2.8 will not rev

[maxd]

Has anybody any idea's on this one? The engine will not freely rev over about 4500 rpm, it starts to pop and bang as if its hit a rev limiter (Which they don't have) If you back off and re apply the throttle you can some time get it to the 6000 rpm, but not under load i.e. on the road. Have so far replaced: Plugs, plug leads, Dizzy cap, coil, injectors, intake pipe and fuel pump. Also have adjusted the mixture on a Gas analyser. The engine has 67K on the clock with good compression on all 6 cylinders ,it starts first time from cold, hot starts ok. Just running out of things to check.

[GreenV8S]

Sounds a bit like a weak spark, check it with a passive strobe.

[Le TVR]

GreenV8S said:

Sounds a bit like a weak spark,

Favourite.

Check and clean all the two connectors to the ignition amplifier module and the connectors to the ballast resistor too.

[maxd]

Have checked timing with an advance/retardable Snap on timing light, but how do you check a week spark with a passive strobe ?

[maxd]

Have replaced ignition amplifier module and the ballast resistor check out as alright.

[GreenV8S]

maxd said:

Have checked timing with an advance/retardable Snap on timing light, but how do you check a week spark with a passive strobe ?

Firstly, see how bright a healthy spark is. If you don't have a known healthy engine to compare, then look at the brightness at tickover as that's your best chance to get a healthy spark but ideally look at a known healthy similar engine. Then see what happens to the brightness as you rev it at full throttle. It should get much brighter as the revs go up and then smooth into a sustained bright light, because you have the same intensity spark happening more often.

[numbnuts]

Sounds like you might have a very bad air leak somewhere, buy coming off the throttle and jumping back on it you say i will sometimes rev out, normally when you do this it would richen up the engine..which would possibly point towards an air leak.
Whats it idling like?

[clarenceboddiger]

Try doing a plug Chop "ie rev the engine as high as you can get it under load then cut the ignition and put the clutch in so the engine stops turning".
Take the plugs out and note the colour,this should give you some idea as to if its running rich or lean at that point.If they are wet it may be a spark prob,white ,too lean etc.Might not help but doesnt take long so may be worth trying.
(PS carefull with the steering lock when cutting the ignition)

[tvrscw]

i had a simular problem with my s1 2.8 and after months of changing pahe faulti traced the fault to the feul enjection distribution unit.i managed to find one and fitted it. after manageing to find someone able to set it now runs like a dream. Hope you have allready managed to fix it