96 850 Turbo Starts but runs rough then dies. Backfires.

[New2Volvo96]

Hi all. I am posting this in hopes to help my father in law figure out what his problem is with his 96 Volvo 850 Turbo. I helped him replace the PCV system and he replaced the PNP switch but after it all got put back together it now will start but dies after about 5 seconds or less. If you keep on the throttle it will keep running albeit very rough, but it backfires and there is a strong gas smell. We tried checking the fuel pump relay and bypassed it didn't help and it sounds like the fuel pump is working though we haven't tested the fuel pressure yet. I haven't cleaned the MAF yet but I scanned for codes and found nothing and can't imagine a dirty MAF would cause this many problems. I'm hoping someone might have some insight as to what might be causing these issues. Possibly didn't get something put back together correct. Vacuum lines look good but it's hard to test them when it's running so bad. Any suggestions would be much appreciated. Also I should note that his car has something draining the battery so it only starts up when being jumped. Thanks guys!

[Clemens]

what about the intake manifold gasket? if there is a leak, it will run horrible.
are all the injectors seated and connected properly?

[abscate]

It’s really easy to pinch something between the manifold doing the PCV

Replace all the vacuum lines that you have no history on, at 20 years old +, they leak now.

[rguzz]

Second the distinct possibility of an air leak at the intake manifold, ie the gasket. It can tear most easily in the upper right corner when replaced, I believe around the upper stud located there, but that is from memory. If it was running fine before taking on this job you will need to retrace your steps, unfortunately. Twice as fast the second time! Get a new gasket regardless. There are numerous step by step guides to help you if need be.

[New2Volvo96]

I was really hoping it wasn't the intake manifold but I had a sneaking suspicion it might not be on correctly or a bad gasket. I'll dive back in there and see what I can find. Thanks all. This forum is super helpful.

[bmdubya1198]

I agree with everyone else, make sure your intake manifold gasket isn't leaking. Also check over all other vacuum lines.

It's unlikely given that this wasn't a problem before this work was done, but the car will struggle to run if the voltage is too low. Definitely do a parasitic draw test once this idle issue is knocked out.

[erikv11]

You're in good shape with all the comments IMHO. A peripheral comment -

... can't imagine a dirty MAF would cause this many problems. ...

If the MAF isn't visibly oily or grungy, cleaning it will almost never make any difference, not even a small one. Basically not worth spending for the cleaner. Do an unplug-the-MAF test first.