Question-------------------------
Followup To
Question -
I am perplexed with the problem on my 84 240 DL with about 105K miles. When I first run it (in the morning) the motor runs normally until about 3-4 minutes later. The motor will then hesitate, sometimes backfire (within the exhaust system), and this lasts for 2-3 minutes with a loss of power. When this happens, if I am above 25 MPH I can maintain momentum; however, if I am at a light/stop sign, I crawl. Fortunately this phase is only transitory. As I come out of this phase, I feel the car surgin in pulses with more power with each suceeding pulse (mostly 4-5 only). Thereafter, the car runs happily without missing a beat. Should I stop for errands, when I restart there is no such problem. However, if my car is parked for a prolonged period of time, upon starting I encounter the same problem. Would you please advise and "Thank you."
Answer -
I would check a few things. First your throttle body could be dirty, causing loss of power. I would also check your oxygen sensor, which could be going bad and causing the car to fluxuate a rich/lean fuel mixture. Finally, I would check that both your fuel pumps and your pump relay are working. A main pump going out could cause the engine to starve for fuel, especially if the intank pump is still functioning (or vice versa). Good luck!
FOLLOW-UP QUESTION:
Thank you for your thorough reply. With the throttle and the pump, if they are going bad, wouldn't they act randomly and at all speeds and times? I ask this because my engine acts this way only after a cold start. I shall check all the items you mentioned but especially the oxygen sensor. Could the cold start valve be the problem? In any case, thank you so much for your time and trouble.
AnswerIn general, a failed pump relay will offer fairly consistent set of problems, however, a failing fuel pump can offer a variety of problems based on RPM, engine temperature, and outside conditions. I wouldn't rule it out as a problem based on the frequency and circumstances of your failure.
As for the cold start valve, it might be worth a check, but generally problems with those will consistently disappear after the car is warm, which may or may not apply to you. If majority of issues happen when your car is cold, it would be worth a check.
Good luck!
