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Rough idle


alzmoore

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  • Gold FFM

You can reassemble that - but I'm looking at that picture and wondering if the pintle shape is correct.

do you have your old one still?

That looks like a 411 pintle - and I think that's wrong !!! Check out that link I put up earlier 

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Barry

 

It won'reassemble, it won't engage internally at all. I'm not even sure if the old one is the right one because when I restarted the car after refitting it, it still idled badly. It kept cycling up and down.. I reset the IAC with freescan, and it has slowly improved.

 

Should I have bought a Dacia Sondero instead??? 

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  • Gold FFM

Get in the sea!

Duplicate of what happened to mine. I too, had the wrong IAC sent to me. Fitted it, the idle was shite, so I removed it, and the photo shows what I found, it had fallen apart. It was also the wrong shaped cone.

Replaced it with a 427 from Rock Auto after Barry's efforts to resolve his issue.

2015-11-22 13.48.11.jpg

Margate Exotics.

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  • Gold FFM

Good picture @ian29gte that's exactly the issue - they are different.

its wrong in a parts cross reference somewhere and cars have had the wrong ones fitted in the past - then often shifted on as they don't run properly !!

whats your old one like @alzmoore??

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  • Gold FFM

Check the Rock Auto website again. They're in stock, they have either Airtex Wells, or Standard Motor Products IAC's both £16.50.

Punch in 217-427 into the P/N search box,

https://www.rockauto.com/en/partsearch/?partnum=217-427

 

Margate Exotics.

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Whilst the GM 17111826 (AC Delco 217-411) is definitely the wrong part (the pintle diameter is too small at 0.47 inches) I am not sure that the GM 17112929 (AC Delco 217-427) is the correct replacement.

The original ISC valve pintle diameter is 0.55 inches but the GM 17112929 pintle diameter is 0.50 inches. Also, the GM 17112929 has three cone angles but the OE has only two cone angles.

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  • Gold FFM

It's possible. But the main point is that the 427 works fine.

The 411 definitely didn't work for me: I fitted it, the engine refused to idle, and when I removed it, it had fallen apart, as my photo shows. I e-mailed Rock Auto, and they sent me a returns label to send it back to them. In the meantime, they replaced it with a 427, with no quibbles, and all at no cost to me. Great service!

Margate Exotics.

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Visually the closest potential substitute I have found is the GM 17112648 (AC Delco 217-421) which looks to have a very similar shaped pintle to the Lotus ISC valve. It has the 0.125 inch flat on the pintle tip too. The only thing that makes me wary of this one is that its earliest use is listed as 1993 from what I can find. 

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  • Gold FFM

411 didn't work for me - nearly killed me with the gas it filled the garage with !!

427 worked absolutely faultlessly - and lots of others seem to have found the same results

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i ordered the Airtex equiv of the 421 and will try it.  I noticed when calibrating idle on my AEM ECU that the 427 will achieve the desired idle but the variation is more than i expected and very small movements produce greater changes in rpm than i would expect as well.  I'll report back when installed

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chris

90SE

just because I don't CARE doesn't mean I don't UNDERDSTAND

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Any chance you could measure the resistance of the coils on the ISC valve when you get it? I'm curious as to what they are on the 217-4xx parts as Wells appear to have them as 50 +/- 2 ohms whilst Service Notes section EMH states > 20 ohms. I'll measure the OE ISC valve later.

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53 ohms on the Airtex version of 421 (pic on right) compared to 427 (on left).  Its hard to tell a difference in performance between the two since i am using an aftermarket ECU in which i can fiddle with the gains, positions and fuel.  It seems like i can get either to maintain desired idle value within 70 rpm, which is slightly better than the stock setup, but i also have sequential COP and 840 fuel injectors so grain of salt sort of thing

 

0904162057-00.jpg

chris

90SE

just because I don't CARE doesn't mean I don't UNDERDSTAND

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  • 8 months later...

I can confirm that the GM 17112648 (AC Delco 217-421) ISC valve has the correct pintle shape. The only difference to the OE ISC valve is the wiring connector is offset 45 degrees from the centreline of the mounting holes (the OE valve connector is in line with the holes).

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  • 5 weeks later...
  • Gold FFM

A bit late, but as you probably know, I've been a bit busy elsewhere.

I exchanged the 427 for a brand new 421 (marked AC 143 on the box) and went for a little run. First impression is that it's OK, no problems whatsoever, however I need to try it again with different loads, in particular the A/C, which was causing my engine revs to drop markedly when the compressor cut out. The plug orientation is the same as the 427, and offset as Derek says, but that's makes no odds.

Margate Exotics.

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  • Gold FFM

Took the car for its MOT today, and ended up doing a good long run, with some town work thrown in. The 421 valve appears to work just fine, and a little better than the 427 (sorry, Barry!). This could of course be me wanting that to happen, but I felt the issue I had with revs dipping so much when the compressor cut out when the engine was idling is no longer as bad.

So, 217-421 it is, for me at least.

Margate Exotics.

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