Mazda Rotary Club

Ok So when the cars cold sometimes, not everytime (this has happened twice now), car will idle at about 1300 revs (somewhere around there at least) and then the revs will drop below 1000 and come back up, and it does this for about 40 sec\'s to a minute. Its not the same as when i had an air lead and the idel was all over the place. I just remember seeing a vid of a TII that had this same problem with the revs, but it was constantly doing it.

Another problem i had on my last motor way trip was that around 3500 revs, when cruising, the engine would seem to skip a beat, which seems to me like really really low compresson on a rotor face. This happened about 3 times on the motor way. But 3500 is suposed to be when the secondary injector/s kick in isnt it? So maybe its a fueling problem? or maybe my fuel pumps shot?

If anyone could shed some light that\'d be awesome!!



cheers

If you are getting hesitation at 3500 you can try a simple fix by runing a bigger earth strap from the top of the inlet manifold to the bulkhead.  You should also check the other earths. (The one on top of the UIM is notorious for dropping off)

i have a HUGE earth strap from the battery to the shock tower - just incase

i got it off the UPS that was being broken down :D

have a read on rx7club.com about the 3800 hesitation - there is loads of info on there about it

Do you think it might be TPS related if its hunting? My FC is having a few issues at the mo as the fuel pump was taken out and now its difficult to start sometimes, you still running your original fuel pump?

Secondary injectors will only come on when your running boost, in the vaccuum part of the map (below 0 on the boost gauge) the secondaries will stay off.  They do come in around 3500-3800 RPM and above 0 psi on the TII.
 
I\'d say the fluctuating idle could be any number of things - vac / boost leak, faulty sensor, faulty/dirty bac valve, fuel flow issue, grounding problem, TPS (throttle position sensor) adjustment, timing out of adjustment...

heres a video of the problem




it only does it sometimes when the car is cold though. You still think its one of the problems you guys have stated above?

Also the car produces a lot of white smoke when cold, this disappears when warm.

oh and where can i get these replacement earth straps?

cheers for the help so far

White smoke could be coolant - check the coolant level and overflow tank.
 
That cycling seems very like TPS is out of adjustment - that hunting over 1000 RPM during the warmup - once it\'s warm it usually stops.  (Basically if the rest point of the throttle is not set correctly on the throttle position sensor, the car will enter a cycling loop as it warms up where it will alternately cut and add fuel - making the engine rev.  If you are watching it on a wideband, you see the car cycle between rich and lean).

Quote from: Prof;542789White smoke could be coolant - check the coolant level and overflow tank.
 
That cycling seems very like TPS is out of adjustment - that hunting over 1000 RPM during the warmup - once it\'s warm it usually stops.  (Basically if the rest point of the throttle is not set correctly on the throttle position sensor, the car will enter a cycling loop as it warms up where it will alternately cut and add fuel - making the engine rev.  If you are watching it on a wideband, you see the car cycle between rich and lean).

is the tps something i can play with? or should i be sending the car off to someone who knows about it?

TPS adjustment is something you can do - although it\'s a bit fiddly and you will have to do it more than once, as you have to set it with the engine hot, but it\'s set with the engine not running - so it\'s cooling down whilst you\'re setting it.
 
Depending on what model car you have TII or EGI - will depend on where the test connector is.  Basically you are setting the narrow range TPS sensor (on some engines they only have this).  There is a 3 pin green connector (on TII\'s it\'s near the oil filler, on EGI\'s it\'s near the shock tower on the drivers side I think) - you need 2 12v leds, or low wattage bulbs - you wire the anodes (if they are leds) to the bottom of this 3 pins test connector, and the other wire from each bulb or led to the 2 remaining terminals.
 
When the car is warm, you should only see 1 of the lights lit at idle.  Rev the engine and both will light, and then 1 will go out.  The lights are just repeating the status of 2 solenoids on the engine.  To adjust the TPS you need to switch the engine off when it\'s warm, and locate the the adjusting screw on the throttle body - it\'s just under the Throttle sensor - which is the rectangular thing with 3 wires coming out of it.  The screw will move when you try and turn it - and you\'ll see the lights go on/off - you need to adjust it a bit then take the pressure off it and see the effects.  The game is to get just one light lit when throttle is at rest.  Once you\'ve got it set the first time, start the engine - warm it up - drive it even - then come back and check it again - it will need tweeking a couple of times to get it right.
 
There is a write up here for the S4:
 
http://www.fc3spro.com/TECH/HOWTO/TPS/tps.html

Im having the same problem with my rx at first i thought it was a tickover adjustment fault and messed with the screw made things worse i read you have to put a jumper wire in a terminal block to sort this out but i cant find the block  its an 89 car which is a changeover year how do i tell if its a 88 spec on a 89 plate

is it a uk car?

if so if its non-turbo then its a series 4
if its a turbo its series 5.

the guide posted on fc3s is for a turbo car

if its not, a uk car, look at the pic on this forum. The series 4 cars have black trim and different bumper to the series 5. The interior is also differe. series 4 has proper carpets

hope this helps

the car is an egi uk spec fully loaded ie air con cruise/con  etc
where on forum is pic?

ah they\'re about.

you\'ve got a series 4.

