My 1988 Alfa 75 3.0 V6 seems to be bogging under acceleration. After reaching operating temperature, it can run fine for a few minutes (plenty of power), but then it frequently has a few bad minutes where it has no power, jerks and hesitates with acceleration and sometimes backfires with a pop. It seems to run poorly after a few minutes of driving.
The car hasn’t been run properly in about 7 years. I had an issue with the fuel injector o-rings leaking air causing a misfire. I’ve since replaced these and it’s now running on all 6 cylinders. (before I replaced the o-rings, the bogging issue was significantly worse).
Another issue is that the car is VERY slow to start – turn the engine for 10 seconds, stop, then try again after a few seconds and immediately almost comes to life but then back to just cranking. Can take 20 seconds of turning engine before it eventually comes to life.
Idle is okay, but every so often runs rough for a few seconds. This occurs during the warmup and then again after the car has been running for a while.
@jackocooper As said before, there are hardly any Alfa mechanics here . It just seems that you would be able to find a place that can solve your problems. Have you even considered that it might be time to move on to another vehicle or bite the bullet and just have the whole thing put back in decent shape.
The fuel pump is brand new, although it does make a loud whining sound which gets louder the longer the car is running. I’ve not ran a fuel pressure test yet
Go back to the basics first. First check that the battery voltage with the engine running is in the 13 - 15 volt range. Next, if it hasn’t already been done, replace the spark plugs, the distributor rotor, dist cap, and the spark plug wires. Check the compression while the plugs are out. Verify the proper warm idle rpm and ignition timing, and that the timing advances with increasing rpm is the usual manner. While you are doing that, you might be able to find a broken electrical connector or a broken vacuum hose connector. Remove the battery and the air intake stuff before you replace the spark plugs, it will make the job easier and you’ll be able to spot problems easier that otherwise you couldn’t see. A fuel pressure test follows all this.
From the looks of things it appears the car uses AFC fuel injection. I don’t know how you’re checking for vacuum leaks but a vacuum gauge is the preferred method as there may be leaks that are not easily visible or accessible.
Some potential trouble spots could be…
Bad gas;you did not state if fresh gasoline has been added after the old was removed.
The temp sensor; a somewhat common issue with AFC.
The airflow meter; the box with the black cover attached to the air filter housing.
You should also consider replacing the spark plugs and fuel filter if that has not been done.
The car has been sitting for 7 years. That can be a problem for fuel pumps, filters, AND fuel injectors as moisture in the old gas can cause rust in the filter elements. Yes, injectors have screens in them also…
I wasn’t sure how to interpret that comment, but if OK4450 is right, the gas is too old to even fool with. And the fuel system is probably gummed up as well.
Work done so far:
I have drained and refilled the tank with fresh fuel.
New fuel pump
New fuel filter
New injector seals
New spark plugs
New distributor cap and rotor.
Compression check - good across all cylinders
Check battery voltage whilst running - approx. 14v
Check fuel injector resistances - all good
Still to do:
Check ignition timing
Check fuel pressure.
The car runs well for a minute or so, then will run poorly for a min or so. When running poorly, there is a lack in power, fluctuating idle, splutter when reving (sometimes with backfire), occasional stalling.
Any other suggestions? Thanks for all your replies.
Haha I thought someone would pick up on that. No, I didn’t miss it off the list. A new set is £100 for this specific car so I’m trying to avoid them I’ve checked resistance across all the wires, and they’re all identical, apart from the ignition coil lead. I’ve also sprayed a water mist over the engine in the dark, and no arcing is visible. The cables have no cracking or wear.
Everything seems fine and the car was running well 5 years ago on these wires. Could these really be my problem?
Well , replacing the wires would give you the answer. Of course my personal opinion is that you are avoiding having a professional mechanic solve this vehicles problems.
Don’t know what that is in US dollars but it seems that throwing parts and money at this thing is what you have been doing. Those could be the original plug wires . As said before I can’t understand why you can’t find an Alfa mechanic .
I’ve checked resistance across all the wires, and they’re all identical, apart from the ignition coil lead. I’ve also sprayed a water mist over the engine in the dark, and no arcing is visible. The cables have no cracking or wear.