Mi16 Icv

[gti_al 1]

I've recently fitted another ICV as the old one seemed to be raising revs at strange times (like when hot in traffic), but this one doesn't seem to do anything. It doesn't raise the idle when cold, but must be doing something as unplugging it kills the engine

 

Do they need adjusting, or is it likely that i have just found a dodgy one? The old one was starting fine, but when it played up the high idle was really irritating

[JeffR 51]

That's weird Al.

 

I ran the engine that icv came from before wrecking it (the car, not the icv) & it was fine. A nice fast idle on start-up. Typical Mi16.

 

Listening to yours idling the other day, it seemed really lumpy for a std engine.

 

I'm sure one of the gurus here will solve it though.

[petert 586]

Sounds like a dud TPS to me. If the idle position microswitch goes open circuit you'll have erratic high idle problems. I can send you the details of how to set the initial butterfly position, but check for continuity at idle first. You should be able to hear it click as you crack off idle, and it should then go open circuit.

 

There are two microswitches in the TPS, to detect idle and wide open throttle. Middle pin to outside is one position, middle to the other outside is the other. Anywhere else in between should be open circuit.

[jackherer 543]

It could be a worn throttle body if its a 1.9 Mi16.

[gti_al 1]

I was wondering about the throttle body/tps/induction hoses etc, but cleaning out the old ICV made it work for a bit... it also seems odd that changing the ICV has seen the issue go from idling too high to idling too low

 

Also, when the idle was high unplugging the ICV dropped it back down

 

Seems a bit strange

Edited March 6, 2008 by gti_al

[gti_al 1]

Sounds like a dud TPS to me. If the idle position microswitch goes open circuit you'll have erratic high idle problems. I can send you the details of how to set the initial butterfly position, but check for continuity at idle first. You should be able to hear it click as you crack off idle, and it should then go open circuit.

 

There are two microswitches in the TPS, to detect idle and wide open throttle. Middle pin to outside is one position, middle to the other outside is the other. Anywhere else in between should be open circuit.

 

To try and eliminate this i went back to the old ICV to see if it would start working again... interestingly it didn't. It seems coincidental that this issue arose exactly when i swapped them over outside Jeff's house though!

 

Now it dies as soon as i let go of the throttle - it seems to be driving fine, but as soon as i slow down it dies. It is possible the TPS was on its way out with the irratic idling, and has now let go?

 

Which bit of the tb wears anyway? The butterfly?

[gti_al 1]

I'll just keep talking to myself...?

 

Tb looks fine, car idles fine once hot... it just doesn't start from cold. Any ideas what tells the icv to open?

[Pugnut 9 1 Cars]

To try and eliminate this i went back to the old ICV to see if it would start working again... interestingly it didn't. It seems coincidental that this issue arose exactly when i swapped them over outside Jeff's house though!

 

Now it dies as soon as i let go of the throttle - it seems to be driving fine, but as soon as i slow down it dies. It is possible the TPS was on its way out with the irratic idling, and has now let go?

 

Which bit of the tb wears anyway? The butterfly?

 

the ecu temp sender tells the ecu which in turn controls the icv relating to the temp ( iirc the idle is suppost to be around 1100 rpm when cold). is the this ok ?

 

its usually the linkage between the top and bottom butterfly that wears, meaning the top butterfly is fine but down at the lower butterfly it is flapping around making the idle erratic.

 

i've also seen throttle cables too tight which prevents the throttle switch from activating

[gti_al 1]

the ecu temp sender tells the ecu which in turn controls the icv relating to the temp ( iirc the idle is suppost to be around 1100 rpm when cold). is the this ok ?

 

Thanks for the reply. When cold it won't idle at all - it just dies for the first 30 seconds or so, then it will drop down to 700rpm ish if no throttle is used. Once hot it is around 1000rpm and as stable as normal

 

Unplugging the ECU temp sensor doesn't help - should i try another one anyway?

[welshpug 1,657]

unplugging the temp sensor should make it loads worse, similar to when the sender gives false readings.

 

check the resistance across it, there were specs for certain temperatures posted recently IIRC.

[Pugnut 9 1 Cars]

Thanks for the reply. When cold it won't idle at all - it just dies for the first 30 seconds or so, then it will drop down to 700rpm ish if no throttle is used. Once hot it is around 1000rpm and as stable as normal

 

Unplugging the ECU temp sensor doesn't help - should i try another one anyway?

 

1000 rpm when hot doesnt sound right either . when hot it should be about 850 approximately.

 

definately sounds like you should try another, especially if everything else mentioned checks out ok

 

are you using a lot of fuel?

 

 

unplugging the temp sensor should make it loads worse, similar to when the sender gives false readings.

 

yeh, its been a long time but iirc it should stall

[KRISKARRERA 2 1 Cars]

Unless the engine's warm. The socket's knackered on mine and it likes to pop off as you approach the redline but the engine doesn't cut out.

[Pugnut 9 1 Cars]

Unless the engine's warm. The socket's knackered on mine and it likes to pop off as you approach the redline but the engine doesn't cut out.

 

i've been thinking about this and its the jetronic that doesnt like being unplugged.

 

the motronic will see the sensor giving a nonsense reading if unplugged and automatically go into limp home mode. if you had the fault indicator indicator wired in it should light up . also the ecu can be interogated for faults

 

Al

[gti_al 1]

1000 rpm when hot doesnt sound right either . when hot it should be about 850 approximately.

