ECU misfire

[gingerclive]

Car keeps stalling & convinced its ecu, go out & get secondhand one (Chap throws in one he says is faulty as a spare!)fit new one & tickover is perfect but now I have a misfire at 2000 revs, swapped them back & misfire goes & stalling returned. Tried the "Faulty one " & runs like a bag of nails. Im wondering if the "New one " is also faulty with a different fault
or is it possible things need adjusting to the new ecu?

Clive

[jmorgan]

Hotwire or flapper. Just asking cos the knowledgeable will want to know.

Mine, hotwire, has had a coil go iffy, thingy bolted to the side of the dizzy (amplifier) go south and dodgy connector to the airflow meter. Oh, and a throttle pot voltage wrong. Nothing to do with the ECU (not saying it isn't though).

Better people will be along I am sure.

[gingerclive]

Thanks Jeff.
Sorry its a flapper

[ed_crouch]

Could be ignition amp.

Invariably the battery voltage is lower at idle, and sometimes a poor idle can be attributed to the early stages of failure of the ign amp.

Worked for me.

[honestjohntoo]

gingerclive said:

Car keeps stalling & convinced its ecu, go out & get secondhand one (Chap throws in one he says is faulty as a spare!)fit new one & tickover is perfect but now I have a misfire at 2000 revs, swapped them back & misfire goes & stalling returned ...... or is it possible things need adjusting ...... ?

Based on the premise that you probably now have two good ECU's and one bad one, you may not be aware that approx 80% of all RV8 Efi faults are due to plenum air leaks and Efi wiring/connector problems, may I ask if you checked out any of that stuff yet?

Of the remaining 20% of faults, there are three or four components that would account for your patchy mixture control problems and the least likely of those is the ECU.

What component testing did you do prior to condemning your ECU?

I you decide to bypass the testing process and make adjustments to suit, one or other of the good ones, then what did you have in mind? Idle screw? throttle pot? CO screw? possibly a rising rate FPR, if one is fitted?

And that's it, that's all there is, except for some serious poking about at the innards of the AFM, but I caution against it.

So what else? The plenum can be caked in crud, internally, with blocked galleries including the breather channels. Did you check the breather, it can play merry games with low rpm mixture control if blocked? Also, is the throttle plate able to operate freely in a clean environment?

On the electrical side, is the throttle pot noisy at low throttle setting, intermittently firing the acceleration enrichment circuits to upset the mixture control thereabouts? Also, the main Efi engine earth is subject to corrosion, introducing unwanted and variable residual voltages in the earth circuit that upsets the signals to the ECU from a couple of key sensors?

If its none of the above then the simple truth is you could have three knackered ECU's, in which case the path to success is clear but its an expensive route.

For reading material on all the possibilities mentioned and many more try this archive:

http://www.vintagemodelairplane.com/pages/Rover_Te...

and this:

Edited by honestjohntoo on Sunday 22 November 22:35

[adam quantrill]

Like HJ2 says it could be a number of things.

The ECU's were commonly matched with the flapper AFM's, so I've heard, so that's another possibility, maybe they are a bad match.

Is it a misfire you have or more like poor fuelling/a flat spot at 2000rpm? The ignition is separate (but feeds the ECU) so I would suspect it's cutting the injectors. You could try reflowing the solder on the new ECU, it takes about 2 hours start to finish but might clear up the problem.

[gingerclive]

thanks for your help folks. Ive done the electrical tests, replaced the pressure regulator as it was playing up a bit, replaced potentiometer,plugs & leads done.I have not had plenum off so that sounds like the next rout then. it feels like a misfire but always at the same revs (2000) it seems ok above that.
Ill let you know how I get on.

Clive

[Wedg1e]

Bear in mind that the same ECU as used on the Range Rover was internally calibrated differently to the requirements of a Vitesse engine (effectively the 350i motor) so what appear to be a rough-running issue may be down to the setup differences.

[adam quantrill]

That breather pipe referred to above is the one that goes in near the throttle body and scavenges air from the block.

It can get blocked in the metalwork - and it's a pain to clean out as it goes around a corner.

To test it, take one of the breather pipes off and attach to the nozzle on the plenum, then blow down it. If you feel any resistance then it's blocking up. To clean it out I use a length of string and blow it down the pipe so I can catch the other end in the throttle opening, then tie a small rag to the string and pull it through backwards and forwards, petrol works well as a solvent.

Also clean out the gauze in the breather can (flame trap) and check the pipes for blockages - the condensate from the engine can block up the system all over the place.

[TVRleigh_BBWR]

If your 95% its the AFM or ECU I can send you my spare set to check.