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Discussion Starter #1
i have been enjoying my 86 alfa spyder for over one year in florida. put in new gas tank, in tank fuel, filter, pump, fuel regulator, new air duct, among the many restorations. was driving fine until, losing power at high end, backfiring into the exhaust at low end rpm and decelerations. barely got it back home. check the sensors and hoses outlined in the Bosch page, replace again, rotor, cap, coil. surprisingly, my variable timing silenoid was not working. connector had voltage when tested. my car starts, revs up, idles irregularly with backfiring into the exhaust with rich mixture. it stalls when i depressed the variable cam rod pin and idles worse with oil cap off.
need more help. i think what is left is o2 sensor and injectors. any suggestions would be appreciated.
leon
 

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Sounds like an air leak in the intake circuit. You will have lots of good advice soon on this BB. Download the L-Jet manual from GHNL or Tifosi, bottom of their posts. They will have you happy quickly. Key words "Air Leaks" or '"False Air". They probably have responded while I am trying to type this.
 

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I'm thinking, I'm thinking. It's hard to diagnose long distance without pictures or even knowing what color Spider is under consideration...


The 'rich mixture'? What are you observing? Could the Cold Start Injector be malfunctioning?

The clue that the VVT system seems messed up might mean something. Are you sure it isn't stuck 'on'?

A bad O2 sensor shouldn't make it run that badly unless the spark plugs are fouled or the catalytic converter has failed & is partially plugged. Usually a partially plugged catalytic converter will allow a normal idle but prevent high rpm operation.

Have you checked distributor timing? Basically, position #1 piston at TDC on compression (keeping in mind the piston goes to TDC twice in one cycle of a 4 stroke engine) then make sure the rotor is aimed at the notch on the edge of the distributor's body. The computer takes care of exact ignition timing - turning the distributor away from the proper position can only make it worse. BTW, when you replaced the rotor did you get a 'wide blade' version? The tip of the rotor can be 'small' (about 1/4" wide) or large (about 3/8" or 1/2" wide). Either will work but the wide blade gives a wider range where it'll run without missing the output terminal of the distributor cap.

You can check for injector operation by listening for each to 'click' while it's running. Rest a long screwdriver's blade against the top of an injector and put your ear up to the handle. The screwdriver will act as sort of a stethescope. Of course clicking doesn't mean squirting fuel...
 

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Bosch 'puter will default rich with any problems. I agree with earlier posts to check for air leaks...especially from the air intake to the plenum.

Years ago, my 82 spider was running just fine and then stalled at a traffic light. I could restart but had no power under load when I tried to get moving. I pushed the car to the side of the road and opened up my hood, not having a clue in hades what I was looking for. I happened to lean my hand on the intake hose and it came loose from the hard plenum tube (the tube across the valve cover). I reconnected the hose and tightened the clamp and took off like nothing had happened!
 

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Query:

I see cap and rotor changes up there, but no mention of the replacement or condition of the wires.

So, with that in mind I ask (1) how old are the wires (2) are they up against something they shouldn't be and gotten scuffed or even aged enough to the point that they cross~talk and (3) when changing the cap, did you get them back on in the proper firing order?

While we're at it, what's the story on the plugs?
Was the cap and rotor a matched set?
 

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Discussion Starter #6
thanks for all your help. save money and time not replacing the o2 sensor. checked my plugs and #1 is normal, #2-4 fuel contaminant, more at #3 and #4. i think my injectors need to be replaced. will check the contacts. may use greg's service.
in the process of checking, my VVT solenoid is out. no one carries this. any one know who can rebuilt this.
 

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Another thought - how are the short rubber hoses between the intake plenum and the engine? Try wiggling the plenum while the engine is running to see if that does anything. If one or more of those hoses are cracked/split it can cause intermittent intake air leaks (aka 'false air'). Those hoses are kind of out of sight/out of mind.

Also, check the wire harness connector to the AFM (Air Flow Meter). Disconnect it (carefully pry the tiny retaining wire open to release it from the catches) and check inside the harness connector for dislodged electrical connectors .
 

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Discussion Starter #8
got new injectors from greg. great deal. my injection hoses were pretty bad. got the solenoid rebuilt.......
... same problem. backfiring into exhaust manifold and pipe. worse at lower rpm and better at higher. tried to adjust the idler nut but no effect in getting idle past 1000 rpm. it starts, sounds better at high rpm.
so far, checked hoses, no leak: new or recently replaced so far: spark plugs, plug wires, cap/rotor, ignition coil, injectors, fuel pressure regulator, fuel pump main/tank, fuel filter, gas tank.
any suggestions appreciated. i am thinking about checking the valve clearances.
thanks,
 

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Fire in the exhaust is usually a result of an air leak.
Possibly a cooked manifold to head gasket.
Hot gasses get into the exhaust stream, cold air gets pulled in and any unburnt fuel then combusts.
(think of it like an oxy~acetelene torch rig: more air = better and hotter burn)

An uber lean mixture can cause it too, which also can be a result of an air leak on the exhaust side rather than something the ECU is doing to the intake side.

Do all 4 plugs look the same AFA burn pattern? (if same, issue is likely on exhaust side, if different could be intake side)
Does it backplop/crackle/backfire, not 'burble', when up in the revs and you use engine braking? (exhaust leak most of the time)
Do you get a fair amount of hesitation on throttle pick~up? (possible intake side leak)
How do the flywheel sensors ohm out?
 

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worse at lower rpm and better at higher.
This could still be indicative of an intake air or vacuum leak. The leak is usually a 'fixed' leak. At idle it is a higher percentage of total intake air, at higher rpm's the leak's percentage of error is less.

tried to adjust the idler nut but no effect in getting idle past 1000 rpm.
The O-ring inside the idle adjuster takes a set with age and refuses to change shape. A new O-ring will allow adjustment. Remove the old O-ring and match it up by eye to a new one at the hardware store.

so far, checked hoses, no leak
Quick, easy test is to remove the oil fill cap while the engine is idling. Doing so introduces a significant air leak (because the engine is supposed to be sealed). If the idle does NOT deteriorate then it is likely there is already an air/vacuum leak.

new or recently replaced so far: spark plugs, plug wires, cap/rotor, ignition coil, injectors, fuel pressure regulator, fuel pump main/tank, fuel filter, gas tank.
Well, your wallet must be quite a bit lighter...!

i am thinking about checking the valve clearances.
OK. Any reason to suspect they suddenly changed?
 

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Discussion Starter #11
no, do not think the valves changed, but i am running out of ideas to fix this problem. backfiring worse at low idle and goes away at acceleration.
#2 and #3 plugs are fouled with gas. #1 and #4 are fine, after all new injectors replaced.
 

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Discussion Starter #12
this is very weird. rechecked the cap and the center point is burnt. my last one was in the same burnt condition.
 

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Discussion Starter #14
Initially I thought I had a bad coil. Test per tech outline. Looked at the cap and the center inner contact was totally burnt. This setup with original wires and bosch platinum plugs went well for over a year until now. Replaced cap and rotor, separately, no set sold locally and upgraded to NGk iridium and Bosch coil. Now the cap is still burnt at the center. Some say need to downgrade to cheap copper plugs and coil?
 

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Discussion Starter #15
went backwards, replaced burnt cap twice, cleaned out ground strap, downgrade oem coil, but kept the iridium plugs. finally my alfa is running again, accelerates much faster may be due to new injectors from greg and fixed VVR solenoids.
thanks for all your help. i enjoyed my alfa much more than my 76 porsche 911.
 
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