rev limiter problem

Hi all.

Not sure if anyone can shed some light on this one as it has me stumped.

Just over a year a go I built a new 4.0 V8 to go in my Peggy. Think there is still a posting on her regarding all the fun i had, But it recently started to get a taping noise on startup but this did clear after a few secs. I decided to open her up again and find the fault. turned out to be nothing more than wear in the rocker shaft assemblies. any hows more new parts fitted and what a difference. it is silent and seams to drive better. or so i thought.

I took her for a run on sat and when i floored the pedal to over take some traffic. the box kicked down as normal but when the revs get to 3000. the engine holds back. its like the engine has hit the rev limiter and starts to bounce. if that makes any sense. I thought the rev limited was set at 5500 rpm on the 4.0 litres....

My thought was. the battery has been off for a few days. and wondered if the auto box and engine manegment have some how defaulted to some factory setting? Is it a mater of reseting all the adaptive values. i was going to give it a go over the weekend. but if anyone has experienced this and may be able to shed some light it would be appreciated.

Thanks

Bryan

im really not sure but a good shot in the dark may be to check out the afm! i here it a lot on here and other forums, they do seem to throw up a lot of faults, i have some experience with this too, bad connection to it, try a replacement !!!!! if for no other reason as to remove it as a possibilty...................

Sounds like the air flow meter to me. Had exactly the same symptoms on my 4.6 a few months ago, wouldn't go past 3000 revs at all. Checked with main stealer they wanted £109 +VAT for a new one. Found a guy on flea bay, got a brand new "pattern" part for £35 delivered. Worked perfectly and the car pulls like a train right through the rev range. Will try to find the seller if you're interested.

Hi All,

Right done some more investigation work over the last week, and this is my findings.

Rangie starts first time with no problems from cold or hot, took her for a run today and its great, pulls right the way through to 5 - 5.5k revs no problems. If I kick the auto box down again no problems. thought great all sorted. however, once the engine gets to operating temperature, thats when it goes wrong. It refuses to go over 3.5k revs. and if i hold the throttle there it is missing like mad....

I have substituted the Airflow meter with a good one. still no joy. I have been round everything i have disturbed from changing the rocker shafts. everything seams okay. All the connections are good and clean.

The only other thing I have noticed. (might be completely irrelevant) but when the engine is idling. all the instrument back lights. HVAC and Message center seam to pulsate with every revalotion of the engine.

Like i say may be completely different fault, and if so anyone got any ideas on that.

Thanks

Bryan

sounds as thought it may have a bad earth somewhere? i wondr if this could confuse the engine management as well?

bad earths cause all kinds of problems!!

Hi All,

Had Another weekend of tinkering, and with the aid of Autologic, managed to check out the engine fueling and air systems. the air flow meter is okay it is giving the right readings and cant make it fail. I was starting to get puzzled as went through all the systems and no faults were logged any ware... The end result was to go for a run and get it to muck around. With Autologic on dynamic I was able to get it to log a fault. Turns out to be a Cam shaft sensor intermittent fault, so the next stage is to check all the wiring, before purchasing a new sensor.

I will let you know how i get on.....

Hi All,

Right tonight was the night.... I found the fault with my camshaft sensor. turned out to be a brake in the signal wire by the multi plug. it took some doing to try and repair as you cant get access to it very easily.

Took her for a run and what a difference. Just goes to show how a small brake in a wire can course so much head scratching.

Well thats another chapter closed in the ins and outs of owning a P38A

Just one wire, well there is one wire which shuts down the whole drivers door electrics, including the speakers, its a purple wire with a black tracer, my dealer stealer couldn't find the fault after 2 days, i found it eventually, someone had used a multimeter and pin pricked the loom under the door edge trim and it gets damp, i saw a spot of green and pulled the outer insulation either side and it just pulled apart, which means the wire had corroded, soldered them back together and CONTACT. MMmm test book couldn't find that

isnt it a wonderfull thing when you manage to sort a problem, i love doing a job on my r/r that actually makes a difference.
i found a broken wire under the expansion tank!, since its repair the sport mode is alive again, i always said it didnt seem to make much difference!