New misfire

[Paulprior]

I have spent the last couple of days rebuilding the shocks and fitting a new exhaust, went for a spin round the block and everything was good apart from the suspension a bit soft, added 2 clicks all round and tested again, feeling much better, put my foot down a bit in third, all good but when I let off the throttle there were a lot of pops and bangs that I hadn’t had before, put my foot down again and struggled to accelerate, after a little while I could smell that something was hot, checked the water temp and it was at 95, normally on a short drive on a day like this I would expect maybe 80 to 85 max, switched off and restart, still the same, tickover about 600rpm, checked the precat area on both sides and both equal, pump sounds good when switching ignition on.
Too late tonight but any thoughts on where to start ?

[Paulprior]

I have installed and connected the RS-RV8 software, below are pictures of what is displayed when the engine is warm, I have the set before starting and when first starting if that’s of use, could someone please help to translate this data ?

[Paulprior]

[Paulprior]

[geordiepingu]

You say misfire but you say struggling. Is the car clearly missing? Is it hesitating? Does it misfire in a regular pattern? Do you see the RPM needle bounce in a particular direction? Is it just feeling down on power and smelling/sounding rich? Unfortunately the Rover Gauge outputs are not always the full story.

My intuition is on the car isn't actually misfiring, but your vacuum advance has failed and the car is running richer up the top due to a more retarded timing setting than your fuel map is expecting. Car will be down on power. I would start by investigating that. Unplug the hose from the plenum while it's idling, and suck on the hose. You should hear a clear change in RPM if your vacuum advance is functioning. Vacuum advance failures will not throw an error code on the 14CUX from experience.

EDIT: Might also be a good idea to check your ignition timing at the same time - just to make sure it's set optimally. When my vac advance failed the distributor was clocked to try and compensate presumably by the specialist for emissions. I ended up having to re-set my timing after replacing my vac advance as it was inaccessible without rotating the distributor.

Edited by geordiepingu on Monday 28th June 20:06

[Belle427]

Fuel trims can tell a pretty good story, it’s hard to make out on the picture but are yours going negative?
If so it’s trying to subtract fuel for some reason, not disturbed the afm connector have you?
Some info on fuel trims here.
https://www.mechanic.com.au/news/understanding-sho...

[Paulprior]

It’s just heavily down on power, all cylinders are firing and to maintain tickover I see that the throttle was at around 10%, to give an idea my daughters fiat 500 would accelerate faster than I can, so no, maybe misfire is the wrong description, huge loss of power would be better, from experience I don’t think the advance / retard would give that sort of loss, when I first bought it the advance unit was faulty, when I fitted a new one I could not notice any difference.
I guess timing going completely out somehow could do it, the dizzy is not loose, I guess I need a strobe to check the timing ?

[AlexanderV8]

Dizzy might not be loose but the rotor arm may be failing.
I had that several years ago with similar symptoms you describe re overheating, scorching smell etc.
The difference though is that mine was a definite misfire, so perhaps that isn’t your issue.
I had really lumpy running and vibration, extreme loss of power but then occasional correction at higher revs. The tickover struggled to keep the engine going and eventually would die and fail to restart.
Spark plugs became fouled with unburnt fuel.
Unless you know your rotor arm is good, it may be a good, easy place to start, at least to eliminate it before you investigate further.

[Paulprior]

Apologies, I seem to have downloaded the data before starting, let’s try again

[Paulprior]

[geordiepingu]

Not familiar with that software or its views - more familiar with Rovergauge.... Is that... adding 40% on the even bank?! Are you sure you're not actually running on 6 or 7 cylinders?! Are those short term lambda trims or long term trims?

Could it be popping because it's overfuelling to compensate for an injector not firing?

I would hold a screwdriver against each injector and listen to hear if it's actuating.

Edited by geordiepingu on Monday 28th June 22:05

[Paulprior]

This pic was taken just a few seconds before the last on a different display, here both short term even and odd are around 40, I don’t know if that’s a % or not as I cannot find a description of the displays, maybe I need to try RG again.
I will try listening to the injectors but I did measure the exhaust temps just after the outlet from the head and they were all fairly even at a bit over 300 C

[Belle427]

Is that no throttle applied?
I see your Tps is at 14% which seems a little high.
Expected range closed is listed at 2% to 10%.

[Zeb74]

I had a bit the same symptom after a full rebuilt, suddenly the engine was getting hot very quickly and then was misfiring, stalling and was able to start again only after being a bit colder.
After trying to eliminate lots of causes, we found that it was due to the plug extenders (we have not checked which but I would say at least 2) on one bank. Unburnt fuel was going into the exhaust which explained the temperature.
We have removed all of them and put angled ignition leads, working like a charm.

[Paulprior]

There is throttle applied, the TPS seems to read correctly, without it the tickover was very lumpy at 500 or less

[Paulprior]

Listened to the injectors, all ticking away nicely, tried to connect RG but my windows laptop doesn’t have a standard usb, only the C type, RG didn’t give me any options of what port to connect too, any ideas on that anyone ?
I seem to think that if I disconnect the vac advance at the plenum and suck on it I should get resistance but I can keep sucking, maybe it is faulty but not sure about making this much difference??
I guess I will take a look in the dizzy tomorrow

[Steve_D]

If you can suck air through the vacuum port then the diaphragm is split. the whole vacuum unit needs replacing.

Steve

[Paulprior]

Hi
I have managed to connect the original RG and have some pictures, when hot I see the short term trim bouncing continuously between 0 and -25, if I apply some throttle to get tickover up to normal then the bounce changes from negative to positive, again around 0 to 25, long term trim doesn’t change, any ideas please ?

[geordiepingu]

Would be good to see how long term lambda reads if left to idle for 3 mins.

Oddly enough that idle stepper value seems a bit much for maintaining idle compared to my HC. It is consistently adding fuel on both banks though on revving which suggests either:

Too much air
Not enough fuel

Fuel - is the fuel pressure regulator doing its job? Fuel pump providing correct flow?

Air - split hoses, leaks etc into the plenum?

Not sure which it's likelier to be, someone on here may be able to identify based on the idle air control value...

Long term trim would be a good way to double check. AFAIK the 14cux needs 2.5mins at a constant rev/load to verify this. Would be useful if you could post those log files, screenshots provide hunches and guesses. Seeing the data log provides insight

May be good if you can data log the following:
3-5 mins of idle
5 mins of driving at constant rpm/load
another 2 mins of idle


I would imagine data logging all ECU parameters and somebody reading that here would provide a eureka.

Edited by geordiepingu on Friday 2nd July 00:54

[Paulprior]

Hi
I will try with some smoke near the plenum and see if that’s shows anything, how do you check the fuel delivery, I guess the pressure will drop if the flow is not enough, but what type of gauge/ connector to use safely without leaking petrol, your average tyre pressure gauge doesn’t seem up to it ?
I can try a log for 3 min at idle, I guess I need to let it warm up, I do have a 3 mile run I can do at a steady speed, I guess I just to go slowly and then recheck the long term trim, at the moment it’s fixed at -20 and -32, the only problem with the logs is that I cannot read them and there doesn’t appear to be anyone who can available to assist