FredR

Arnoud,

Are you sure it is not your good self that is expecting too much?

Remember the control system is feedback based and when the throttle is slammed open too quickly there is a real danger of leaning out as the system tries to play catch up when it is always one step behind. The programming tries to compensate for this by temporarily enriching the first few firing strokes when the throttle is opened but again this is still a feedback scenario. Such parameters can be tuned using ST2 albeit I have never felt a need to play around with such too much.

For whatever it is worth I am pretty sure I could get my motor to stutter if I jumped on the throttle hard enough but I simply do not do that because I feel I know what the motor can and more to the point, cannot do.

Remember- cars are designed by computers, built by robots and driven by idiots!

Mrmerlin

So you can make the engine stumble by opening the throttle very fast?
This might be close to normal operation
How does the car drive? Its not a race car.

Arnoud

Thanks Fred and Mrmerlin/Stan for your follow up feedback, please keep them coming because that way I will get it solved (sooner or later).

Let me assure you both, that the stutter is not just a stutter nor do I drive my car like a race car (as it isn't a race car):
- When giving quick throttle and it goes wrong, it end's up with the whole engine not wanting to rev up and making a rather horrible "gurgling" kind of a sound when trying to rev it a bit. Only by waiting for 10+ seconds or so, and then gently feathering the throttle does things go back to normal.
- Also: it should be fine to do many low - from idle, like e.g. standing still at a traffic light, or when driving on the German autobahn and going through the gears - to high revs pulls after each other. Of course nothing stupid/idiots like (Fred: that last sentence of yours made me laugh very loud: good one!). Before this fault "suddenly appeared out of the blue" during July 2017 (while during May 2017 I had attend the Euro 2017 meeting in Reims/France, and did a further road trip to many other European countries - and all was very fine then) , I was certainly able to do so as often as I wanted.

I will rectify the mixed patrol mess I created, and then try again - and report here. Any and all idea's in the meantime: I'm all ears!

SeanR

What MAF did you put in to test? Had as similar problem on an ‘88 that has everything new (I rebuilt the engine this past winter) and suddently this sort of issue popped up. I put a JDS rebuilt MAF in yesterday and the issue disappeared and literally everything running wise was much, much better. No small stumble in neutral with a jab of the throttle, no slight bogging down when taking off from a stop and smooth as butter at WOT. I’d had two other MAFS that had been rebuilt by other parties and the same issue kept popping up along with other oddities.

Kevin in Atlanta

I searched this thread and saw no reference to testing fuel pump flow. How old is the fuel pump?

Arnoud

Sean: thanks for sharing your similar experiences, that gives me hope "we" (as alone I seem to not be able to find and fix it, thus far) here on Rennlist will be able to narrow it down and find & fix the root cause. Current MAF is my own's car MAF, which was rebuild by John Speake himself during March 2013. I did retested it last year 2018 after my intake refresh, with another local MAF: same results. I see if I can find another 3rd local good known MAF, just to rule it out...

My LH has been rebuild by JDS as well, at the same time then.

Kevin: thanks for your good valid question. You are correct, I have till date not tested the fuel pump flow. The fuel pump I renewed during November 2012, as part of my preventive maintenance (i.e. there was nothing wrong with the original one then, apart from age). I put a new fuel filter in then as well - all that is about 25K km ago. The in-tank fuel pump I have long removed, and replaced with the factory strainer.
The fact that I can have 5K+ rpm fine, tells me logically that there is/should be enough fuel flow.

FredR

Arnoud,

If a problem suddenly appears that previously did not exist then obviously that suggests something has gone awry. Cannot remember off hand what you have replaced albeit I remember a list of such somewhere in the thread. but just remember that replacement is no guarantee of problem elimination- just more unlikely to be such.

When it comes to MAF related issues one should always be sure that the cable loom as it enters the MAF is sound as that is common issue due to the way the loom is necked. The LH itself has a number of common failure characteristics but it also has some obscure ones.

FredR

I think you can rule out the MAF itself.

Do these problems occur when fuel levels are low by any chance?

Arnoud

I agree: something went awry during July 2017. Finding out what has been a process of elimination thus far, while having found - and fixed - some real other problems in meantime (like you and others pointing out that the PS cam must have been retarded, and it was). And my intake refresh + timing belt replacement were soon coming up anyway, so all good that way. I will check the MAF wiring, from the connector to the computers - and report back.

