SOLVED Hiccup from Stop When Hard Accelerating AFTER Engine is warmed

matreyia

Major
Apr 19, 2017
1,627
OK folks... I have solved the hissing sound, but the hiccup still persists. Here is the summary:

From full stop, hard acceleration in any drive mode results in hiccup... this happens AFTER engine reaches operating temperature. It does not do this if cold start and before reaching 160F. This leads me to suspect the PCV Solenoid hose is not working correctly since the PCV solenoid activates only after reaching operating temperature and not otherwise. This hose/solenoid comes out from the firewall and connects directly to the throttle body and the RB external low side catch can hose connects perpendicular to this hose at the mouth of the throttle body.

This is what has been done so far:
1. Replaced all hoses and connections, clamps and couplers to all possible hose connection points on every engine and turbo part.
2. Replaced with brand new throttle body.
3. Cleaned all PCV valve adapters.
4. Replaced crankcase sensor.
5. Ran Fuel Cleaner for e85 tank.
6. Reset all adaptations in MHD
7. Battery is 100% level, all connections checked and tightened front and rear.
8. spark plugs new.
9. spark plug wires, new.
10. replace both camshaft sensors.

This is what will be done next:
1. replace PCV hose/solenoid
2. check transmission fluid level.

This problem manifests in any drive mode and regardless of traction control on/off state.
Again...only after operating temperatures are reach does it begin to hiccup and only hard acceleration from full stop.
It does not hiccup AFTER going into motion no matter how hard I slam on the pedal.
It does not hiccup from full stop IF I feather the pedal conservatively and ease into motion.
The engine feels and sound super strong, stable, smoother in idle, in park, or in drive with the brakes depressed, or in reverse with brakes depressed, and after it is in motion and under WOT. When in motion, throttle response is predictable and stable... only from a dead stop after operating temps reached does it hesitate under hard pedal press.

The last option is contacting my tuner to check the tune and logs.

Any ideas welcomed.
 
Last edited:

doublespaces

Administrator
Oct 18, 2016
8,651
AZ
Nope. Why do you think that would matter?
You said the hose connecting to the throttle body has some sort of solenoid that flips on when the car is warm. That hose runs back to the DMTL pump doesn't it ? I was just saying disconnect it from the TB and block it off if you think it's creating an issue
 

matreyia

Major
Apr 19, 2017
1,627
You said the hose connecting to the throttle body has some sort of solenoid that flips on when the car is warm. That hose runs back to the DMTL pump doesn't it ? I was just saying disconnect it from the TB and block it off if you think it's creating an issue
I don't think it is that simple. The entire system is interconnected with sensors. So if you plug it up, and the rear reaches conditions where it is supposed to release pressure of excess hydrocarbons which are supposed to be burned in the front...and the front does not receive it, and the o2 sensors don't get signals, the ecu may get confused and it may cause misfire because the ecu is now thinking that there is something wrong in the vacuum line...like a leak and attempt to compensate with AF mixture...this may cause stumbling, stalling, hiccup, hestitation or choking. That purge solenoid is electrically activated in accordance with operating temperature and load requests. It can get stuck open or closed if not working correctly. Either case is not a good thing.

A malfunctioning purge solenoid may also affect STFT ...which I have major issues with. And horrible MPG...which I also have issues with.
 

matreyia

Major
Apr 19, 2017
1,627
Mine was broken open and half of the canister missing. I got a check gas cap warning.

That was my limited experience
For me, there was an error last year and I simply replaced the DTML and that was the end of it. Currently though, there are the following issues all are classic signs of the Purge Valve Solenoid.
1. super loud intermittent ticking left side manifold next to throttle body area.
2. jerky, hesitation AFTER fully warm engine.
3. horrifying MPG

The MPG and hesitation are also signs of bad camshaft sensors...that is why I am going to just replace them also so there is no doubt. Will also replace the fuel vapor scavenger hose that connects to the purge valve solenoid just to be extra sure.

I tested the unit and it is stuck closed permanently. This means that the hydrocarbon vapors that would have added more energy inside the combustion chambers are not being allowed to go into the intake manifold via the throttle body and thus the car is losing that bit of residual potential energy...basically no burnable vapors are being harnessed and they are being blocked off completely purging into rear atmosphere...leading to worse mpg.

