I have a 2001 Accord V6 with about 160K miles on it that I'm having a problem on I can't seem to solve.

When the car is run for a while, and the engine is warmed up, if you then park the car for few minutes and shut it off, when you restart it, the car hesitates at low speed under light throttle. It only seems to happen within the first minute or two after you start it, with the engine still warm. After a couple minutes it drives fine. Or if you push harder on the throttle it seem to do ok. It is only under light throttle application at parking lot speed that the problem occurs. It almost feels like the entire engine just dies for a few milliseconds, and then it comes back to life.

I don't get any engine codes or light.

It almost feels like a dead spot in the throttle position sensor. If you push down further on the pedal, the engine will jump back to life, and jerk the car hard in the process. But it only happens on light throttle application, and only right after you start the car. It drives normal at all other times.

I have removed the intake manifold and cleaned out the EGR passages, though they weren't very dirty at all. That had no effect. I also tried fuel injection cleaner and gas dry in the fuel, thinking maybe I got some water in the fuel. That didn't help either. Neither did replacing the plugs.

I've read on some other threads where the alternator can cause this. Does this make sense?

I've also read where some folks claim it is a bad O2 sensor, or a plugged up catalytic converter. Still others have suggested the TPS sensor is bad.

From all the threads I've seen on here about this issue, it sounds like it may be a common problem. Has anyone ever fingered exactly what the cause of it is?

Any and all help most appreciated.

 

Just went out and tried to duplicate the problem with the engine cold, and I can't make it happen. It only occurs after the engine has first been warmed up, and then the car shut off for a few minutes and then restarted with a still warm engine.

 

If you have a obd2 scanner that can track fuel trims, you should investigate Long Term Fuel Trim (LTFT) when engine is warm. Engine may be changing LTFT rapidly due to some temporary (no check engine light) problem causing a lean engine stumble. This would be indicated by rising positive LTFT.

Why? A slow responding O2 sensor might cause this problem. Forum occasionally sees drivability issues resolved w/ replacing the O2 sensor. If it's been over 100K miles, this is certainly something to consider.

If no indication from LTFT, the problem might be electrical ignition, but this seems less likely.

good luck

 

How many O2 sensors does this car have?

I tried wiggling the key in the ignition switch to see if it was a faulty switch, but that doesn't make it die, so I think the switch is ok.

I did replace the alternator about 8 months ago with a rebuilt one. But I don't know why it would only act up occasionally if it was an alternator issue, and I don't know why some folks claim that causes an engine misfire or hesitation issue.

I'll keep looking to see if I can find the problem. If I'm able to pinpoint it, I'll come back and post what I found.

I'm open to any and all suggestions.

 

Only one primary (upstream of converter) O2 sensor is necessary.

Wiggle test may not be enough to rule out electrical problem. I recollect this vintage Accords were notorious for ignition switch problems. A better indicator is all the panel lights go dark when engine stops. From your description, this does not seem to be the case.

good luck

 

I started trying to pay closer attention to the tach when this happens, and now I'm thinking it may be a transmission problem, because it looks like the engine rpm is increasing, but the car is hesitating because the transmission is slipping. The engine on this car is so quiet, it's hard to tell what is going on with it without watching the tach. I need to do more tests to confirm it, but now I'm thinking it may not be engine related at all.

 

Well, I'm back to square one. After more testing, I've ruled out the transmission. While the transmission does occasionally slip between 1&2 at a low speed, this isn't the issue. While closely monitoring the tach when the problem occurs, I can see the tach drop off when I hit about 1,200 rpm or so under light throttle application at very slow speed (around 10mph). The gauges do not die, so the car still has power, it just stalls for a few seconds, almost like a lean surge.

It seems to be heat related. When I drive the car and then park it for about 10 - 15 minutes, the problem will reoccur right after engine restart with an already hot engine. It only happens for the first couple minutes after restart, then it goes away.

I'm thinking that when the car is parked and the heat from the engine rises into the engine bay, it is heating up a component and then failing. Once you start the engine and the coolant starts to flow, then it works ok again.

 

An obd2 scanner may reveal some sensor value that is perhaps off; Inlet Air Temp, Coolant Temp, etc.

Another explanation for this behavior is coolant leaking into the cylinder head when engine is shut down and missing on startup. I had this behavior on 94EX and head gasket leak was problem.

good luck

 

Just a thought.

Some of the 6th gen v6's had an issue with vapor lock, this seems to show up more in the winter months with the use of winter blend gas.

 

Maybe I'm missing something here, but I thought the vapor lock issue was remediated in the 2001 and later V6 engines. Yes, no?