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Discussion Starter #1
Hi everybody,
Well, after many years of lusting over Alfa Romeo's I finally took the plunge and brought home a (what appeared to be) well sorted '85 GTV. Things were great for about two weeks, minus some driveline vibrations, missing steering column tilt handle and pretty much inoperative turn signals - nothing that new guibos, Ebay and ground cleaning can't fix. All that mattered was that it drove great, was free of rust and looked good!

Unfortunately now it seems to have developed a bit of a misfire... It happened after a relatively long (1.25 hr) highway drive on a warm day, pulling away from an intersection at the exit ramp the engine began to stumble and there was a noticeable loss of power - somewhat similar to "limp mode" on more modern vehicles.
Any suggestions on where I should start with my troubleshooting? The misfire happens at both idle and under load. There is loss of power and engine seems reluctant to rev above 3000rpm. There is no smoke or coughing so it doesn't look/sound like a fuel pressure issue. So far I've just done the basic stuff, checked for obvious vacuum leaks, checked for loose wiring and replaced cap/rotor, which didn't help much. Given how it happens at idle and under load, I think I can eliminate the coil, AAV and TPS from my suspect list. Is it likely for the AFM to go bad? What are the chances of a 1,000 mi old timing belt that sat for a year to skip a tooth?

Appreciate any ideas.
Thanks,
 

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What do the spark plugs look like?

Triple check for intake air/vacuum leaks - L-jet is very intolerant of air/vacuum leaks. Check that the flap in the Air Flow Meter moves smoothly through its range of motion.

May we presume you are aware of Greg's L-jet diagnosis/tune up guide?
 

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I once had the same problem with my car after purchase. There was a loose connection going to the fuel injection unit. I find usually that when these cars ahve a problem or hiccup it is almost always electrical in nature, not mechanical. If you go the the front of the engine bay on the driver's side, and find the plug connector that goes to the fuel injection, open it up and clean the contacts and make sure all the contacts arent loose, I bet that immediately clears up the problem. I would start there first before looking at the spark plugs and vaccuum leaks etc.
 

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Does your car burn oil? Does your car have a catalytic converter? Does it "smell" different when misfiring?

Also - is it a misfire OR definite pinging/pre-detonation?

As others said, CHECK your spark plugs. Deposits can collect (especially if your car burns oil [or coolant!!]) and can close the gap on the plugs, effectively causing it to spark earlier.

You mention that you replaced the cap and rotor, but did you pull spark plug boots to check connections or debris in the well?

Report your findings. These issues can become a good resource (if resolved in the thread!) to those who have the same/similar problem in the future.
 

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I will bet money it's a loose wire on that connector I mentioned. Your symptoms are PRECISELY what happened to my car. Even the fact that it happened when "pulling away" from a stop. Suddenly it sputters like it's losing power, but then when you go below 3K RPM it sort of picks back up again, right?
 

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There is no smoke or coughing so it doesn't look/sound like a fuel pressure issue
A fuel pressure problem can feel like a rev limiter. When it happened to me it was the fuel pump.
 

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I will bet money it's a loose wire on that connector I mentioned. Your symptoms are PRECISELY what happened to my car. Even the fact that it happened when "pulling away" from a stop. Suddenly it sputters like it's losing power, but then when you go below 3K RPM it sort of picks back up again, right?
Brad,
This is the connector you're likely referring to:



And - just to be more specific so you don't chase the wiring on the wrong side of the engine bay - this isn't the fuel injection nor part of the fuel injection harness, but rather it is the ignition module.

Since your car is an 85, it has the later style ignition advance system. It has its own wiring on the driver side of the engine bay and terminates up under the dash, right above the fusebox.
 

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Discussion Starter #8
Thanks everybody for the replies! I love the enthusiasm and responsiveness on this board.

wonderbrad - your symptoms do sound very similar to mine. The car seems to have almost normal response in 1st gear at low revs, but as soon as I try to accelerate up to speed and shift into 2nd it falls flat on its face. I am going to check/clean the connector that you mentioned tonight after work. Just to clarify, you are referring to the connector at the coil/amplifier unit, correct? Did you also have a rough(ish) idle condition?

ghnl - I did read and print out the Greg's L-Jet diagnostic guide - it's a great resource! However, with me being rather impatient (I know, not a good trait to have with an Alfa) and feeling that some of the steps didn’t apply to my symptoms I wanted to determine which troubleshooting checks would be applicable to my symptoms. However, if all of my fault locating shortcuts do fail to pinpoint the issue I will go through the guide step-by-step.

racingswim2006 – with my car being relatively new (to me) I can’t tell if it’s burning oil or coolant yet. The exhaust doesn’t smell abnormal (ruling out O2 sensor IMO) or smoke. I’m going to check the plugs tomorrow. As for wires and plug boots they appear clean and wires were replaced recently by the PO.

