Hi folks,

I have a 2007 HCHII (Civic Hybrid) that has had quite a few issues, but my local mechanic is a bit stumped. The car stalls periodically, seemingly when switching between gas and electric drive. We replaced the ECU (and immobilizer) had the dealership reprogram it, and finally replaced the IMA battery with a new one from Bumblebee Battery as others recommended here. However, the car still seems to be periodically just stalling while driving. A shady Honda dealership recommended replacing spark plugs and an O2 sensor a while ago but I'm not getting any trouble codes to indicate why the car is stalling.

Does anyone have a diagnosis tip or parts suggestion?

Thanks much.

 

Plugs
Coils
EGR port cleaning
EGR valve clean or replace

I had a failed coil that wouldn't show as misfires, but I could feel it as a hesitation during acceleration.

If you don't know that the plugs have < 100K on them, then replace with the OE style Denso or NGK iridium plugs - there are 8 of them, 2 per cylinder.

Do you have ANY other symptoms of ANY kind?

 

Thank you so much for the reply, S Keith. You have helped a ton of people here and I hope everyone appreciates your efforts.

So to update, here are all the repairs completed on this car recently:

Repairs

• Full set of new plugs late 2018
• Oil & filter change late 2018
• New 12v Battery March 2019
• New (used) engine ECU (PCM) and immobilizer set March 2019, reprogrammed at dealer
• Brand new Bumblebee battery April 2019
• Full set of new ignition coils July 2019
• New Inverter and DC/DC converter assembly from Greentec Auto July 2019 (Just completed with full removal and reinstallation of hybrid system, finding no errors)

The dealership kept replacing random parts for high cost with no clear diagnosis so I took it to a mechanic I trust. He was stumped, but suggested the PCM, battery and inverter replacements. We did those and no improvement.

I then sent it to Greentec Auto to diagnose, and they reinstalled the hybrid side parts, test drove it for several miles and the car did not exhibit symptoms, so they concluded that if there was a problem with the car it was not on the hybrid side. They drove it in relatively cool weather.

After we picked up the car and drove it about 30 miles in 90+ degree heat, the symptoms appeared again but with NO engine codes. Here is what is happening as best I can describe:

Symptoms

• While driving and more often than not when releasing the gas pedal, the car suddenly loses power, and stepping on the pedal provides minimal or no power to accelerate the car. Only after pulling over and letting the car sit for a time does the car start up again and allow full power acceleration. However, the "power cut" happens again after a short time, requiring pulling over. The car has cut power 10 times in a 35 mile drive, and we have to wait at least 5 minutes before it will accelerate.

Could this be EGR valve related, or some other combustion side problem? I am ready to shoot this car with a shotgun but I'm so deep into parts bills that I feel determined to get it running again...glutton for punishment I guess. I know I should have taken S Keith's recommendation in another thread and let the car die when it first had problems last year, but here we are with over $3,000 in brand new hybrid parts and I want this thing to work.

Can anyone steer me in possible direction for another part to check? Many thanks for any help you can offer.

 

What engine codes previously occurred? In your opening post, you said there were none. Are you using a professional grade code-reader to obtain codes, or are you relying on a consumer grade reader?

"full set of new plugs" = you replaced all EIGHT plugs with the NGK or Denso OE style iridium plugs? (expensive)
"full set of new ignition coils" = you replaced all EIGHT coils with the Hitachi OE style or Honda coils?

If you replaced either with anything but "equivalent to OE style", then those issues are still on the table. That would be $360 in coils and about $64 in plugs if you obtain the correct parts from RockAuto (last time I checked).

PCM can also cause the stall and fail to restart for several minutes. If you obtained a salvage unit and had it reprogrammed, that's still on the table.

If the car has over 100K on it, I guarantee you the EGR valve and/or EGR ports need to be cleaned and can definitely effect smoothness of the gas engine operation if they are having an operational issue.

