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Old 01-22-2002, 00:41   #1 (permalink)
NB & NCII V8 Fairlanes
 
Join Date: Feb 2001
Location: Bibra Lake Western Australia
Posts: 2,858
Newly Rebuilt Engine Stumbles

BACKGROUND

Rather than tacing onto EELFALCON's the "EA running problems" thread I thought it was time for a new one; I'm getting desperate.

I recently rebuilt the 3.9L MPEFI engine in my 89 NB Fairlane. In doing so, I fitted new engine mounts, gaskets, rings, bearings, oil pump, distributor drive gear, timing chain and overhauled the hydraulic valve adjusters. Cylinderes were ridge reamed and honed. It runs like a car with and old style vacuum advance where either the vaccum hose has come off or there is a vacuum leak

SYMPTOMS:

Engine looses revs, hestitates or stumbles at tip in or intitial acceleration from rest or from any closed throttle to acceleration situation (ie going around a corner) in any gear and neutral and park. Continual throttle blipping at idle causes backfiring in inlet manifold. Spark plugs have dry black coating (rich mixture?). No scan codes (now), clean exhausts, good idle.


TESTS AND FIXS TRIED SO FAR (the ones I can remember):

New plugs, points HT leads and distributor cap and rotor.

Checked TFI earthed.

Checked no water in fuel and filled with fresh premium unleaded.

Checked for vacuum leaks by spraying CRC, water, detergent and carb cleaner at inlet manifold head joints. Nothing happens.

Checked all vaccum hoses connected and have suction.

Checked with vacuum gauge - within specs but lower than I expected.

Checked cannister purge valve by pinching vaccum line; no change.

Checked fuel pressure; within specs.

Cleaned ISC valve (foam air filter oil gunked) this cleared code 13 that I did get initially.

Checked compression at 6 cylinders (worrying I'd lined up the ring gaps by mistake).

Removed timing cover and double checked cam timing.

Reset base timing (with scan tool connected and checked with two different timing lights)

Reset base idle.


Checked TPS - resistance varies with throttle and voltage within specs.

Checked ISC valve - opens and closes; voltage within specs.

Checked MAF as far as I could - removing and blocking vacuum line changes engine behaviour. Voltages within spec and continuity with ECU.

Cleaned blue oil gunk from foam filter out of throttle body.

Pulled each lead from each plug in turn; engine revs fell in all cases.

Checked ECU earthed.

Checked alternator output.

Listened to injectors opening and closing with stephoscope and also checked with noid lights. Even plug colour and plug lead pulling test suggest they are behaving equally.

Swore at engine and kicked wheel (I didn't even feel better).

Called on divine assistance from various gods and dieties (no response yet).

Found a silly reason to blame the wife (felt worse - guilts).

Tried retail therapy at local auto shop; felt more guilty about unwarrantewd spending.

Had a beer - helped for a little while.


Please don't be afraid to suggest the obvious or question the thoroughness of my checks. I feel I have missed something obvious and simple like a hose all plug I reconnected improperly or not at all. I promise not to be insulted by even the most obvious questions or suggestions.

My next step will be to fit a new thicker inlet manifold gasket in case there is a leak I can't detect and re-run all the test again/
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Old 01-22-2002, 02:35   #2 (permalink)
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You didn't mention anything about checking the coil.Check whether the coil is breaking down under load(plugs seem to be indicating it is getting fuel but not burning it - though it also depends upon how/when you read the plugs...)
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Old 01-22-2002, 02:37   #3 (permalink)
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You could try checking the distrubutor. My father had an EA that was causing problems similar to what you detailed. I think it ended up being either wore bushes on the rotor shaft or some electronic drama in the ditributor.
All the best.
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Old 01-22-2002, 03:21   #4 (permalink)
NB & NCII V8 Fairlanes
 
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Yes; I've thought about the coil but it's a bit hard to get at to test. It might be easier (but not cheap) to simply replace it. I've just been out fiddling and for a short time the problem seem to go (no stumble but more backfiring). I'd just checked that earth wire near the ISC valve throttle body; anyone know what that earths.
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Old 01-22-2002, 03:27   #5 (permalink)
NB & NCII V8 Fairlanes
 
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Thinking of the coil a light bulb just went on in my head. One thing I found when I took the engine out was the suppresion condensor on the coil was connected. I connected when I put the engine back. I wonder if it was stuffed and it was (given how hard it is to get to) disconnected rather than replaced. Well that will be an easy test.
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Old 01-22-2002, 03:39   #6 (permalink)
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...and I can test the coil from the TFI plug.
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Old 01-22-2002, 03:50   #7 (permalink)
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I think you are on the right track with ignition,coil etc.What a top place to put a coil ?[b.s] Plenty of heat and bloody hard to get to, I bet you put a new one in the same place? I'd go inner guard.

Another thing to check is the hego [02] senser on your exhaust system.You may have some crap in there, not working properly..
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Old 01-22-2002, 04:35   #8 (permalink)
NB & NCII V8 Fairlanes
 
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Well I have now tested without a suppression condensor on the coil and with a new one;no change. The wire fell off the condensor when I tried to remove it so I don't think it was doing much. I'm waiting for the engine to cool before I check the coil via the TFI connection as I want to reduce the inevitable burns to 2nd and 3rd degree ones....though perhaps some nice 1st degree burns will cauterize the cuts from my previous ventures into that fun area under the inlet ram tubes.

BTW I replaced the dizzy bush (soaked for a week in oil 1st) when I put the new gear drive in. I also cleaned up the balance of the wiring in the dizzy when I put the new TFI module in (when I plugged it in the female wires lucar type connectors inside the dizzy came out of their fittings).


Hmmm not sure where I will put a repalcement coil; at the price they perhaps I should display on top of those inlet ram tubes; wouldn't need to rewire as the existing wire should jsut about reach.
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Old 01-22-2002, 04:45   #9 (permalink)
NB & NCII V8 Fairlanes
 
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Hmm I'll test the Hego as it's a quick and easy one though I didn't think it would cause the symptoms I've got. Just read that a faulty PIP module in the dizzy can cause these problems and the only test is replacement. I guess in playing with the dizzy I might have somehow accidently damaged it.
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Old 01-22-2002, 06:47   #10 (permalink)
NB & NCII V8 Fairlanes
 
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Hego tests OK; fluctuating voltages as required and no fix if disconnected.

BTW can someone please pop the bonnet on a EA/EB or NA NC MPEFI six and tell me where the battery earth wire is connected. I have connected it to the spare hole near the engine mount; is this the right place? And on the LHS we have a earth runnibg from the bell housing to the body under the car. I've been reading that improper earthing can effect the ECU and cause these problems too. Grasping at straws maybe but......
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