Chazz

RX8 won't rev beyond 3,100rpm in 5th and 6th gear

175 posts in this topic

Okay here's what happened tonight/morning...

Belting up a steep incline of approx. 50/60 degrees to get on to the M50 motorway in 3rd gear @6,200rpm approx. Slapped her into 4th, no problem.

On the motor way at this stage and travelling downhill, put her into 5th gear and she started to loose power.

Put her back into 4th gear and the revs and speed picked up, but once she put into 5th and 6th gear I can't get her to rev beyond 3,100/3,300rpm.

She'll go beyond 7,500rpm in 2nd and 3rd and more if there were no speed limits!:ph34r:

Pulled in and she idles ever so slightly rough.  911rpm, 6.07 MAF, Engine Temp 86 degrees. Turned off engine and back on again, no problem.

Engine was rebuilt July 2015, only approx. 24,000km on her at this stage. D585 ignition system, all new plugs and leads all fine. Mini-mapped. Oil changed every 3500km approx. Gutted CAT. VFAD put back in its original flow position 2 weeks ago (drinking petrol otherwise).

Now I have the Secondary Air flow pump removed about 6 months and a blanking plate in place and still get the CEL P410 and P2259 now an then and I clear them.

Those are the only two OBD2 codes that ever come up.

I'll take a look at the MAF tomorrow morning, but anyone on here any other thoughts?!:huh:

 

 

 

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MAF would make sense alright, might be to early in the morning for me but can't think what else would do that in 5th and 6th only. I'm not big on gearboxes but ours don't have any fancy stuff that would regulate like that do they?


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Check your plugs and leads are all still tight Chazz after that, maybe fuel pump or injectors - it sounds like it might be getting starved of fuel or spark

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Update - Today.:angry:

 

Well the MAF was spotless, so nothing there. No OBD codes other than P2259 and P0410 for the removed secondary air pump.

 

So I disconnected the battery for about 20 minutes, then reconnected and did the 20 stomp dance on the brake pedal within 8 seconds to be sure I'd reset everything.

She started up fine as usual and I took her for a good 86km spin on the M50 to test her out. Southbound then northbound, then back southbound.

 

1st gear took off fast as usual, revving to 4,000rpm before changing to 2nd gear. Same again for 3rd and 4th gears. I always take her to 4,000rpm before changing gear, traffic permitting.

 

So all was fine, 5th and 6th gears revs, speed pickups, all normal, (didn’t go beyond 7,000rpm), till 60km in. Noticed a slight hesitation when trying to pick-up speed through ALL the gears. At one point taking off in 1st gear felt like trying to take off in 3rd or 4th. Example was when taking off in 1st, revs up at 4,000rpm but moved off slooooowly!

 

Pulled her up and she idled badly around 920rpm. I could feel vibration through my seat!

Turned off the engine, waited 10 minutes then started her up again and she was hesitant for about 5 seconds before she coughed and spluttered to life as if there was too much fuel dumped into the engine.

So after total 87km test run was none the wiser. Coils, leads, sparks, MAF all fine. Can’t find any air leaks either. Decided to rest her up and have a thing for a few hours….

 

Update – Tonight.:(

 

Ignition on, she fired up after a splutter. Took her for a spin AGAIN, but this time I kept the revs under or on 4,000rpm through all the gear range. Travelled 22km this time under the “no going over 4,000rpm” I set myself and she performed perfectly as normal, fast take offs, pickups quickly as long as she’s not pushed beyond 4,000rpm I've concluded from test run earlier today.

 

Pulled in, turned her off. Waited…turned her back on and she fired up perfectly without hesitation.

So, as @REX said and my thoughts are, I’ve a fuel and or air starvation when I go above the 4,000rpm mark.

VFAD problem? Fuel pump problem? These are at the front of my mind at the moment or am I WAY OFF!

 

All other thoughts, conclusion, are most welcome at this point!;)

 

Now I'm off to smash all the light-bulbs at the top of the forum page...might make me feel better!:lol:

Edited by Chazz
Aido 8 and littlefeck like this

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Hmmmm - really sounds ignition related @Chazz especially with the spluttering and rough idle. Have you checked all the leads for damage at the connections, pulled the plugs ? 

Could be a coil also.

i doubt if it's the vfad as the symptoms sound too severe. I have herd of the odd case where a connector has worked loose around the ECU causing limp home mode with no cel but it doesn't seem like yours is in limp home. 

If you have spare leads, plugs etc I'd start there.

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Just as a quick check before you go too in depth. Can you check the earthing point from the battery negative to the the cross bar that runs under the air box.  May be worth removing it the cleaning with a wire brush. This could cause the symptoms you describe. It would also be worthwhile adding a new ground wire from this point to the engine as the grounds will be getting worse depending on car age.

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Will do Jamie, thanks
I'll do so tomorrow.
What I did do yesterday was, as I found no problems with the ignition system (D585 rig), reversed the VFAD one-way valve again so it's permanently in the OPEN state, took her for a good 114km trashing and no problems whatsoever .
No CEL on dash either. However, I did do a OBD scan and the P0420 came back. It's a strange one!

bf62732faff1f37a46b4130654cd1210.jpg
5261b1a2677cbeae0af3979b5d8add88.jpg




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Chazz I wouldn't mind plugging the laptop to recheck the flash. The p0420 would still show up as a pending code with the obd reader but would not trigger the check light

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Posted (edited)

Okay here's an update to my RX8 power woes.

Took out the spark plugs, all fine nice brownish colour, NOT white or black. Leads, no breaks, seat tightly on plugs and coils. D585 Coils perfect, same with the harness.

