Sudden misfire in all conditions - where to start?
 

Hi everyone,

I'm new to this forum and new to Volvo ownership - I bought a 1988 745 GL 2.3 two months ago and have been very pleased with it so far. It starts on the button even in freezing weather and has never missed a beat - until now.

I started the car and it ran like normal, then I drove 50 metres down the road in 1st gear, came to a stop, and then the car started misfiring rather badly. It seemed like it was almost stalling at idle unless I gave it some gas. I have had occasional misfires on other cars that went away with a bit of engine revving, but that didn't help here. The misfire was still present and the car didn't have much power and wouldn't seem to go over 3000 RPM.
I pushed it back and went looking for faults.
I took out each sparkplug and they all looked fine with a consistent dry, medium grey/brown tone. Spark plug wires look decent and the connectors at the plug ends looked alright, but I don't know how old they are. I tried to start the car again, but the fault was still there, and now it actually stalled - at this moment I could hear that the fuel pump was still running.

Now, I'm an amateur mechanic at best. I have done a lot of basic maintenance and repairs, but my troubleshooting skills are rather limited. And I really don't know much about these old 740s. So where would be the first place to look for the cause of this?

One note: The only "issue" I have had with the car has been a very small lack of power/hesitation at WOT around 2000 RPM lately, but it has only been a few times and mostly when the car was cold. Could this be related?

Thanks in advance.

I did some more reading and apparently it might not be an actual misfire, but could also just be some very rough running due to other causes? I read about the MAF sensor several places and I removed that and sprayed it with isopropyl alcohol before I went to work, so it's currently drying until I get home. It didn't look that dirty to me though, but I've never dealt with a MAF sensor before.
I have been looking for the diagnostics thingy in the engine compartment with no luck so far - I thought it was supposed to be behind the drivers side strut tower? Is it possible that my car doesn't have one? Would be nice to get some error code readings...

Also read something about a Hall sensor, which I have never heard of before on the other cars I've had. Could that cause this kind of trouble?

Cleaning the MAF sensor did not help. The car won't start (it hasn't started since it stalled yesterday)

an 88 won't have the OBD, that was added in 1989.

ignition off, unplug the MAF, then try and start the car. if it runs, albeit poorly, but wouldn't run with the MAF plugged in, then its a bad MAF. otherwise, ignition off, and lpug it back in, and you'll probably have to start troubleshooting from scratch.

some troubleshooting tips here. https://www.volvoclub.org.uk/faq/Eng...Stall_Problems

fyi you have LH 2.2 if its a Bosch system... 89+ cars have LH2.4 (or Regina).

Sounds like a large vacuum leak to me.

Seems plausible. How would I go about diagnosing that with a non-running engine though? Most diagnosing guides I've found online assume that the engine can actually idle...

visual inspection of the air path from the MAF to the intake manifold...

A large vacuum leak would not cause a no-start situation. Need to chase that down first. Check for fuel and spark and chase it from there.