Hi Guy's,


Ok strange one here but maybe some of the wiser guy's might know what's going on.

Well I only use my car on warm days during our brief British summer, and as a result only manage 600 to a 1000 miles a year. Anyway, last year after another trouble free summer driving I put the car away in October removed the battery as usual and covered her up.


Forward to May of this year and I go back to the car reconnect everything and start her up as I always do every year, only this year I notice an irregular "thump thump" coming from the exhaust (engine). Like the engine has a slight misfire. It only starts after the idle settles to around 1000rpm on start up. I know the car always idles (when warm) at 650rpm in D,N or P it's done that for years, but now it will sometimes idle at 650 and sound fine, no missing in D, but as soon as you move into N or P it's goes up to a fairly steady 750rpm and sounds rough and slightly missing.


She starts fine every time, never stalls or even sounds like she's going to stall, move away from idle and apart from maybe a slight miss if i'm reversing she pulls away smoothly and just glides along. She hasn't even thrown any trouble codes. Friends can't see what I'm going on about but I know something's not quite right.


I replaced just about everything 4 years ago (knock sensor, distributor including ICM, EGR valve, MAP sensor, IAC valve,ignition coil, all 6 injectors, etc) the only things i haven't changed are the air charge temp sensor and the TPS.


I checked the timing and it's fine at about 11' BTDC, I've checked for vacuum leaks and again nothing to report. Whilst I was checking the timing i put the inductive pick up of the timing light on all six (new) plug leads and got pulses from them. I also got my stethoscope and listened to all the injectors and heard even clicks from all of them. I've even tried the idle learn procedure that I've read about to no avail. The problem only shows up at idle and vanishes once you move away from this.


The only thing I haven't done so far is pull all the plugs (which I'm going to do this afternoon)

to see what state there in. I thought I'd see what you all thought I could check next as although it's not a real major problem at the moment I'm not happy unless she's running 100%


Any ideas are greatly appreciated..


Speed.

 

I had a similar issue and it was my coolant temp sensor.

 

I suppose it could be but it appears to be working fine, plus it was one of the sensors that I replaced 4 years ago. How would a failing one make the computer send the idle off though?

Speed.

 

it effects fuel so it can make it run rich and idle like crap. Just happened to me. Not sure that is your issue, just sharing my experience.

 

samething happen to me once on my old v6 bird. found i had a vacuum hose leaking around the back of the intake. made it idle crazy and act up even at highway speed. took me forever to find the problem after spending a lot of $$$ on parts not needed.

 

Ah right I get ya. Well that's something else to look at I guess thanks for that.

Speed.

 

Yeah I've been round with the scope and the carb cleaner looking for leaks but haven't found anything. Plus sometimes (especially when left in drive) she sometimes idles quite normally Grrr! :s

Speed.

 

thats what my bird did.. idle bad when cold but when warm sometime idle great. its got to be a vacuum leak somewhere. just keep looking im sure u will find it.

 

Yeah, think I'm goig to have to give it another look round it's confusing as hell!

Speed.

 

Can anyone give me the IAC valve base setting please in mm? It only gives inches in the book!

Speed.

 

Ok so a brief update,

I've replaced the TPS as it's the only sensor that had been on there since new, and the problem is still there.

The only thing different now is that she threw a code 35 whilst sat for the published 45 seconds. Idle is 650rpm in 'D' 800+/- 100 in 'P' or 'N'
She also audibly missfires in reverse which isn't noticable at all in drive!

I took out the IAC valve and noticed that it was way out at 30mm!! I've re-set it and even put the old IAC I took out last year in and both end up going back out to 30mm and throwing code 35.

She still starts, runs, stops, with no problems or hesitation at all (exept in reverse) it's got me scratching my head this one

Speed.