4.6 idle problems.... Ideas?

[daljames]

Hi All,

Since i changed my GEMS injectors to bosch GEN III injectors ive developed an idle problem. It also did it when i first got the car and degreased the engine bay, but went away. Now its back to stay.

When i start it from cold or hot it will idle around 1200 even go to 1800. If i put the car in gear it will settle to 800-850. Take it back out of gear and it will settle around 900. Hot or cold.

Ive cleaned the idle control valve. I hooked up a basic obd tool and it tells me my throttle position sensor at idle is 17%. When i put my foot on the accelerator and then take it off it goes up and down in percentage. Holds steady if i hold the pedal steady.

Any ideas??

[clubagreenie]

Try to get a spare TPS and swap out to see if it fixes it. If it's seeing 17% TPS then it'll raise RPM as it thinks there's a foot on the accelerator. Seems most likely as when it's touched it drops back to idle speeds.

[Rupert Prior]

17% is slightly high for throttle closed but only by 1 or 2%. try bringing it back to 16% and checking for air leaks.

[daljames]

thanks heaps. I didn't know you could adjust them. How do you lower the percentage?

[PhilipA]

The accelerator cable wouldn't be too tight by any chance?
You would have had to remove it to remove the plenum.
Regard sPhilip A

[daljames]

Hi Philip, the throttle cable has just a slight amount of play so it it is ok. I have checked the intake and it is fully closed. Im guessing it is either the idle control valve or TPS. Im just trying to guess which one now i think...

[Rupert Prior]

it is possible to adjust the throttle pot on its two mounting screws (above the stepper motor) but you should never normally touch these. usually the problem is something else. check there is some slack in the throttle and cruise cables.
check there are no air leaks into the manifold from, split hoses,
bad gaskets, injector o rings or incorrectly fitted vacuum tappings.
check the throttle blade has at max 2thou top and bottom and
does not jam closed in the body. (if it is slightly out top and bottom, losen the 2 screws on the blade and let it slam shut 2 or 3 times then tighten the screws and recheck. if it is still out repeat the procedure but let it shut on an old 2thou fealer gauge).
check live readings and check throttle position and if possible the learned throttle closed position, 0.6v to 0.85v.
now depending on what model lucas system your car has and what scanner you have you can go further with adaption resetting but it would be easyer if you phone me (0421 509 083)

[daljames]

Thanks Rupert. About to head overseas tomorrow so its a job for when im back in a couple of weeks. Ill be in touch then. The throttle cables have slack and the throttle blade all operates normally. I tried the allen key screw. Whilst this reduced the idle, the problem still exists as when i start it it is excessive until i put in gear then settles back in the same manner, its just the whole process just occurs at lower revs with the screw adjusted. If i order a new TPS, do i have to get the ECM reset??

[Rupert Prior]

the adaptions should be reset but you don`t have to do it. also if you reset the adaptions on some early models they will run rich until an open loop tune is done.
if your tps reads ok there is probably nothing wrong with it.
i have a new tps as a test unit if you want to try it.

[cockie55]

If this occured imediately after you changed your injectors then highly likely it is related and simple, particularly with those things thjat have been disturbed during fitting of those injectors. For instance check hoses and plenum/ram bolted connections (used a light non setting sealant??) for air leaks, all cables inc cruise, TPS, ICV, fuel and engine temp sensor connections etc.

One other thing your new injectors will atomise better and cause fuel to burn faster and sooner. I recall you have a Unichip so amount of advance might need to be backed off a couple of degrees with new injectors, particularly if it was agressively tuned at setup using old injectors.

[daljames]

Thanks heaps. I did use a non setting sealant so will re clean and apply a setting sealant when i get back from hols. I ran it this morning with the drivers side crankcase breather removed and had little change to idle speed,slight increase. I've still ordered a new tps, think ill have to get a faultmate! Any good advice on sealant? Also I removed the unichip.

[cockie55]

Thanks heaps. I did use a non setting sealant so will re clean and apply a setting sealant when i get back from hols. I ran it this morning with the drivers side crankcase breather removed and had little change to idle speed,slight increase. I've still ordered a new tps, think ill have to get a faultmate! Any good advice on sealant? Also I removed the unichip.

You misread my post ....you need a "non-setting" sealant. Hylomar which is a solvent-based gasket that remains pliable is specified by LR. Use Light which is a liquid (available in 50ml bottle, tins and spray) on smooth true surfaces or Medium (100 g tube aerograde in Oz) which is a paste when faces are not true or a bit rough. Loctite #2 is also solvent-based and equivelent to the Hylomar Medium. These also make good gasket dressings.

Providing you removed PCV tube at plenum then with little change to idle you must have a bad air leak somewhere,.....use a aerosol of starter, carby cleaner etc to locate the sucker.

If Unichip was removed without resetting the ECU there may be a ECU fault (attached to timing / knock sensors) sitting there causing it to run retarded and rich but safe.

[RR P38]

I have had a similar issue with my P38.
I removed the stepper motor, when i did it fell apart.
At this point i patched it up and presented it to my usual mechanic.
A new stepper motor was installed and the high idle disapeared a few weeks later on start up the idle would run at 1200-1300.
If you shut down after start up the idle returns to normal range.
I also have intermittent hot start stall problems.
Could be the stepper motor adjustment??

[willem]

Go somewhere where you can access an Autologic or similar computer and find out what faults come up. Then have those faults cleared from the memory and go for a drive and recheck. That will locate the problem for you. Clearing the faults will make the car run happier too! I did that with mine and located problems I had been trying to find for months.

Willem

[daljames]

Hi all, back from trip o/s... Re-sealed the plenum and ram housing today. Mustve had some leaks. After about 2 mins idle went from 1800rpm gradually back to 1200rpm. Went back to 1800 on next start but gradually comes down again. No air leaks that i can tell. All new injectors have been seated properly. Cables VERY loose. I got a new stepper motor and TPS while o/s so i will try these tomorrow...

[daljames]

Update...

Ok so today i adjusted the fuel rail a little lower thinking that maybe the injectors where leaking air around the intake manifold holes they slide into. I also checked all high tension leads and adjusted them at the coil ends. Idle fell to about 1200 (from 1800). I put the UNICHIP back in, restarted and idle came up to 2000rpm... So back to the bridging wires. Idle back to 1200.

I gave up and lowered the idle speed with an Allen key on the adjuster above the idle speed control valve. Ill leave it like this until my Faultmate MSV 2 arrives for my birthday and reset the learned settings and start again then. At least my fuel economy remains awesome. Often better than 15l/100km and im on the hilly Northern beaches.

[daljames]

Oh and put in a new TPS. Although my basic OBD scanner only showed a 2% difference in position.

[daljames]

OK, bought a Faultmate MSV2 and reset the adaptive settings. How good are they?! A bit hard to get going on my Windows 7 computer i bought (thinking any Windows would do... Idiot i am. I know even more why i like Apples. So much easier for an idiot like me to use!). But the breadth of things you can do. $900 well spent for this delicate piece of machinery!