rough idle,hard starting,hunting tach?tps intermittent volta

[skipper6567]

Hi all I have 99 i30 that seems to run fine above idle,there is some "hunting" at higher rpm. The problem is at idle,starting. The engine first fires up and tach goes to 12-1500rpms,drops to 500-650rpm almost immediatly.I have gone to the j/yard and got all sensors, I have removed plenum and throttle /iac /egr tubes all map/bro/swirl valve/camshaft sensor/map/ cleaned and checked all these components,The engine seems to have a steady miss? I do NOT have a check engine light at this time. I do get knock code sometimes. The tps seems to have intermittent voltage without engine running? Its hard with digital meter but seems like one of my probes is being tapped on the battery ground. 12vdrops to 0 back to 12-3-11-12-3-12 all this in a matter of seconds? should be constant? correct? what send the signal to the tps? Im running out of sensors and things to test..also all coils/plugs replaced,no smoke or carbon in exhaust.The egr tubes were blocked solid. now they are all clear.seems that I'm not the only one with this problem. Just that no code?? I also want to add that when engine is running and I disconnect iac=no engine change,front o2 sensor disconnected =no change=egr=no change??tps=no change??

[tigersharkdude]

first off...the 99 cars have bad ignition coils (just read you replaced the coils and plugs, what coils did you get, and what plugs did you get?). They may not trigger a check engine light but they tend to go bad. Do the RPMs drop like you said in the winter?

Mine starts the same way in warmer weather. As soon as it fires it goes up to around 1300-1400, and then drops to about 700-800 (idle).

It sounds to me like your idle speed needs to be increased...One more question, what does the car idle at when you are driving and stop at redlight?

[skipper6567]

The idle is up and down,if I put the ebrake on and put the car in drive it stays running but surges back and forth.I have 15 or so oem coils,its like the engine is hunting to find the ideal idle speed, the exhaust pipe sound like the engine fires then dies then fires and dies ect..it has like a "cycle"up and down at the same speed..?