Another bouncy idle

[PhilA]

Hey,

Having re-read the bouncing idle and wierd idle and wont take gas threads, I'm here to say HELP

The GTA is back to being an arse again.

Started it up, it runs at idle ok but refuses to move at all, full range of pedal movement other than idle causes it to cough and die, or sput sput VROOO sput sput VROOM sput sput

It gets better when it's warm but it still stinks rich.

Leave it to idle and I have unplugged the IAM so it's not that doing it- along with plugged all the vacuum lines to see if they were leaking and they aren't..

It idles rough at 800rpm, rises the revs slowly to a smooth 1400 rpm idle for a few seconds then drops back quickly to a rough 800.

Unplugging the lambda doesn't change it.
Unplugging the CTS doesn't change it.
Unplugging the IAT makes it run like crap.
Unplugging the MAP makes it die.
Unplugging the IAM doesn't change it.
Unplugging the knock sensor doesn't change it.

Listening to the throttle it whistles at the low, rough idle, then the pitch of the whistle changes when it revs up.

Which is odd because the throttle plate isn't moving. I could understand the pitch change but there's no bypass valve on this throttle body, it just moves the throttle stop with the IAM. IAM moves as it should when it's plugged in. Closed-throttle switch works.

Help?

--Phil

 

[Chris H]

this sounds exactly like the problems with the 5's with injection.

Renaults solution is a new ECM.

My solution is another bigger engine!

On the 5's over here the idle usually goes up to about 2 or so krpm with the map sensor unplugged but the car will drive. However even if you suck on the map pipe the car will stall or idle low and won't take revs.

However thats on a basic 1.4 SPI engine in the 5 and usually if you examine the ecu it is damaged.

However yours is a bit more sophisticated I think.

For the revs to be rising it either has to be adjusting the fuel amount or the air amount. This would be telling me lambda. I know its not meant to work during cold start enrichment but there may be a sensor issue as well.

Have you cleaned the lambda? Also when its unplugged it will still look for its input until a drive cycle has occurred therefore cycle up and down.

Sensor issues, the senders are crap, I have 2 new ones in the chammy and the white chammy, neither work properly. Sure they at least don't drop out when the temp increases or goes down but they have a ceiling. the ceiling is only 84 degrees on the blue one and 86 on the white one. A blowtorch on the end they won't read higher. The white one before I changed it was bad, read fine until a warmish temp dropped to 0 and the car either stalled or idled badly, warmed a bit over it and it was fine again. This goes for air temp senders as well.

To really see if they are working you need to scope them.

the tps may also be causing a big issue, can you start the car with half throttle and when doing so does it rev up?

checked all the wiring loom? they rot, sneakily inside the insulation you need to tug at them.

 

[PhilA]

Chris,

I haven't had the lambda out. Probably should lift it and blowtorch it- when I took the engine apart it had signs of running real well up until recently whereby the deposits were a thin layer of black on top of biscuit brown.

Pulling the idle air motor connector off makes no difference, the revs rise, so it's doing that either by changing the fuel or ignition timing.

The air and coolant sensors seem to be okay, tested the air sensor and it read well over range, ceiling was over 100c.

Putting my foot half down on the throttle and trying to start it results in non-starting with occasional cough sput but no start/rev.

Odd because the TPS gives a nice smooth arc of resistance measured at the ECU.

ECU is possibly not reading it right, I need to see what voltages are present. Going to go check the connections to it.

--Phil

 

[PhilA]

ahahahahhaaahaha

The fuel pump just died.

:x