I just rebuilt my engine because of a spun bearing. I also changed the timing belt when it was all taken apart. I just started it today and it has a misfire on cylinder 4. Along with the misfire it is making a very weird sound I have never heard before. It sounds like a popping sound. Also it does not stay on for a while. After about 30 seconds it will die off. I switched coil packs and the misfire stayed with the cylinder. I pulled the plug and it was a little wet on one side which makes me think its a spark issue? I checked for codes and got 55. I checked the PTU connectors and they looked fine. I also checked the CAS connection it was good as well. I would upload a video of the sound but I do not know how to do it on here. Any ideas??

Check the injector. Ohm test should be between 10-14 ohm's. If it is not, thats the issue. It very well could be stuck open causing it to foul the plug and create a no spark issue.

[youtube]http://www.youtube.com/watch?v=9xfhItaVPZA[/youtube]

Video of misfire and weird noise.

Along with the noise and misfire, it will not stay running. It will turn on for about 10 seconds then it will die.

Could all of these problems be caused by bad timing with the timing belt? How would I check that? Tomorrow I will be swapping spark plugs, checking spark, and checking the ohms for the injector. Also I think I'm going to try to do a compression test and see what I get. Any responses would be appreciated.

I found out that there was low compression in the cylinder. What do you guys think would make that awful sound?

Better video!

[youtube]http://www.youtube.com/watch?v=ERTN4GTb ... e=youtu.be[/youtube]

I've got a car doing the same thing after i pulled the plenum. I'm pulling my hair out trying to figure it out. I've got different codes tho.

Well I just realized that the popping sound could be an exhaust leak. But that still wouldn't explain the low compression unless my piston rings or valves are bad..

solaire wrote:I've got a car doing the same thing after i pulled the plenum. I'm pulling my hair out trying to figure it out. I've got different codes tho.

Check your exhaust and see if it leaks and lmk ASAP so I can stop stressing.

Yea I have an exhaust leak. I hear the ticking. Occasionally I'll get a puff of smoke in the driver side

solaire wrote:Yea I have an exhaust leak. I hear the ticking. Occasionally I'll get a puff of smoke in the driver side

Hm, okay so that popping sound could be exhaust leak then.

As for low compression in one of my cylinders, could this scoring cause the problem? I can barely feel it if I run my fingers across it.

probably not. You should have done a wet test before pulling the head. That would tell you if it was in the rings or the valves. How low was low compression? If it was around 100psi then it could be a valve issue. Take the head, turn it upside down and put some carb cleaner in the combustion chamber. If it leaks out then you've found the problem and where it leaks will tell you the problem.

It was around 30 PSI. I did that with the valves and no leaks. This tells me its the pistons rings right?

yep that or head gasket was bad. If you used china piston rings then it's likely rings. Generally tho they hold up for awhile just burn oil later in life (like a week later)

I ohm checked my injectors today and found #1 was 17.1 ohms and #3 was 12.2 ohms. I've got a misfire on #1 and #3 and #3 is getting fuel fouled so I think it's time to put a set of injectors in this 91. Guy who owns the car said he's had "Some injectors replaced" turns out it's got a replaced one in #3 and 5. I bet they're cheap aftermarkets knowing the owner so I don't doubt that #3 is stuck open. I can disconnect and reconnect and it'll effect engine running. Guess replacing the connectors fixed one problem that was masking another.