740 poor running and stalling

[Beadybc]

Hello here's a video for you to watch that shows a typical 10 minute stint of the car running:

https://www.youtube.com/watch?v=5kKeaRPm-I8

I have also attached some photos.

The car is running poorly, sometimes on three cylinders and most of the time not in a smooth manner causing the car to shake. Sometimes as you can see in the video, any level of input on the throttle causes the revs to drop dangerously low before they then go to where they should be however a few minutes later the car will respond normally to throttle input as long as you don't go over 20% throttle, its very on and off. I have noticed that as the car warms up the revs will drop below the 900rpm it's supposed to stay at but adjusting the idle screw makes no difference and adjusting the timing just lowers it even further.

Once it has warmed up, the big problem is letting off of the throttle. If I can rev the engine, as soon as I let off the throttle, the revs drop and it stalls (again this can be seen in the video). Also visible in the video is the fact that once it has warmed up and then stalls, starting it back up is impossible however after say an hour turned off it will start again fine.

Things that have been done so far:
-Cleaned throttle body
-Correctly adjusted the throttle position
-Replaced the Fuel: In tank pump, Main Pump and Filter. All are functioning.
-Checked and it is definitely getting sparks from all plugs
-Flushed out coolant system and replaced coolant
-Replaced gaskets around the inlet system
-Checked for accessible vacuum leaks using wd40 whilst it is running, found nothing

Things that are probably wrong but haven't been fixed yet:
-You will hear in the video that the water pump is making unhappy noises but only after about 1.5k rpm

-Now that I have listened to the car through headphones I can hear what might be a knocking noise coming from the engine after I let off the throttle.

-The battery was flat when I picked the car up so we charged it, the sides of the battery did bow out slightly whilst doing so.

-I've also read that a dead Idle Control Valve/ Air Auxiliary Valve could be the cause so I connected it directly to the battery and it did eventually close however I'm not actually sure how it is supposed to function so if anyone knows how it would be useful.

-When I picked up the car brambles has gotten into the engine bay and into the vent in the photos, my biggest fear is that one of them got behind the firewall and punctured something there that is causing a massive vacuum leak. Is there anything that goes into the firewall that could cause this much damage if punctured and where should I test vacuum pressure on this engine?

Could any/all of these be contributors?

The car is a 1989 740 Wagon B200E 2L

Any help is appreciated.

[lynns hubby]

The one obvious thing you haver not done is a new distributor cap, rota arm and leads.
If its sat there that long, damp/ corrosion could have set up in side the cap. Have you at least took it off to have a look?

[griston64]

Leads look pretty new to me

[Familyman 90]

Replace the plugs. They can appear fine but then start breaking down when under load. Ditto the leads.

[griston64]

Has anyone looked at the pictures of the leads and dizzy cap ?????

[john.wigley]

How much fuel did you put in the tank, 'Beadybc'? The gauge suggests that you are near empty - or is it misreading like many 7 series cars do? If it's really low, the pump(s) are having to work much harder - best not to drop below 1/4 full in normal use.

Regards, John.

PS Also agree with leads and plugs breaking down under load. J.

[griston64]

Originally Posted by griston64

Has anyone looked at the pictures of the leads and dizzy cap ?????

The PDF attached to the post shows pictures of the engine bay with what looks like to me brand new leads and dizzy cap

[Laird Scooby]

Originally Posted by Beadybc

Hello here's a video for you to watch that shows a typical 10 minute stint of the car running:

https://www.youtube.com/watch?v=5kKeaRPm-I8

I have also attached some photos.

The car is running poorly, sometimes on three cylinders and most of the time not in a smooth manner causing the car to shake. Sometimes as you can see in the video, any level of input on the throttle causes the revs to drop dangerously low before they then go to where they should be however a few minutes later the car will respond normally to throttle input as long as you don't go over 20% throttle, its very on and off. I have noticed that as the car warms up the revs will drop below the 900rpm it's supposed to stay at but adjusting the idle screw makes no difference and adjusting the timing just lowers it even further.

Once it has warmed up, the big problem is letting off of the throttle. If I can rev the engine, as soon as I let off the throttle, the revs drop and it stalls (again this can be seen in the video). Also visible in the video is the fact that once it has warmed up and then stalls, starting it back up is impossible however after say an hour turned off it will start again fine.

