QuestionQUESTION: My altima recently started stumbling off idle while pulling away from stop and bogging completely with large throttle inputs. I'm a fairly knowledgable mechanic and have tried the usual remedies. I replaced all timing components and found that it had indeed been out of time. I'm sure I have the valve timing correct but the problem persists. I have also tried replacing the TPS,plugs,wires,cap,rotor,and even the distributor. The check engine light isn't on so I'm a little lost. The problem seems to get worse as the engine heats up to normal operating temp. Again it stumbles off idle and will bog and stall with large throttle inputs. Thanks for your help
ANSWER: Hi Nicholas -
Have you checked the fuel pump? For pressure and volume. Could be starving for fuel under load.
Also what alerts me is when you say it gets worse when the engine is warmed up. That could alos be a sign of the ignition module failing. Have you checked that one? It is located in the distributor. With all that heat in there, it is a common fault.
Hope this helps -
aloha
calvin
---------- FOLLOW-UP ----------
QUESTION: the fuel pump seems to be putting out plenty of volume and pressure although i have no way to quantify this, it just seems like a good strong flow to the fuel rail. The distributor and ignition module are brand new. I discovered tonight while troubleshooting that the issues improved vastly if i unplugged the pigtail side of the tps sensor. The car is driveable with this unplugged. However upon plugging the pigtail back in the engine stumbled and bogged with even small throttle inputs. Strange thing is that the TPS is new as well. I am lost and getting very frustrated. This problem does not seem to follow any logical patterns that I have seen before.
AnswerHi Nicholas -
yes, no logic. The only thing I can think of is you have a defective TPS.
They do have devices to check the fuel pump. Might want to take it to a competent mechanic, just so that you can rule the fuel pump out.
Hope this helps -
aloha
calvin
