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**RESOLVED**At a total loss, cold start issue!!

mdubya79

mdubya79

Member
Joined
Aug 14, 2024
Location
Hertfordshire, UK
Ok, I have a late '95 940 turbo. I had a budget to spend on her which is now depleted!!! There are a few gremlins that I can deal with but the most annoying is when I first start her, she seems to run on 3 cylinders, rough as a badgers arse. You rev up to 2k revs, hold it there for a few seconds and she then idles nicely. First minute of driving there is a slight hesitation pulling off from a standstill, then she runs and idles beautifully with no further issues throughout whatever journey.

So far I have done:

Reconditioned Injectors
New Fuel pressure regulator
New Distributor cap
Rebuilt distributor seals
New HT leads
New Sparkplugs
Cleaned MAF sensor
Checked all vacuum hoses
Cleaned PCV system
New O2 sensor
New Engine Coolant Sensor

Non related:
Timing belt & tensioner
Front crankshaft seal
New heater matrix

I don't mind spending money on all of the above as I want her to be reliable and a keeper but I'm now stumped 🤔

Only one thing I haven't looked at is the idle air control valve. The guy I bought it off replaced that a day before I got the car, it's very shiny and new but is a cheapo Chinese one.

Please help!!!
 
How did you clean the MAF?
While possibly not the culprit in this scenario, did you inspect the crank sensor?
 
Maybe a leaking injector? From cold, you could try running it for only a few seconds, then pull and inspect the plugs to see if one of them is wet (post plug pictures here). Or, if you have a schrader valve on your fuel rail, and the appropriate fuel pressure gauge+fittings, you could see if the pressure drops after shutdown.

After you've rev'd it up, you could try a power balance test -- unplug one injector at a time and see if they all behave about the same, you may need to give it some gas to keep it running on 3 cyl.

quickie edit: per stevE85's comment, how does it sound during cranking? Is it a nice even cadence or does it spin through one of the cyls a little faster?
 
stevE85 said:
Might want to try a compression test and/or a leak down test to rule that out. Could be something mechanical.
Click to expand...
Compression test is good on all cylinders 170 pretty much on all.

Asbi said the engine is perfect after the initial hiccup, runs very smooth and quiet
 
bobxyz said:
Maybe a leaking injector? From cold, you could try running it for only a few seconds, then pull and inspect the plugs to see if one of them is wet (post plug pictures here). Or, if you have a schrader valve on your fuel rail, and the appropriate fuel pressure gauge+fittings, you could see if the pressure drops after shutdown.

After you've rev'd it up, you could try a power balance test -- unplug one injector at a time and see if they all behave about the same, you may need to give it some gas to keep it running on 3 cyl.

quickie edit: per stevE85's comment, how does it sound during cranking? Is it a nice even cadence or does it spin through one of the cyls a little faster?
Click to expand...
New injectors installed today, fully checked, I have done a full flow test on my machine before installation

Haven't really taken notice of the starting sound, doesn't sound odd or I'd have picked up on it
 
I would pull the plugs and put a borescope into the engine after it has sat overnight. Maybe you have some coolant intrusion.

Another thing is make sure you don't have any air leaks. I would smoke/pressure test with soapy water
 
ZVOLV said:
I would pull the plugs and put a borescope into the engine after it has sat overnight. Maybe you have some coolant intrusion.

Another thing is make sure you don't have any air leaks. I would smoke/pressure test with soapy water
Click to expand...
Oh bugger, hope there isn't any coolant getting in 😞

There's absolutely no smoke coming from the exhaust at all, both on starting or driving if that makes any difference??
 
ZVOLV said:
You could also unplug one injector at a time to see which cylinder isnt firing.
Click to expand...
I'll try that when I have a chance. It's so frustrating! If there is coolant seeping into a cylinder would it not get steam coming from the exhaust???

Also thinking/worrying about coolant leaking into a cylinder, would that not cause idling issues when hot and the coolant system is under pressure, assuming pressure would cause coolant to be pissing into a bore at force??

As I said after a rev for a few seconds it's runs and idles fine, after one or two very slight hesitations after I first set off it's then perfect
 
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Have you disconnected the battery and let it "relearn" after cleaning the MAF and doing your other services? My old 940T ran like total crap after replacing the rubber intake boot(between turbo and MAF) for one that wasn't leaking. Disconnected battery and got slowly better after multiple warm-up/drive cyles.
 
stevE85 said:
Have you disconnected the battery and let it "relearn" after cleaning the MAF and doing your other services? My old 940T ran like total crap after replacing the rubber intake boot(between turbo and MAF) for one that wasn't leaking. Disconnected battery and got slowly better after multiple warm-up/drive cyles.
Click to expand...
Yes, had the battery disconnected the last few days, cleaned the MAF and installed the new injectors and fuel pressure regulator then re connected the battery. Took it for a 20 mile drive motorway and lanes and after the initial hard start and bit of hesitation it ran really nice, smooth and quick. I'll see what it's like in the morning starting up, not holding my breath
 
ZVOLV said:
I would pull the plugs and put a borescope into the engine after it has sat overnight. Maybe you have some coolant intrusion.
Click to expand...
This is a task for Mr. Wiggles! (Depstech DS630)

[There are lots of cheap USB borescopes available, just none so fun - look for one with a small diameter and a right angle mirror attachment]
 
mdubya79 said:
Yes, had the battery disconnected the last few days, cleaned the MAF and installed the new injectors and fuel pressure regulator then re connected the battery. Took it for a 20 mile drive motorway and lanes and after the initial hard start and bit of hesitation it ran really nice, smooth and quick. I'll see what it's like in the morning starting up, not holding my breath
Click to expand...
If it's any consolation at all, I remember mine taking about 2 weeks of driving to finally get back to smooth again. Hopefully, it's just relearning for you.
 
ZVOLV said:
I would pull the plugs and put a borescope into the engine after it has sat overnight. Maybe you have some coolant intrusion.

Another thing is make sure you don't have any air leaks. I would smoke/pressure test with soapy water
Click to expand...
I had similar symptoms with the same engine and the head gasket was letting a little coolant in. Once you boil off the coolant pooled up in the cylinder, the leak is slow enough to not affect how it runs. You might be able to smell a little coolant in the exhaust but doubt it would produce noticeably more vapor in the exhaust. A bore scope will tell you for sure. If one cylinder is really clean, that’s the one that has a coolant leak. Might even be able to tell by looking at the plugs.
 
bobxyz said:
This is a task for Mr. Wiggles! (Depstech DS630)

[There are lots of cheap USB borescopes available, just none so fun - look for one with a small diameter and a right angle mirror attachment]
Click to expand...

That is a neat borescope. I have tried $10 cellphone ones that kinda work, up to $500+ overpriced name brand (Snapon etc) ones and I have yet to find a borescope that is easy to use. I usually end up selling teardown $$$, to really tell what is going on inside a damaged engine. That Mr Wiggle borescope seems neat to use.

Yeah those 2.0 turbo Cadi engines were known for blowing pistons. You could tell by pulling the oil cap and the excessive crankcase pressure was sometimes very obvious.

It doesn't take very much coolant to cause a cold start misfire. It isn't a very common issue on these engines, but it could happen. Like mentioned, you would be looking for a "steam cleaned" piston or a puddle of coolant with a borescope. You may also see some crust or other sign of the issue on the spark plug tip.

It is tough to do internet diag. Did the issue always happen with the car since you have bought it, or did it start to happen once you started working on it?
 
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