 

Thanks so much for continued help! To answer your questions:

• I believe my mechanic said he saw an "Oxygen Sensor code" before we swapped the PCM, but I can't pinpoint which one.
• Full set of new plugs = the dealer said they did this, I don't know for sure.
• Full set of new coils = we replaced all eight coils with
  these QYL coils
  these QYL coils
• I used my own Bluetooth OBD2 code reader with Torque, which I have used for years on many cars.
• I am wondering if we replaced a bad PCM with another bad PCM, but in my prior experience with other cars, if these things fail due to heat, they just fail outright, and don't work fine when cold then "sort of work" when hot, but I am unfamiliar with this car. I could be wrong here...
• The car has 188k miles on it and EGR valve has never been cleaned to my knowledge. Sounds like some EGR work could be justified, you mentioned that before too.

One more thing to emphasize: the power cut generally does not happen when the car is cold, it seems to only happen after continued driving and heating the car up. We did just try running the car parked to turn on Air Conditioning, and it just stalled out without even touching accelerator.

Does that help?

 

O2 sensor codes are very specific, and you can watch how they respond by plotting the voltage. Rare to not be able to pinpoint them on codes alone. The extremely expensive upstream sensor is the most likely to fail. I had to replace them on both of my '06s.

I guess we'll trust the dealer at their word.

I wouldn't trust those coils at all. They are probably just marked-up versions of the $20 ones from China on ebay. Hitachi or go home.

Bluetooth OBDIi readers + Torque or Torque pro are VERY limited. i know a dozen Prius codes that they can't read, and I would assume the same of Honda codes even if I can't think of any. If you get CEL or IMA light, there is a blink procedure to blink the CEL/IMA light to identify the detail codes (some codes have multiple detail codes associated with them). It involves using a paperclip to short two pins of the OBDII port.

The ONE encounter I had with a bad PCM behaved exactly as you described. Worse when hot. The PCM is in a place that gets **** hot and has a plastic heat shield over it... is your heat shield intact?

Item 4:

https://www.hondaautomotiveparts.com...-engine-room-1

On my 150K HCH2, EGR valve fine, severe carbon build-up on ports, but none were closed.
On my 220K HCH2, EGR valve fine, 3 of 4 ports completely plugged

 

I'm now wondering if I should just order a replacement EGR valve and gasket on RockAuto and have the ports cleaned and new valve installed at a local mechanic. I am sick of the scamming dealership...

 

Thanks!

So, there is not now and has not been for a very long time any check engine light of any kind. Does this car generate codes without tripping the CEL or IMA light at all? I suppose there could still be an O2 code, but Phil at Greentec Auto hooked it up yesterday to his pro reader and there were zero codes of any kind.

I can't access the car right now (friend has it) but I can check the PCM shield later. Does that plastic shield really dissipate any heat?

I hear you on the coils, maybe they are still bad, but I'm not hearing any misfires or detonation and there are no codes.

Could be mountains of gunk in the EGR ports for all I know. Maybe that's a place to start?

 

Don't know Phil, but the only reason to replace an inverter and DC-DC is because you're throwing codes associated with those and have an IMA light, so I'm not inclined to trust Phil based on the info you've provided.

You'd be surprised how much heat a piece of plastic can block.

There can be "pending" codes. It means the condition has been detected, but it hasn't met the full critieria to make the code active.

Also, PCM intermittent failure has an associated code.

EGR ports is 30-60 minute job. EGR replacement is quick too.

Fuel filter ever been replaced?

 

Yeah, so I went ahead and ordered a Greentec Auto inverter based on my other mechanic's recommendation and had it installed. I towed it to Phil to inspect, which he did, and he told me he didn't think I needed to order it but it was already done. He did not charge me for several days of hybrid system teardown, diagnosis and reinstallation, so I think he's OK.

I mentioned the EGR possibility to him and he said he has seen that before but never without some code being thrown, which is my experience as well.

I don't know if the plastic shield is in, will have the dealer check that.

Fuel filter has never been replaced as far as I know.

So we are back to the strong possibility that I replaced one bad PCM with another bad PCM, I suppose. Towing the car to the dealer now, who I'm sure will charge me a fortune for a new PCM.

The design of this car is absolutely infuriating. Who puts a computer right next to an engine block with no active cooling? That is just stupid...