Questions and Answers

Nissan Pathfinder Hesitation Q. Hi Vincent, Got a question that I hope you can help with. First, the details of my vehicle. 1987 Nissan Pathfinder 2.4 liter 4 cylinder Z24i engine Manual transmission 170,000 miles Throttle Body Injection 4WD P/S, A/C

Here's the deal. At the end of May, I took the vehicle off-road (mudding) and managed to completely cover it with mud. Well, I just so happen to be in the Navy, so the next day I parked it and it sat for about two months while I was at sea.

I get back, get in, and when I go to accelerate, I have some hesitation and stumbling. Well, I check it and find a vacuum leak in the manifold, so I fix that. Still does it.

Here's what I can't figure out; when I leave in neutral and hit the accelerator wide open, no problems. I can do that either under the hood or driving down the road, and it'll go no problem with it wide open.

When I put it in gear and put a load on it, I can accelerate slowly, but if I put the pedal to the floor, it starts cutting out and jerking. I can't tell if it is the fuel pump or something with the ignition. I checked all the primary and secondary ignition systems with a multimeter, including the cap and wires, for the proper resistance and everything was in specs.

So, my deal is; is there just a short in the injection system somewhere that I'm not seeing or does the fuel system need looking at? I am wondering if water might have messed up the distributor, but I don't know how to check that without just replacing the whole thing.

I tend to think the ignition system, because of all the water and mud, but would leaving it sit like that for two months cause something to go bad? I can't seem to find a pressure gauge anywhere that will work with the throttle body ignition system so I can see if the fuel pump is putting out the right pressure.

At any rate, that about sums it up, so I hope you can shed some light, this is starting to get frustrating!

Thanks for your time, too!

A. Nissan has always had problems with their distributor caps cracking, so I would suggest replacing the distributor cap and distributor rotor. If it's been a while, new spark plugs and ignition wires would be a good idea also.

If the problem is still there, the next thing to do is look for codes in the computer. This hesitation is most likely being caused by the Throttle position Sensor (TPS) or the Air Flow Meter (AFM).

If there are no codes, the TPS may be physically bad or out of adjustment. MAC Tools sells a Fuel Pressure Gauge that will work on that engine. It tees in the fuel line between the fuel filter and throttle body.