Things that have been done so far:
-Cleaned throttle body
-Correctly adjusted the throttle position
-Replaced the Fuel: In tank pump, Main Pump and Filter. All are functioning.
-Checked and it is definitely getting sparks from all plugs
-Flushed out coolant system and replaced coolant
-Replaced gaskets around the inlet system
-Checked for accessible vacuum leaks using wd40 whilst it is running, found nothing

Things that are probably wrong but haven't been fixed yet:
-You will hear in the video that the water pump is making unhappy noises but only after about 1.5k rpm

-Now that I have listened to the car through headphones I can hear what might be a knocking noise coming from the engine after I let off the throttle.

-The battery was flat when I picked the car up so we charged it, the sides of the battery did bow out slightly whilst doing so.

-I've also read that a dead Idle Control Valve/ Air Auxiliary Valve could be the cause so I connected it directly to the battery and it did eventually close however I'm not actually sure how it is supposed to function so if anyone knows how it would be useful.

-When I picked up the car brambles has gotten into the engine bay and into the vent in the photos, my biggest fear is that one of them got behind the firewall and punctured something there that is causing a massive vacuum leak. Is there anything that goes into the firewall that could cause this much damage if punctured and where should I test vacuum pressure on this engine?

Could any/all of these be contributors?

The car is a 1989 740 Wagon B200E 2L

Any help is appreciated.

First of all, did it run at all before you replaced the fuel? Second, how much have you put it? Third, how long was the car stood?

Fourth, go to your local Toolstation and buy :

https://www.toolstation.com/methylated-spirit/p99550

Add the contents to the fuel tank, start the car and let it run for 5-10 minutes then see what it does.

What gap did you set the plugs to when you did them? Should be 0.65-0.7mm (0.025-0.028")

Sixth, the timing is non-adjustable on that engine.

Seventh, you only have an AAV (Auxiliary Air Valve) you don't have an AICV (Air Idle Control Valve) so the idle speed won't be maintained at 900rpm regardless. The AAV is working, you've proved that.

Eighth, inspect that rubber sock between the throttle body and the fuel distributor for splits, perishing and security - any leaks there will cause your symptoms.

Ninth, buy some Carlube ATF-U, NAPA MV or Dexron III synthetic ATF. Buy a gallon of petrol in a fuel can and add ~1/4-1/3pt (150-200ml) of the ATF to the fuel, replace the lid and give it a shake to mix it then add it to the fuel tank - don't add any more fuel at this stage. Also add about a pint (0.5L) of the ATF to the engine oil.

Start the engine and let it run for 15-20 minutes at idle - don't be tempted to blip the throttle to "test it" - once it's run like this for 15-20 minutes, gradually push down on the accelerator and see how it goes.

Tenth - remove the trim panel under the dash below the steering wheel. Look up and you should see a single ECU for the ignition - there should be a neutral coloured nylon tube ~4mm or 3/16" OD going to it with a short rubber link tube about 25-30mm long (about an inch) to connect it. Make sure this is connected.

Lastly, let us know how you get on. It sounds suspiciously like lack of use combined with condensation in the fuel, dried rubber seals and/or sticking components in the fuel distributor and possibly splits in the air sock between the fuel distributor and throttle body.

Also worth cleaning the PCV system out but that won't normally cause the problems you've got, at least not on a K-Jetronic engine which is what you have there. Just to clarify things, it doesn't have a Lambda-Sond badge on the radiator grille, a catalytic converter and Lambda sensor does it? If so that makes it a KE-Jetronic which increases the fun-factor ten-fold! (For "fun" read complications!)

Oh yeah, check the air filter is clean as well.

[Beadybc]

Sorry for not replying sooner everyone you've reminded me of things that I forgot to mention.

-I have checked the distributor cap and rotor arm. There wasn't any damp or corrosion and no pitting just a small amount of white residue on the contact points. Both were replaced along with the plugs and leads probably not too long ago in terms of mileage, I say 'probably' because the mileage stopped going up around 5-6 years ago however that full service was a whole 11 years ago now.

