RangeRovers.net Forum banner

1 - 8 of 8 Posts

·
Registered
1970-1995 Range Rover Classic
Joined
·
182 Posts
Discussion Starter #1
In my 1994 RRC I replaced the IACV with a generic Chevy unit a few years ago. It does function, but the distance per step is too far. Meaning it will open the valve on engine shut off, but when it closes it, it happens too fast (each step moves the valve face too much). When cold, not an issue, it just shuts down to 600 or so RPM really fast. When hot, it will close so fast, the ECU doesn't have enough time to react as the RPMs come down, and it will often stall, or it may catch it just before stall and open the valve fast again, then settle in. Then you can fire it back up again and it might be fine... Or stall.

So for a long time I've had the theory that distance per step is too much. Guess, what, I was right! WIN!

I found another cheap unit on ebay, from seller 'tomautoparts' . It is advertised as an AC1, but looks like many others. Got it in 2 days from this link:
https://www.ebay.com/itm/BRAND-NEW-FUEL-INJECTION-IDLE-AIR-CONTROL-VALVE-FOR-CHEVY-GMC-HUMMER/221988464766

Price: $8.50 delivered! 1 year warranty.

So I connected it, and it started, held at maybe 1200 RPM or so, for about 10 seconds, then beautifully, slowly, began to inch the throttle down ever so nicely! The unit was backed off quite a ways to avoid damage during first install (smart), and this probably accounts for the small delay before I noticed actual throttling. Tried it again, and it definitely backed off the correct amount and did another perfect throttle down from about 1200. So, hey, if you have any trouble, it's worth a swap out at that price!

I have exactly 2 cycles on it, so that's all I know about longevity. This one definitely controls the engine right though! Yay!!!
 

·
Registered
1970-1995 Range Rover Classic
Joined
·
77 Posts
As the saying goes, your mileage may vary. I've bought several generic chevy astro van IACV, very cheap sure and some had a white AC1 stamped on them. Most seem to work fine at first but seem to start sticking at about 20,000 to 30,000 miles. I've bought at least 2 that had problems right out of the box. I have a 95LWB, 236,000 miles on it. They seem to clean OK, but then stick again in a year or less. The current IACV I'm using came off a 1994 LWB in a scrap yard with 117,000 on it. I've added 10,0000 to it and it is fine for now. I carry a spare (they are small) and just consider it something that needs to be replaced ... like the spark plugs. I suspect the Rover OEM IACV is higher quality than most of the ones that fit and work for a while. Jon G
 

·
Registered
1970-1995 Range Rover Classic
Joined
·
182 Posts
Discussion Starter #4
Or... Maybe not... Now the new unit acts like the old unit. I think both are fine. When new, maybe the ECU detects an open circuit and does very modest adjustments for a while. But after it has learned the final positions that worked last time, maybe it goes to the normal position a lot faster. Not sure. Now I'm checking whether maybe the coolant temp sensor is not to spec since it only happens hot. 27 ohms hot currently, about 140 after 1/2 hour, but still pretty hot. Not sure what is correct. I'm going to disconnect it for a few minutes and see if it resets to the slow motion mode. But it looks like the ECU is sending the steps too fast. Anyone have a coolant temp chart ohms vs temp?
 

·
Registered
1970-1995 Range Rover Classic
Joined
·
13 Posts
do you have new gaskets, so that the depth is correct ? also - have you de-carbon'd your intake (spray, etc...) ?

I would think a big quality leap is made to the rover unit, however, it might be about the same as the GM difference between OE and aftermarket.

Great cross sourcing ! you will find it soon... keep looking..
 

·
Registered
1970-1995 Range Rover Classic
Joined
·
77 Posts
Four thoughts here on chasing an intermittent fault, on my 95 LWB the first time I cleaned and re-gasketed the entire intake assembly, at around 135,000 on the engine there was a lot of built up carbon every where... so yes, I agree, make sure it is all clean with new gaskets. There are some good step by step, how to's on how posted. Second I have messed up the IACV by forgetting to screw the pointy tip all the way in after cleaning, before reinstalling it. Seems like I ruined some plastic threaded component inside and it would work only intermittently, or stick sometimes. I should repeat... the carbon buildup at 135K was impressive... not sure why as it still doesn't use much oil. Maybe 1.5 quarts every 5000 miles, and most of that leaks out. BUT I've gotten over 100,000 MORE miles out of the same engine. Third thought; I've had issues with the 4 wire connector plug that connects to the IACV too. That plastic is typically old and brittle; is the spring tab that holds it secure still there? OK 4th, that really cheap part may not be very high quality and it failed already. Jon G
 

·
Registered
Joined
·
13 Posts
I bought the same part recently, and just installed it yesterday. It starts, and runs, but acts the same as the old IACV acted. That said, the plug does not seem to want to plug in the entire way, and a bit of the green rubber around the plug can be seen even thought it will not go in any farther. But, for $8.50 shipped it was worth a shot.
 

·
Registered
1970-1995 Range Rover Classic
Joined
·
102 Posts
You could just screw out the base idle screw a couple of quarter turns. As in, get an Allen key that fits the screw, drive around until it tries to stall, pull over and give it a quarter turn. Do that a few times just until you aren't about to stall.

Some folks will say "But you're masking the problem!!! Don't touch the screw, the IACV does all that." And it theory it does, but in reality it sometimes doesn't do a great job. Worst case you screw the base idle screw out a tad too far and it throws a code. Just screw it back in a couple of quarter turns and clear the code.

Besides, isn't that what the base idle screw is for?
 
1 - 8 of 8 Posts
Top