engine still runs erraticly - Alfa Romeo Bulletin Board & Forums
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post #1 of 16 (permalink) Old 04-10-2018, 02:58 PM Thread Starter
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engine still runs erraticly

Is it possible that after the battery has been disconnected for a long time that the ecu has to re learn it's self ,meaning that the car should be driven to reprogram the computers?

Last edited by long john; 04-10-2018 at 03:01 PM. Reason: mistaK
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post #2 of 16 (permalink) Old 04-10-2018, 06:22 PM
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If you're asking about an L-jetronic car then, no, the computer does not do any 'learning'.

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post #3 of 16 (permalink) Old 04-11-2018, 03:42 AM Thread Starter
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Yes i was asking about L jetronic. Sorry about being so vague but i needed to find this out because i was told this could be the problem with my 84 alfa spider. I thought it could also be fuel pressure but when i checked it it was 31 Lbs with the vacuum regulator on and 36.Lbs with it off. Cant be an ecu problem because i had them repaired by the ecu doctors. took a compression test all cylinders are 118 give or take a Lb.or two. Had the engine out for the fourth time because the timing was wrong and did what you told me to do so now that's ok. Seems that i lose fuel pressure right after i stop the engine. Can't find any air leaking in the system, the transmission sensors are new . Found a problem with two of the new injectors and sent them back to San Diego and the replace them but the engine still runs rough and i get black soot from the tail pipe. Also Checked valves and found to be within specifications. Checked pressure regulator and it is also ok. I have to tell you i am running out of idea's and a bit discouraged as i have been trying to get this engine running now for a little over a year.
Any help or idea's are appreciated.
Thanks John
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post #4 of 16 (permalink) Old 04-11-2018, 07:13 AM
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Seems like you have looked at every thing. How old are the plug wires and are they on the right plugs? I know I missed a bad fuel pressure regulator and did not discover until I broke the vacuum hose from the fuel regulator and it started sucking air to the point I could hear it and found it wet with fuel just enough to give my 84 a rough idle and engine surge.
You mention lost fuel pressure right after you turn the engine off and that is the first thing to solve and find out why? You may retain pressure in the system but still have a small leak from the diaphragm in the regulator back into the plenum.

I don't know the history of your engine and all you have done but don't loose patience its a learning process and when you do find out share it so we can log it in our brains for next time. ... Shasta

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post #5 of 16 (permalink) Old 04-13-2018, 07:02 AM
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I had a Twin Spark with Bosch Motronic a few years back.
I chased an intermittent electrical problem with it for nearly two years.
While driving, the engine would suddenly drop to idle but never cut off.
Very un-nerving at highway speed with a big truck right behind me!
I finally tracked it down because it got progressively worse.
The contacts inside the wiring harness connector for the AFM were corroded.
I wrote down the color coded wire sequence, clipped the pigtail off, crimped new connectors on, plugged it back together and it was fixed for $2!
Check the connection contacts on both devices and wiring harness connectors.
Also, the spark plug wire contacts inside one of the distributors were corroded as well.
Good luck!

Last edited by 1978alfa; 04-13-2018 at 12:34 PM.
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post #6 of 16 (permalink) Old 04-13-2018, 07:16 AM
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How fresh is the gas? In my experience, today's gas does not store well (and ethanol laced gas is even worse). A few weeks is probably OK but a few months = stale gas.

Have you checked all the engine grounds? Did you remember to re-connect the ground strap between the bell housing and the transmission tunnel?

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post #7 of 16 (permalink) Old 04-13-2018, 11:24 AM
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Try fuel injector cleaner 1st!!! A good brand, your injectors may be stuck. Tectron.
Vacuum leaks are big as well, must check. Take off the rubber plenum that goes from the air filter to the troddle body and look for cracks. Had this on my 82 Spider took a hard curve and it would die. Cracked in the bottom.
Grounds very important, especially the one with 20 Grounds near the troddle body
Bosch injector modules are bullet proof. It's NOT a computer!
It's engine management system using the 2 Fly wheel sensors and the Hall Effect Transistor in the distributer to fire the engine in the correct time.
The connections may get corroded to the box, but maybe if the car was under water.
I have 4 Bosch cars and the top 3 suggestions have always fixed mine.
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post #8 of 16 (permalink) Old 04-13-2018, 08:56 PM
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Question Black soot at tailpipe?

