Rover V8 IACV

[lrdmod]

Have an issue where my IACV is staying open, Rover V8 3.9 14CUX with R380. Motor came from a 91 classic, I used a Rovergauge to switch the ECU from AUTO to MANUAL

I have a VSS fitted, the code 68 gets thrown pretty quickly but doesnt seem to matter the idle is high (1200-1500) randomly. Sometimes I can blip the throttle and get it to come back down but not always. I did try replacing the IACV no fix

I never have an issue where coming to hault it wants to stall.

Anyone have this issue?

 

[evilfij]

Air leak on intake hose?

 

[expanse]

I never have an issue where coming to hault it wants to stall.

what are the o2 sensors showing? are the values fluctuating - and + or just + numbers?

edit; does this stalling happen the second you start the truck or once it gets warmed up?

 

[rocky]

I read that as it doesn't stall when coming to a stop. Intrigued to know whether this high idle speed is present when hot and cold?

Coolant sensor fail rarely, but if the ECU isn't seeing a signal due to a failed sensor or broken wire, then its not going to run right. If the wiring has continuity you can replace the sensor cheaply.

 

[Robert]

Have an issue where my IACV is staying open, Rover V8 3.9 14CUX with R380. Motor came from a 91 classic, I used a Rovergauge to switch the ECU from AUTO to MANUAL

I have a VSS fitted, the code 68 gets thrown pretty quickly but doesnt seem to matter the idle is high (1200-1500) randomly. Sometimes I can blip the throttle and get it to come back down but not always. I did try replacing the IACV no fix

I never have an issue where coming to hault it wants to stall.

Anyone have this issue?

rovergauge cant do that. you need to put a resistor in place of the park/neutral switch to tell it is a manual. the resistance is in the rave manual and the 14cux manual

 

[lrdmod]

Idle changes at random, cold or hot. Sometimes it acts up, sometimes it will be fine for a few weeks. It will also change while driving. (750 rpm then later at 1500). Never have an issue with stalling.

No vacuum leaks but will re-check

I didnt check the 02 sensors but will, thanks!

Temp sensor is fairly new but will check continuity and sensor, make sure they are reading and ohming out

There was a button to switch to manual but I will check which ohm resistor I made, I did put one in.

Thanks!

 

[evilfij]

So the random idle I had was a crack in the air intake hose, not a vacuum leak. The only way I found it was to take the intake hose off and really inspect it.

I also had something similar where the temp sensor wire was swapped with an injector, but that threw a code.

The bad part about 14CUX is that the sensors can go bad (o2, TPS, coolant and I suppose MAF but they are pretty durable) and do weird stuff without throwing a code.

Edit: I assumed that you replaced the VSS (aka road speed sensor) since that was the code you were getting. Did you?

 

[lrdmod]

Ill have to check the intake hose too, it is new but hey you never know...

I have the aftermarket TPS sensor (all you can get now)

Yes a new VSS, seems that it doesnt matter if the code is thrown or not on it. I have reset the ECU, code clears and still acts up...then later it will throw the code again.

 

[evilfij]

Do you have a spare ECU to try?

I know this is the most hack thing ever, but I just swap parts until I fix it. Lol.

You might also have a connection issue with the wire to the VSS.

 

[rocky]

Do you have a spare ECU to try?

I know this is the most hack thing ever, but I just swap parts until I fix it. Lol.

You might also have a connection issue with the wire to the VSS.

Sounds familiar SOP to me. I had a mystery no start scenario every so often, especially in high humidity or rain scenarios. Finally changed out the ECU after it gave us some weird numbers. Interior was corroded.

