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Discussion Starter #1 (Edited)
I'm at my wits end, and don't know how to resolve my problem on my '86 GTV6 with a 75 3.0 motor.

Three years ago my timing belt jumped teeth and valves and pistons got together for a party on the one head. Repairs went well until it came time to start up at the local specialist, but it refused. I spent weeks with the diagnostic tester and while all tests checked ok, the car refused to fire up. We replaced everything we could think of, but to no avail.

In desperation after 2 months fiddling at the dealer I took the plugs out, got them **** hot and re-installed. The car started but blew clouds of black smoke. It was running very rich but had no power, but at least it ran. With a lot of fiddling it started running as smooth as the V6 should, on the odd occasion.

Driving it home I got about a kilometer, the car hicoughed, had no power and once again smoked like an old diesel truck. Passers-by said it stank of petrol but I don't have a sense of smell, so I took their word for it. The car idles without a problem, but any attempt to rev it results in coughing and spluttering without any power.

So it's been parked off. I've replaced ECU, all injectors, wiring loom to injectors, 3 coils, got on a first name basis with every connector, wire and fuse in the car but am unable to get to the root of the problem. We are convinced it is an electrical problem and the car is over fueling.

The car will idle and rev in my driveway without a problem, but cannot be driven for more than a kilometer. So it seems to be heat related. Two attempts were made this week to get an mot, but the first attempt the car was ok until it started running rich on the brake tester, and lost all power. The second attempt the car could not do the kilometer to the testing station. Both times the local garage mechanic was driving, I was not present.

If the car is left to cool down completely the problem will disappear. It never missed a beat or gave any problems until the heads came off, and pretty much has not run since.

If you've read this far, thanks very much. If you are able to help in any way I would be forever grateful.

My final desperate attempt would be to dump the factory system and install a Megasquirt or equivalent. But I would hate to spend a lot of money, when it could be something small. :smile2:
 

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Have you checked the fuel pressure? If that is OK then check the injectors. You could have high pressure or leaking injectors. The L-Jetronic experts will probably tell you of other potential culprits - maybe the coolant temperature sender.
 

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Discussion Starter #3
I've checked fuel pressure and replaced the injectors.

I'm glad you mentioned the temperature sensor. I realised today that it is the one part I have not replaced. I was looking at a few of the sites tonight here in the UK for a sensor, but am unable to locate one. Don't know how it could cause the problem, but perhaps when the thermostat opens it somehow causes the car to miss. But how that doesn't affect the idling is strange. A quick look on eBay also failed to locate a sensor.

It's cheap enough, so will do it and let you know.

Thanks.
 

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But Mad North-Northwest
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This procedure has the test specs for the coolant temperature sensor. I'd suggest going through the whole procedure and checking everything.

L-jetronic Fuel Injection Technical Troubleshooting Article

The CTS is a good thing to check. Other random thoughts under "things that might cause a weird step change in running when warm":

-You should make sure your cold start retard sensor is disconnected per the Alfa tech bulletin: that might screw things up. See details in procedure above

-Make sure you've got the other connections at the thermostat wired up in the right places and didn't swap the two Bosch connectors or something

-Make sure all THREE of the injector ground terminals are well-connected at the AAV on the right side engine cover
 

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After further thought I would disconnect the cold start injector and pinch off the hose to it after the engine has warmed up and see if it makes a difference. There is also the possibility that you have mixed up the wiring to the sensors while you first had it apart. It is next to impossible to predict the results of that.

Was the fuel pressure good while the engine was misbehaving?
 

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Shot in the dark here but could it be throttle body icing? This could be choking the air supply off and causing it to run rich and die before the engine reaches operating temperature.
 

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I'm at my wits end, and don't know how to resolve my problem on my '86 GTV6 with a 75 3.0 motor.

Three years ago my timing belt jumped teeth and valves and pistons got together for a party on the one head. Repairs went well until it came time to start up at the local specialist, but it refused. I spent weeks with the diagnostic tester and while all tests checked ok, the car refused to fire up. We replaced everything we could think of, but to no avail.

In desperation after 2 months fiddling at the dealer I took the plugs out, got them **** hot and re-installed. The car started but blew clouds of black smoke. It was running very rich but had no power, but at least it ran. With a lot of fiddling it started running as smooth as the V6 should, on the odd occasion.

Driving it home I got about a kilometer, the car hicoughed, had no power and once again smoked like an old diesel truck. Passers-by said it stank of petrol but I don't have a sense of smell, so I took their word for it. The car idles without a problem, but any attempt to rev it results in coughing and spluttering without any power.

So it's been parked off. I've replaced ECU, all injectors, wiring loom to injectors, 3 coils, got on a first name basis with every connector, wire and fuse in the car but am unable to get to the root of the problem. We are convinced it is an electrical problem and the car is over fueling.

The car will idle and rev in my driveway without a problem, but cannot be driven for more than a kilometer. So it seems to be heat related. Two attempts were made this week to get an mot, but the first attempt the car was ok until it started running rich on the brake tester, and lost all power. The second attempt the car could not do the kilometer to the testing station. Both times the local garage mechanic was driving, I was not present.

If the car is left to cool down completely the problem will disappear. It never missed a beat or gave any problems until the heads came off, and pretty much has not run since.

If you've read this far, thanks very much. If you are able to help in any way I would be forever grateful.

My final desperate attempt would be to dump the factory system and install a Megasquirt or equivalent. But I would hate to spend a lot of money, when it could be something small. :smile2:

Have you checked the AFM? It is very possible that a backfire (possibly from valve bend event) could cause the air flow meter vane to have become bent. I have dealt with very similar symptoms on a 3.0 powered car that ended up being a bent/scraping vane in the AFM. Swapped out for another unit, all good.

