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Old 02-09-2013, 08:45 AM   #1 (permalink)
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Question MDX stalls while driving

Hi all, first time poster to this forum and unfortunately did not see a lot on this topic. My 2002 MDX is stalling randomly while the vehicle is moving. I am concerned that this is going to be an expensive part swapping exercise. Has anyone else had a similar issue?

Vehicle: 2002 MDX, 153K miles.

Symptoms/Scenario:

MDX stalled several times in the past month while driving at speeds greater than 40 miles per hour. When the condition occurs, the engine becomes non responsive to accelerator changes, engine RPM slowly bleeds down to zero. Power steering and brakes are lost. After putting the transmission in park and attempting a restart, the engine will not start anywhere from 2 to 10 minutes. The engine will turn over, but will not start (not a battery problem). After this time, the vehicle will start and operate normally with no fault codes displayed whatsoever. All electrical systems appear to be functioning properly when this event occurs (not an electrical power disruption, at least not in the cabin).
The problem seems to be random, it occurred with the transmission set in 5th gear, 4th gear, and 3rd gear.
Timeline:
1. First occurrence, after running for about 30 minutes, engine died and restarted 10 minutes later. Drove vehicle home and tried several engine starts. Engine sputtered but would not start in driveway. Next morning, the vehicle was fine.
2. Second occurrence was about a week later. Vehicle was running for at least 30 minutes when it happened.
3. Replaced the EGR valve and added a can of seafoam to the tank. I was thinking perhaps I had bad gas. I have had two EGR valves replaced already on this car, thought it might be the problem again.
4. Problem did not occur for two weeks, I thought I had it solved.
5. Problem reoccurred about 1.5 hours into a drive to North Carolina.
6. On trip back from North Carolina through high elevation and hilly terrain, problem occurred 4 times, about 20 minutes apart. After this period, problem did not reoccur for the remainder of the drive to Atlanta (about 1.5 hours).
7. Dealer replaced fuel pump due to low fuel pressure and debris in the pump.
8. Vehicle stalled 45 minutes into the drive home from the dealer, but this time the vehicle died while accelerating through a stop light. The engine would sputter when a restart was attempted, then would not sputter at all. Engine restarted 5 minutes later.

Any insight would be appreciated!
Shack
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Old 02-09-2013, 11:20 AM   #2 (permalink)
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MDX stalls while driving

Man that sounds like a tough one.


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Old 02-09-2013, 11:52 AM   #3 (permalink)
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Your problem has similarity to Main Fuel Relay problem common on other Honda/Acura products. When no-start condition is present, turn keyswitch to ON and listen carefully for fuel pump to run for 2-3 secs and cut-off. If you don't hear fuel pump, engine won't start.

MDX has two fuel relays that couple power to the fuel pump. One of these may be the problem if you don't hear fuel pump.

If you hear the fuel pump, problem may be an ignition power problem which would suggest a ignition switch assy problem,...another common honda/acura problem. In this case, you should notice whether Alt, Check Engine, and Oil Pressure lights come on when engine dies. If not, ignition switch assy is likely.

good luck
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Old 02-09-2013, 08:33 PM   #4 (permalink)
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Thanks, if it happens again I will attempt to listen for the pump; usually I am too busy trying to get the M off the road and not getting run over. I dont think it is ignition because the RPM does not drop to 0 instantaneously, its like a slow death. My thought is that the ECU is getting bad feedback from sensors causing it to screw up the air/fuel mixture and stall. But I dont understand why waiting for a few minutes clears the problem. Anyway, back to the dealer. Talking to the service rep, I think they are going to start looking at grounding and electrical related to fuel, since they already replaced the pump. If and when this gets solved, I will post.
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Old 02-09-2013, 08:37 PM   #5 (permalink)
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It's the ignition switch assy problem !!!!! I ran into the same problem with my 08 Honda Accord 4 yrs ago.
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Old 02-09-2013, 09:44 PM   #6 (permalink)
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Quote:
Originally Posted by Shack View Post
Thanks, if it happens again I will attempt to listen for the pump; usually I am too busy trying to get the M off the road and not getting run over. I dont think it is ignition because the RPM does not drop to 0 instantaneously, its like a slow death. My thought is that the ECU is getting bad feedback from sensors causing it to screw up the air/fuel mixture and stall. But I dont understand why waiting for a few minutes clears the problem. Anyway, back to the dealer. Talking to the service rep, I think they are going to start looking at grounding and electrical related to fuel, since they already replaced the pump. If and when this gets solved, I will post.
Definitely post back once you have a diagnosis of this issue. I've never heard of this happening but it certainly sounds like a potentially dangerous scenario.
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Old 02-10-2013, 05:28 PM   #7 (permalink)
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The linked thread is quite interesting regarding the fuel pump relay failure mode. I may try and reflow the solder joints as a test but ultimately I think I will replace it. I did verify I could hear the pump run for a few seconds when I turn on the ignition so I know what to listen for next time it fails.