All earths clean and tightly fitted. MAF clean, and air box and filter spotless. Throttle body clean as well.

No air leaks either.

Now when I had all the above out of the car and the Negative terminal on the battery disconnected, I noticed that the earth lead from the D585 coil harness adaptor was no longer attached to the negative terminal connection where I had connected it originally. It was now connect to an earth point under the air box by the engine rebuilder.

Hmmm I thought!;) Maybe I've a bad earth connection, looked pretty grimy. So I put it back where I had it before, on the negative terminal battery connection, and that's when I noticed that the Positive battery terminal connector was loose, as in NOT making a good connection.

Ah Ha! That could be the problem after all!:)

Put everything back together and off for a spin now!

Edited by Chazz
Rex Ruthor and jp like this

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Well back from my spin and f*&$ %t.:angry: :angry:

All seemed fine through the gears till I got her over 6,000 rpm this time and a ping ding noise and a short splutter every now and then until I eased off.

Coupled with the sounds as if something was hitting off the exhaust and loss of power in the 4th, 5th, and 6th gears in the high rev range (6,000 - 7,200 rpm).

Now it wasn't cutting out, just dropping to 3,000 rpm and running sluggishly through all the gears, like in limp mode. No CEL's or anything to report.

Even in 1st gear taking off from lights it was like driving a bus. The cyclists were faster.:wacko: Oh the shame!:ph34r:

So after some thought I believe she's having breathing / pressure problems, and I've a gutted CAT, so I think the exhaust back-box maybe knackered with a blockage.

Reason for this latest belief, is that the car runs perfectly as long as I don't take her beyond 6,000 rpm in any of the gears putting her under any adverse load.

She quite happily hits the Beep when not in gear only, but will NOT back fire and she does try too.

So tomorrow I'll take the exhaust system off and have a look see. I hope I find a blockage in the exhaust system.:)

 

 

 

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12 minutes ago, Rex Ruthor said:

Doozy @Chazz - fuel pump is all I can think of at this stage 

Was thinking that too @Rex Ruthor and even the injectors but, if they were the case, I'm thinking surely she'd have problems starting and running at all?

Anyway, fingers crossed it's the exhaust system as I've watched the YouTube vids on removing the fuel pump etc., and it's not an easy job.

 

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Thanks @Rex Ruthor I'll let you know.

Unfortunately I didn't get to the exhaust today due to rain.

However, I checked the SSV actuator and VDI actuator in case either one or both valves where blocked or sticking...both moved freely, so no issues there. Same with VFAD.

Tomorrow I'm heading up to Dungannon in Antrim and back again so I'll have a better idea as to WFT is going on.

The long trip should give me a better idea as problems arise. I'll have DashCmd running on the Tablet to record live data as I go.:wacko:

Now I will slacken off the bracket between the mid-pipe and the back-box, thereby creating a leak for gases to escape and drive her like I stole her.:lol::P

If that works I then believe the back-box is the problem area. If not, back to the drawing board.

 

Will update tomorrow evening.:rolleyes:

 

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I was having similar trouble a few weeks back and after fitting the coils and leads you loaned me the car is running better than ever.

I bought the d585 coils, leads to match and the harness adapter about a year ago but never got round to fitting them. Your more than welcome to the lot and see if you see any difference?? Worth a shot.

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@Kuro 078/500,@Doobert, @Rex Ruthor thanks for the offer guys

Trip up and back from Dungannon Co. Tyrone was a hit and miss. Problem occurred then disappeared then reappeared and disappeared. It's a head scratcher, in fact it's beyond than, it's more a ball scratcher at this stage.
There's no problems starting, all is fine. I can travel for ages without issues one day and the next she becomes problematic going over 6500/7000 rpm.
She doesn't conk out or anything just doesn't want to pull quickly.
More tinkering with her tomorrow.



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Best of luck, hope you get to the bottom of it.

If you need it the cat back it's there for you anytime.

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Has anything hit your crank angle sensor recently?

And where did you get the harness for your D585s? Might be worth checking the continuity on each of the wires for it if you've not swapped in an alternative set of OEM coils in the meantime. I've a set down in Jamie's (near-new Mazda C-coils) so if you're down that way before Saturday you're welcome to try them out; otherwise I may bring them back with me to South Dublin on Saturday if you fancy trying them out.

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Crank angle sensor? I'll have a check on it. Thanks JP


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While trying to find what's causing my problems I noticed this bolt loose.
Photo below.
0ce3e16ea36b37031ad2f6d6a37fed35.jpg

Just as well@JP I took your advice to check the crank sensor otherwise I'd have never known that that bolt was loose.



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So took out the crank sensor and cleaned what little dirt was on it.
ed7cbdff8990d91e2083a1d35381952b.jpg
Looks fine and good plug contacts.

Tested the continuity on the spark plug leads, all 100%.
Tested the continuity on the D585 harness, earth and all other points, 100%.

So took a look at the D585 coil packs again and this is what I found.
Photo 1 - 3 of the coils look like this. Good clean brassy electrodes.
2a6ec060d5091dd225ad745b9b4fa5c3.jpg

Photo 2 - 1 of the coils electrodes, the L2 on my setup, is not so clean and brassy.
d40b3d940594e739b66fc63ece81df24.jpg

So I believe I may have found my problem. Bearing in mind I'm not getting any CEL codes pertaining to ignition etc., I think I'm getting arching between the spark plug lead and the coil electrode on the coil in photo #2 above.
Tomorrow I'll pull out the L2 spark plug and see if there are any issues with it.



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