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Rough idle - TPS? 

 

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 Post subject: Rough idle - TPS?
Posted: Thu Nov 22, 2012 11:14 pm 
Getting Side Ways
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Ride: EF XR6 Wagon, AU2 XR6 VCT

Power: 148 rwkw

Location: Auckland
New Zealand

Last week, my AU2 XR6 VCT suddenly developed a rough idle (fine driving to work, rough as soon as I started the car to head home). It feels like a lumpy cam - NOT like running on five cylinders. There is also mild popping out the exhaust at idle. Fuel economy is unaffected, not running rich, and idle RPM is normal - not hunting. It's especially noticeable when crawling along at idle riding the brakes in heavy traffic - very jerky. It runs perfectly normally at anything other than zero throttle.

So far:
- new coilpack
- new spark plugs
- checked ignition leads (all fine)
- cleaned throttle body and ISC valve
- checked intake manifold, vacuum hoses & brake booster for leaks using start spray
- checked PCV valve

Tonight I checked the throttle position sensor. Volts are 0.6V zero throttle, 4.2V WOT; manual says approx 0.7V and 4.5V. Resistance is 7K ohms zero throttle, 3.5K ohms WOT; manual says 3K and 500 (0.5K) ohms, respectively - quite a difference. Could this be the cause of my rough idle? ECU not recognising that the engine is in idle mode? I tried cleaning the TPS with Contact Cleaner, but it made no difference. And I don't have access to a scantool to pull fault codes.

Thanks for your help.

EDIT: Have bought a used TPS; will install on the weekend and let you know how it goes.

 

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95 EF XR6 wagon, 17" FTRs, DBA, QFM, KYB/Koni, AU block, ported EF head, SS Inductions, Territory intake, MLS gasket, milled, Franklin RH24B cam, Coby headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip

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 Post subject: Re: Rough idle - TPS?
Posted: Fri Nov 23, 2012 5:23 pm 
Getting Side Ways
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Joined: 1st Apr 2005

Gallery: 4 images

Ride: EF XR6 Wagon, AU2 XR6 VCT

Power: 148 rwkw

Location: Auckland
New Zealand

Well, it wasn't the TPS. The new (used) one made no difference. I have a spare set of injectors, so will try that next, I think - unless someone has a better idea.

 

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95 EF XR6 wagon, 17" FTRs, DBA, QFM, KYB/Koni, AU block, ported EF head, SS Inductions, Territory intake, MLS gasket, milled, Franklin RH24B cam, Coby headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip

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 Post subject: Re: Rough idle - TPS?
Posted: Fri Nov 23, 2012 5:29 pm 
Getting Side Ways
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Ride: 5 speed XG ute

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When its idling and you blip the throttle, the revs will rise (obviously) but then do the revs drop right back to basically nothing? or just go back to normal idle?

 

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 Post subject: Re: Rough idle - TPS?
Posted: Fri Nov 23, 2012 5:31 pm 
Getting Side Ways
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Posts: 836

Joined: 1st Apr 2005

Gallery: 4 images

Ride: EF XR6 Wagon, AU2 XR6 VCT

Power: 148 rwkw

Location: Auckland
New Zealand

The revs go back to normal idle (750 rpm), but sometimes hang at 1000-1200 rpm for 3-5 seconds. I don't think that's new though.

 

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95 EF XR6 wagon, 17" FTRs, DBA, QFM, KYB/Koni, AU block, ported EF head, SS Inductions, Territory intake, MLS gasket, milled, Franklin RH24B cam, Coby headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip

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 Post subject: Re: Rough idle - TPS?
Posted: Sat Nov 24, 2012 10:00 am 
Getting Side Ways
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Posts: 836

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Gallery: 4 images

Ride: EF XR6 Wagon, AU2 XR6 VCT

Power: 148 rwkw

Location: Auckland
New Zealand

Well, replaced all the injectors with clean used ones, and no change. Tried all the vacuum lines and intake manifold gaskets with start spray, and no leaks that I could find. Unless it's one of the lines inside the dash actuating the ventilation system.

I have disconnected the battery to reset the computer, to see if that helps. Failing that, I have a spare ECU I can swap in.

Any other suggestions?

 

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95 EF XR6 wagon, 17" FTRs, DBA, QFM, KYB/Koni, AU block, ported EF head, SS Inductions, Territory intake, MLS gasket, milled, Franklin RH24B cam, Coby headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip

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 Post subject: Re: Rough idle - TPS?
Posted: Sat Nov 24, 2012 10:34 am 
Getting Side Ways
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Posts: 836

Joined: 1st Apr 2005

Gallery: 4 images

Ride: EF XR6 Wagon, AU2 XR6 VCT

Power: 148 rwkw

Location: Auckland
New Zealand

Resetting the computer did nothing.

I swapped the ISC valve - it made no difference. Disconnecting the ISC dropped the revs by about 100rpm, but it still idled rough.

Next is swapping the ECU.

Any other suggestions?

 

_________________

95 EF XR6 wagon, 17" FTRs, DBA, QFM, KYB/Koni, AU block, ported EF head, SS Inductions, Territory intake, MLS gasket, milled, Franklin RH24B cam, Coby headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip

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 Post subject: Re: Rough idle - TPS?
Posted: Sat Nov 24, 2012 7:12 pm 
Getting Side Ways
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Posts: 836

Joined: 1st Apr 2005

Gallery: 4 images

Ride: EF XR6 Wagon, AU2 XR6 VCT

Power: 148 rwkw

Location: Auckland
New Zealand

Found the problem. Intake manifold gasket was leaking. Could only find it by spraying start spray with the nozzle basically touching the gasket. When I took the gasket out, it was so brittle that it broke into multiple pieces. Replaced it, and it's sweet again.

 

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95 EF XR6 wagon, 17" FTRs, DBA, QFM, KYB/Koni, AU block, ported EF head, SS Inductions, Territory intake, MLS gasket, milled, Franklin RH24B cam, Coby headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip

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 Post subject: Re: Rough idle - TPS?
Posted: Sat Nov 24, 2012 8:26 pm 
Getting Side Ways
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efxr6wagon wrote:
Found the problem. Intake manifold gasket was leaking. Could only find it by spraying start spray with the nozzle basically touching the gasket. When I took the gasket out, it was so brittle that it broke into multiple pieces. Replaced it, and it's sweet again.


That test work better with carby/throttle body cleaner. Just give the manifold gasket area a good soaking. the engine will smooth out when you hit the section of gasket that leaking.
It's pretty common on AUs these days.

 

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 Post subject: Re: Rough idle - TPS?
Posted: Sat Nov 24, 2012 8:41 pm 
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Ride: 2002 AUII Fairlane Sportsman V8

Location: Roxby Downs
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efxr6wagon wrote:
but sometimes hang at 1000-1200 rpm for 3-5 seconds.

This should of been a fairly good indicator that the inlet manifold gasket was leaking.

my sis's EF was doing the same but sometimes at 2000RPM's
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