Hmmmm.

I've experienced about every possible issue imaginable with my engine, but none included black soot from the tailpipe and frankly, don't believe I've seen it reported as a symptom here...ever.

When was the last time the engine ran properly and what, if anything may have been done in the interim to change the situation?

It would be of interest to know if the problem is shared by all cylinders. I have an inexpensive IR, hand-held temperature sensor from HF (with laser pointer!) and by aiming it at each exhaust header I was able to determine, when the engine was running poorly, that all the headers were of equal temp. If nothing else, I was confident the problem did not lie in any particular cylinder. Turned out to be a loose connection on the coolant temperature sensor. The spring retainer was missing.

May I presume that while the engine idles (such as it does) you have performed the "wiggle" test of all electrical and air connections?

Also, a bit of ether (starting fluid) sprayed around the various plumbing connections should result in a noticeable change if there is a leak. As others have noted, air leaks are the Achilles Heel of LJets.

Still puzzled by the soot, since that would obviously indicate unburned fuel from a mis-firing cylinder(s) or more fuel being injected than the cylinders can handle with available air. When does the soot present?

Finally, regarding the distributor, I believe it is simply a rotating switch and ignition is triggered by the (wait for it) ignition ECU.

Finally, finally, take a few minutes to fill in your details via User CP. Saves a lot of questions.

Steve Waclo Carson City, NV; '87 Spider QV, ES Champion, 2018 Reno SCCA (125k);'93 Honda Nighthawk 750 (105k);'03 GMC Sierra SLE 2500HD Turbo Diesel (155k);'08 Altima Coupe 3.5SE, 6sp (125k)
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post #9 of 16 (permalink) Old 04-14-2018, 11:06 AM Thread Starter
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Had my son over last night to do some kind of injector flush, he is a certified mechanic. I removed the fuse for the fuel pumps and we hooked up this canister that injects this injector cleaner and turned the engine until the container was empty, then reinstalled the fuse and fuel line. Then we started the engine. For the first time in a year and a half that engine was running smooth, but only for a about five minutes then it started to run unevenly, but nowhere as bad as before. Maybe this could be the result of the gas being too old it has been in the tank for at least 8 months. I will put fresh 93 octane and a can of injector cleaner in to see if it corrects the problem. I also noticed that the fuel pressure drops of to zero right after i shut off the engine, could this be another reason that i am having these problems. All engine grounds are ok, clean and tight as well as the ground strap. The rubber plenum is fine, checked all connection with my unlit propane torch, and both flywheel sensors are new. Checked all my sensors, coolant temp switch was 2.853 at about 65 degrees. The one thing i haven't tried is the wiggle test i will try this in the upcoming week as we are expecting an ice storm here for the next two days here in Nia. falls.
P.s Stevew mentioned something about user CP ,I have no idea what he means by that.
Thanks guys for all the useful information. I think i am getting closer to a great running car.

Last edited by long john; 04-14-2018 at 11:30 AM. Reason: forgot text
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post #10 of 16 (permalink) Old 04-14-2018, 11:58 AM
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Check the cold start injector and the AFM

Hi

Okay you said

"....Seems that i lose fuel pressure right after i stop the engine.

Well that's an easy one. Integral to the electric fuel (the big fuel pump external to the tank, not the small one in the tank) is a check valve that prevents fuel from draining back into the pump when the car is turned off. Since your fuel rail is losing pressure when the car is turned off, this valve has failed. However this only makes the car hard to start, it's not the source of your bigger problem

. I have to tell you i am running out of idea's and a bit discouraged as i have been trying to get this engine running now for a little over a year.

I know the feeling. I once had a drive-ability problem in my Milano that took months to solve. Car started like a champ, but a 3,000 RPM had a crippling misfire. Turned out there was damaged connection in the power supply wire to the ECU. The ECU simply didn't have enough power to do whatever it does to make the car rev over 3K. Which is weird because the ECU doesn't supply the injectors with power . The combo relay does that. The ECU just provides a switched ground.

Your car is getting too much gas.

