My car: 1992 Camry, 4 cyl, automatic, 266,000 miles.
About 4-5 months ago I was driving on the freeway at about 65-70 miles an hour and slowed down for heavy stop and go traffic. Upon coming to a stop the car nearly stalled. Each time I barely pressed the gas peddle to move forward in the stop and go traffic the car would nearly stall. I exited the freeway and tried to recreate the stalling in a parking lot but it ran fine. I was able to make it home no problem. The next day I tried to recreate the near stalling again and the car seemed to operate fine until it got warm.
I took the car to my mechanic and he could not recreate the issue or find a problem.
The car still has the problem and I can't seem to determine what it is. The car is tuned up fine and otherwise runs great. With my Haynes repair manual I have checked several items and still can't determine exactly what's causing the issue.
Here's exactly what happens; I start the car just fine. The car idles fine and smooth at 800-900 rpm. In park or driving I press the accelerator slightly to bring the rpm's up slowly. When the rpm's exactly reach 1,500 the engine nearly stalls and the rpm's drop to approx 500. I let off the accelerator and the car returns to idle fine. If I continue to press the accelerator during the rpm drop it will recover but sputter until 2,000 rpm exactly. The car runs perfect above 2,000 rpm. After checking this repeatedly the car only hesitates/sputters between 1,500-2,000 rpm. All other rpm conditions are normal. On occassion I notice an unburned fuel smell coming from the exhaust but not always.
With my Haynes repair manual and this forum I have checked the following;
1. I disconnected the MAP sensor connection and the car almost stalled at idle. Check engine light comes on. Reconnect sensor and car idles perfect.
2. I disconnected the "Coolant temp sensor" and car idles horrible. Check engine light comes on. Reconnected it idles perfect.
3. I disconnected the upper oxygen sensor on the exhaust manifold (single wire) and there is no change in performance. No check engine light comes on.
4. I disconnected the lower oxygen sensor on the exhaust manifold (2 wine) and there is no change in performance. No check engine light comes on.
5. I have cleaned out and checked the "EGR Vacuum Modulator" and connecting vacuum lines and there is no change in performance.
6. I have checked for trouble codes using a jump wire and get no codes indicating no known problems.
7. I intend to clean out as much of the throttle body with carb cleaner as I can today to see if that helps.
My thoughts are the problem may be with one of a couple things;
1. EGR Valve has gone bad. Can this be cleaned or must it be replaced?
2. Upper single wire oxygen sensor bad?
3. Lower 2 wire oxygen sensor bad?
If you have any ideas, things I should check, or thoughts I'd appreciate your response.
Brian