first infiniti. like it but the misfiring has me baffled

[AVGQ45]

Hey so I got a 94 pearl white q45t its really nice on mature 20" rims got it from mexican coworker for $800. Said it misfires. It sure did. Woildnt hold an idle until I cleaned the maf. Now my cylinder 6 wasnt firing I knew by unplugging coil and it didnt idle any worse. Figured it was that coil so I used the #4 coil. Same issue #6 cylinder when I pulled off the coil plug no rpm difference aka same issue. U guys thinkiing it could be spark plug? Havent been changed in 30k has ngk iridium the really expensive ones. Now before I buy anything im doing a compression test tomorrow and if its ok im buying one new plug and seeing if the miss stops. Any other suggestions?thanks

-Tone

i forgot you guys like pics right? not bad for $800, yes?

[elwesso]

Injectors.. 99% chance that's what the issue is.

http://www.q45.org/ohminjectors.html..

Welcome to NICO!

Our sponsor deatschwerks (http://www.deatschwerks.com/) sells brand new injectors. I just paid $100 shipped for a new injector.

[Q451990]

to NICO!

Ditto on the injector diagnosis. Coil packs on this version of the Q are pretty much bulletproof. If the spark plug on that cylinder looks badly fouled, be sure to clean it after you replace that injector.

Good luck!

Heath

[OwnerCS]

Welcome to NICO! When I bought my Q almost 3 years ago, I thought it could run better with new plugs. So when installing new plugs I found the plug wells for cylinders 1 and 2 contained a large amount of oil from a leaking valve cover gasket (note 90-93 use RTV) instead of a gasket. I replaced the plugs and noticed an improvement but it still lacked the power I thought it should deliver. About two weeks later I developed a miss that turned out to be two failed injectors. An item to note about the VH45DE is it will seem to run ok on 7 cylinders with a failed injector. When the 2nd injector fails then you will really notice a miss.

Over the past year my 16 yo son has been with me when we looked at a couple of used Qs for sale. He will put his hand on the plenum and give the engine a slight revup where he pointed out something is wrong like the engine is running on 7 cylinders or less.

After two injectors tested bad, I decided to replaced all injectors, all under plenum hoses, heater pipe, knock sensors, and the knock sensor wiring harness. If you get ready to tackle pulling the plenum we can show you some pictures and there are many threads on here about pulling the plenum.

[AVGQ45]

Thanks for the advice. Pulling the plenum is nothing. Ill ohm test the injectors and see whats going on. Thanks again though, ill get on it this weekend. Cant be harder than fabricating up triangulated four links on rock crawlers..

[AVGQ45]

Im testing the resistance today on that injector after I do a compression test on that cylinder to check for bad piston rings or bad valves. Im really hoping the compression is okay im not about to get into the bottom end of this motor. Itd be different if it were a v8 with a solid front axle like im used to where I have room under there and around the engine bay. U can probably guess I'm a truck guy and used to getting under trucks and working on them and Solid front axles and all that. but I'm trying to make this car work or at least turn a profit by selling it or I might keep it for a while if it's just a bad injector.ill let u guys know compression results and ohm readings as soon as im done. http://Www.q45.org is a god send.

[AVGQ45]

Okay so comoression was good 150 in cylinder 4 & 6 (6 being my troublemaker ) so I was happy there. Put a new ngk spark plug in cylinder 6 praying itd be that simple but of course not . Tried to check the injectors resistances (ohms) with my multimeter following that guide with the positive probe on positive battery terminal and negative probe touching each pin an I only got 8 on the meter on each pin with no fluctuation so it must have malfunctioned. What to do now? Its gotta be that injector I mean I feel it missing hard when im flooring it on the road flat or uphill. Also its skippin at idle but its still driveable but I want this fixed as cheaply and as quickly as possible. Infiniti/nissan tech said he'd diagnose it for 75 $. Think thats worth it to find out for sure? But I mean what can he do that I cant besides maybe he has a noid light. Should I go to him or just buy an injector and chance it?

[Q451990]

Makre sure the ignition switch is on (not accessory, but gauges on - engine off) when completing the ohm test. At some point the injectors moved to a switched circuit. I believe it was for the '94 model year.

Heath

[AVGQ45]

Okay I did it with everything off. Ill try again tomorrow. And god its so sluggish. I put it in first and tried to get it to chirp or break loose doing a wide u turn and it just bogged out. Wtf? This is a v8 for gods sake!

Edit: but why would the ignition being on have anything to do with testing the non 12v side of the fuel injector harness? I just dont get how the resistance could be measured more with draw on the battery.

[OwnerCS]

When you need to pull the plenum, you may want to refer to some of the under plenum pictures in the following slide show. There are some hoses that you will be tempted to cut that are actually connected to metal hoses that are bolted to the bottom of the plenum.


http://s286.photobucket.com/user/Ridgel ... der_Plenum