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Diesel Hesitation

jayok

jayok

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CRV / S2000
Hi All,

I'm currently troubleshooting an Accord diesel that has an intermittent hesitation when the car is floored or when the engine is under load (for example at 80mph). The hesitation presents itself as if it takes about 1 second for the engine to respond to the throttle. The car has been in with a Honda dealer and they can't find the problem, so it's a bit frustrating.

Now, the ERV and FSV was replaced by Honda (at a horrendous cost) but the problem remains. I stripped out the MAP and IMRC body and it was fully of oily sludge so gave it a good clean up, along with an ECU reset (disconnected power), but still the hesitation remains. Once the 1 second has pass the car pulls like a train.

Also, it's not a clutch/DMF as there's no signs of slippage its just as if the engine need a second to get going! It almost reminds me of the delay with kick-down in an automatic.

Could this be the MAF or TPS?

There's no engine light shown and after the 1 second the engine spins up normally. Not stalling at lower revs either.
 
As Trev said this will probably be your EGR valve at fault
 
HuskyMan said:
Have you cleaned out the EGR valve?
Click to expand...

Nope haven't cleaned the EGR .... yet! I ***ume this would throw an engine error though?
 
No the valve will stop working as it should. Try cleaning it.
 
Right so stripped out the EGR valve and it was pretty clean. There was a fine level of soot on there alright but nothing major. Hesitation still remains. Any other suggestions?
 
Oh and as a test of the TPS the cruise was engaged at 60mph, brakes applied to disengage the cruise down to 40 and the resumed - the hesitation still remains :(
 
Isn't there another filter in the IMRC system which gets clogged? I'm sure someone replaced it with a cut out circle of an old air filter and fixed the hesitation? It was somewhere where nobody thought it would cause an issue.
 
HuskyMan said:
Isn't there another filter in the IMRC system which gets clogged? I'm sure someone replaced it with a cut out circle of an old air filter and fixed the hesitation? It was somewhere where nobody thought it would cause an issue.
Click to expand...

Hmmm... well I checked the pipe work from the EGR value into the IMRC and it was pretty straight though, the pipe work is just a cooling element and it was pretty clean. At the IMRC side of things the pipe work comes straight up from the intercooler and into the swirl flaps. Interestingly, disconnecting the FSV makes no difference to the hesitation (other than throwing an engine management light)
 
I would test your injectors on HDS to see if they are all working correctly next - is it any worse on a cold engine or the same all the time?
 
Have you read the hesitation thread cover to cover?
http://typeaccord.co.uk/forum/topic/1127-slight-missing-or-hesitation-excessive-smoking-etc/
 
m444lyx said:
I would test your injectors on HDS to see if they are all working correctly next - is it any worse on a cold engine or the same all the time?
Click to expand...

It's the same from cold (i.e. just as we start-off) and after the car is fully warmed-up after say a 2 hour motorway spin. I ***ume if the injectors were giving grief we'd have other symptoms. Re the HDS it was in with a Honda dealer and they can't find an issue - then again I've no faith in the dealer network here, all they seem to want to do is charge excessively for a basic service and sell you a new car. Anything more complex and they are out.

HuskyMan said:
Have you read the hesitation thread cover to cover?
http://typeaccord.co.uk/forum/topic/1127-slight-missing-or-hesitation-excessive-smoking-etc/
Click to expand...

Yep, all 15 pages of it! Between the OT rambles really it seems to summarize the following possibilities:

1. Fuel filter
2. EGR
3. IMRC
4. FSV / ERV soleniods
5. MAP
6. MAF
7. Injectors (in there too)
8. High-pressure pump

Oh and fuel filter, but check the fuel filter :lol:

So the following's been done

1. Fuel filter
2. Cleaned EGR vavle
3. Cleaned IMRC
4. Replaced FSV
5. Replaced ERV
6. Cleaned the MAP
7. Cleaned the MAF

I'm not too sure on the injectors or the fuel pump as I'd expect an error, also once we get going (i.e. 1 second after the hesitation) the car pulls fine.

