3.9 EFI slow hunt at idle.

**Homestar** · 8th January 2016, 05:15 PM

No aircon to worry about yet - that's on the to do list, and I still need to find someone who is able and willing to do that.

I cleaned the maf and the stepper but it's still the same - haven't cleaned the throttle body or anything yet - I'll do that in the morning.

The slow operation of the stepper at startup does have me thinking it's on the way out. The other worry is how hard it revs with little oil pressure when it's cold - it builds pressure quickly, but it can't be good for the engine. How quickly should this drop the revs back to idle? It takes around 10 seconds at the moment.

The engine and trans is a transplant out of D1 into an 85 RRC, so it's as basic a setup as you can get - no O2 or VSS.

Apart from that, everything seems fine - it has plenty of power (for a rover V8

) and drives well.

Another quick one I'll tag in here - the temp sits on about 90 the whole time - is this normal? What thermostat do these run? From the engine temp, I'm guessing about an 88 degree? Is it worth while putting something cooler in or am I just being paranoid? Last thing I want to do is cook this engine (although that would give me an excuse to drop a 350 Chev in it) but I don't want to be doing that any time soon - it's taken me 3 years to finish this conversion off, and it was a straight bolt in...

**PhilipA** · 8th January 2016, 07:53 PM

Another quick one I'll tag in here - the temp sits on about 90 the whole time - is this normal? What thermostat do these run? From the engine temp, I'm guessing about an 88 degree?

Yes they have an 88degree thermostat.
You could try an 82 but be aware that in winter the car may stay in enrichment as 80c is the cutoff for enrichment in the ECU. It is not a lot at approx 5% but probably enough to affect fuel economy.
Regards Philip A

**Homestar** · 8th January 2016, 08:15 PM

Thanks, I'll see how it goes. The entire cooling system is in very good condition so I'm not expecting any dramas - I'll see what it's like on a hot day and decide after that. The 3.5 ran at 82 so just trying to establish a base line for this engine.

**aussearcher** · 2nd February 2016, 09:09 PM

Bacicat,
I have a '98 V8 D1 (3.9 now 4.5) with the same symptoms. The stepper motor is always the most likely culprit, but after two new steppers and three "known to work" used units I decided that this was not the problem on mine. (Based on this, you'd be right in concluding that I'm a slow learner...). The problem I had was that the fault was intermittent. Whenever I took it in for a diagnostic it ran perfectly. Another twist is that when a fault code showed up it was the stepper. Anyway, it has been with the experts for the last couple of days and they have decided that it is an intermittent fault in the MAF, which is causing overfuelling that the stepper can't adjust for. So, a "known to work" second hand MAF on it this afternoon and we'll see how we go. If it doesn't I'll just bite the bullet and change out all the input devices - speed sensor, the throttle position sensor, and the two temperature thermistors. I'm not a fan of the aftermarket MAFs and OEM ones are either ridiculously expensive or unavailable, so on that front I'm investigating the alternatives the TVR and Ginetta crew are using in the UK.

**Homestar** · 3rd February 2016, 05:14 AM

Thanks for that - it's now developed different symptoms - the idle won't come down at all now - it runs up to 2,500 RPM when started - and stays there....

It wasn't much fun moving it the other day I can tell you - the driveline took a beating when I put it in gear...

So, got to sort that one out now.

**aussearcher** · 3rd February 2016, 07:09 AM

Sounds luck a stuck stepper...
Not sure about the rules of this forum regarding mentioning vendors, so I'll PM you.

**Homestar** · 3rd February 2016, 08:13 AM

Originally Posted by aussearcher

Sounds luck a stuck stepper...
Not sure about the rules of this forum regarding mentioning vendors, so I'll PM you.

Thanks - got your PM.

. I think I've been putting off buying one, but I might have to just suck it up and grab one. I'll be in the city later today - I'll swing past BCC and grab one.

You can mention vendors on here as long as you aren't bagging them out (name and shame)

Cheers - Gav.

**PAT303** · 3rd February 2016, 04:49 PM

Mine did what your described and it was the stepper,I cleaned it first and it worked well for another few weeks and then started again.One thing I found is to not use the gasket but gasket goo,the plenum is alloy but the bolts are steal which causes them to loosen over time,use non hardening gasket goo with thread locker on the bolts with a new stepper and see how you go. Pat

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