Had engine bay cleaned = rough idle, horrible fuel consumption, plus... (95 Q)

[mcastro]

I had a local shop perform some minor service my car recently, and the tech suggested I degrease the engine, which was needed due to a leaky valve cover gasket. Seems like a simple task..the engine bay looks great, but after I picked the car up, the drive afterwords was not. Idle was rough and would die, and although it performed well under acceleration and at freeway speeds, I was surprised to see my gas gage literally drop after a few miles of driving. I returned back to the shop, and the technician said that this is a common occurrence and that things should return to normal after letting the engine dry. I was not very convinced, but I thought I would give it a chance to dry overnight

The next morning, new symptoms: idle was rough but was holding around 600 Rpm, but performance was not good as the engine also ran rough under acceleration and at low speeds, the exhaust was dark and smelled (almost like a cleaner...could have been just poorly combusted fuel). Before I could get it back to the shop, the engine just wouldn't turn over, so I had to have it towed (flatbed).

Here's my concern...the technician recommended swapping out the plugs (OEM only) and all coil packs, as he has diagnosed a weak spark. I would assume the plugs have become fouled, a result of a bad fuel-air mix or something else causing the problem, perhaps due to being exposed to excessive moisture (I suggested they test the MAF, but I was told that no codes were generated on the diag on the non-running engine). I am not going for the coil pack analysis, and am perturbed that the plugs need to be swapped out. Car was running fine prior to the "degreasing"exercise.

Two questions: coil packs (all 8), isn't that a blanket guess? And, what might be the cause for the sputtering idle and resultant fuel consumption after the cleaning?

[Infinitiguy19]

Your "Mechanic" is a retard. Look into the MAF sensor as the culprity with the symotms you posted. If you have weak accleratiuon then its TPS issue.

Or if you are really unlucky you might have killed one or more fuel injectors.

Did you cover the electronics when you "cleaned" the engine?

[qship96]

What makes you so sure the problem is even related to the engine cleaning process and not something related to the repairs they performed???? Could be a loose/disconnected vacuum hose or wire or vacuum leak, etc. What did the initially "fix" while you had the car in their shop?

[mcastro]

The service I had them perform was to swap out the tension rods and perform an alignment. I was under the impression that the degreasing was to just clean the lower part of the engine bay (beneath the valve covers), but they did the whole thing. I did not get the impression they covered the electronics (I did not see ay moisture around the fuse/relay box). My immediate thought was the MAF connector

I was not expecting to get into any engine maintenance or repair. And although the shop is reputable and the technician is a ASE certified master tech, I have been around this board a long time and am always concerned about the lack of experience with the G50. I had to make a go/no go decision about the plugs, but once they get the engine turning over, I am going to be overly "suggestive" about their course of action!

I appreciate any recommendations I could throw their way (aside from insulting epitaphs)!


Modified by mcastro at 9:46 PM 2/5/2010

[Infinitiguy19]

See my signature if you want to learn a lot about the Q45.

But c'mon you go in for suspension related things and they clean your engine? You would'nt go to a denist for a broken bone would you? Everyone has there specialty and barely any people know about the Q45 (Some can't spell Infiniti correctly).

Best thing to do I suppose is run from that "Mechanic" and read as much as you can about the car and let the car dry and see what that yeilds.

[goody90q45]

Take a look at both the MAF connector and the CAS (distributor, driver side front of engine) connector for moisture and corrosion, clean them up, tighten the pins, and lube with dielectric grease. These two connectors, as well as the two sub-CAS connectors are a different plug and don't seal as well as the throttle position sensor type connector, especially if a high pressure wand is held close. Also look under the plenum and make sure the valley and KS aren't flooded.

You own a 95Q- There's nothing wrong with the coils.

[mcastro]

Take a look at both the MAF connector and the CAS (distributor, driver side front of engine) connector for moisture and corrosion, clean them up, tighten the pins, and lube with dielectric grease. These two connectors, as well as the two sub-CAS connectors are a different plug and don't seal as well as the throttle position sensor type connector, especially if a high pressure wand is held close. Also look under the plenum and make sure the valley and KS aren't flooded.

You own a 95Q- There's nothing wrong with the coils.

Thanks, Mike. Sounds like both those things could cause these initial symptoms; appreciate the confirmation on the coils as well. Exactly the kind of feedback I was looking for!

[3Q Jay]

coil pax sudden multiple failure unlikely, but highlypossible that the 'bath' got into the coil harnesses and or plug holes. changing the plugs should remedy any trapped moisture under the coil pax and around base of plugs,but i would have them inspect andmake sure all of those are dry. put stabilant-22 on all the harness to coil connx. also agree with goody that you should check CAS for moisture.