 

[pmatusov]

Have an issue where my IACV is staying open, Rover V8 3.9 14CUX

Have the same issue with a 3.9 in a Classic with ZF auto. I noticed that even if I pull the PCV hose off the port on the throttle body (one that connects PCV filter with the throttle body), the IAC valve moves to 30% closed. In my case, I suspect the PCV inlet port is completely plugged - however, the IAC valve remains open even with the oil cap removed.
PCV filter is clean.
Still investigating this thing.
Now, idle issue: if someone messed with the curb idle setting and opened it too much, it will cause fast idle that won't / can't be fixed with IAC valve (since it is already fully open). You can also look into the throttle cable linkage - make sure the throttle plate is closed.

 

[WeBeCinYa]

14CUX is trash. I’ve spent more time and money chasing issues on my trucks than I have on 4 boats. My last issue was broken wire. Good times.

 

[lrdmod]

Yeah, I have thought about going Holley EFI or something like that...lose direct injection but..

This issue is intermittent..it will be fine for a month no problem and then one day ill be coming to a red light and the truck will sit at 1500rpm and not drop for a week.

Then one day ill start it and be completely fine

 

[evilfij]

Just find a bunch of spares and swap as needed. Outside of one really weird one (intermittent short near starter than was frying ignition module — not the fault of 14CUX) I have been very happy with the simple 14CUX system. Then again, I have been around them for 25 years ….

 

[pmatusov]

Just find a bunch of spares and swap as needed. Outside of one really weird one (intermittent short near starter than was frying ignition module — not the fault of 14CUX) I have been very happy with the simple 14CUX system. Then again, I have been around them for 25 years ….

In my experience, a GEMS engine will run nearly perfectly until something fails catastrophically (the only such failure in 290kmi of my D1 was reluctor ring falling off the flywheel). In comparison, 14CUX will run progressively worse until it starts failing smog checks or becomes borderline undrivable.
If I could choose between the two, GEMS wins by a large margin.

 

[evilfij]

My experience with GEMS is that they run, but then the valves get coked up and you get misfire codes. Also, I have seen (but not had) issues with security system and swapping ECUs etc. they also don’t like it when the cats get themselves blown out.

Horses for courses but ….

 

[mgreenspan]

So the random idle I had was a crack in the air intake hose, not a vacuum leak. The only way I found it was to take the intake hose off and really inspect it.

I also had something similar where the temp sensor wire was swapped with an injector, but that threw a code.

The bad part about 14CUX is that the sensors can go bad (o2, TPS, coolant and I suppose MAF but they are pretty durable) and do weird stuff without throwing a code.

Edit: I assumed that you replaced the VSS (aka road speed sensor) since that was the code you were getting. Did you?

I had a similar issue once except the crack was in the intake plenum. I was not able to diagnose this, but Pikes Peak Rovers did.

 

[pmatusov]

I had a similar issue once except the crack was in the intake plenum. I was not able to diagnose this, but Pikes Peak Rovers did.

Interesting. I'll take a look.
I've been looking at the 3.9 crankcase ventilation scheme and parts - and found ERR4765 tee/restrictor. I need to check if on my truck it has been replaced by a simple tee - which would "short" the air input to IAC valve to the intake vacuum, essentially disabling it.
Bought the part on Amazon for $13; but, in a pinch, it should be easy to fabricate out of a tee.

 

[KGH]

Fully Programmable Engine Management Kit - Lucas 14CUX Rover V8 -

This is the complete kit to convert your Lucas 14CUX Rover V8 engine to a fully mappable fuelling and distributor-less (DIS) engine management system.

www.lloydspecialistdevelopments.co.uk

I have a little experience with their GEMS stand alone, and would think the 14CUX version would be just as capable.

 

[pmatusov]

Fully Programmable Engine Management Kit - Lucas 14CUX Rover V8 -

This is the complete kit to convert your Lucas 14CUX Rover V8 engine to a fully mappable fuelling and distributor-less (DIS) engine management system.

www.lloydspecialistdevelopments.co.uk

I have a little experience with their GEMS stand alone, and would think the 14CUX version would be just as capable.

LOL, £3200 buys more than one complete GEMS engine with ECU and wiring harness
14CUX is not as capable as GEMS for many reasons.