Misfire under load (again &again & again)
Discussion
Hi All,
Symptoms : misfire under load then revs out as normal after 2k. No misfire when revving normally without load. I pushed #3 lead back on and ok for 10 minutes then started again.
Coil packs brand new, leads, plugs and big fuse about 3k ago
Action so far:
#3 & 5 plug leads keep jumping off; I put back on with boots up, making sure on fully
checked all leads and secure; checked in dark for sparks
checked plugs and gaps
used EvoOllies program & adjusted throttle and pots; lambdas switching ok
checked wiring to fuel rail and good
Forums state that once lead plugs removed they are “loose” is this true? I have tightened them since. Surely if the lead keeps jumping off it would misfire all of the time?
Also my battery is a little low.
Any help appreciated as now becoming v annoying!
Symptoms : misfire under load then revs out as normal after 2k. No misfire when revving normally without load. I pushed #3 lead back on and ok for 10 minutes then started again.
Coil packs brand new, leads, plugs and big fuse about 3k ago
Action so far:
#3 & 5 plug leads keep jumping off; I put back on with boots up, making sure on fully
checked all leads and secure; checked in dark for sparks
checked plugs and gaps
used EvoOllies program & adjusted throttle and pots; lambdas switching ok
checked wiring to fuel rail and good
Forums state that once lead plugs removed they are “loose” is this true? I have tightened them since. Surely if the lead keeps jumping off it would misfire all of the time?
Also my battery is a little low.
Any help appreciated as now becoming v annoying!
Loose plug leads will burn the plug tops and the inside of the plug lead terminals, it's worth taking a look
Do you have an Alternator Warning Light come on at the same time as the oil light when turning the ignition on, if the warning light circuit isn't functioning correctly the battery wont be charging until the Alternator cuts in at high Revs, the Alternator cuts in at lower Revs when the warning light circuit is functioning correctly
Do you have an Alternator Warning Light come on at the same time as the oil light when turning the ignition on, if the warning light circuit isn't functioning correctly the battery wont be charging until the Alternator cuts in at high Revs, the Alternator cuts in at lower Revs when the warning light circuit is functioning correctly
Edited by Penelope Stoppedit on Monday 27th November 11:39
Stick a meter on the battery. My alternator semi packed up and I got a nasty misfire under load due to a weak spark. You want to be seeing 13.6 min at idle and 14+ at 2k rpm upwards.
Also worth checking that there is a good 12V at the coil packs while running. Can't remember which terminals are the 12V supply though.
Also worth checking that there is a good 12V at the coil packs while running. Can't remember which terminals are the 12V supply though.
Hi...same thing happened to me to other day...i even put up a post about my issues..car was stalling really badly and misfiring at low revs..i haven't got my car on a trickle charger and try to give it a run out once a week...no warning lights on whatsoever...i decide to charge the battery because the cerbs drain them when sitting idle and low and behold the car is back to normal...maybe coincidence but the car has give me no trouble in the past...
Maybe lack of charge in the battery opens up a multitude of sins...
Maybe lack of charge in the battery opens up a multitude of sins...
Thanks for the quick replies. Will definitely assess the battery. Unless I charge/ trickle it the starter motor sometimes “pauses” before it kicks in. This is a definite delay. Then it turns for a a short while or so before starting. This will be an easy fix if it is the battery (fingers crossed) as all of the start up lights come on/go off as normal.
Even when charged the starter motor always turns over a few times before it catches and it has always been like this so I assumed “they all do that sir”!
It is frustrating that some of the plug leads keep coming off - I spent some time a few weeks ago ensuring every spark plug and lead were connected fully.
Even when charged the starter motor always turns over a few times before it catches and it has always been like this so I assumed “they all do that sir”!
It is frustrating that some of the plug leads keep coming off - I spent some time a few weeks ago ensuring every spark plug and lead were connected fully.
Do you have a distributor cap? It may be the centre carbon.
I ask because on a completely different car, an old fiat, I was struggling to find a misfire under load. It was also perfect when cold but got worse as the engine warmed up.
Tried the usual suspects, plugs, temp sensors to ECU etc and it turned out to be the centre carbon brush had almost worn away and had no spring action left.
I ask because on a completely different car, an old fiat, I was struggling to find a misfire under load. It was also perfect when cold but got worse as the engine warmed up.
Tried the usual suspects, plugs, temp sensors to ECU etc and it turned out to be the centre carbon brush had almost worn away and had no spring action left.
Ok - 13.4v at tickover (1000 or just fractionally below which is where it usually sits).
13.97v at a steady 2000 revs (with my 13 year old loving pushing the throttle)!
I’m not convinced the battery is the cause and the usual lights come on and go off upon start up.
I can still feel a slight misfire on Rickover as not really smooth.
Need to sort out a diagnostic computer as my old company gave up last week.
Any other suggestions - the alternator seems ok as lights do not dim or brighten with revs and no battery light on whilst driving etc.
13.97v at a steady 2000 revs (with my 13 year old loving pushing the throttle)!
I’m not convinced the battery is the cause and the usual lights come on and go off upon start up.
I can still feel a slight misfire on Rickover as not really smooth.
Need to sort out a diagnostic computer as my old company gave up last week.
