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Rb30 Hesitation

FMA

By FMA,
in Classic & Vintage (1950's-1980's)

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FMA

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;)

This is my first post so naturally I have a problem. I have a 1987 Silhouette which has only had to have the fuel pump replaced in the 11 years I have had it. BUT this week it started to lag BADLY under any acceleration. The car idles well and revs well NOT under load. It's as if you're dropping the clutch HARD when you go to pick up speed. I have changed the plugs, cleaned the dissy cap, checked the resistance in the plug leads, done the self diagnosis test (speed sensor code but speedo still working OK), checked the timeing. After this I was able to drive for about 4klms (from cold) before it started to play up again.

Does anyone have ANY suggestions?

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QUIKBLADE Collaborator

QUIKBLADE

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Unmetered air leak? Causing rich condition and fouling plugs and hence no spark and hence no power?????If it drove for 4kms before it did the same stuff I'd say then it might take 4kms for them to get fouled????.... I'm guessing here as not sure about the engine specs. Best of luck.

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SteveL Mentor

SteveL

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:)

This is my first post so naturally I have a problem. I have a 1987 Silhouette which has only had to have the fuel pump replaced in the 11 years I have had it. BUT this week it started to lag BADLY under any acceleration. The car idles well and revs well NOT under load. It's as if you're dropping the clutch HARD when you go to pick up speed. I have changed the plugs, cleaned the dissy cap, checked the resistance in the plug leads, done the self diagnosis test (speed sensor code but speedo still working OK), checked the timeing. After this I was able to drive for about 4klms (from cold) before it started to play up again.

Does anyone have ANY suggestions?

First thing I'd check is the spark leads with the bonnet open and engine running on a (very) dark night, looking for arcing. Your symptoms are suggestive of spark lead insulation break-down. I've they are 11+years old (even orignals ??) I'd be replacing them. The fact that the problem occurs after things have warmed up under the bonnet is another pointer to electrical issues.

Other possibilities are corrosion of the connectors to the CAS and AFM (very common at the CAS connector on the RB30); AFM on the way out (but you said no error code so perhaps not); and break-down of the ignition transistor and/or coil.

Edited by SteveL
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FMA Rookie

FMA

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;)

Unmetered air leak? Causing rich condition and fouling plugs and hence no spark and hence no power?????If it drove for 4kms before it did the same stuff I'd say then it might take 4kms for them to get fouled????.... I'm guessing here as not sure about the engine specs. Best of luck.

Maybe but it only has one big hesitation and away it goes. (The engine is standard.)

It idles well and revs well when not under load. Before I checked and pulled apart a number of leads it would not go 200mtrs before the trouble. :)

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SteveL Mentor

SteveL

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:) I checked the resistance of the leads which were OK but I will check for arcing tonight.  My wife keeps saying I am a DOPE so could you "please explain" CAS and AFM ( is that the Air fuel meter)? The ignition transistor and coil sound feasable. How would I check the transistor?

The resistance won't tell you if the insulation is breaking down.

CAS = Crank Angle Sensor, which is built into the distrubutor. The black, multi-pin connector at the 'top' of the distributor is the connector to it. It's quite common for the rubber boot on the connector to crack with age and then water gets in causing corrosion and then ignition problems.

AFM = Air Flow Meter (you were close....). Measure air flow into the engine, but if that were failing it should trip an error code (code 12).

As far as the coil and transistor are concerned, porbably best way to check is to swap for known good ones, but in the first instance check the 2-pin connectors to each for corrosion and other damage. Transistor is bolted to the side of the distributor, coil is obvious.

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FMA Rookie

FMA

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:mellow: SteveL I checked the plug leads in the dark , no shorts. I disconnected the wires to the coil, dissy, and a few others and cleaned them but the problem is still there. It seems as though it is only under initial accelleration. The car does not have to go very far as today I only went about 1klm before it started. Whilst it was idleing I disconnected the EGO for about 10-15 sec. and there was not change in the idle. Should there be in that time? What checks can I do on the CAS? I have a good multimeter.
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SteveL Mentor

SteveL

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The main thing to check with the the CAS is corrosion at the connector. If the engine runs otherwise normally then the CAS is probably OK. I'll see what I have on more detailed checks of the coil, etc. Beyond that it's things like:

fuel filter - when last changed ??

air filter - ditto.

injector conectors - damage/corrosion ?? (not uncommon)

is it idling normally (900 rpm or so) ??

all engine hoses, etc in good nick (no cracks etc)

Disconnecting the EGO should have no affect at idle, AFAIC.

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FMA Rookie

FMA

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:lol: SteveL the fuel filter is brand new, replaced because of this problem, fuel filter could be cleaned (K&N) but driveb without with no improvement, no problem with idle at all, checked all hoses as best I can ( had to tighten a few). I have not disconnected the injector connectors yet. will try when I can probably in a few days.

:lol:

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FMA

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:lol: QUIKBLADE I have had the car 11 years and NO modifications have been made. The car is a manual and no work has recently been done to the clutch. The problem is worse when it's warm and it's a miss and lack of power in any gear but only under ANY accelleration.

:lol: :lol: :lol:

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QUIKBLADE

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:lol: QUIKBLADE I have had the car 11 years and NO modifications have been made. The car is a manual and no work has recently been done to the clutch. The problem is worse when it's warm and it's a miss and lack of power in any gear but only under ANY accelleration.

:lol:  :lol:  :lol:

Well, yeah, if no work has been done to the clutch in 11 years, then if she is slipping.... it will be in all gears, and will appear like a lack of power (cold and warm)... has it been tested eg: put in 5th @ 60km/h, floor it, and the revs climb but the speed doesn't?...

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FMA Rookie

FMA

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:lol:

Well, yeah, if no work has been done to the clutch in 11 years, then if she is slipping.... it will be in all gears, and will appear like a lack of power (cold and warm)... has it been tested eg: put in 5th @ 60km/h, floor it, and the revs climb but the speed doesn't?...

:lol: :):):( I pulled the new plugs again today and they are all sooty. So I would say that it is a fuel problem. Maybe the AFM but how do I check it?

:lol: :P:( <_<

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