Poor cold start 1993 940 2.0 turbo

[besidetheseaside]

Decided to start a new correctly titled thread about this as my original one ( clicking surging + revs dropping ) was incorrectly titled. Also needed to step back, take stock and pause for breath. Many thanks to all who have been helping up to now especially Dave.

So, poor cold start, just started doing this one morning a few weeks ago, car starts then within a few seconds peters out and stops. It can be kept running if you feather the throttle ( induces misfire ) and once the car is warm it drives and performs fine, apart from a slight hesitancy on acceleration, also if you pull the plug off the MAF it will tickover, put it back on and the engine stops or stutters. If you try to drive the car when cold it bogs down and tickover can surge especially when in traffic. Once car is warm you would think there is nothing wrong with it, warm starts are fine as well.

Up to now I have,
Replaced plugs and leads, NGK ( all plugs same colour on removing ) and Bosch.
Took dizzy cap and rotor arm out they are ok and are fairly recent.
Replaced fuel pump relay, no change.
Fuel pump and filter were replaced last year.
Throttle body is clean and TPS clicks nicely.
Activated diagnosis mode and fan came on, injectors clicked and IAC valve clicks.
Fuel pump can be heard priming when ignition is turned on.
New CPS fitted.
CTS replaced with generic item car would not start. Seller replaced item car would still not start. Bought 039 Bosch as 032 seem to be unavailable, car would not start, put old CTS back in car starts. Unable to get a test ohms reading off any of the new sensors, strange.... Tested old one and it seems to be within specs.
Replace MAF with generic item, no change, put old Bosch MAF back on after cleaning thoroughly.
Air filter to turbo pipe rotted at turbo end, cut down and refitted.
All vacuum pipes replaced, crankcase breather pipe replaced.
Full bottle of Redex injection cleaner put in tank today.
Unplug vacuum pipe off FPR, no leaking petrol and idle goes up which I believe means FPR is ok.
Unable to hear in tank pump but I have 3/4 of a tank in and as I said cars performs perfectly when warm.
Lambda and in tank fuse is ok.
Apologies if I missed any thing but I think that is it up to now. I have excluded some items that I have not tested as they obviously work when the car is warm, in fact everything works perfectly when the car is warm. Have looked at lots of loads of old poor cold start threads on various forums and there never seems to be a definitive "this fixed it" answer. Still have some bits to do that Dave has suggested but back to work today so that will slow things down a bit.
I am going to carry on using the car as it is from now on, just need to warm it up for 10 minutes before I pull away.
Thanks for your help guys, I truly appreciate the time and effort that you all put into this forum.

[Forrest]

I guess you may have read my saga here.

https://www.volvoforums.org.uk/showthread.php?t=313229

In my case it turned out to be faulty HT leads that were the real culprit but I also had genuine faults with the in-tank pump, turbo air hose and distributor cap.

I’d recommend getting a fuel pressure test gauge so you know you’ve got pressure at the fuel rail. Your car almost certainly has a schrader valve under the rail between 1 and 2 injectors. You’ll need one with a right angle fitting or flexible hose to attach to this. A failed in tank pump is unlikely to cause a poor start condition. In fact mine ran perfectly well with one for ten years and 100k miles.

Definitely follow through on Dave’s suggestions. It was his guidance that enabled me to solve mine.

[besidetheseaside]

Just read your thread, very interesting reading, especially these cars being able to carry on running with numerous faults. I have made copious notes during this problem and will be referring back to Dave’s suggestions as time now allows. I least I will not freeze to death working outside this week lol.

[besidetheseaside]

The worst issue up to now has been trying to find a new CTS that actually works in my car so I can cross it off my list of checked items. I now have 3 new ones that I cannot get an ohms reading off, including a Bosch one, when they were fitted the car would not start. So I bought an Intermotor NOS one, tested it before I fitted it and got an ohms reading, result, or so I thought. Fitted it in the car, starts up and cuts out again, same as it has done for weeks. I pulled fuse one before fitting and refitted it after. So car starts, goes to about 1200rpm then peters out quickly. The only way to keep it running is to give it throttle to 2000rpm and keep it running ( it has a slight misfire during that time ) until it is warm and then I can drive it, it does not perform perfectly but it gets me there and back. I honestly thought the CTS was my problem but obviously not so my search continues........

