Feels like a misfire under load 🤷****♂️
 

Hello all.

I have a 2.7 2002. The car starts okay and drives okay as long as you stay on a constant throttle. As soon as you try to accelerate a bit harder the car judders and appears to be misfiring. I have change the plugs and a couple of coil packs which looked bad. I have plugged the car into a Durametric (just arrived) and it shows no misfires on any cylinders. I’ve removed the oil filler cap With the car running and the car does idle worse so I’m guessing it’s not the air oil separator.

At any time when driving, if you hold a constant throttle the car runs great, but as soon as you put the car under load you get this big juddering. I will post a picture of the Durametric read out in a while. I only purchased the Durametric tool recently so any advice on how to use it to see what’s going on will be very helpful. By the way the geometric is showing no fault codes at present when driving.

Here’s a list I’ve compiled in case someone sees something I should do first….

Crank position sensor?
O2 sensor?
throttle calibration ?
air leak- vac leak test with smoke?
How test fuel pump is okay?
Idle control valve ?
Dirty throttle bodies?
Fuel pump relay?
Injector sticking open?
Injector seal issue?
Check MAF voltage- new one now installed.
Unplug MAF to see if anything changes?
leak in the intake manifold?

First thing, are there any codes? With the way you are describing it, there should be codes. MIL ever come on, flash?

If you replaced the maf, was it aftermarket or porsche? exact same pn?

cps wont be the issue cause the car starts
o2 sensor - maybe but you need to look at fuel trims & all of the voltages....or just throw parts at it
icv - There isn't one
throttle body - never hurts to clean it properly
fuel pump relay - doubt it,the car starts & runs
injector - possible
intake leak - possible

Proper diag is needed before just doing things.

Video also helps to show what it is you mean. You say constant throttle it is ok, but that is putting load on the car...then you say putting load on the car causes it. Kind of confusing with that. Load is anything above idle.

So how about giving us some background on the car.
How many miles?
Any problems in the recent past??
Any work done on it besides changing plugs and coils in the recent past?
Any Modifications to it?
Are you running a stock air filter??
Automatic or standard transmission?
Has the Check engine light ever come on or flashed?

With performance issues you want to stick to basic diagnostic rules.
The primary rule is:
Simplest things first...... Then work you way up the diagnostic tree step by step from the simplest to the more complex.

With that in mind you could start with re-calibrating your E-gas pedal.
Also a simple "Vacuum test" with a PROPER VACUUM GAUGE.
Not a smoke test.

Those two things are very simple to do.
A proper vacuum gauge is very inexpensive and a valuable diagnostic tool.
The first Vacuum test to do is:
Find a place to connect the gauge directly into the intake.
Have the car fully warmed up:
Let the car just Idle (I believe you Brits call it tick over):D
Record the reading and very importantly the action of the needle if any.
Ideal reading is 18-22 in.hg with a rock steady needle.
Watch the gauge for several minutes at idle look for any changes in reading or needle action.

Let us know how you go.

Look through mine & gabedrummin recent posts if unsure, wealth of info in both of them

Maybe a good fuel system cleaner.?

Sent from my SM-G991U1 using Tapatalk

After market MAF
Nope, no codes, no MIL, doesn’t flash
Throttle body now all cleaned
Yes was thinking of doing a fuel pressure test STL- hoping to get a kit tomorrow

As for the injector- is there a a way to test at home or is it a whip out and take to a specialist thing?

Hi Blue.

How many miles? 147’000 miles with recon engine in 2014 so around 110,000 miles all in on this present engine
Any problems in the recent past?? Nope
Any work done on it besides changing plugs and coils in the recent past? Nope
Any Modifications to it? No mods at all
Are you running a stock air filter?? Yes stock
Automatic or standard transmission? Auto
Has the Check engine light ever come on or flashed? No buddy

Lol at ‘tick over’. Aluminium gets me.

I’ve read your post which relates and thank u for the information.

Yes good idea- I’ll do a video later when I’m with the car 🙏

I’m new to the Durametric myself so is the Egas recalibration done via the Durametric?

