1500 FI stalls during warm up phase

Setting the idle:

1. Losen the TPS (important because the TPS can keep the throttle plate open)
2. Close the big screw on top of the throttle housing completely
3. With engine running use the small accelerator stop screw to adjust to 800 rpm.
4. With the big screw I then turn the idle up to 900/1000 rpm.
5. Adjust TPS so that it clicks when the throttle is operated and tighten screws.
6. Check that idle has not changed in step 5.

Actually I follow exactly the procedure as described on page 21/22 on the diagnosis manual. Except that it doesn't mention the unbolting of the TPS.
 
Yes, exactly as in the shop manual.

What would happen if you started the car from cold and then immediately pinched off the AAV hose that goes into the plenum? It should lose RPM and maybe even stall.

Do you have access to known good parts to swap in, like a spare known good AFM or ECU?
 
The engine will shut down. I also tested without aav. The hose attached with tape.the engine will idle very high. By pinching the hose the idle can be lowered. If the aav would be able to open more, my problem would have been solved. I have adjusted it with the little bold, but still no cure.
 
I don't think switching to 20w50 would have changed much.
Or did you see a change between summertime and now.
 
Difficult to tell. I have tried so many different things overtime.

As far as i can tell from the ljetronic bible there are 3 processes involved:
1. The aav is open and allows more air into the throttle air
2. The coolant temp sensor informs the ecu that the engine is still cold
3. Based on the info from the coolant temp sensor the ecu decides to inject fuel more frequently.

1 and 2 checked and working. I assume 3 is not happening. Why not?
 
It's a technicality, but when cold the ECU increases the pulse length of the injectors. IOW it keeps them open longer so they can squirt more fuel.

The frequency of the opening and closing is not variable within the ECU itself, as it is determined by the engine RPM signal the ECU gets from its wire to the coil.
 
Do you have access to a spare heater control valve? If so, graft that into the hoses in place of the AAV and see if the manual control you get from the heater control valve better regulates the engine speed during the warm up phase.

Or you could use a suitable ball valve and nipples/barbs from a local hardware store or plumbing supply store.

Many many period European cars have used this Bosch system, and there are posts in many car forums about what others have done to address their frustrations with AAVs that do not operate properly.

Some have used ball valves or heater control valves in place of the original AAV, and have connected a manual choke cable set up in the passenger compartment to these valves, and in a sense they manually adjust the valve to regulate air flow, just like a manual choke from the old days.

Example: http://www.alfabb.com/bb/forums/alfetta-gtv6-1972-1986/180338-manual-aav.html
 
Yes, try this...

Sometimes an older engine will have trouble idling during warmup if the idle is too low. You can bump the idle so it's at or just below 1000rpm when hot, this is also good for coolant flow at idle.

If your compression is uneven, or the valve lash is out of spec, the uneven intake vacuum can make the AFM flap jump around too much and cause the dual relay to turn the fuel pump off.

You mention that your cold idle is 1000rpm, it should be higher than that. Try setting it so that the hot idle is 1000rpm.
 
When hot the idle is around 1000 rpm. When i adjust idle to 1000 when cold, the idle when hot will be around 1200/1300 rpm. So maybe the problem is a high idle when warm?

I have a spare heater control valve and will try that this weekend.
 
Another country heard from...my $.02

You might want to test your thermo time switch. Yes I know it doesn't sound correct but.....

I have always had a hot starting problem but also a few other oddities in conjunction with that problem. These slight abnormalities included starting right up cold but wanting to stall until a bit warm, an idle that would increase a bit after warm and an a dimly lite O2/oil dash light after warm up.

I'm sure I drove everyone nuts with my questions. I read the trouble shooting guide. Thought the having to feather the gas for 5 mins when cold was the AAV. Checked for vacuum leaks, removed cleaned and fridge tested the AAV and reinstalled. Slight improvement but not much. Tested coil, checked connections/grounds/etc. All good. Had Jeff upgrade my ICM (thanks Jeff great job and great deal). No noticeable improvement.

Last week my car would start but no longer would stay running no matter how much throttle feathering I would do. Sprayed some starting fluid in the air cleaner and bingo the car starts right up and with throttle feathering would stay running. Tested my TTS and the readings were out of spec both cold and hot. Looked at some other websites (not sure may have been the Bosch website) and read that a bad TTS may also cause Check Engine light to come on (remember I mentioned that my O2/oil light would dimly lite when hot).

Changed TTS and now starts fine hot or cold, no more idle increase when hot and no O2 light dimly lite.

Not say saying it's your problem but why not test your TTS.
 
Mxgrds said:
When hot the idle is around 1000 rpm. When i adjust idle to 1000 when cold, the idle when hot will be around 1200/1300 rpm. So maybe the problem is a high idle when warm?
Click to expand...

