ignition coils on 99 q45t

[arjoe]

Hey guys,I own a 99 q45t with about 85000 miles on it. The check engine light came on recently. The dealership and a local shop both say one or more ignition coils are bad and they should all be replaced. Obviously, thats expensive.I did a quick search here and on line, but can find very little if any info on this problem. I guess what I want to know is if there is another (less expensive) reason for this error? Are the mechanics missing something by just running the diagnostic and reading back the results? If I do have to replace the coils, are aftetmarket parts ok or should I stick to Infinity parts? Any advice is welcome.

[maxnix]

Welcome to NICO, arjoe.

There are a couple of treads on this, probably in Infiniti Online Mechanic.

First, you need to know which cylinder is sending the misfire code, then you need to switch coils and monitor for the next misfire code. It it follows the code, then voilá.

Presume you have ohmed your injectors, checked your O2 sensors and cleaned plenum, EGR and IAC valves and TB.

Finally, for a second opinion, take it to T-3 on Cobb.

[bullittandy]

Welcome to NICO, arjoe.

There are a couple of treads on this, probably in Infiniti Online Mechanic.

First, you need to know which cylinder is sending the misfire code, then you need to switch coils and monitor for the next misfire code. It it follows the code, then voilá.

Presume you have ohmed your injectors, checked your O2 sensors and cleaned plenum, EGR and IAC valves and TB.

Finally, for a second opinion, take it to T-3 on Cobb.

South Cobb drive in Smryna.

Did you guys know that I live 9 minutes from T-3.

[arjoe]

Thanks for the replys. I don't have the diagnostic report with me, but both mechanics said it does not give a specific cylinder, so single coil replacement would be a 1 in 8 proposition. Thanks for the heads up on T3, only a couple miles down the road

[maxnix]

...both mechanics said it does not give a specific cylinder, so single coil replacement would be a 1 in 8 proposition.

That's why they are mechanics and not technicians. Amateur autoproctologists.

Trust in T-3.

[Q45tech]

There are random misfires [rolling from cyclinder to cylinder] and cylinder specific repeatable misfire codes.

One installs new plugs, replaces both front O2 sensors, gives it an induction service and BG44k...................before replacing the first coil pack if you get the random misfire code.

Trying to give the ecu computer more leeway into developing a cylinder specific code.

Or just change all the coils or just a bank of coils and see what happens.

Without a specific code an EXPERT TECH can spend hours and hours narrowing it down and may get it wrong easily especially with 2+ bad coils or coils which only get flakey HOT..............or as they warm up and get ok when HOT.

[Q_SHIP]

I highly doubt it's a coil. Do you have a miss while idleing?

[Q45tech]

It's almost always a coil.............assuming you have replaced spark plugs.

[Q_SHIP]

Not in a y33. I have diagnosed numerous misses and it has never been a coil with almost 200k on the clock.

[Q45tech]

We work on hundreds betweeen the 3 shops...........ATL is the used Q [even Y33] of the world popular with clients because of low price...............as with the early Q, ATL is the elephant graveyard of Infiniti.

That said our fuel in conventional and contain no ethanol [nor previous MTBE] so injectors are never the problem unless the vehicle is a recent import from an oxygenated area.

Then failing or dirty or funky injectors are always a consideration.

When we take a new client we are careful to have them provide location history.

We have 97 clients with 300,000+ miles these guys drive all the time creating EGR deposits.............how we found out egr even works at 85-90 mph on cruise.

200k [highway] is just getting broken in well with proper PM.