Regarding a place on the imlet Manifold to do the pressure test- do you know a good place possibly?

Note- by steady throttle, I mean- take car judders badly under acceleration but take the car upto any speed or rpm’s while driving and then hold the pedal still and the engine sounds perfect (eg at 30mph on a flat road the engine and car sounds as it should). As soon as you depress the gas pedal the juddery missfirery situation comes back again.

To recalibrate the e-gas:

Disconnect your battery for around 15-20 minutes so the computer can drop learned values.
Reconnect battery.
Turn key to on position for 1 minute. Do not start engine... do not touch throttle.
Turn key off for at least 10 seconds.
Start car let it idle for a few minutes to relearn idle fuel map.
take car for a test drive and see if it changed anything.

For vacuum testing go to the thread titled Car Dies go to post #50 on page three
look at the hose marked with the yellow yes you want to tee your vacuum gauge in where it meets the intake just before the resonance flapper.

Let me know how you go;)

Was I correct?? Do you call idle tick over??:D

Damn I almost forgot these cars do not do well with after market MAF sensors.
The only brand you want to use is a Bosch. (Porsche MAF sensors are rebranded Bosch)

Is this the same car that you replaced the VarioCam solenoid in?????

Lol! Tbh I’d say 60 percent say tick over but real petrol heads and older people say Idle 😀

[QUOTE=colacharlie;639911]Lol! Tbh I’d say 60 percent say tick over but real petrol heads and older people say Idle 😀

Sorry about that Blue - I sent my reply at 3am while just up for a bleary eyed wee wee and forgot - yes I did the variocam Unit and solenoid last week as my local garage (who had no Durametric kit) said they interpreted the code as a bad solenoid. Pretty gutted after allot of work to replace it but hey ho, at least it’s ruled that out 👍

Tried that buddy but thank u for your input 👍

[QUOTE=colacharlie;639912] What code? You said it wasn't showing any codes.

At this point it would be a good idea to just do a video of what it is doing. Also with duramtric running graph the following and post a screenshot:

rpm
cam deviation (all values)
cam angle (all values

Do another one with:
rpm
misfires (all cylinders)

Stl unfortunately the garage wrote a code down from their standard diagnostic and then looked it up on their PC to find it was the camshaft actuator at fault, but they deleted the code and we have no record of what it was.

Heres a video of the car after the egas Pedal calibration (batttery off for 30 mins etc process as suggested) ....

https://www.youtube.com/watch?v=I4-RdyNMT94

I’ll do another video today with the durametric data you’ve suggested

‘’A proper vacuum gauge is very inexpensive and a valuable diagnostic tool.
The first Vacuum test to do is:
Find a place to connect the gauge directly into the intake.
Have the car fully warmed up:
Let the car just Idle (I believe you Brits call it tick over):D
Record the reading and very importantly the action of the needle if any.
Ideal reading is 18-22 in.hg with a rock steady needle.
Watch the gauge for several minutes at idle look for any changes in reading or needle action’’



Guys I’ve read your other posts like ‘car dies’ but can’t work out where I’m meant to be connecting for the vacuum test. Might you post a pic of an arrow pointing to the location of it in the engine bay please?

there is a picture in that post

Your engine is a little different then mine (I have a 2000S 3.2) so layout may be different.
But if you go to post #50 in the "Car Dies" there is a picture of part of the intake.

Also anyplace after the throttle body that you can attach your vacuum gauge to.
The gauges usually come with a section of hose and "TEE" fitting. So look for a small hose coming off of the intake then use the "TEE" fitting to connect up.
If that is of no help let me know and we will get you sorted.

A few questions:
If you sit in neutral or park can you make the engine judder or misfire by working the throttle or does it on happen while driving.?????

In the video you exhaust sounds a little odd to me even at idle.
Is there any possibility of an exhaust leak????

Could just be the fact that is is a video.
But need to rule things like that out.

Is it a stock exhaust system or aftermarket???

Try this as a test:
Disconnect your MAF sensor (just unplug it) then take the car for test drive. Let me know if it changes anything.

Some things may be slightly different too cause you will have a ROW tune.