-I picked the car up in November of last year, before that It had been sitting for at least a year. The previous owner had a mechanic out in January 2019 attempting to fix it but to no avail. In my ownership it has never run correctly.

-The fuel gauge doesn't work but I know it has a full tank cause the fuel reached the filler cap.

-I have checked the gap on all plugs and set them all to within spec, they were quite sooted.

-I will check the rubber sock and ignition ECU.

-The manual states that the B200E doesn't have K-Jetronic, it states "CI-Injection" but if you say that it is K-Jetronic then that's useful as I haven't been following other forums' advice for K-Jetronic engines out of fear that it would cause more damage. How/Where would I check to see if it has a Lambda sensor, I can't see any sensors going into the exhaust if that's it?. It has two converters on the exhaust and no Lambda-Sond badge anywhere on the car.

-The air filter looks almost new and is clean.

-By 'adjusting the timing' I meant just turning the distributor cap whilst it was running.

-Adding things to the fuel was the next thing on the list to try so If everything else is ok then I give it a go, when you say add the contents of the methylated spirit, I'm assuming you mean the 500ml bottle not the 2L one?

-Where is the PCV on this engine?

I have attached the photos again this time I've added / rearranged photos of the exhaust system.

[Laird Scooby]

Originally Posted by Beadybc

Sorry for not replying sooner everyone you've reminded me of things that I forgot to mention.

-I have checked the distributor cap and rotor arm. There wasn't any damp or corrosion and no pitting just a small amount of white residue on the contact points. Both were replaced along with the plugs and leads probably not too long ago in terms of mileage, I say 'probably' because the mileage stopped going up around 5-6 years ago however that full service was a whole 11 years ago now.

-I picked the car up in November of last year, before that It had been sitting for at least a year. The previous owner had a mechanic out in January 2019 attempting to fix it but to no avail. In my ownership it has never run correctly.

-The fuel gauge doesn't work but I know it has a full tank cause the fuel reached the filler cap.

-I have checked the gap on all plugs and set them all to within spec, they were quite sooted.

-I will check the rubber sock and ignition ECU.

-The manual states that the B200E doesn't have K-Jetronic, it states "CI-Injection" but if you say that it is K-Jetronic then that's useful as I haven't been following other forums' advice for K-Jetronic engines out of fear that it would cause more damage. How/Where would I check to see if it has a Lambda sensor, I can't see any sensors going into the exhaust if that's it?. It has two converters on the exhaust and no Lambda-Sond badge anywhere on the car.

-The air filter looks almost new and is clean.

-By 'adjusting the timing' I meant just turning the distributor cap whilst it was running.

-Adding things to the fuel was the next thing on the list to try so If everything else is ok then I give it a go, when you say add the contents of the methylated spirit, I'm assuming you mean the 500ml bottle not the 2L one?

I have attached the photos again this time I've added / rearranged photos of the exhaust system.

I hate Haynes for referring to K-Jetronic as CI - K is short for Kontinuierlich which means continuous. They are one and the same.

You shouldn't be able to turn the distributor cap whether the engine is running or not, it's fixed to the cam carrier and driven off the rear end of the camshaft. The EZK ignition ECU above the pedals does all the timing adjustments needed.

If your fuel tank is full, you need to empty 3/4 of the tank. You will need the full 2L of meths, not the silly little 500ml bottle as that won't do any good. The ratio is important, about 10% meths to fuel so 2L of meths to 18L of petrol which is about 4 gallons. I was going on the fuel guage reading, normally 7xx don't give a reading at all if the guage isn't working.
That's why i linked to the 2L bottle of meths and NOT the 500ml bottle!

With the extra info that it has never run right in your ownership, was sat for at least a year beforehand etc i would definitely suggest condensation in the fuel. Hence the meths. Try the things i mentioned in the order i mentioned them (unless already done like the plugs) but you need to reduce the amount of fuel in the tank to make the 2L of meths effective or increase the amount of meths to 6L which probably won't even fit in the tank if it's full.


*** EDIT *** Just had a look at your extra pics and can't see a cat, Lambda or anything else to suggest it's a KE-Jetronic so pretty safe to say it's a standard K-Jetronic