[Laird Scooby]

This is a long shot Don, i have several reasons but also several doubts so this may prove a fruitless check but could be worth it.

Can you locate your Lambda sensor and follow the wiring back to the connector on/near the bulkhead? Should be a pink, black and a green wire going into it on the car side.

With the engine hot, insert your multimeter +ve probe into the green wire on the back of the connector so it contacts the terminal. Do similar with the -ve probe into the black terminal. Set the volts to 20V DC to start with and start the car and let it idle.

Should be reading less than 1V and if so, turn the range down to 2V and you should get a voltage that goes on a cycle from near 0V to nearer 1V with the centre point around 0.45V - it should cycle up and down regularly.

If you can do that please and report your findings it might give a clue but as already mentioned, it may not! Should eliminate something a bit oddball from the diagnostic process either way though!

[besidetheseaside]

Thanks Dave, I had considered the Lambda but thought it only comes into play when the engine is warm ?? However I will put it on the top of my next to do list

[Laird Scooby]

Originally Posted by besidetheseaside

Thanks Dave, I had considered the Lambda but thought it only comes into play when the engine is warm ?? However I will put it on the top of my next to do list

You're spot on Don, it does only come into play once warm but it seems when you have a working CTS and you've reset the ECU (pulled fuse #1) you get one good cold start and then after it has warmed up, it reverts to the previous state of being a pig to start and keep running when cold.
This has made me wonder if the Lambda sensor has altered the fuel trims so it's enriching the cold start mixture too much because the Lambda is lazy.

Bit of a long winded explanation but those are the basics! Worth testing as i say, if only to eliminate it from the diagnostics.

[besidetheseaside]

Thanks Dave, I understand your point. I have just googled lambda cold start and it does bring up some interesting reading. Soon as the rain stops, if it ever does, I will be back on the case !!!

[besidetheseaside]

So finally managed to get a new CTS that I could get ohms readings off so fitted it in the car but there was no change, starts but still peters out. So yesterday I tested the lambda hot and it was giving readings within limits. This morning I decided to test the lambda cold for resistance and voltage. Resistance checked out ok but needed the car running to check the voltage. So started it up and it ran perfect, no petering out and revved clean, voltage gave good reading. Now the only difference between yesterday and today was the outside temperature, sun was out and it was really warm this morning. Car drove ok but still bogged down until warmer.
So went out to the car this afternoon and it is back to square one, starts, peters out snd stops. Only way to keep it running is to Rev it to 2000rpm for 10 minutes then you can drive off. So the only difference it seems between broke and fixed is temperature ?? I will try a cold start tomorrow and see what happens, this car is trying my patience but I will fix it !!

[Laird Scooby]

Originally Posted by besidetheseaside

So finally managed to get a new CTS that I could get ohms readings off so fitted it in the car but there was no change, starts but still peters out. So yesterday I tested the lambda hot and it was giving readings within limits. This morning I decided to test the lambda cold for resistance and voltage. Resistance checked out ok but needed the car running to check the voltage. So started it up and it ran perfect, no petering out and revved clean, voltage gave good reading. Now the only difference between yesterday and today was the outside temperature, sun was out and it was really warm this morning. Car drove ok but still bogged down until warmer.
So went out to the car this afternoon and it is back to square one, starts, peters out snd stops. Only way to keep it running is to Rev it to 2000rpm for 10 minutes then you can drive off. So the only difference it seems between broke and fixed is temperature ?? I will try a cold start tomorrow and see what happens, this car is trying my patience but I will fix it !!

Just sent an email with a possibility i hadn't previously thought of Don - fingers crossed!