poorly 3.9 efi any thoughts?

hey all.......ok so my heads got re-con'ed about 3 months ago, and since putting it back together again, its been running really really badly......i have checked all ignition parts etc, most were new but now all are new, leads coil, amp etc.... timing has been check etc,........so its running really lumpy and erraticly at idle, and under load sounds like its running on three cylinders.....almost impossible to drive.......i have shimmed the rocker pedistals etc as thought it might have been the valves being held open....but no, i also have near perfect compression on all, so i dont think its the heads, just seems strange to have been running also most fine before rebuild and now like crap...... any ideas?

Double check that you've got the plug leads going to the correct cylinders.

lol cool, yeah i have checked that as at first they were on wrong.....really wrong.....but now they are 100 correct, fitted a new coil, plugs, leads, amp, vac advance, cap and rotor, and the dizzy is about 6 months old.....

Try pulling the plug leads off one at a time and see if you can find one (or two) that makes no difference to the running.
H&S - rubber gloves, insulated pliers etc.

lol cool wil do ill try it now.......tbh thats ones job i hate doing lol even with insulated gloves and pliers lol

ok i pulled each lead off and a few made a differance, but other didnt seem to, or at least wasnt obvious, as it running really rough anyway, i checked each lead with a spark plug tester and they all seem fine, once it cools down a but ill try unplugging each injector and see if that makes a differance or not..

if you are sure that the plugs/dizzy/leads/timing/ignition are ok then it is probably a fuelling issue.

Check the AFM (by taking it off and just running through the plenum) and then the fuel rail itself before you go faffing around with the injectors - they are the most unlikely items to be faulty.

Also check the ECU is plugged in properly.

ive checked the ecu and tried another just in case, i have had the maf unplugged as well to check that........if i had hair id pull it out lol

your engine is 180 degrees out of phase??

chrisrawe said:

ok i pulled each lead off and a few made a differance, but other didnt seem to, or at least wasnt obvious, as it running really rough anyway, i checked each lead with a spark plug tester and they all seem fine, once it cools down a but ill try unplugging each injector and see if that makes a differance or not..

Click to expand...

Pulling the leads off is not to check the spark but to check that it's arriving at the correct cylinder at the correct time. If you pull a lead off and the running gets worse then you assume that that one is correctly connected. Concentrate on the leads that seem to have no effect. These should come in pairs.

This is all assuming that you've done all other checks. You've triple checked the engine timing, you haven't got a blocked exhaust, air supply or fuel line, you haven't left anything (rag) in the engine during the rebuild?

infrared thermometer or drops of water on exhaust manifold can help you to identify the hot/cold exhausts so you can pinpoint which cylinders are firing and which are not and then focus your work on them.

if you have good compressions then you do not have a cylinder problem.

cheers

timing is definately spot on, it was 180 out at first but then sorted it.... I'll try the water droplet idea thats a good one....gonna have another play tomorrow as i have to clean the bbq tonight

ok so checked plugs for any signs etc... 3 plugs were wet so brought some new leads, and after having a look my mate told me i had the wrong plugs in it as well, i ordered the right ones but apparently the wrong ones turned up, stupid me for not checking part no.s, anyway put the right plugs and new leads on and had the timing checked, so now it runs a little bit better but still crappy and terrible under load, back to the drawing board

Oh and my maf is shagged as well lol

ok so had someone have a look at the old girl, and couldnt find anything wrong so now shes stripped down again and waiting for new gaskets etc, the only thing i found was that the sealent i used on the valley gasket was usless and the gasket just lifted off with very little resistence, so as much as the gasket should have sealed it up iam feeling that this may have induced small air leaks etc so once mr posty arrives ill find out....

stripped down, re rebuilt, and still a pile of turd..... apart from stripping right down and having the heads checked, i have no idea...

O.K. then let's see what's what.

If I understand what you are saying then engine has a rough idle and a possible misfire under load. You are happy your ignition system is spot on. I assume the fuel system is O.K.

So it seems this is probably an EFI gremlin. I would suggest you check each component: Fuel temp. thermistor, coolant thermistor, throttle potentiometer, air flow meter. You said your air flow meter was faulty - have you replaced this with a new one or a known good second hand one? Your ignition parts - are they genuine Lucas or are they pattern? If they are pattern take them off and fit genuine.

If you do a search there is plenty of info for testing the various EFI sensors. Post back here with results.

Also check and test your battery and alternator. Have you replaced the fuel filter? Oh and is this an RRC or a Disco?

my next step is to check my fuel pressure and regulator for faults, its rrc 3.9 in a defender but as far as the engine is concerned it might as well be a rrc, 100% ignition and when my fuel pressure gauge turns up ill know the fueling is 100% except for injectors, i have re checks the valve clearances and they are 100% and the same for air leaks..... iam going to check all the electrical componets next as you suggested...... Many thanks ill get back once i,ve done these things

even new ignition parts can be ****e now, no matter what brand (except for magnecore , so far) as most stuff seems to be made in the third world. if it ran ok before you did the heads, in terms of ignition anyway, try putting your old bits back on and see if it sorts it. its free to try lol

ok so i fitted a fuel pressure gauge and going by a guide i found for 14cux diagnostics, i got the following

rail pressure shouldn't drop more then 10psi in 1 minute @36psi.......i got 36psi and a 16/17psi drop in 1 min........so iam guessing either pressure reg or injector leak.....any more guesses?

i also check my electronics..............all fine...

and i checked my injector resistances as by the guide and the results are ......good actually....

left bank......should be 4-4.5 ohms.............i got 10 ohms indicating 2 injector faults
right bank......should be 4-4.5 ohms...........i got 10 ohms indicationg 2 injectors fooked..

so iam going to get 8 new injectors and test again and then if need be a new pressure reg............lets see what happens next lol