No. Started in July 2017 with about 30 liters in the tank, and currently I have 40+ liters in it.

GregBBRD

I've not heard this part of the running problem. Interesting.

Arnoud

Thanks Greg, for continue to follow and comment on my thread. As I can do with all the help I can get, so to find and fix my root problem and get my car back on the road again (it's been of the road for close to 2 years now due to this problem, super sad. As any previous maintenance work never took me more than one or max two weekends...).

Hereby a further update of what I did/checked the past few hours, and it is getting even more interesting. In order of what I did and happened:
- Rather then getting all the mixed (old + new) patrol out, I decided first to drive it once more and try to record the engine / exhaust sound once it would go wrong, so to post that here.
- Disconnected the battery for several minutes, so to have the LH + EZK computers starting from scratch.
- Before starting the car, I checked all computers with Theo's tool: LH, EZK, PSD, Alarm and Airbag computers all work fine and none reported a single fault.
- Started the car, and carefully drove it warm for up to 30 minutes. Stayed all the time in "D" and drove not faster then 40 km/hour.
- Engine sounded fine, however I did notice that - as per the original problem from almost 2 years ago as per my post #1 - that the idle was not stable after that warming up. Every 3 or 5 seconds it drops for a moment the idle rpm's under 600 rpm, like 570 - 590 rpm, then to go back to around 675 rpm. I know that rather precisely, because of the TechEdge wideband O2 controller/monitor I have. That TechEdge wideband O2 controller/monitor is connected to the PS exhaust of my X-pipe, before the PS catalyst converter (while the factory narrowband O2 sensor is in place in texactly the middle part of the X-pipe).
- Then shifted to "2" and stopped the car so it shifted itself into 1st gear. Drove it around for several minutes between 2-3000 rpm, and the engine sounded and went all fine.
- Then I gave it full throttle to over 5000 rpm: that all worked fine and went as it should, including even more acceleration when the flappy opened around 3600 rpm. That all lasted only a few seconds, as expected.
- But: when then going of the throttle, the main problem immediately came back: all power gone, not wanting to rev and the engine sounding like - no offence to anybody - a very badly warn out old VW van from the 1970's...Not at all as the normal sounding smooth engine it should be, truly horrible sound!
- I drove around for a minute or so, while trying to record it (with my mobile phone, so not the best recording quality). Windows Media Player will play these. And yes: that is a misfire "bang" you can hear in the first five seconds of the 3rd audio clip.
- I did checked the ICB relay: neither the red nor the green leds were on, meaning: all it's leds were and stayed off.

And then I noticed a glow, stopped the car and the engine and yes: that is both of the catalyst converters (each is a 200 cpi race-cat) glowing red hot...


All of these are the outcome symptoms of my main problem. With that I mean: for example I do not think I have clogged up cats, because why am I able to drive and rev the engine fast over 5K rpm fine (yesterday it was several times in a row, today only once), and only then getting problems?

Having written all that: I really need all the help I can get, so to get my root problem find and solved. I'm open for any logical - and less logical - suggestions, while keeping in mind that I have renewed a lot already (changed about every engine sensor there is for new, full intake refresh, etc. etc.).

FredR

For your info

Well if nothing else you should not suffer from piles with that under your ***!

SeanR

At first that sounds like a Temp II or Temp II connector issue........but.

You have a serious over fueling issue or your ignitions system is not doing anything correctly. Coils/Amps/wires or or a combination. Did you by pass your IMS relay just for testing? I'll admit to not reading the entire thread so sorry if it's been covered.

Mrmerlin

remove the wide band O2 sensor from your computers and see if anything changes.

If not then put your LH into another car and see if the problem follows.
Has the voltage regulator ever been replaced?
Have you checked the charging system for voltage output at 1500 RPM? SB 13.6V to14.2V

NOTE if you remove the O2 sensor from the header pipe and fit a pressure gauge tap port ,
you will be able to check if the cats are plugged .
you should not see any appreciable pressure rise while blipping the throttle

GregBBRD

Do you have access to a Sharktuner to use as diagnostic tool?

I'm thinking something very strange is happening....like the full throttle micro switch sticks closed after the throttle is opened more than 3/4...and then eventually opens on its own.