1994 Q45 engine bucking/jerking

[logisoft]

My 1994 Q45 with 145k miles is acting funny. After the car warms up andusually while driving on the highway I feel a bucking/jerking. At65-70mph it will act like the engine is getting starved for fuel and buck. If I shift into neutral at speed the engine revs smoothly with noproblem. Also, if I kick it hard it accelerates just fine without any buckingat all, so I was able to "kick it" home. WHen I got off the highway I wasexperiencing this bucking at lower speeds, too. I checked the transmissionand it seemed a little low, so I added fluid. Because the engine runs sosmooth in neutral, I was thinking transmission. This seems to be only aproblem after the system has warmed-up. Any ideas?

[maxnix]

Fuel pump noise form the rear? How new is you fule filter? Unfotunately we can't tell where you are from with your incomplete profile (please complete as requested in the sticky note above), so don't know if fuel blends could be contributing long term.

Welcome to the board.

[logisoft]

I had the pump replaced 2 winters ago. No noise now. The fuel filter was replaced this spring when I had the engine replaced with a used one with 65k miles. As I mentioned, when I feel the bucking I can put the car in neutral and smoothly rev the engine. That's what made me think transmission. I'm in Chicago.

Thanks

[eric8859]

I have exactly the same symptoms, see my thread from today at eric8859hesitation 94 q45

the reply i received was possibly a MAF Sensor, Mass AIr Flow Sensor, I am going to clean sensor chamber tonight and connections. part costs $430 or so.

[logisoft]

Jesda Gulati [[email protected]] sent me this with a step by step cleaning process for the MAF. I'm going to try it, too. Good Luck.http://www.q45.org/maf.html

[eric8859]

Sounds good, hopefully it will work, let me know how it works out!

[logisoft]

Well, I bought some electrical parts spray cleaner yesterday. At my location, I had nothing but a crescent wrench but I still wanted to experiment. I disconnected the air cleaner housing from the big hose and turned it sideways to expos the MAF sensor. I gave it a couple of sprays for maybe 20 seconds on each side. The screen in the housing was black, sooty looking and now it's bright and shiny. So is the MAF. Put it back together and took it for a drive. Everything seems fine. Since the problem was intermittent I can't say it's fixed for sure but it runs just great. I'll let you guys know if the problem reappears. Thanks Jesda!

[fxjackso]

It almost goes without saying but is that a newish Nissan air filter in there? Keep it clean after your good work.