I just picked up a 91' Max (120k on the clock, 5sp) a few weeks ago and am having a slight problem. Ever since I bought the car, I noticed that above 4k rpms or so it would buck / lose power for a fraction of a second. Since I rarely drive in that rpm range and it didn't happen every time I didn't think much of it.

Fast forward up to a week ago. I changed the oil, and air / fuel filters and it was running like a champ. Then two days ago I started getting bucking / loss of power all over the place and it's even having trouble idling at times. It hasn't actually died quite yet but sometimes feels like it might.

It's looking like something ignition related. Any thoughts?

 

Hmm, could be a few things. Injectors, bad spark plugs, spark plug wires, and coil pack just to name a few.

Start of by checking your spark plugs.

 

How is it idling?

 

It's idling fine most of the time. I'd say one out of five starts over the past two days it's stumbled quite a bitfor at least a minute or so. The "bucking / stumbling" doesn't seem to be tied to any rpm range or other event. Sometimes it does it at idle, usually during accel, sometimes when at a steady speed. I have noticed it seems to be more common when I let off the gas then get back on it.

 

if it does it when the engine is warm, check the o2 sensor, that was the case with mine, i had the same bucking and stalling issues. My idle is still rough but that's another problem i'll need to tackle.

 

It's done it cold and warm. The o2 sensor is probably due to be replaced anyways so I'll give that a shot.

 

i think it could be your MAF dying

 

Any way to verify this? Would cleaning the maf help?

 

Also, I know this is a stupid question but....

Where are the coil packs and ecu in this thing?

On my past vehicles they were easy to pick out...

Thanks to everyone for helping out a noob

 

ive got a 92 SE and the coils are different from the 91s, and i think ECU might be in a diff place too, so a 91 guy could help you out with that

as for MAF... its just that your symptoms sound a lot like mine when i first started having this problem. I dont think theres a super accurate way to test it, but one popular method that worked for me is wait for your car to have the intermittent idle problems. Then try tapping the MAF with a screwdriver , and see if that changes the engine performance a lot. You sohuld also check the MAF connector for corrosion I've heard of people cleaning their MAFs, but ive been told that its very sensitive and doesnt respond well to cleaning so I'm not going to reccomend it

If the tapping the MAF test doesnt seem to do anything, I'd just start by ruling other stuff out. Test everythings thats been listed in this thread, plugs coils injectors, plug wires, FUEL FILTER, clean the throttle body, maybe check out PCV valve? if none of that does anything may wanna check fuel pressure and EGR valve

 

The VG motor's coil pack is located just below the distributor. It's usually covered by a shroud.

 

Update: The car was idling pretty bad this afternoon so I took the opportunity to try out your advice and lightly tap the maf. The engine almost stalled when I did. It had the same effect when I tried two more times. A light tap and it almost dies. Sign of a bad maf?

 

Hi, my (working) MAF certainly doesnt respond to light tapping. and my symptoms sounded a lot like yours at first (they eventually got worse and more consitent). So I guess there's a good chance the MAF is the problem.. I feel sort of uncomfortable telling you for sure though since im just basing this off my experience, and not any training or vast mechanical knowledge, ya know? So if you're at all unsure, get a second opinion before purchasing anything.

by the way when mine died I got a used MAF for like 30 bucks thats still going strong, so if its at all possible that might be a good idea... new they can get pretty pricey

 

Thanks again for the advice. I'll try to pick up a used MAF and give it a shot. If I have to end up buying a new one, I might try a few other things first

 

if you dont mind used and dont mind waiting alittle bit... try ebay. i got a whole intake system (for a VG) for $35 + shipping. after mine was doing the same exact thing. it almost felt like i was in a gear to low and just jabbing and quickly letting go of the accelerator. if you dont wanna wait and money isnt an issue, just go to nissan although MAFs are pretty dang expensive

 

you can always buy a rebuilt one.

 

MAF will run you well over $400 bucks so u can easily see why most people are reluctant on changing it out...heh....tapping mine didn't do anything to my engine when it was running and having problems and they recommended me to do it for my bucking and stalling problems. Chances are after running that test that it is the MAF that's giving you the problem, so i'll second the motion on that being the problem. (Thank God mine was only the O2 Sensor - 100 bucks)

 

the Maf is only about $200., rebuilt

 

jesus christ the 02 sensor alone is $100?!
Sorry I just brought this thread from the dead, but my car gave me a EGR system Hi/Low Flow code and I'm trying to figure out what are the symptoms of a bad EGR system... or faulty should I say.

 

o2 is only $60

 

Oh... good lol I was about to sh*t myself, I also had a Front Left Heated O2 Sensor code

 

you do realize you're in the 3rd gen forum......

 

i know... lol at first I didn't notice, but when I read the price of $100 for a sensor I was like what heck shouldn't it be cheaper... anyways I look what part of the forum this thread was in and was hoping it wouldn't be the same price for the 4th gen/VQ30DE.

 

some times they are.

 

My 92 SE with 135k miles is doing the same thing. It started doing this over 5 years ago but the problem was so rare I kept putting it off. Last week though the car went crazy. At every intersection (always at the intersections) it would take off fine, get to around 3,300 rpm and stall. It wouldn't restart until I pulled to a stop. Putting it in nuetral and cranking while still rolling won't do it. I also noticed that after it started stalling I could hold the throttle wide open with the clutch in and the engine would rev to 3,300 rpm's and bounce off it, almost like a retarted rev limiter. I restarted the car and it stopped.

I took it to a longtime trusted mechanic. The car actually stalled on him and right away he said it was electrical. After charging me $200 to replace the main fuse and the positive battery cable, I took the car home. The next day it stalled again. 6 times in a 15 minute drive . My mechanic did say the next thing he'd look at would be the ignition coils. I ordered one left and one right from Autozone and will switch them around in the engine to hopefully find the problem. I'm going to try and find a used MAF too.

Let us know what happens Faikius. Hopefully you can fix it.