorted.

[Snowcat]

Since adding the Cataclean and driving hard for 20 miles or so the cars been filled up with Shell V Power and driven another 50 miles and there has been some improvement. The idle speed is marginally higher by around 100rpm and now seems smoother too, this most noticeable following the tankfull of Shell. Or it could have been the benefits of the Cataclean taking effect, either way the Tacho needle has moved in the right direction.

Also neither of the previous fault codes have shown up over the last few journeys, so hopefully that`s also sorted, now if I can just get the youngsters to stop driving their glorified shopping trolleys 6 inches off the rear bumper I`d be even happier

Thanks for the advice and recommendations.

[warpc0il]

Glad to hear it's sorted, and you're enjoying it

[Ainmhidh]

For the shopping trolley problem you need a full decat and a pops and bangs map!

[Snowcat]

Sounds like an excellent solution and possibly some flames from both pipes might dissuade the wannabes