Sorting Out Rough Warm Up and Idle on an 87 TR

Today, on a sunny wintery day I decided finally to get to grips with the rough warm up. The car would start fine in all weather, hot or cold. But the idle would oscillate wildly between 500 and 1000 rpm until the engine was at full operating temperature. It would often stall and the only way to ensure the engine kept running would be to keep the foot on the accelerator at 1000 rpm or over. Once revving above 1500 rpm the engine ran great. Once warmed up the engine idled fine but not what I would call excellent.

Previously I checked the auxiliary air valves. Both sides were operating correctly - open when the engine is cold, and closing then closed as the engine warms up.

The first check today was for primary fuel pressure as many problems can occur if this is wrong. My TR manual only shows the early model with the K-jet injection. Luckily on the KE-jet the connection is by the cold start injector which is very easy to access. Before attaching the pump I created the jumper connector described in the manual that would cause the fuel pumps to run with the engine off. Here's a stock picture from the web and it's exactly what I created. The fuse box cover mentions left and right the wrong way round to me - I always thought that sides are determined in the direction of travel but here right means the driver's side (in US and EU but not UK).

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I connected the fuel pressure tester and activated the correct pump with the jumper connector. The checks proved that fuel pressure was correct on both sides. In fact it was 5.4 bar on each side. Perfect.

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The next check I wanted to run was for CO emissions. I recently acquired a Gunson CO tester. This device calibrates in open air and then shows CO levels via a probe inserted into the exhaust. This tool is a saviour to a home mechanic on a budget. While it may not be as accurate as a professional tool the gauge would show if the two sides are running differently.

After spending 15 mins calibrating the tool and making sure that the TR is totally warm - fans engage and oil temperature is up. I inserted the probe into the right exhaust. On my TR the right exhaust comes from the right bank, i.e. there is no cross-over. (See my earlier posts for a picture of the unit.) The gauge showed the correct CO output. Next I moved the probe to the left exhaust and it showed that the left bank was running very rich. In fact I'm surprised that the engine ran as well as it did with so much unburnt fuel.

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It was time to do my first CO adjustment. The protective allen bolt came out easily and I was able to use a long thin flat screwdriver to turn the hidden adjustment screw one quarter of a turn anti-clockwise - to make the mixture less rich. The engine sound changed immediately. It sounded more harmonious. I revved the engine a few times (as required by the gas tester instructions). Then after recalibrating the tester I inserted the probe first into the left exhaust and then to the right. It just so happened that I turned the screw the right amount - both banks were in sync.

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It is not a good time to take the TR out - too much grit on the roads. So I'll have to wait for the weather to warm up and for the rains to wash away the grit before I give her a proper road test. But so far, so good...

 

The LM-2 Basic (successor to LM-1?) seems to be double the price of the Gunson. Probably not worth it for amateur use. But glad to hear that there is a way for cars with catalysts to be checked easily. In the UK pre 1993 cars do not require a catalytic converter if not fitted originally. Mine has straight thru pipes with minor baffling. Sounds awesome and can measure emissions at the outlet!

 

Turbo-Joe, on mine protective screws are Allen bolts. Both of them. Will take a pic next time. I couldn't see inside the hole to see what the adjustment screw was like but a thin screwdriver fitted perfectly either way.

Now that I have a CO measuring device I'll be able to tell if either side drifts. As to why it was off so much - I don't know.

 

I've not tried checking the throttle balance yet. Something for another occasion.

The car has been running fine when warm and there were no misfiring or ignition issues.

 

Today went to start the TR from cold and..... my CO adjustments made no difference what so ever to the cold starting problems. So will need to check more components when time allows but it definitely idles better once warmed up.

Incidentally, what should be the RPMs at idle on cold start? Should they be above 1000 rpm?

 

I've had another opportunity to examine the warm-up idle on the TR today. It was 4 degrees C outside and raining. Not fun.

Having done a fair amount of reading around KE-Jetronic it became clear to me that warm up regulation is governed in part by a thermistor whose resistance drops with coolant temperature. There are some great posts on this forum about this. Specifically I found this useful: https://www.ferrarichat.com/forum/threads/87-tr-rough-idle-and-stalling-surging.529535/. Steve Magnusson provided a great picture that shows the expected resistance versus temperature - https://www.ferrarichat.com/forum/attachments/tr-ke-jetronic-coolant-thermister-resistance-testing-diag-sheet-6-nr-2-jpg.2277402/

My results came back good. The two sides show virtually identical resistance at the same temperature. The variance is under 2.5%.

Cold. 4 degrees C - 4500 ohms
Warming up ~60 degrees - 700 ohms
Fully warmed up ~80 degrees - 400 ohms

So the problem is clearly not with the thermistor.

What else can cause the idle to be too low when warming up requiring one to keep the foot on the accelerator? I will check the balance of the throttle openings, once I learn how to do that. Both auxiliary air valves are open when cold so it's not that.

 

To be honest, after I did the CO adjustment it definitely idles better once warmed up a bit - one to two mins in today's weather.

Once it's stabilized (and I can stop keeping my foot on the accelerator) the idle settles at about 800-900 rpm based on the tachometer. What I am not experiencing is starting and idling at 1300 then slowly revs going down as it warms up. I have to keep my foot on, holding it around 1000 until I can feel it stabilising.

 

Chapter D is the one that I've been reading up on. I have a Merc with standard K-jet and that's a much easier proposition with a mechanical WUR. Anyway, mine is an 87 TR with KE-Jet and no catalytic converters, engine F113B. I don't have the Ferrari KE Supplement but do have a copy of the KE-Jetronic book from Bosch and another publication that covers miscellaneous old Bosch FI systems in varying detail.

Not checked the protection relay for voltage so can do that the next time. The AAVs are indeed open when cold and close as the engine warms up.

If there's an online copy of the official Ferrari KE diagnostics then I'd very much appreciate getting a copy

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Thanks a lot, Steve. Downloaded and looking forward to getting better acquainted through reading with that glorious Flat 12.