Fuel Pump Relay Problem... - AcuraZine Community
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Old 02-11-2013, 08:27 PM   #8 (permalink)
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I drove the car to work today (about 35 minutes) without incident. Just for fun, I tried a restart after I parked. There was no fuel pump sound after I turned the ignition on, and no start either. Turned the ignition off and removed the key. Repeated several more times with the same result. After about 5 minutes, I tried again. This time I heard the pump start and the engine started too. I took the car to the dealer during lunch and shared this info with the service rep, they haven't gotten back to me yet with their diagnosis. BTW I checked on the price for a new main relay from a different Acura dealer - 75 bucks.
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Old 02-16-2013, 08:34 AM   #9 (permalink)
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Update - I took the car back to the dealer. They called me two days later and said the main relay worked fine and they were still looking for the problem. They even took the relay apart and inspected per my suggestion. I told him to replace the relay and save it for me. A day later, he calls again and says all they did was replace the main relay and reattached the grounds for the pump. The tech drove it to and from his home one night without incident so they think they fixed it. I picked it up yesterday and so far so good. I took the relay apart and attached the photo. In it you can see a "cold" solder joint in the center of the relay, and some discoloration where it may have overheated. Time will tell if this was the problem but this is clearly not in good condition. I will post back after a "problem free" period.

Shack
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Old 02-16-2013, 11:12 AM   #10 (permalink)
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Poor/failed solder jts are not obvious. You need a really powerful magnifying glass to examine. Usually, just a dark circle around a vertical wire is all you can see. Repair usually consists of re-solder all the jts rather than trying to detect bad jts.

I did a bit of experimenting w/ an Accord MFR and found that temps of certain jts reach 140F when operating. Not surprising these jts fail in time.

good luck
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Old 02-17-2013, 09:35 AM   #11 (permalink)
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We have powerful magnifying glasses at work so I plan on taking a closer look (just for fun), but if you zoom in on the photo at the center contacts you can see the joint is definitely malformed; this is the relay contact that is in series with the pump (no surprise there). Also, I googled "honda main relay schematic" and found all kinds of useful information on this problem.

The original diagnosis was debris in the fuel pump and low fuel pressure. I do wonder if the pump was indeed going bad or clogged causing more current draw, ultimately accelerating the failure of the solder joints. Or, was it a complete waste of time and money to replace the pump. My advice to anyone with an MDX of this vintage would be to preemptively reflow or replace the relay to avoid this serious problem. Thanks TexasHonda!
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Old 02-17-2013, 10:22 AM   #12 (permalink)
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Your fuel pump could have been faulty. They are very reliable, but do occasionally fail.

I had a fuel pump fault on my 94EX Accord that took a lot of diagnosis, replacement of MFR, and hand wringing before I finally determined the pump was "hanging" when first powered on. I rigged a tell-tale light to power supply feed in the trunk and found pump was not running w/ power supplied. If I turned keyswitch on/off/on/off...it would eventually catch and run. New fuel pump resolved long running intermittent no-start issue.

Fuel tank was pristine on this now almost 20 yr old Accord. My "backup" car currently.

good luck
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Old 02-17-2013, 10:47 AM   #13 (permalink)
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Hi, glad you found your problem without enduring an expensive part swapping exercise. Thought I'd mention for future reference that there is a useful procedure for diagnosing weak fuel pumps; the speed of the motor can be figured out by using an ammeter clamp probe around the power feed wire and looking at the waveform pattern on an oscilloscope (such as the Snap On Vantage power graphing meter)

I know this is probably a bit advanced for the average owner, but your local repair shop should have a driveability technician that has the equipment and knowledge.

This test is very useful for intermittent problems, where the fuel pump pressure and volume are within specs.
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