MPG is one thing... I can tolerate that since the car is at 600+whp...but the jerky hesitation/semi-stalling from warmed up motor at a stop light under hard acceleration...that I will not tolerate. This will be solved. No mechanical issue is supernatural. I will figure this out, even if I go bankrupt. Entropy can kiss my grits.
 

matreyia

Major
Apr 19, 2017
1,627
The stumble is usually a vacuum leak or some solenoid or pcv valve issues where something is not working correctly.
Yes. When all hoses and connections were replaced the stumbling went away in cold temperatures and a little in warm. Now it only happens on warm temps. So definitely the purge solenoid which is controlled by dme which gets its signals from the engine oil temp sensor on the oil filter housing. When the temp is reached, the dme sends commands to the the vent solenoid to open to feed the hydrocarbon vapors into the intake manifold to be added to the normal fuel burned in cylinders. This helps with efficiency and emissions. Saves a little fuel too.

When vent malfuntions and does not follow dme commands, the afr will be thrown off causing a chain of related issues. Timing, misfires, sluggishness, hesitation, stft, less power...etc.
 
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matreyia

Major
Apr 19, 2017
1,627
Any logs of the phenomenon? Cold versus warm? That might help you figure out what’s going on.
I only have warm logs. Very apparent. Cold felt totally normal so didn't log. .
 

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matreyia

Major
Apr 19, 2017
1,627
Just installed brand new camshshaft position sensors. Test drove and no change. Still hesitates on hard acceleration after engine is at operating temperature from a full stop. <---- only in this very specific situation. In all other situations, the car is ultra smooth and responsive. So long as it is moving first...even if only 5mph, you can stomp it and it won't hiccup...but if you are totally stopped on at a light and you stomp it, she will hiccup and feel like she fidna die out, then she comes back to life and scares the Bejesus out of you.

The purge valve solenoid should arrive by Friday and I will repeat the test after installation. After that...I will contact Twisted about looking at logs and possible adjustments. Or could be the bosch port injectors maybe bad, or the PR coils are starting to go. who knows...
 

matreyia

Major
Apr 19, 2017
1,627
Have you tried resetting the throttle body adaptations, have you tried a different throttle body?

I had this happen before on another car before it shit itself.
This is what has been done so far (this list is at the start of this post)
1. Replaced all hoses and connections, clamps and couplers to all possible hose connection points on every engine and turbo part.
2. NEW THROTTLE BODY.
3. Cleaned all PCV valve adapters.
4. crankcase sensor.
5. Fuel Cleaner for e85 tank.
6. Reset all adaptations in MHD
7. Battery is 100% level, all connections checked and tightened front and rear.
8. spark plugs new.
9. spark plug wires, new.
10. NEW camshaft sensors.

This is what will be done next:
1. replace PCV hose/solenoid
2. check transmission fluid level.
 

matreyia

Major
Apr 19, 2017
1,627
Have you tried resetting the throttle body adaptations, have you tried a different throttle body?

I had this happen before on another car before it shit itself.
Again... this only happens AFTER operating temperatures are reached and ONLY from full stop under hard acceleration. If feathering pedal, car accelerates smoothly, like it should. If car is in motion, there is absolutely no issue at all no matter how fast the pedal is jammed to the floor.

EGR system, including the vent solenoid works based on idle vs. hot engine. When the car is slowing down and temps are lowering, the ECU sends commands to the solenoid to slowly close...if the solenoid does not function, there will be incorrect AFRs in the intake manifold, which is what the solenoid connects to directly as it funnels hydrocarbon vapors to be burned at set temperatures.
 

matreyia

Major
Apr 19, 2017
1,627
Hmmm...well this is interesting.
Cylinder 6 rust powder in hole.
From using BMS cowl filter and modifying stock cowl by cutting it to lose weight and gain easier access... apparently, water does get into the plug holes if the cowl is cut. I installed everything back to stock now. Will test drive tonight.
20200513_202614.jpg
20200222_102850.jpg
 
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Reactions: NoQuarter

matreyia

Major
Apr 19, 2017
1,627
Hmmm...well this is interesting.
Cylinder 6 rust powder in hole.
From using BMS cowl filter and modifying stock cowl by cutting it to lose weight and gain easier access... apparently, water does get into the plug holes if the cowl is cut. I installed everything back to stock now. Will test drive tonight.
View attachment 37632View attachment 37634
And...done. No more bms filter or fake m3 cowl modification.

15894239919003742944414811325624.jpg
 
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Reactions: doublespaces

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