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Injected TR8 searching for idle

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gozto11 Avatar
gozto11 Todd Bermudez
Cincinnati, Ohio, USA   USA
Hi there

New issue after a couple years of trouble free running

Once the engine warms up, it starts hunting for idle. It's a factory injected car. The computer was done by Jim Tencate.

Before I start swapping parts, is there anything that's common?

When I brought it back to life, I'd had the ECU checked and re flowed, replaced all fuel lines, fuel pump(Bosch), filter, wires, pertronix dizzy, intake gasket...yada yada

Regards

Todd

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darrellwalker Darrell Walker
Vancouver, Washington, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
There isn't any active idle speed control, so nothing there to suspect. How old are the O2 sensors? I might try replacing those (or even just disconnected them as a test) to see if they might be affecting the mixture. Same for the TPS, I've not heard of issues at idle, but you can disconnect it to see if it makes a difference.

Also confirm there are not any vacuum leaks, and check that the AFM isn't sticking.



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA

gozto11 Avatar
gozto11 Todd Bermudez
Cincinnati, Ohio, USA   USA
I'll check for air leaks...didn't replace many or any of the air hoses.

As for the O2 sensors...I had the exhaust replaced so they're just hanging there doing very little. Should they not be permitted to hit metal?

Todd

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darrellwalker Darrell Walker
Vancouver, Washington, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
So by hanging there, out in the open air? If so, they probably won't report anything the ECU will pay attention to, since they need the exhaust heat to get up to temp and do anything. It might be better to unplug them altogether, though. So that would mean you are running open-loop (no air-fuel ration feedback to the ECU). That will not allow the ECU to make fuel adjustments, so any thing else that is out of spec will be more apparent. It might also mean you are running rich or lean at idle, and one of those can cause a hunting idle (I forget which).



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA

Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1485004 by darrellwalker There isn't any active idle speed control, so nothing there to suspect. How old are the O2 sensors? I might try replacing those (or even just disconnected them as a test) to see if they might be affecting the mixture. Same for the TPS, I've not heard of issues at idle, but you can disconnect it to see if it makes a difference.

Also confirm there are not any vacuum leaks, and check that the AFM isn't sticking.

Either the air flow meter (AFM) or the throttle position sensor (TPS) is most likely on its way out. Since they are difficult to find, you should start with the cheap easy stuff even though it is less likely. The coolant temperature sensor comes to mind. Also, if the thermostat is acting up, the wrong temperature, or stuck open, the coolant temperature will not be correct, and the ECU will get confused. It could keep the cold air valve from closing, or the ECU might think the car is not warming up.

And if it were me, I would have an exhaust shop weld some bungs in your new exhaust, and reinstall the O2 sensors. The whole fuel injection system is predicated on the O2 sensors working, and if they are not then all bets are off as to how the engine will behave. Whoever told you to ignore the O2 sensors was no expert in FI systems. I suppose that Jim Tencate may have reprogrammed the controller to not use the O2 sensors (European cars did not have them) in which case you should disconnect them entirely. Short of that, you should get them reinstalled in the exhaust system.

If that doesn't do it, you need to look at your AFM and TPS. The AFM can be rebuilt by a specialist if it is worn out. The TPS sensor can be replaced with a substitute.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

gozto11 Avatar
gozto11 Todd Bermudez
Cincinnati, Ohio, USA   USA
Yeah they're open air for lack of better words

It hasn't made any difference in running in the past 2 - 3 years.

I've been reading where the aux air valve can possibly cause goofy idle too. It starts right up

navydiver Rob Cornick
san diego, california, USA   USA
1975 Triumph TR7 "The Pumpkin"
1977 Triumph TR7
1978 Triumph TR8
1980 Triumph TR7 "The Plum"    & more
If it's hunting I'd suspect an air leak, could be from any of the vacuum pickups, the vacuum to the distributer, or the brake booster the EGR valve. quite often the rubber elbows have hardened and have micro cracks which admit air. could also be the cold start injectors leaking.



1975 TR7 FHC Ca Spec ACL 4spd
1976 TR7 FHC Ca Spec 4 spd (Temp add)
1977 TR7 FHC ACW 5Spd
1978 TR8 DHC ACT FI development car 5 Spd
1980 TR7 DHC FI Spider 5spd
1980 TR7 DHC FI Spider 5Spd
1980 TR7 DHC FI 5spd
1980 TR7 DHC FI 5 spd
1981 TR7 DHC FI 5 spd

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Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1485105 by navydiver If it's hunting I'd suspect an air leak, could be from any of the vacuum pickups, the vacuum to the distributer, or the brake booster the EGR valve. quite often the rubber elbows have hardened and have micro cracks which admit air. could also be the cold start injectors leaking.

I had forgotten about the cold start injector.

YES! That is a good suggestion, so +1 on that.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

gozto11 Avatar
gozto11 Todd Bermudez
Cincinnati, Ohio, USA   USA
So unplug it...see what happens?

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navydiver Rob Cornick
san diego, california, USA   USA
1975 Triumph TR7 "The Pumpkin"
1977 Triumph TR7
1978 Triumph TR8
1980 Triumph TR7 "The Plum"    & more
unfortunately it doesn't work like that in my experience, if the fuel rail is pressurised the injector will leak. you have to disconnect the fuel line from the injector and plug it.



1975 TR7 FHC Ca Spec ACL 4spd
1976 TR7 FHC Ca Spec 4 spd (Temp add)
1977 TR7 FHC ACW 5Spd
1978 TR8 DHC ACT FI development car 5 Spd
1980 TR7 DHC FI Spider 5spd
1980 TR7 DHC FI Spider 5Spd
1980 TR7 DHC FI 5spd
1980 TR7 DHC FI 5 spd
1981 TR7 DHC FI 5 spd

carltr7 Avatar
carltr7 carl g
halifax, ns, Canada   CAN
I believe hunting is caused by a lean condition.

on an EFI this means the ECU isnt commanding enough injector time.
its doing that because its got the wrong idea about how much fuel it needs from it lookup tables.
the lookup table say "for this amount of O2, you squirt this amount of fuel".
it reads its lookup tables based on data from the sensors.
the sensors responsible are the MAP (or MAF) and O2.
map/maf measure how much air is coming in and can be disrupted by IAC, MAP and/or MAF problems, connection problems and IAC problems.
O2 measures how much air got burnt and can be disrupted by O2 sensor problems stuck EGR or bad connections.

Ive probably missed some out tongue sticking out smiley

dhuddleson Avatar
dhuddleson David Huddleson
Manotick, Ontario, Canada   CAN
Even though the ECU has been serviced by Mr. TenCate, do you have access to another ECU that you could swap over? I would want to rule out the ECU since it is easy to test (but only if you have another to test with...).

gozto11 Avatar
gozto11 Todd Bermudez
Cincinnati, Ohio, USA   USA
In reply to # 1494208 by dhuddleson Even though the ECU has been serviced by Mr. TenCate, do you have access to another ECU that you could swap over? I would want to rule out the ECU since it is easy to test (but only if you have another to test with...).

I do actually.

So we made it out to Hershey PA & back for 6-pack TRials. On the way back it quit on the interstate...while decelerating. It likes to backfire. Anyway, pulled over and it restarted. Made it another 4 hours without issue. Then the wife is out driving it, and the battery light comes on. Of course I haven’t driven it yet. The alternator is a new Saturn conversion

I’ll get it out one of these days

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