1.9 Mi16 Hot Idle Problem

[dino20vt 3]

Once the engine get past half way on the temperature gauge, the engine seems to idle anywhere between 1.5k and 3k rpm and when blipping the throttle the over run seems slower to settle to idle speed.

 

From searching I've discovered it could be a faulty TPS or it's connectors, worn throttle body linkages or butterfly , or the throttle cable.

 

Although the cable operation felt smooth, I lubed it anyway and adjusted as it was before ie TPS clicks once on throttle and full range of motion.

 

Not checked anything else but wondered if anyone had anything to add.

 

Cheers

Edited November 27, 2010 by dino20vt

[Baz 421]

My bet is on the TB butterfly spindle/bushes being worn and not full closing to the same position each time, it's very common.

[dino20vt 3]

Are they repairable?

Does the idle problem usually only occur when the engines hot?

[Baz 421]

Sorry yes i kind of overlooked that! So it's absolutely fine when cold, and idles as it should around 1k rpm?

[dino20vt 3]

Yea fine when cold or when at normal temperature, idle spot on and snappy response ie revs drop as they should. As soon I hit traffic and it gets a bit warmer it plays up

[large 33]

I had a similar problem a couple of weeks ago, turned out to be a bad connection to the ecu temp sensor.

[dino20vt 3]

I had a similar problem a couple of weeks ago, turned out to be a bad connection to the ecu temp sensor.

 

I changed it a couple of months ago but it was a pattern not genuine Bosch part so I'll bear it in mind, cheers

[dino20vt 3]

Forgot to mention, when I'm sat in traffic and its revving it's nollocks off (upto 3000 rpm) I can bring it down to a less embarrassing level of 1500 rpm by hooking the pedal up and holding firmly.

 

When it's cold and behaving itself pulling the pedal up has no effect on the normal idle speed (approx 900 rpm)

 

Id say there's a good chance it's the throttle body unless anyone has any other ideas.

Edited November 30, 2010 by dino20vt

[happygoron 2]

I'd say it's a good chance your throttle cable is sticking somehow.

[Alan_M 66 1 Cars]

Forgot to mention, when I'm sat in traffic and its revving it's nollocks off (upto 3000 rpm) I can bring it down to a less embarrassing level of 1500 rpm by hooking the pedal up and holding firmly.

 

When it's cold and behaving itself pulling the pedal up has no effect on the normal idle speed (approx 900 rpm)

 

Id say there's a good chance it's the throttle body unless anyone has any other ideas.

 

I agree, sounds like the TB itself. I sometimes did the same thing, hooking the pedal up to try and bring the idle down, your taking the play out of the spindles by doing this. Good luck finding another decent Mi TB, most are shagged. I did investigate refurbing them, but the spindles aren't available anymore. Bushes are generic and are readily available, and could probably get the spindles knocked up at work but I ended up grafting a GTi6 inlet & TB instead. Idle is spot on now

[dino20vt 3]

Once the weather gets abit better I'll remove the TB and investigate where the play is coming from, hopefully the bushes and not the spindles are worn if its possible they can fail independently.

[JRL 14 1 Cars]

Once the weather gets abit better I'll remove the TB and investigate where the play is coming from, hopefully the bushes and not the spindles are worn if its possible they can fail independently.

 

it might even be that it needs a bit of a clean...

[Simes 248 2 Cars]

I've a spare throttle body that was working fine on my car, if you're interested.

Pm me

 

Thanks

[Alan_M 66 1 Cars]

Once the weather gets abit better I'll remove the TB and investigate where the play is coming from, hopefully the bushes and not the spindles are worn if its possible they can fail independently.

 

They'll wear together, which will mean a dead TB....sorry another dead Mi16 TB. Should be able to check play without removing it, disconnect the cable and give each spindle a wiggle. Any play should be clearly evident. I could move the top spindle on mine 2mm each way!

 

I took the TB to a Weber carb specialist in Reading, who had never come across it. Confusing as they had comprehensive info on all Weber stuff from back in the day, and the Mi16 TB clearly has Weber stamped on it. Only thing they concluded was it was a hotch-potch of parts from random 38mm carbs, and I started looking at technical drawings only to give up. I had the GTi6 inlet & TB in the garage, and it was up & running in an afternoon. If anything, it runs much nicer now, always idling spot-on whether hot or cold and has improved economy slightly (low 30's on everyday driving with mild cams and 1.6 box).

[JRL 14 1 Cars]

There is the AMC mi16 throttle body and the one you mention the webber. On the AMC tb both the butterflies open simultaneously whereas the webber doesnt I wonder if the AMC tbs were of slight better build quality. dino20vt what make is yours out of interest?

[jackherer 543]

They both fail, AMC or Weber.

[dino20vt 3]

I've a spare throttle body that was working fine on my car, if you're interested.

Pm me

 

Thanks

 

Cheers for the offer i'll pm you now.

 

 

I'll also double check for play.

[dino20vt 3]

Had a bit of a play today and found the issues are down to the throttle body as once hot and when blipping the throttle the revs are slower to fall and don't settle at 900 ish rpm.

 

Twisting the cable cam brought it down to what it should be and it seemed like the spring doesnt have enough tension keep the butterfly closed.

 

I then removed my TB to find it had very little play compared to the second hand one I'd bought so I attempted to wind the spring around an extra time on mine to give it more tension when closed.

 

That didn't exactly go to plan as I ended up with the stop tab snapped off and the main spring fubared so I nicked those parts off the other TB and set the tension to standard with the addition of an extra spring off the later TB.

 

Refitted the original throttle body to find it behaves as before.

 

Currently I've got the stop screw set so the main butterfly (the one directly driven off the cable) fully closes ie fully wound out for slowest idle.

 

I haven't touched the other butterflys stop screw (the one underneath) as both mine and the second hand TB seemed to have been factory set to the same amount plus its an arse to adjust once on the car.

 

I want to know why the fault only appears once the engine is warm, do under bonnet temperatures affect the springs tension or does the air flowing through TB become more powerful when hotter and open the butterfly more.

 

Where does the idle control valve become envolved?

 

Would running rich have and effect as it does smell at the minute. I did try to set it up today at my mates garage on the gas analyser but having idle issues put a stop to that.

 

Any info appreciated.

Edited March 26, 2011 by dino20vt