What's suspect about a high idle when warm? I have mine set around there (on board tach being useless says it's 2000 but it's closer to 1300 hot). Car likes it there, that's all I know.:confuse2:
 
Did some testing today.

The tacho meter in the car is correct. Give exactly the right RPM.

Started the car, drove 400 meter. Stopped, Engine stalls. Adjusted idle to 1000 RPM. Started again, drove, engine keeps running, although with low idle (500 RPM) in the first 2 seconds after letting go of the throttle. After that the idle climbs back to 1000.

Thats what happens. Directly after I release the throttle, the RPM drops dangerously low and then climbs back to the correct RPM. When the engine is cold it stalls. When the engine is warm this dropping of the RPM is not happening. But with the cold idle on 1000 RPM, the warm idle is now 1500 RPM.
 
I'm thinking that you may want to do a close inspection of the throttle plate, to see how it seats in the throat of the plenum snout.

Some variability there driven by temperature could be the culprit. IOW, when cold the throttle plate closes too tightly to the throat of the plenum vs when it warms up and closes less tightly. Too tight would cause the low idle/stalling, but changing dimensions are masked by the idle setup when warm.

Do you have access to a flex head flashlight with a smaller head? If so, remove the fitting for the AAV hose that goes into the plenum, and remove the air snorkel hose. Using the flex head to put light behind the throttle plate as best you can, use a mirror to look down the throat of the plenum snout and see if you can see any light as you manipulate the throttle, letting it snap shut on its own, letting it gradually shut on its own, and then repeat with the engine up to temp, see if there is a smoking gun there.

Have you had any of the throttle plate assy apart while troubleshooting this issue?
 
I did take the throttle plate assy apart to clean it and checked it. Looks pretty good. Closes fully when cold. Did the light check. Not sure how to do it when engine is warm.

I also checked the tps if it gives the right signal at the ecu. It does. Because the idle drops when the tps gives the idle signal to the ecu.
 
Today i removed the aav and connected the tubes. The engine idles high. Actually it starts searching. But when driving and stopping it still stalls. I didn't expect that. It looks that when stopping the fuel injection is stopped to long.
 
silly

stupid thought
check the air flow meter flap doors for bending. there was a TSB to install a rubber plate due to a backfire issue until they made them standard on all replacements. the afm tells the ecm how much air is being drawn in, and tells the rudimentary l-jetronics system how to compensate accordingly. and more air or the door doesn't respond due to the bend and leads to problems like this.
just a thought before you beat your self up digging to deep.
mikemo
 
Checked the double relay. No issues. Maybe the fuelpump switch in the afm is interrupted when stopping due to a full back swing of the afm? Shortcircuit the switch so that the fuelpump always pumps. Still stalling. Afm works correct, cold and warm. Flap swings smooth.

Today i drove in the morning, engine stalls. Later in the afternoon, after cooling down of the engine, i drove again. The warm up idles at 1200 rpm on a cold aav, as it should. After 6 minutes the idle speed dropped to 900/1000 rpm. The aav has closed. Fine.

My opinion:
When the engine is completely cold the standard setup isn't able to keep the engine running. Something makes it heavier. The extra oxygen through the aav is not enough also not when openend as far as possible. A little bit more would keep the engine running. What can cause this heavy resistance when cold? Oil 20w50 for classic cars, wrong exhaust (carburreta exhaust).
 
From the Bosch Ljetronic Technical Instruction manual:

Start - Cold start valve and thermo time switch
After start enrichment - has to last about 30 seconds, 30 to 60% more fuel injected
Warm-up phase - follows the previous fase. Slight enrichment of the mixture needed. Controlled by the engine temperature (CTS). Last about 90 seconds, depends on temperature?

(the manual is a bit unclear if these are subsequent phases or the same phase)

and then follows:

"During the warm-up phase the engine receives moire fuel due to the influence of an auxiliary-air device. This it to overcome the frictional resistance in the cold engine and to guarantee a stable idle speed.

There is an increased frictional resistance present in a cold engine which must be overcome at idle speed. The engine is therefore allowed to take in more air through the auxiliary-air device by bypassing the throttle valve. Since the additional air is measured by the air-flow sensor and is taken into account when the air is metered, the engine receives more air-fuel mixture. With a cold engine a stable idling speed can therefore be achieved. "
"

Since my engine starts well and idles during the first 2 minutes pretty good ( I can get of the driveway withoput stalling), my problem is in the last phase.
In the last phase there are 2 variables:
1. friction of the cold engine
2. the additional air bypasses by the aav

I have checked 2 more than a couple of times. Seems to work okay. That leaves the friction of the engine as the reason for stalling when cold, right?

Today I started the engine and keeps running at a very low idle of 500 rpm. But I had the clutch pushed down. When I released the clutch (not in gear), the stalled. More friction.
 
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