 

definately sounds like you should try another, especially if everything else mentioned checks out ok

 

are you using a lot of fuel?

yeh, its been a long time but iirc it should stall

 

The hot idle seems pretty normal - most of the time it is slightly under 1000rpm, and seems pretty much the same as other mi16s.

 

It seems as economical as ever though, and behaves fine once warm. It is just really hard to start from cold, and nothing obvious seems to be wrong. I'll try another ICV though to rule it out

 

Thanks for the suggestions

[jackherer 543]

behaves fine once warm. It is just really hard to start from cold

 

I hate to repeat myself but it sounds like exactly what mine (and others I've seen) was like with a knackered throttle body. When its cold and not idling try gently nudging the linkage between the two butterflies and see if correcting play there corrects the rpm.

[gti_al 1]

I hate to repeat myself but it sounds like exactly what mine (and others I've seen) was like with a knackered throttle body. When its cold and not idling try gently nudging the linkage between the two butterflies and see if correcting play there corrects the rpm.

 

It would make sense... it might explain why it idles so much lumpier than others too

 

It never idles when it is cold now, so i'll have a look next time i start it up.

[gti_al 1]

I hate to repeat myself but it sounds like exactly what mine (and others I've seen) was like with a knackered throttle body. When its cold and not idling try gently nudging the linkage between the two butterflies and see if correcting play there corrects the rpm.

 

That worked... is there meant to be a bit of play? Does that definately mean that the throttle body needs replacing?

Edited June 9, 2008 by gti_al

[nick 3]

Try adjusting the idle mixture on the AFM. I had idle issues last week after finishing my conversion (stalling, revs hunting up and down etc...), I leaned out the idle mixture and it is fine now, rock solid tickover hot or cold.

 

Nick

Edited June 9, 2008 by nick

[gti_al 1]

its usually the linkage between the top and bottom butterfly that wears, meaning the top butterfly is fine but down at the lower butterfly it is flapping around making the idle erratic.

 

Interesting... that is exactly what it looks like is going on. The linkage moves from side to side a bit, and when you put pressure on it the thing idles much better

 

Is this what jackherer is referring to though, or is that an issue around the butterflies?

 

Thanks for that nick - will try and focus on one potential issue at a time though.

[jackherer 543]

That is exactly what I was referring to, I seem to remember bodging one with a shim once but I've never permanently repaired one. IIRC I simply used an electrical ring connector bolted to one of the lower throttle body mounting bolts with the 'tail' located so it acted as an end stop for the linkage in its closed position. That worked for a while but I fitted a gti6 before I fixed it properly.

[gti_al 1]

That is exactly what I was referring to, I seem to remember bodging one with a shim once but I've never permanently repaired one. IIRC I simply used an electrical ring connector bolted to one of the lower throttle body mounting bolts with the 'tail' located so it acted as an end stop for the linkage in its closed position. That worked for a while but I fitted a gti6 before I fixed it properly.

 

I am suprised it is that... i was convinced it was going to be something electrical, but when i had the radiator out before i had a look. I'll replace the whole thing i think, as when i put a cable tie on it before the car started and idled by itself.

 

Thanks again - i can't believe you got that one straight away! Does anyone know if 405 8 valve two butterfly body is the same as the mi16 tb?

[jackherer 543]

Thanks again - i can't believe you got that one straight away!

 

I spent a long time thinking about the symptoms when I had this problem so it seemed very familiar.

 

Does anyone know if 405 8 valve two butterfly body is the same as the mi16 tb?

 

They are very similar externally but the bore is smaller. Also its worth noting that mi16 bodies can be made by either Weber or AMC and not all parts are interchangeable.

[gti_al 1]

That is exactly what I was referring to, I seem to remember bodging one with a shim once but I've never permanently repaired one. IIRC I simply used an electrical ring connector bolted to one of the lower throttle body mounting bolts with the 'tail' located so it acted as an end stop for the linkage in its closed position. That worked for a while but I fitted a gti6 before I fixed it properly.

 

I fixed this today. A mate gave me a spare throttle body in bits, and putting it back together looked like a total nightmare. The other linkage seemed pretty similar too, so i had a closer look

 

Found that it is easiest just to extend the stop at the bottom of the linkage. It has a thing there which it sits on when closed, so i just glued a bit of plastic to it. Now it is perfect. I certainly wouldn't bother replacing the whole throttle body for this - it took about 15 minutes to fix, and i think it will last

 

Thanks again for the help though. My favourite thing about this engine was how easily it started, and it has been really annoying me

[jackherer 543]

I certainly wouldn't bother replacing the whole throttle body for this

 

You might if they were as cheap and readily available to you as they are to us in the UK

 

Glad you got it sorted

[gti_al 1]

You might if they were as cheap and readily available to you as they are to us in the UK

 

Glad you got it sorted

 

It seemed sorted, but has progressively got worse again. Now it is so lumpy sitting in traffic is unpleasant, but i've noticed that as soon as you open the throttles it evens out.

 

I'm guessing it isn't only the linkage that is causing problems. As replacement tbs are expensive, rare, and likely to have the same issues, should i swap any bits from my stripped spare one? Someone here said something about spindles wearing - could they be swapped?

 

I'm interested in fixing this now, preferably with what i have here. It would be interesting to find some answers on this problem too... it seems to be getting fairly common