1994 Q45 Rough Idle

[Albiebear]

I have a 94 Q with 129K miles. Engine recently lost No 1 injector. Dealer said it was bad connection and fixed it. Two weeks later, it went out again. I replaced with BOSCH injector. Engines runs on 8 cylinders under power but idles rough and feels like a cylinder is misfiring. I've traced it to the no 1 cylinder. Idle is unstable.
No "check engine" light under most circumstances although on the odd occation the engine starts on 7 cylinders and runs at power on 7 cylinders with the check light on. Within 15 seconds, the problem corrects itself.


I wondered if the aftermarket injector isn't quite the same as the OEM injector at the lower end fuel flow for some reason.

Any thoughts?

[maxnix]

The Japanese Bosch is a different company.

Why wouldn't dealer use OEM? About $143 from www.everythinginfiniti.com

[Albiebear]

Dealer did not recommend replacement. They corrected a "bad connection" at the connector. The injector went out two weeks later and I ended up replacing the injector (open circuit on the terminals). I didn't buy OEM because the BOSCH injector was $117 which was cheaper than the dealer quote. At this point, I had not heard of everything nissan.

I've read threads that indicate that the OEM injectors are better. I've also asked about the dot color differences (in case I put the wrong injector P/N in by mistake) but it appears there are no real differences between the "dots" based on info from the dealer.

The engine has not run properly since the very first injector error. I'm going to pull the spark plug and injector to figure this thing out.

[maxnix]

Originally Posted by Albiebear

I've also asked about the dot color differences (in case I put the wrong injector P/N in by mistake) but it appears there are no real differences between the "dots" based on info from the dealer.

No color codes on rotary disc injectors on later G50 (1994+) Q45. Only applied to earlier single pintle injectors.

Check out www.nicoclub.com for more information. May want to post in Infiniti Mechanics Forum there.

[Albiebear]

Update:

After months of this problem, I took it back to the dealer and they diagnosed the #3 injector. I then replaced it myself (had to remove the intake which was fun...actually got it loose enough to remove the injector and then put it back on.) Went to fire up the engine and it was worse. Would crank forever before finally starting and then was rough. I then decided to check and replace all spark plugs (turned out these had about 130K on them - gaps were large but the number 3 was black- not firing). Engine was still missing a cylinder.

I took it back to the dealer (engine improved during trip- still missing) and they put the consult back on it and verified the Number 3 cylinder wasn't firing. However, after they cleared the computer, the engine cleared and ran fine (dead cylinder okay and would start very easily). The engine now runs really well. Just changing the parts didn't do it. The computer had to be cleared as well. I also noticed that the idle was a bit unstable for the first day or so after the problem cleared, but within a day afterward, it steadied back out. I am not a control module expert, but the car seems to compensate for issues through a type of learning...this one had gone so far with the spark plugs, it took a day or two for it to stabilize. Engine has done 6,000 miles since without a hitch.