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Discussion Starter #1
My LS turned 100000 miles a little while ago and the engine started to miss/hesitate when warm/hot and idling at stop.

I thought it's about time to replace the stock plugs so I had them replaced with new ones. However, It looked like the plugs might have been replaced some time earlier at one of the timing belt service...

Anyways, replacing all plugs did not make the miss go away...

I've tried techron
wiggled injector wirings
no engine code

What should I look for next?

Thanks!

jess
 

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Could be bad coil pack maybe? Pull the cover over the coils and see if you see a light show happening! I know from other 24V owners that the coil packs can cause all kinds of weird things to happen. Hope that helps you out,

Jon
 

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Discussion Starter #3
Thanks, i'll give that a try... i don't recall seeing any lights for the front bank.. the rear bank would be a little more work to clear things away...

Any other known way to diagnose the coil pack? (that'd be too easy isn't it :)

jess
 

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Maybe put some kind of insulation between the coil pack and the valve cover. Maybe get a sheet of rubber and cut some kind of base that would go underneath the coil packs. I know junglejustice tried I think Mylar, but still had problems. Interestingly while chatting with a 164Q owner at the alfa meetup on saturday he said that he replaced all of his coil packs because his car was running poorly. Took him a while to figure out why, but now he sais that the car runs better then ever. Problem is I think those suckers are not cheap, but look at it this way, even if it does not solve the problem, you have new coil packs! For a source I know that Alfissimo sais he has some new ones at a fair price, give him a call if the insulation try does not work. Best of luck,
Jon
 

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Maybe put some kind of insulation between the coil pack and the valve cover. Maybe get a sheet of rubber and cut some kind of base that would go underneath the coil packs. I know junglejustice tried I think Mylar, but still had problems. Interestingly while chatting with a 164Q owner at the alfa meetup on saturday he said that he replaced all of his coil packs because his car was running poorly. Took him a while to figure out why, but now he sais that the car runs better then ever. Problem is I think those suckers are not cheap, but look at it this way, even if it does not solve the problem, you have new coil packs! For a source I know that Alfissimo sais he has some new ones at a fair price, give him a call if the insulation try does not work. Best of luck,
Jon
Yes, they are not super cheap but I would not say for sure it is the problem until you diagnose them. They could have fine cracks in them causing arching. The rubber boot sometimes can get cracked, etc...
Might be a sensor.
At worse an ECU. I have seen a lot of these ECU's take a dump and cause similar issues. But that is last resort.

Jason
 

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Coil Packs

Usually but not always you can hear em popping and arcing---- did you try the fuel filter? How is acceleration and decel--what is your typical gas mileage? Air filter? check for air leaks, etc?Does the car run good besides the idle lump? Cam timing is always a wildcard --
Sorry to throw so many items at you but more info is needed to narrow it down
 

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I would also check the air hose between the AFM and the throttle valve, sometimes these can leak and can be hard to detect
 

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Discussion Starter #8
Thanks all! I haven't had much chance to work on the car, but adding an insulation is a sound solution, i'll try borrow an ECU.. i think it's behind the center console tunnel.. which isn't too bad to reach. I'll go over the air hoses... though I am pretty sure I've checked that while replacing the spark plugs. Let me see if I get to work on some over the weekend. Hm.. haven't replaced fuel filter, I do have a spare part to go in any time. I'll do that anyways :) Thanks for the suggestions!!

goats don't worry about listing many! they are all wondeful suggestions I didn't think!

I hope I don't have to replace all ignition packs.... :)

Thanks all, let me try update after the weekend works :)

Jess
 

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jess here is a tried method

Before you mess with ECU and coil packs--- do the simple stuff- fuel filter, air filter, and then...

Go to your local electronics store and buy some "contact cleaner' in an aerosol spray can. Start your car up from cold and spray that stuff all around the rubber hoses, idle air controller, intake runners, air hose, etc., in short, anywhere where air gets pulled or vacuum lines. Listen for a jump in engine RPM. Thats the evidence of a leak -- pulling in the volatile contact cleaner and goosing the engine. Try to do this while the engine is not too hot-- otherwise keep a wet towel or CO2 fire extinguisher handy in case it ignites
 

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Re: coil packs...when they go bad they tend to arc and cause misses at idle when the engine is hot. If you are getting misses when the car is cold it is probably not the coil packs. That said, they have an expected life of 90-100,000 miles.
 

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Discussion Starter #11
absolutely i'll leave the expensive parts to the last :) I spend some time going thru the vacum hoses and electric connectors. I know all about the contanct enhancers as I am a big believer of the DeoxIt and ProGold. They saved me many times in the past! Every time I get into engine bay, and reaches connectors that I don't usually see, i'd always give them fresh DeoxIt/ProGold just in case. Air filter looks clean, oil was replaced little while ago and fresh.

Next on my list is the fuel filter. Looks like a simple... but slightly messy task (gasoline)

Thanks all!

Jess
 

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Fuel filter is slightly messy, but not too bad, I had a bear of a time with mine, though having the proper size spanner for the filter would have made it a snap. Instead I had to use my king size crescent wrench, not fun.
 

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Fuel filter is slightly messy, but not too bad, I had a bear of a time with mine, though having the proper size spanner for the filter would have made it a snap. Instead I had to use my king size crescent wrench, not fun.
Helps somewhat if you start engine and pull fuel pump relay near coil (one without red stripe to kill engine and fuel pressure before you remove fuel filter.
 

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The fuel filter under the car isn't that bad of a job. Just have a drain pan under it when you disconnect. Crack the fitting to bleed off any residual pressure in the system. Be sure you put new copper washers on the new filter (should come with the filter).

The coil packs crack and start to arc. They are hair line cracks that are easily missed. If anyone wants to send me their old coil packs I will gladly take them off of your hands as I am going to see if I can resurrect them.

If nothing else see if there is a common fault with them.
 

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Maybe putting some epoxy on the cracks can help? This is one instance where I am glad I do not own a 24V car. Then again, when I got my foot down in my L I wish I had the extra power, all in all its a trade off.
 

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silicone sealant on the coil packs

Clean em real good with isopropyl alcohol first, then apply the acetic-acid cured silicone sealant (a la clear bathroom tile sealant). Use a putty knife to get a good smooth finish and voila-- usually works for arcs to local grounds.
 

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Hi,

I have a 1995 24 with 104k miles on the clock and pretty much the same problem - drives well on power, the more power the better, yet at idle when warm is a bit of a dog.

Also changed my plugs, had injectors ultrasonically cleaned, tried swapping ignition bank feeds between front and rear - all to no avail.

As the front bank seems to be running fine (checked by disconnecting the injectors at idle, one by one) I am aiming to swap their coil packs with those on the rear bank and see if the situation reverses. If it does it is dead easy to then replace those then on the front bank. If it doesn't .... HELP!!!! :)
 

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Discussion Starter #18
Jason, how much is the ignition pack?... i am about to give the car to the mechanic ... for I don't have time to keep trying...

Will keep all updated on the finding, thanks !

Jess
 

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You guys need to check your cam timing!
 

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Maybe putting some epoxy on the cracks can help? This is one instance where I am glad I do not own a 24V car. Then again, when I got my foot down in my L I wish I had the extra power, all in all its a trade off.
Where abouts do the cracks occur? Will try and take a look at mine. Thanks.
 
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