Resurection!

Did you sort this in the end? Im having a similar thing with mine now. I get a hesitation (feels a bit like a miss fire) between 3k-4k when on boost. I also get a slight change/hunting revs on warm up. The warm up doesn\'t bother me as its not major but the hesitation is worrying. I thought it was about to go pop when it first did it.

sounds like yours is doing the 3800 hesitation aswell

if you have a decent multimeter - you can check the resistance between the earths and the battery - if its really high - then i think it means its stuggling to get a good earth

might be worth just adding some better earths - at the end of the day - it wont do it any harm !

I don\'t know if it\'s the same on the coupe\'s - I suspect it is - the ecu grounds onto the engine and the engine takes it\'s ground from the chassis.  Where the engine ground is - I noticed a lot of crap on the earth tag\'s - as Grinder says - earthing is a biggy for these cars - as the sensors all take their ground reference from the engine itself.
 
Others have found problems of hesitation and poor idle down to :
 

• Fuel pressure - check for leaks / check fuel pressure
• CAS sensor - Pete Taylor had issues with this - check the connector and unscrew the top plate and check all the teeth are intact.
• Spark plugs - dirt or fouled

I ended up taking the car to rotechniks who sorted it by playing with the tps some thermowax stuff? Think the egi\'s are extremely different though. As for the hesitation, that sorted itself out

I had my intercooler off today with the intention of finding the source of my bad idle but i have no idea what im looking at.

I understand that the TPS could be out and i could see two sensors with plungers acting on one end of the throttle assembly.

I could see various adjustment screws but without knowing which does what i wasn\'t prepared to screw anything up so i took a few photos to see if any of u guys could identify some of the parts.

(http://i664.photobucket.com/albums/vv7/identiti1/Picture021-1.jpg)
(http://i664.photobucket.com/albums/vv7/identiti1/Picture013-1.jpg)

Allso what is the spherical object above the throtlle cable?

(http://i664.photobucket.com/albums/vv7/identiti1/Picture014-1.jpg)

That object is the dashpot, its basically a damper for the throttle pulley so when you let off the throttle the last part of the throttle travel doesn\'t slam the intake closed, but closes it more gently, just smooths out the transition to idle :)

Oh right cool,im now not as lost when i look at my engine lol cheers

The screw you want isn\'t in the piccies.
 
If you look at the 2 plunger thingies - the grey/black rectangles - these are the throttle position sensors.  One is in contact the whole time, and covers the entire throttle travel - that\'s the wide one - don\'t touch that one ;)
 
The other one - the outer one, is only in contact with the throttle mechanism for part of it\'s travel - that\'s the narrow one - the one you adjust.  Underneath the narrow range throttle sensor and visible from the front of the car with the stock intercooler off, is a screw about 1 inch long with a spring on it. It adjusts the narrow range tps \'home\' point.
 
Don\'t forget - it needs adjustment when the engine is fully warm - if you note the positions of the throttle in relation to things when it\'s cold, and then again after the engine has run - you\'ll see they change. :Thumbs-up

would adjusting the bac valve help with the idle?

righty ho ill attack it tomorrow with her warm and see if will make any difference.

This all helps to narrow the problem down.

found this link regarding BAC valve cleaning.

http://www.1300cc.com/howto/how2/bac.htm

Well I\'ve managed to sort my crap idle.It turns out it was the throttle cable was really slack so once I had tightned it up so there wasn\'t any slack the 3000rpm warm up started to work again and any surging in the revs at idle have gone.

My car allso suffered from bad juddering off the throttle which has now all but gone.
I had a quick fiddle with the narrow range tps which has allso smoothed out any small lumps in the idle.
Cheers for the advice chaps as it\'s a small step in the right direction to having my car running as it should.

I allso managed to do a compression test and it returned with 6.0bar even on all chambers.
Is 6.0 bar fairly good for a turbo 13b or should I start saving for a rebuild lol?

Quote from: Adam fc;666948I allso managed to do a compression test and it returned with 6.0bar even on all chambers.
Is 6.0 bar fairly good for a turbo 13b or should I start saving for a rebuild lol?

Any idea what RPM you had during the compression test ?
 
8.0 BAR is excellent (new engine), 7.0 BAR is good, 6.0 BAR ok but getting tired, 5.0 BAR - expect starting problems and an imminent rebuild.
 
But these readings are based on a test at 250 RPM.  There is a graph in the Service Manual - that shows how to factor up the readings to 250.  Basically - a reading of 5 BAR at 200 psi is the same as 6 BAR at 250.  This means if you\'re revs were a little down during the test due to a tired battery or starter motor, the readings may be better than 6.0 BAR.
 
The main thing is that they are even - which is a good sign.