Hello everyone. I've been having a few issues with a potential misfire? I actually don't know the exact problem, just that it should not sound like the way it does, and poor revving and acceleration. So far, I have found out that all 6 injectors are clicking, and I think every cylinder is getting spark. I replaced the plugs with NGK gapped to about .42, and did a valve adjustment to factory specs. Here's my thoughts:
1) poor fuel pressure? (clogged line or filter, bad fuel pump) I know I can find out the pressure very easily I just haven't had the time. Maybe it doesn't have enough pressure to get to all the cylinders?
2) out of time? The distributer is all the way advanced, but I THINK (emphasis on think) it is at 10 degrees BTDC, I think I confirmed with a timing light. With the way everything in front of the engine is placed, was hard to get a clear reading. Is there an easier way to confirm that it is timed correctly? The previous owner did say that he redid the ignition system, maybe he dropped the distributor in too advanced or retarded. This also makes me think that the timing chain possibly slipped or something.
3) bad vacuum lines? Theres so many with the emissions regulations, have not had the time to go through the system and check.
4) possible wiring issue? I don't know much about the system, but nothing is impossible on a 40 year old car haha.
I don't even know where to start, so anything would be helpful at this point haha. Would love to hear if anyone else had this problem and/or how they solved it.
Thank you!

 

1) I doubt it is a fuel pressure issue, though possible. Test your fuel pressure when you have time. In the mean time, take the fuel filter off and see if you can blow through it freely. It will be like blowing through a straw if it is clean (shouldn't have to blow super hard) and gas should pour freely out of both sides. If in doubt, just change the filter, they're about 10 bucks give or take depending on where you buy them.

Is your voltage regulator working? What does the ammeter say when you rev it up? Do all the lights get brighter when you rev it? If the voltage to the fuel pump is too high it will make the pump act crazy and fuel will cut out making the car hard to drive at anything more than slight throttle. It's internal to the alternator so if bad it would be easiest just to replace the whole thing, though usually it's not actually failed more likely is just a loose wire to the alternator.

2) It's an interference engine, if the timing chain slipped you would probably have valves crashed into your pistons and a VERY unhappy engine, much moreso than a misfire. Even if it was off by one tooth it would probably barely run, you say poor acceleration so the fact that you are able to even drive it somewhat normally and it just sounds bad/ revs poorly makes me think it's not that. If the distributor was in 180 degrees backwards or something it wouldn't run at all, and IIRC it only fits in those two positions (been a while since I had mine out, though there was a point when I did about a dozen times). If you said it's all the way maxed out in adjustment that does not sound right. Without getting too technical and trying to set the timing just right, simply try turning the distributor a little and see if it clears up or gets worse. If it does seem to make some difference THEN you can worry about getting it dialed in perfectly.

3) Bad vacuum lines can make a car run rough, but it it was a bad enough leak to make it run the way you're describing it would idle poorly too, and you would be able to hear a hissing sound coming from under the hood while it's running.

4) check the wires going to the injectors, the clips like to break. You said they're all ticking away, but are they all working all the time? If they're loose connections they may be intermittently cutting out. Are you POSITIVE all plugs are getting spark? If not, it's quick and easy to check, just to rule it out.


There are a bunch of things it could be, just start going over everything. Make sure all connections are good and no raging vacuum leaks. Check your coil, AFM, distributor, etc. Make sure the ECU in the driver's kick panel isn't all corroded and crappy.

Good luck

 

Hello, I have been having misfire issues with my z, the car was running fine until one day I ran out of gas once i refilled it and went to drive it was misfiring in high rpm's and wouldn't even go up a hill, i checked the spark plugs and noticed that the had a lot of carbon build up, I have only driven the car around 60 miles since we rebuilt the engine. Any help would be appreciated!