You could have a leaking cold start injector (CSI). That is the cold start injector is always dribbling some fuel into the intake manifold. Since you can't see into the manifold, you can't tell this is going on. Also unplugging the electrical connector won't solve this problem as it is the result of a failed seal in the CSI. As long as there is pressurized fuel going to the injector, it will leak. You need to unbolt the CSI make a blanking plate for it, disconnect the electrical connector for the CSI, and start the car with the injector hanging free.

Cover it with a clear plastic bag, in case it is leaking.

Finally reach out to other local Alfisti to other help you, particularly other L Jet spider owners. In these kind of cases it's very useful to be able to swap in a known good AFM or other component and see if that's the problem.

Report back with the results.


Bye
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post #11 of 16 (permalink) Old 04-14-2018, 08:22 PM
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"but none included black soot from the tailpipe"

I wouldn't worry too much about the black soot if it is a cold start. Usually there is a little on a cold start when the condensation starts mixing with the exhaust particles. Our Milano does this, and yet it has always run perfectly with decent gas mileage. Starts instantly, and usually the soot goes away pretty fast. Any more, persistent, then maybe. I kinda like the idea of the CSI leaking a little.

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post #12 of 16 (permalink) Old 04-14-2018, 08:32 PM
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fuel filter/pump

I am having similar problems. Replaced my head gasket last fall and after putting back together the engine is not running right. It runs very rough at high rpm. Now that I have pulled out of barn for spring, it has been hard to start. fires right up but dies after a few seconds? I have gotten it to run a couple of times but still have problem at high rpm. I thought maybe ignition but now feel it must be fuel issue? I feel it is getting to much fuel? How does the bosch system work when engine is cold? I feel I have all wires back in correct spot on intake manifold but do not possess skills to diagnose problem? should I start with filter then pump? any help would be greatly appreciated. It is a 1985 spider graduate.
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post #13 of 16 (permalink) Old 04-15-2018, 06:14 AM
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Quote:
Originally Posted by jdiprisco View Post
I am having similar problems.

I thought maybe ignition but now feel it must be fuel issue? I feel it is getting to much fuel? How does the bosch system work when engine is cold? I feel I have all wires back in correct spot on intake manifold but do not possess skills to diagnose problem? should I start with filter then pump?
I'll counter that you probably do have the skills to diagnose. But you can't do it by 'feeling'. Go through the systems step by step and find all the problems (just because you find a problem does not mean you found all the problems). See the link in my signature for a page of info about how to diagnose your L-jet Spider. A simple VOM (Volt Ohm Meter) will help you diagnose 90% of the issues with L-jet. Add a fuel pressure gauge to diagnose fuel supply. This is a lot better than randomly throwing new parts at it...

An easy check for a failed Fuel Pressure Regulator is to remove the small vacuum hose from the top. Check for the presence of raw gas (sniff). There should not be any gas on the vacuum hose side. Another question is how old is the gas in the tank? In my experience today's gas does not store well. A few weeks is OK, more than a couple of months is likely stale.

- - Eric
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- -~ 1981 GTV-6 ~
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post #14 of 16 (permalink) Old 04-15-2018, 06:46 AM
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Run issues

The basics on Bosch injection:

1-Check the crossover plastic tube for cracks or leaks from shrinking
2- check the connections on the mass air meter and it`s internals for
obstructions (Barn=rats/mice)If the mass air meter with the door
cracked open with a screwdriver resolves the run problem then
clean and lube the door pivots and electrical connectors.
3- Fuel pump relay (under rear parcel shelf. Run 12 volt wire from battery to hot side of the fuel pump under the car. Start engine, if it continues to run then the relay has a problem.

Richard Jemison
RJR Racing

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post #15 of 16 (permalink) Old 04-15-2018, 10:14 AM Thread Starter
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Checked the CSI the way Milanoguy told me to do and there was no leaking. I reinstalled the connector and tried it and it gave just a little squirt of gas, so i guess all is ok with that CSI. Tomorrow i will try some fresh fuel and a can of good injector cleaner because as Eric has said the fuel might be too old, and besides i am almost out of gas anyway. Oh by the way i could not smell fuel at the pressure regulator and it holds it's vacuum with the tester.
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