I'm thinking about swapping the EGR, MAP and MAF from a known good engine and seeing what happens.
 
What year is your Accord? If it is the facelift, then it has the vacuum operated EGR and it is most likely that. I see this all the time and EGR OFF map cures it.

The EGR will pass the EGR test on the HDS, but the driver always feels this slight hesitation, it's basically a weak actuator starting to show signs of failure.
 
It's a 2005 so the EGR is solenoid actuated. How does the EGR move? Would any one have a cabling diagram and I'll put some current and pulses into it and see how it moves.
 
In that case it has an electronic actuator which doesn't suffer the same issues normally i.e. it's either open or closed (unless it's jammed in which case you would get an insufficient flow error).

This is a weird one.. It's possibly a turbocharger problem then, either sticking actuator rod or build up of carbon on the vanes causing the flutter.
 
Remove the injectors and have them tested.
 
F6HAD said:
In that case it has an electronic actuator which doesn't suffer the same issues normally i.e. it's either open or closed (unless it's jammed in which case you would get an insufficient flow error).
This is a weird one.. It's possibly a turbocharger problem then, either sticking actuator rod or build up of carbon on the vanes causing the flutter.
Click to expand...

I think there's more to the EGR that just open or closed. There's 5 electrical contacts on the top of the solenoid, so it looks like it's pulse controlled (i.e. variable level of flow depending on the pulses into the solenoid). I can only imagine there's +12V, GND, Input level, Two outputs?? maximum and minimum? Not sure, but if the opening level is being reported incorrectly, etc the it could be the issue. I'd also imagine that this unit provides the feedback to the ECU to give the "Insufficient EGR flow" - I can't see how else the ECU would find out.


Also we did have boost problems being reported by the ECU initially (P1237) but this turn out to be a failing ERV solenoid. So now, it pulls fine and the turbo spins up ok, I'm not convinced it's the turbo.

hondavtecr said:
Remove the injectors and have them tested.
Click to expand...

Given that once the once initial hesitation passes, all goes well, surely the injectors are not failing to fire?
 
jayok said:
I think there's more to the EGR that just open or closed. There's 5 electrical contacts on the top of the solenoid, so it looks like it's pulse controlled (i.e. variable level of flow depending on the pulses into the solenoid). I can only imagine there's +12V, GND, Input level, Two outputs?? maximum and minimum? Not sure, but if the opening level is being reported incorrectly, etc the it could be the issue. I'd also imagine that this unit provides the feedback to the ECU to give the "Insufficient EGR flow" - I can't see how else the ECU would find out.
Click to expand...

Ok, some progress, I've replace the EGR from a working Accord and now the hesitation is gone! :D

With the old EGR I took it to the bench and applied +12V across the bottom two terminals (GND on the left as it faces you and +12V on the right). Pop - the solenoid flew open and looked ok. For fun, I applied a varying pulse of +12V across the EGR and right in front of me the thing stuck for a split second! It had been cleaned, checked, re-cleaned, so it looks as if the return spring is sticking somehow in the ***embly. Anyhow, this is now solved.

However, while the hesitation is now gone acceleration is fine, I still get an occasional blip in power while trying to hold a constant speed. For example, if I set the cruise to 70mph on a straight, flat motorway every so often (randomly) it's drop to speed to say 69mph for a split second and recovery. Now it does this whether the cruise on on or not at any speed - the drop in speed is related to a change in engine rate. It almost feels like the engine burps??

It feels like another sensor - any suggestions
 
I did say stuck EGR mate, this is why we our EGR OFF has been such a big success.. It's possible your replacement EGR is also sticking ever so slightly.
 
F6HAD said:
I did say stuck EGR mate, this is why we our EGR OFF has been such a big success.. It's possible your replacement EGR is also sticking ever so slightly.
Click to expand...

And you were right! :) The replacement EGR is from a donor car that doesn't have the problem, so I'm kind hoping that this is no longer an issue.
 
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