Once again, thanks everybody for your input
 

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Yes that is the plug in the photo above. I guess it is for ignition, not fuel injection so i made a mistake! On my car this plug is located at the front of the engine bay on the driver's side, not far from the headlight area. I would tug on each wire going into it and see if any of them just come off or seem loose. This is what caused my car to misfire. One of the wires had come out of the plug, basically.
 

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Discussion Starter #10
Short update; I located the ignition module. Curiously enough it's only a 6-pin (Bosch p/n 0 227 100 111) as opposed to the 7-pin in the picture posted by racingswim and replacement units online. I wonder if it makes any difference.
Didn't get a chance to try it with cleaned contacts because my battery gave up the ghost (another possible cause of the misfire?).

On a positive, and unrelated note, I did manage to fix the turn indicators and located the steering column tilt adjuster, which PO hid under the steering column cover. So it wasn't a total waste of a day..
 

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Short update; I located the ignition module. Curiously enough it's only a 6-pin (Bosch p/n 0 227 100 111) as opposed to the 7-pin in the picture posted by racingswim and replacement units online. I wonder if it makes any difference.
Didn't get a chance to try it with cleaned contacts because my battery gave up the ghost (another possible cause of the misfire?).

On a positive, and unrelated note, I did manage to fix the turn indicators and located the steering column tilt adjuster, which PO hid under the steering column cover. So it wasn't a total waste of a day..
It could be a 6 pin. I just grabbed an image quickly of one that looked very close.

Many cars use similar modules with similar numbers of pins, but with a different pinout.
 

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If the car was running great and then suddenly started running as you say:
developed a bit of a misfire... It happened after a relatively long (1.25 hr) highway drive on a warm day, pulling away from an intersection at the exit ramp the engine began to stumble and there was a noticeable loss of power - somewhat similar to "limp mode" on more modern vehicles.
Any suggestions on where I should start with my troubleshooting? The misfire happens at both idle and under load. There is loss of power and engine seems reluctant to rev above 3000rpm.
Stop driving the car before you do some damage.
1) Chk distributor vacuum advance.
2) Double-check the timing marks at crank, both cams, and distributor. May have jumped a tooth retarding your timing.
3) A fuel injector may have given up. Check Ohms at each. While engine running, remove bosch electrical connecor from one at a time, replace and move to next. Engine rpm should drop and engine stumble. Bad one will show no change is current bad idle state when disconnected.
 

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Discussion Starter #13
I'm running out of ideas now.
My symptoms have changed from the thing having an apparent misfire to it barely running and having no throttle response.
I disassembled, checked and re-assembled all vacuum lines. Checked and cleaned all connectors in the engine compartment.
The symptoms have changed a bit. Now it starts, but it runs very rough and tends to die a few moments after I try to apply throttle. Throttle response is non-existent. This made me suspect the fuel supply, so I changed the fuel filter, which didn't do much. However, when I was changing the filter, I noticed that there was very little pressure in lines, which led me to suspect the fuel pump. So today I changed the pump, started it up, it ran fine on the first test, all of about 20 secs, at idle. I then tried to drive it, it took off fine, but then a few feet later it started stumbling again and got progressively worse.
At this point it's back to barely running, having no throttle response and/or dying on throttle application. I'm running out of ideas now... I got a fuel pressure gauge set from a friend and planning to check the pressure out of the fuel pressure regulator, but I don't think it's likely to cause the symptoms that I'm experiencing. I'm also fearing the worst - crud in the fuel tank/lines, which would be a royal P.I.T.A. But then if that's the case, I don't understand why it ran fine for the 40-50 secs after I changed the pump. I'm confused...
 

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Let us know what the fuel pressure is at idle and when you try to rev it. It is less expensive to change out parts based on data rather than on a hunch.
 

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GTV6noob,
Did you ever solve this problem? I'm still having prob's with my 85, symptons similiar but not the same. Will start to miss around 4000 rpm and if I hit the throttle real hard, it will clear up and red line easily. I'm running out of ideas. Too rich?
 

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Discussion Starter #16
bayalfagtv6, your symptoms are different from mine. My car couldn't even get above 3,000 rpm. I remember seeing another post that dealt with the mid-range miss. If I were you, I'd probably start by checking the resistor track on the AFM for wear and read the sparkplugs to see if you have a faulty injector/weak spark.

As for my issues, I guess I should give a long-overdue update:
My excessively rich running condition was quite a learning experience for me. The troubleshooting ended up taking much longer than necessary as a result of a well known board member first selling me a wrong AFM and then shipping me one (that was supposedly "tested and in perfect working condition") that was full of moisture and corroded internally beyond repair. Took me a while to sort through the multitude of symptoms caused by it until I finally decided to crack open that "supposedly good" AFM... But I digress. The root cause of my poor running was a fried L-Jetronics ECU, most likely the result of a short to exhaust manifold on my O2 sensor wire. I found that the signal wire had contacted the exhaust manifold and melted the insulation.
My theory is that in case of a failure, the ECU defaults to maximum rich setting to preserve the engine. Please correct me if I am wrong on this. At any rate, a new ECU finally fixed my poor running condition.
 
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