Any other suggestions - the alternator seems ok as lights do not dim or brighten with revs and no battery light on whilst driving etc.
Leads - black race tech for AJPV8
Coil packs brand new : any suggestions how to check resistance with this type as I know the tube design but not these. Misfire symptoms are exactly the same as before replacing the coils so I don’t think they are to blame. I cannot swap them out anyhow as no one else here in Perth, Western Australia owns a Cerb (I’m the only one) or a Citroen!
3 ECU electrical connectors - reseat etc - do you mean the 2 on each coil plus another? Not sure which ones you mean.
Cheers.
Coil packs brand new : any suggestions how to check resistance with this type as I know the tube design but not these. Misfire symptoms are exactly the same as before replacing the coils so I don’t think they are to blame. I cannot swap them out anyhow as no one else here in Perth, Western Australia owns a Cerb (I’m the only one) or a Citroen!
3 ECU electrical connectors - reseat etc - do you mean the 2 on each coil plus another? Not sure which ones you mean.
Cheers.
ianwayne said:
Do you have a distributor cap? It may be the centre carbon.
I ask because on a completely different car, an old fiat, I was struggling to find a misfire under load. It was also perfect when cold but got worse as the engine warmed up.
Tried the usual suspects, plugs, temp sensors to ECU etc and it turned out to be the centre carbon brush had almost worn away and had no spring action left.
Wrong V8 I ask because on a completely different car, an old fiat, I was struggling to find a misfire under load. It was also perfect when cold but got worse as the engine warmed up.
Tried the usual suspects, plugs, temp sensors to ECU etc and it turned out to be the centre carbon brush had almost worn away and had no spring action left.
Wolvesboy said:
Leads - black race tech for AJPV8
Coil packs brand new : any suggestions how to check resistance with this type as I know the tube design but not these. Misfire symptoms are exactly the same as before replacing the coils so I don’t think they are to blame. I cannot swap them out anyhow as no one else here in Perth, Western Australia owns a Cerb (I’m the only one) or a Citroen!
3 ECU electrical connectors - reseat etc - do you mean the 2 on each coil plus another? Not sure which ones you mean.
Cheers.
Sorry! thought you had a Speed 6 engine Cerb.Coil packs brand new : any suggestions how to check resistance with this type as I know the tube design but not these. Misfire symptoms are exactly the same as before replacing the coils so I don’t think they are to blame. I cannot swap them out anyhow as no one else here in Perth, Western Australia owns a Cerb (I’m the only one) or a Citroen!
3 ECU electrical connectors - reseat etc - do you mean the 2 on each coil plus another? Not sure which ones you mean.
Cheers.
However the AJP V8 and Speed 6 cars both used the MBE 914(?) ecu, So, I'm referring to the multi-pin connector(s) into the ecu itself. Think I'm right in saying that the (early) Cerberas used an early version of the MBE ECU with a single multi-pin connector into the ECU. The basic premise is the same - the connections get a little oxidisation on them over time - un-plugging and re-plugging the connector cleans the contacts up a bit.
Nick
I wish it was as easy as unplugging/ re plugging the ECU!
I did that (big black connector) last week trying to get my son’s Galaxy S4 to connect its the RSAJP.
Misfire still exactly the same. Double checked the plug connections tonight and all good and tight.
I’m going to check the sparks from each plug Friday evening after charging the battery. I’ll disconnect the fuel and plod through them all.
Fingers x.
I did that (big black connector) last week trying to get my son’s Galaxy S4 to connect its the RSAJP.
Misfire still exactly the same. Double checked the plug connections tonight and all good and tight.
I’m going to check the sparks from each plug Friday evening after charging the battery. I’ll disconnect the fuel and plod through them all.
Fingers x.
Ok, I tested all the lead sparks against the exhaust with another spark plug and all except 7, 2 & 4 were obviously strong. Those three were good also just not as visually strong as the others.
So the next step would be plugs or something else? I just don’t see it being the plugs as I removed them and cleaned them up a few weeks ago.
I’m going to change the big fuse to see if this does it - I lost my cover a while ago and it has been hot here with some days at 35+. The Cerb has otherwise worked well and although ran hotter than the usual 78. It also cooled down well with the rad kicking and when finally moving in traffic. There is no denying it though it did get pretty hot “under the hood.”
I’ve been thinking about the well known misfire with the 4.5 but not from 1800 to approx 2200? Plus the obvious was it was not there when I bought the car initially.
I’ve checked the coil pack wires, throttle pot wires, ht leads to coils.—- Jeez, otherwise I’m running out of ideas.
So the next step would be plugs or something else? I just don’t see it being the plugs as I removed them and cleaned them up a few weeks ago.
I’m going to change the big fuse to see if this does it - I lost my cover a while ago and it has been hot here with some days at 35+. The Cerb has otherwise worked well and although ran hotter than the usual 78. It also cooled down well with the rad kicking and when finally moving in traffic. There is no denying it though it did get pretty hot “under the hood.”
I’ve been thinking about the well known misfire with the 4.5 but not from 1800 to approx 2200? Plus the obvious was it was not there when I bought the car initially.
I’ve checked the coil pack wires, throttle pot wires, ht leads to coils.—- Jeez, otherwise I’m running out of ideas.
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