Engine jerking back and forth at 1500 rpm

Mr Morlock · Postby **Mr Morlock** » Tue May 20, 2014 8:31 pm

I still think the car needs to be looked at by a competent technician / mechanic and a process needs to be applied.

project.r.racing · Postby **project.r.racing** » Tue May 20, 2014 8:55 pm

does sounds like IAC then. I first time I found out I have a dodgy one was upon decelleration and low rpm 2nd or 1st gear feels like you are driving over multiple speed bump in a row. clutch in prevents this issue.

it is probably a blocked IAC. i did clean my about 6 years ago, and it was good for 2ish years, then came back.

by putting 12 volts into your iac, you probably had the motor push the pindle right up and pushed all the crap/dirt out of the way. over time the crap/dirt came back.

you looked on ebay for a cheapie? also 96-98 mazda 323/ford lasers have the same iac as nb8.

speed freak · Postby **speed freak** » Wed May 21, 2014 5:42 pm

Mr Morlock wrote:I still think the car needs to be looked at by a competent technician / mechanic and a process needs to be applied.

IT HAS BEEN! Like I said its been looked at by many now and specialty mx5 workshops and they cant really pinpoint the issue.

project.r.racing wrote:does sounds like IAC then. I first time I found out I have a dodgy one was upon decelleration and low rpm 2nd or 1st gear feels like you are driving over multiple speed bump in a row. clutch in prevents this issue.

it is probably a blocked IAC. i did clean my about 6 years ago, and it was good for 2ish years, then came back.

by putting 12 volts into your iac, you probably had the motor push the pindle right up and pushed all the crap/dirt out of the way. over time the crap/dirt came back.

you looked on ebay for a cheapie? also 96-98 mazda 323/ford lasers have the same iac as nb8.

Yes thats exactly what mine does only at low rpm and yea really jerks back and forth and slaps the gears around a bit until it settles itself back down again.

I was just thinking though, I mean the IAC makes sense, but when you are in gear off the throttle and coasting isnt the momentum of the car keeping the engine alive? When you clutch in or come to a complete stop wouldnt the IAC take control of the airflow then or even when coasting because the TB is shut?

Yea the idea of the 12v thing was to make it open up completely or whatever it does inside since it only normally see's 8v or something we were trying to 'wake it up' and it seemed to have worked.

I had a quick look last night and I did find a few actually. I might need to get a TB too as the screws the connect the two on mine are stuffed due to age, I could try drilling them out but dont want to stuff the thread, because then Id be stuffed until I found new parts.

project.r.racing · Postby **project.r.racing** » Wed May 21, 2014 9:04 pm

attach a 9V battery to the iac. drive around. if it revs of its nuts on idle and doesn't do the jerking, then you have found your issue.

if you bolts/screws are stuff, get a whole tb unit.