broncoguy

Hi-
I have a problem I can't figure out....seems like I am not firing on one cylinder- (front right, as you are facing the car). Car has been running rough, especially at idle. Exhaust makes sound like "puff, puff, puff". Pulled plug wire on that cylinder, no change in idle. Checked plug, looks fine. Swapped wires to see if I had a bad one- no change. Did compression test on all cylinders. Readings on all cylinders were from 180-190, except for that cylinder, which was 200. Checked injector, sounds like it is firing. Cleaned injector contact and put some dielectric grease on it.

Car has 175K on it, and I know I have a broken exhaust stud on that particular cylinder, if that makes any difference. Only thing I have not done at this point is check the ECU codes.

Anyone have any thoughts????

eric93SE

iTrader: (1)

Check the resistance on that injector, compare it to the others.

Matt93SE

iTrader: (44)

don't know how you would do it, but check the vacuum on that cylinder too. my wife's altima had the same symptoms, and it turned out to be a bad intake manifold gasket. at idle, the vacuum was high enough that it caused air to seep in through the leaking gasket and cause the cylinder to misfire. soon as you gave it some gas, the vacuum dropped off and it quit leaking.

broncoguy

OK, I'll check that out- Thanks. Resistance should be between 10-15 ohms, correct? Also, in terms of the gasket- do you think the broken manifold stud would have anything to do with it? It does leak from there with the characteristic sound.
One more thought- I had read somewhere that the leaking exhaust could cause the exhaust valve to have problems. But, if I were having any kind of valve problems, wouldn't I get a bad compression reading?

subs1000w

10-14 ohms and it sounds like an injector

Jeff92se

iTrader: (82)

If the exaust leak is really bad, it could very well cause that cylinder not to run right. How bad is the leak? Leaks all the time or just when the engine is cold? How is the plug? Black and wet or just like the other plugs? You could try swapping coil paks/plugs just to elminate those items. You could also try swapping injectors if it's the front bank but you will need to buy new o-rings and be very carefull about removing them.

broncoguy

Jeff-
All of the plugs looked pretty much the same- whitish deposits on all of them, none with black/wet deposits. The leak is pretty much all the time- the exhaust stud on the bottom side for that cylinder is broken off and missing, the top side is OK and tight.
Cylinder in question is in the front bank, farthest to the right when facing the car. I was hoping to know for sure that the injector was bad before tearing into it (replaced them on my 92 Stanza- not fun)so I will ohm it out when I get home tonight and see. Like I said, I can hear it firing, so seems like it should be working. Already tried swapping plugs with a brand new one, no luck. Last question- what is a coil pack, and where do I find it?

broncoguy

OK, checked the Chiltons- Looks like mine does not have coil packs, since it is a 90 model with a distributor ignition system...

Jeff92se

iTrader: (82)

Well I think the exhaust leak is a fairly big problem. SLIGHT leaks will screech when cold but will expand and close the leak when warm. If your's leaks all the time, you are probably not getting any decent power out of that cylinder.

You car features a VG30? You mentioned plug wire so I assume it is. I thought you had a coil on plug ignition(you do not sorry). So then I revise my reply to.... you can try to switch plug wires to make sure that wire is not internally shorted.

broncoguy

yep, VG30E. Yep, did the wire swap too- no change. Just seems like I have done everything I know of to find the problem at this point. I will check ECU codes tonight along with ohming out the injector....I understand what you are saying about the exhaust leak and low power, but I don't think I'm getting anything at all out of that cylinder.. thanks for your help, though.

broncoguy

OK, looks like an injector... ohmed out the one that's giving me a problem, and got 81 the first time, and 79 the second. checked 2 others and they were 13.3 and 14. Guess I'll be replacing that injector..thanks for all the help, guys. Anything I should know about replacing them specific to the Maxima? I've done it on my 92 Stanza, so I've got the basic idea.

subs1000w

lube it up will vasiline or somthing equivelent very well before installing