engine misfire?

[1gage1]

Hi there guys new to the vw and diesel world and just had some questions. My car is a 91 vw golf 1.6 N/A with 210k

i was getting some air in my fuel lines from the filter so i changed it but im still getting a little bit of air. also if i rev the car up a little bit it sounds like its missing and starts running rough after 5 seconds. my friend said he saw a few sparks come the the exhaust. the exhaust is straight piped

my main concern was the small sparks coming from the exhaust

If you guys have any info on my problem it would be greatly appreciated
Thanks!

[Dakotakid]

That's because you have one of the few cars ever sold in the USA with the optional (one-year only) "Batman option."
Your nights must get pretty dark......huh? Unburned soot of some sort I would imagine. Maybe injectors not properly shutting off or something.

Your car probably still has the factory plastic-tank water separator in the fuel system. It is located (on the bottom of the car) roughly under the rear passenger seat. This fragile (from the passage of time) plastic box no longer plays a useful role in your fuel system. With age, the plastic cracks and is a continual source of air drawn into the system.....seriously. They have actually been outlawed in Gotham City.

Simply remove the tank and splice in a short piece of fuel line. And....don't cut the Joker any slack.

[air-cooled or diesel]

or somewhere @injector pump air is getting in. check all connections from before pump to injectors where air is getting in, afterwards you can run lubromoloy thru and flush, after you shouldnt get sparks out of exhaust. hopefully that should clear up, check for a bad injector(s), 1st check on air getting in, could be a bad inj pump shaft seal, or a connection you have to trace down that needs to be tightened.

[1gage1]

i do have air coming through from filter. just changed it. when there was air in the line it would still run before.  when i went to start it the other day it ran rough for 5 seconds then wouldnt restart. when i do crank it i do get a little smoke/soot. i will delete the water separator and order some of the diesel purge  then see if i can get it to run. is it possible the timing belt slipped? looks pretty worn and will be replaced before its on the road

Thanks again guys

[Dakotakid]

Honestly, you don't know what you have until after you remove that plastic water separator box. Yes.....they REALLY are that notoriously troublesome.

As for timing: timing on these cars does not really "slip" as such and you need to get away from "wife-taily" sort of reasoning when working and relating to this car and engine. That is not an insult. It is just that these engines work in fairly defined parameters. Even a very loose belt will not affect timing until it either BREAKS or steps off a tooth (and the latter is actually a very rare, obscure occurrence).

About the only way timing is affected is if the fuel pump rotates in it's 4 bolts and we are in obscure-land again.

You should replace the cam belt tensioner pulley along with the cam belt. And, please don't buy a cheap belt OR tensioner. And, of course, please buy the proper tools and a Bentley manual well ahead of the task......unless you personally have a very helpful friend breathing down your neck.