Cylinder 3 dead, any suggestions?

[AllWheelRS]

I recently started having idling trouble with my 92' laser which quickly turned into a nasty miss under boost. It turned out to be a blown intake manifold gasket so I replaced it, boost leak tested and my lower injector seals were leaking. Tried to replace those but napa sent me upper injector seals instead of lowers (should have known when our shop cost was only $3.94) so instead I put an O ring under the grommet on the upper part of the injectors which solved the leaking seals. another boost leak test and intercooler was leaking, fixed that and all was good. I then let the car idle for half hour while I did other work, took it around the block and boosted with no issues. Parked it, finished work and got in to drive home 45 mins later and I got a nasty miss at all rpms. First I thought it would smooth out because the car has done this to me before when started warm, it will miss for a minute or 2 and then go away, but not today I had a nasty miss all the way home 25 miles. So I have to wait til I get to the shop tomorrow to diagnose it any further but heres what I have done and plan to do. Pulled all wires 1 at a time, cylinder 3 is defenitely misfiring, it has spark and the injector is clicking but I can't pull the plug until I get to work tomorrow as all of my tools are at the shop. Tomorrow I'm going to swap injector 3 with another and see if the miss moves and also do compression test on all cylinders. No smoke from the tailpipe or anything, doesn't smell rich, just cylinder 3 is completely dead.

Any ideas on what else I should try if that doesn't get me any closer? All emissions have been removed including Fuel pressure solenoid, and I tried letting the car cool down for 2 hours and still misses.

 

[Vladimir]

well i agree with doing the compression test and swapping injectors that will help you a lot. Also check the condition of the spark plug and the wire, look for excess moisture in the cylinder maybe injector is leaking, alltho it pulsing. Also you can check the duty cycle on that injector to see if the ecu is doing its job, that is if you have a tunnning device. Check the wiring. Also check the spark for continuity.

 

[AllWheelRS]

Plugs are brand new last week, but I also intend to pull them all and check the condition, wires are all between 3k and 5.6k ohm. No tuning at all on this car just stock ecu, and I do have spark at all 4 cylinders. by excess moisture/ leaking injector do you mean it's stuck open? I hadn't considered that, will def check tomorrow when the plugs are out.

 

[Vladimir]

yeah, if it stuck it will flood the cylinder. It could still make clicking noise but wouldnt close all the way. That ohm reading is good as long as long as the insulator is not cracked and sparking agains the valve cover in a certain position.

I've had good resistance before but a problem with a wire. The insulator was cracked and in some position a spark was coming out of the wire sparking against the vale cover

 

[AllWheelRS]

If it's wires I should be able to swap #3 with another if the 2 are long enough and miss should move, I'll defenitely try that too tomorrow thanks again.

 

[GSTurbo1]

1.) compression test
2.) leakdown test
3.) problem found as far as piston/cylinder condition

 

[AllWheelRS]

1.) compression test
2.) leakdown test
3.) problem found as far as piston/cylinder condition

Don't think it's a compression issue but will be checking anyways.


Just started it up cold/runs great again, drove up to temp and stopped, went to start 20 mins later and cylinder 3 is misfiring again, I'm really pointing toward that injector being bad.

edit: swapped injectors 3 and 1, cleaned all 4 and checked resistance. When cold 3 of the four have 4.2 ohms resistance, the third which was originally in cylinder 3, the misfire cylinder was over 8 ohms. I haven't been able to get it to misfire today so I can't be positive, but I do believe when that higher resistance injector gets real hot its acting up, still haven't figured out why it does it on warm starts and not while driving once the car warms up. So for now I'm assuming I should be looking for new injectors, I'm keeping my multimeter in the car so if it acts up again, I can check the injector resistance.

 

[AllWheelRS]

Finally did it again today a week later and the miss was at cylinder #1 which is the cylinder I put the suspected bad injector in so it is defenitely an injector issue. It only seems to happen on days above 80 degrees, wish I knew why this injector is acting up but I'm happy to at least have figured out exactly what the problem part is.