Questions and Answers
Pulsar Won't Go Fast
Q. I have a 1988 Nissan Pulsar. It has a 1.6 engine with automatic transmission. I use the car to scurry all over southern California. At 160,000+, Baby is getting tired, uses a quart every thousand and the tranny leaks, but it is stone reliable and all I have at the present time.
Two months ago it started to what miss a little at cruise, like it was starving, just a split second every once in a while, thought it might be the fuel filter and replaced that. got progressively worse last month, until at about 4,000 rpm cruising the bottom would fall out and I would back off and the engine would catch again and everything would be fine. I was worrying about the fuel pump and dreading the R&R of the thing.
I pulled the plugs and saw the problem was not starving but a severely rich condition. The plugs were pitch black with carbon dust. I put a new set in and changed the wires and cap and rotor and drove it. It was better since the plugs I just took out were severely fouled. I took the car up to cruise speed and the over rich condition was still there, pretty smooth until 3,500 and then I would nurse it past that. It would miss and flutter and would only smooth out when I backed off the pedal and brought the car down to about 3,000 rpm. If I pushed passed that it would miss and flutter with black smoke out the tail pipe. When I got back after 6-10 miles the plugs were solid black again.
Conditions now:
Cranks every time and idles smooth.When accelerating runs good till about 3,500 and not much more, every once in awhile will take off and run ok to 4,100 rpm for a 1/4 mile or so and then start to miss and flutter till I back off to around 3,000 rpm.
When driving at minimum throttle at 3,500 rpm the slightest incline (load) will cause the motor to start missing and load up till I back off the throttle a little more and will not gain rpm till I get back on the level terrain.
The car will negotiate all terrain at 2,500 rpm with no problem, just seems at larger throttle openings when the problem is most severe. There are no codes in the ECM and no "check engine light", I have a spare (known good) ECM and changed it out with no difference in performance. Plugs stay black and sooty, severely fouled.
I took it to the local Nissan dealer because I was up against it. He trouble shot the car and came back in a hour telling me I had a bad ground to the Mass Air Sensor and he would fix it in another hour. This sounded logical to me because I had it go bad 8 months before and the car would limit itself at 2,400 rpm and would cause a fuel mixture problem if it went crazy.
After another hour he came back and said he fixed that problem(by soldering on a ground wire at the sensor location and securing it to the timing cover bolt) but he had "bad news" for me.
The Nissan Repair people told me that I had a transmission problem and it would not upshift to third gear and that caused all my problems. I had the mechanic come to the front desk and explain why this was the problem since it shifted fine all the way to the shop. They told me the engine was fine and the plugs were fouling because the transmission was not up shifting and it was putting undue load on the motor. This was pure crap to my thinking because the engine would load AFTER it upshifted and not at the top of the lower gear. At that point they lost all credibility with me and I paid for their two hours labor at $80.00 an hour and drove home with the motor they said was fine.
The problem with the upshift he was experiencing was, the engine shifts at around 3,500 to third and it is running so poor at that point it's not making enough power (vacuum) for the damn thing to take third until you back off a tad and it will take the next gear. What a bunch of flakes. I paid $80.00 an hour you for that diagnosis.... jeez.
What ya think, where should I start? Way rich, no codes and down to 18 mpg from 28 mpg.
Help!!
JoeA. Well Joe, if it were me working on your car, the first thing I would have looked at is the Throttle position switch (TPS). This is classic TPS symptoms. Nissan had a run of bad TPS's from 1986 to about 1992. What would happen is that a bad spot in the TPS would develop and everything the throttle hit that bad spot, the engine would crap out. There is a special tool that the dealer should have to test the TPS but I'm pretty confident that the TPS is the problem.
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