the saga continues...

Hello again...
Still having problems with my fuel/air system, I think. If anyone remembers, about a month ago I replaced my stock airbox/intake with a new AEM brute force (97 k1500 5.7l). I started to have idle problems which were addressed by GMMerlin(thanks!) and others. Went to a performance shop in Omaha, Ne. and the mechanic pulled the codes which he said meant I had 4 bad fuel injectors. I was not surprised (160k miles) but declined his offer to replace the 4 for upwards of 750.00! I ordered an entire assembly including fuel meter and all 8 injectors from a company called Lingenfelter (sp?) for 349.99 and installed them myself. Great improvement! Mileage increased from 12.5 to almost 17mpg, and the truck started faster and idled a little better. HOWEVER, the $%*?!@ thing still runs poorly at below 1500rpm, especially in gear. It starts right up and idles well for about 30 sec, then begins this choppy idle alternating from 400 to 800 rpm. Back and forth, back and forth, and when I put it in gear, it dies! :banghead: I went to the local Advance Auto and used their code puller which gave me po172 and 174, which according to my trusty chiltons means I am lean on both cylinder banks! Both the AAguy and my local NAPA guy told me it sounded like a vacuum leak. They also both gave me the same way to diagnose. While the truck was running, I sprayed carb cleaner around the intake manifold and all the vacuum lines, nothing! No racing, no dying, no change at all. Now I am completely stumped. At first I thought O2 sensor, but I think I would get a code for that. Nothing in the codes at all about the MAF, but could that be it? I am completely out of ideas and would appreciate your help. Thanks in advance for you attention and sorry this was so long....
Chris

I work for a Nissan dealer. EVERY time I have had a Nissan vehicle that was lean on bank one AND two, it has been caused by a mass air flow meter. I have had Toyota's do that as well. If you have access to a scan tool you can check the long term fuel trim on both banks, if both are being leaned out its probably a mass air flow meter problem. Sometimes you can actually clean the wire and they will work better. (the new MAF sensors on Nissans can't really be cleaned anymore due to their design, older ones usually could.) I just spray the wire with a good carb cleaner to remove any dirt. If that doesn't work, you might try swapping it with a friends MAF sensor to see if it helps if you know someone with the same truck. Good luck!

I've heard of people testing for bad MAF's by simply unplugging it to see if there is a change. Naturally it will throw a code, but if the idle improves the slightest bit then your MAF is on it's last leg. I even seen people using diodes as jumpers to trick the computer into thinking the MAF is saying all is well and leaving there MAF disconnected usually kills MPG though and causes engine to run rich.

The one Nissan (Maxima) I owned for 9 months constantly killed MAF's without ever throwing a code, and really affected the car in power and idle.

Finally got around to replacing the MAF today...No change at all. Still starts fine, idles roughly and surges between 4-800rpms. Often dies when placed in gear. Runs fine at speed. Anyone have any clue?

Finally got around to replacing the MAF today...No change at all. Still starts fine, idles roughly and surges between 4-800rpms. Often dies when placed in gear. Runs fine at speed. Anyone have any clue?


I WENT THROUGH THE SAME EXACT THING. IT WOULD EVEN HICCUP/MISS. IT TURNED OUT TO BE A BAD ENGINE FUSE UNDER THE HOOD. I REPLACED IT DISCONNECTED THE BATTERY JUST TO BE SURE. AND ALL WAS FINE.
THAT FUSE MADE IT SO I COULDN'T CLEAR MY P0102 CODE.

Finally got around to replacing the MAF today...No change at all. Still starts fine, idles roughly and surges between 4-800rpms. Often dies when placed in gear. Runs fine at speed. Anyone have any clue?

3 things I can think of to look at. 1 - the Fuel Pump Relay. 2 - the Fuel Pump and 3 - the Idle Air Control Valve