Serious missfire fixed

[stopover]

It all started toward the end of a long continental trip. As I got on the last leg home she started with a rough idle but was ok driving. A week later and the rough idle had developed into a bad missfire. The car is a 2000 4.6 Thor. Prior to the trip I had replaced the head gaskets and fitted reworked heads with new valves etc. So first thing was onto T4 diagnostics which indicated lean fueling on both banks, lambdas only just working so I decided that I would replace those and do a de-cat at the same time. I changed the MAF and spark plugs too. More power yes but still the missfire!! and it was getting worse so did a compression check - 160plus on all so not that. The next thing the diagnostic indicated was (maybee) low fuel pressure but a pressure check ruled that out. Next injectors so off came the plenum and out with those, all very good!!!!!!! Noticed a thread on this forum where someone found water in the ECM engine control module, pulled it out and hey presto lots of water all over the leads, took all the tape of the lead packs and dried everything out with WD40, compressed air and switch cleaner. Started he up and sweet as silk, well not quite as she has done 180,000 miles but pulling well and the de-cats have given much more urge! Off to Scotland next week, should be good, just need to do the brakes and put another couple of air bags on the back but I am feeling good now engine sorted.
I do diagnostics but got caught out on my own car!! another lesson learnt.

 

[StuckAgainSteve]

Shame you've gone to all that effort to end up with an unMOTable car - no cats, no MOT on a post 92 car.

 

[StuckAgainSteve]

Scratch that - just noticed you live on the IOM.

 

[stopover]

Shame you've gone to all that effort to end up with an unMOTable car - no cats, no MOT on a post 92 car.

Made them easy to swap to old system, twenty mins tops if needed. Oh yes.. live in Isle of Man. Makes a lovely sound now. When I did this the first attempt was too raspy so added a couple of small straight through stainless exhaust boxes just after the lambda s, fantastic a lovely V8 low burble that grows to a nice but undestated howl/growl. Its behind you so no headache on long journeys.

You are right about doing all that work just to find it was the ECM. But because I had replaced the head gaskets I was thinking too much that something was related to that.

 

[V8HSE]

I Noticed a thread on this forum where someone found water in the ECM engine control module, pulled it out and hey presto lots of water all over the leads, took all the tape of the lead packs and dried everything out with WD40, compressed air and switch cleaner. Started he up and sweet as silk, .

Where is the ECM located?

 

[eightinavee]

It all started toward the end of a long continental trip. As I got on the last leg home she started with a rough idle but was ok driving. A week later and the rough idle had developed into a bad missfire. The car is a 2000 4.6 Thor. Prior to the trip I had replaced the head gaskets and fitted reworked heads with new valves etc. So first thing was onto T4 diagnostics which indicated lean fueling on both banks, lambdas only just working so I decided that I would replace those and do a de-cat at the same time. I changed the MAF and spark plugs too. More power yes but still the missfire!! and it was getting worse so did a compression check - 160plus on all so not that. The next thing the diagnostic indicated was (maybee) low fuel pressure but a pressure check ruled that out. Next injectors so off came the plenum and out with those, all very good!!!!!!! Noticed a thread on this forum where someone found water in the ECM engine control module, pulled it out and hey presto lots of water all over the leads, took all the tape of the lead packs and dried everything out with WD40, compressed air and switch cleaner. Started he up and sweet as silk, well not quite as she has done 180,000 miles but pulling well and the de-cats have given much more urge! Off to Scotland next week, should be good, just need to do the brakes and put another couple of air bags on the back but I am feeling good now engine sorted.
I do diagnostics but got caught out on my own car!! another lesson learnt.

T4 is an excellent tool - despite what is said about it.But,it will only get you part way with more awkward problems - time to buy a Picoscope methinks...

 

[Saint.V8]

Where is the ECM located?

Under bonnet behind battery....

 

[rewmer]

Under bonnet behind battery....

Thor engines it's right hand side at the back looking at the engine.

 

[Rick-the-Pick]

Jon, I thought you already used the Pico?

 

[eightinavee]

Jon, I thought you already used the Pico?

No Rick, I meant Stopover - I've had a Pico for nearly 10 years,recently upgraded it to the latest version,top piece of kit.I wish all the other diagnostic tools were as good....

 

[Rick-the-Pick]

I keep promising myself to get a Pico. I bought a Mac one years ago in the states & all the time it does the job i'm reluctant to upgrade.
Diagnostics only take you so far.

 

[eightinavee]

I keep promising myself to get a Pico. I bought a Mac one years ago in the states & all the time it does the job i'm reluctant to upgrade.
Diagnostics only take you so far.

Very true,and the beauty of the scope is that you can use it on just about any circuit.Besides modern LR products I've used mine on allsorts of old stuff too,going back to a 1917 two stroke single with trembler coil ignition - gave me the answer I needed....
Next time you see a Pico on demo have a go with it,very easy to set up and use - even I can do it !