You can use a 2.5 or 3.0 AFM to check. Or, you could remove the black plastic cover on the AFM and start the car and watch. If it won't start, you can manually move the vane. It should be very smooth, without resistance, and should snap back to closed readily.

Good luck.

Oh-and as Ed says- check the CTS (coolant temp sensor). It has a big impact on mixture, but I've not seen one fail in this mode.
 

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Yes, check the air flow meter and the pins and inside the plug that connects to it. My Motronic system had corrosion on the contacts inside the plug. Also, my throttle position sensor was failing. Good luck with it.
 

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Coolant temp sensor tells the ECU how much fuel to inject depending on load. An open cts tells the ECU that the engine temp is -40 f and it will go pig rich. So rich that you will have difficulty starting, and flooding the engine. you should be able to find one fairly easily. It's a common Bosch part. Last one I bought for my GTV6 was about $20.
 

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I second Racingswim's suggestion. I happen to be present when he discovered his AFM issue.

Also, you didn't mention your distributor. I had a broken rotor that had the firing sequence all fouled up. It sputtered and backfired a ton. The key was broken out of the rotor.

Keep us posted on your progress.
 

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You might be overrich or you might not. L Jet can enrichen the mixture by increasing fuel pressure or lengthening the injector pulse duration. you should recheck your fuel pressure and make sure the fuel return line is not blocked. You should also do as suggested and make sure your CSI is not leaking badly or running when it shouldn't.

Under normal running conditions, mixture is mainly controlled by your O2 sensor. If you're unsure of its condition/age, you should just replace it with the proper heated variety. Vacuum leaks at the injectors can trick the O2 sensor into thinking you're lean when you're really not.

It's possible that L Jet is providing the right mixture but your timing is off or the advance is malfunctioning. It'll spin up under no load but otherwise not, and will stink of gas.

If your CTS2 is open (ie infinite resistance) the engine won't run at all, at least it won't on my '82.

Verify that your TPS is within spec and properly adjusted. A WOT signal will override the O2 signal.

The problems started when they redid the heads, so it's more than possible that they're not set up correctly. You should at least check the compression and pull the cam covers to make sure the cams and timing belt are correct.
 

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But Mad North-Northwest
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Yeah, but if the problems are as described (runs okay sometimes, then step-changes into running poorly) a mechanical problem with the heads seems unlikely. Sure sounds like something electrical.
 

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Weird, I think I know what maybe wrong, Long Shot! I've seen this a couple times and the problem was it was off by 1 PLUG Wire. Idled and started fine, step on the gas poop. You may want to validate this. The cars timing adjustment location was really weird so when I returned it to TDC, doing the initial setup 05-27 in the book and looked at the cap it was the wires that needed to be moved 1 slot over. I as well though it was gas related, but this was the problem.
 

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Discussion Starter #14
Thanks for all the suggestions.

My next steps will be to replace the coolant temp sensor as it has been mentioned by many, and has never been done, then complete the comprehensive check from Greg Gordon. I've done it before, but as so much has happened, and due to the age of the car, I will go over the procedure again. Weather permitting here in the UK of course.

After reviewing Greg Gordon's check list one point is clear. There are so many items that he suggests can cause hard starting, missing and running rich. All these apply to what is happening even when my car is at its best at present.

To those who suggested the AFM, it has been checked (and rechecked by the mechanic this week) and it operates smoothly, both by hand and when the car is running. He also redid all the ground points so those are good.

alfasrule - Thanks mate, I intend to pull the leads and rotor and will make sure it goes back as per the shop manual.

Thanks for all the help and I will update sometime after the weekend.

Cheers, Steve.
 

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Discussion Starter #15 (Edited)
It seems to be fixed!! I had almost given up hope of getting it running again.

It was the temp sensor that was faulty. I replaced it yesterday and the car fired up immediately. It was a very hard starter previously. At this stage I can't road test the car and a bit more work to do for the mot that should be sorted this week.

It could run a bit smoother so I will do Greg Gordon's check list after resolving mot failure issues.

I find it disappointing that the local dealer had the car for 2 months, and while we both worked on it, he never mentioned the sensor. We replaced afm, ecu, coil and a few other bits, but not the sensor.

Thanks to everyone for all their suggestions and willingness to help.
 

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Discussion Starter #16
My elation was short lived.

After sorting the mot failures and replacing coolant temp sensor I returned the car to the mot center today. An item that was a previous failure was rear brakes imbalanced. The mechanic and I assumed it was due to lack of use. So I had adjusted the handbrake, hoped the few drives on the road would bed the pads in again after being parked off for 3 years.

Once again the car failed. Same old running rich when warm and it broke down at the mot station again. But for me, the journey down there in the morning was uneventful with the brakes seemingly ok during the 1/2 km trip. Failures were emissions and brakes at rear unbalanced. The comment was 'the brakes are worse than they were before'. Once again the car had broken down on the brake station and had to be pushed off.

I found on the way home that there were no brakes. The booster was not working at all. With foot on pedal and starting the car there was no difference and the pedal remains solid. Now I know where the fluid has been disappearing.

There is no doubt that the cts sorted hard starting and rough idle.

Have I been chasing multiple problems and the temp sensor fixed one? I feel I need to go back to the parts previously replaced and retry them. Do any of you feel the booster could cause the over-fueling problems when warm?

I will remove the booster pipe from the plenum and run the car to see if it breaks down in the drive. But as it has never broken down in my drive, regardless how long I run it, it will be no guarantee.

What other issues could trigger the ecu to over-fuel (if that is what is happening)?

I'm back to my opening statement: 'I'm at my wits end with this car'

And that banging/rattle from the prop shaft is driving me nuts. But one war at a time for now.

PS. Rear calipers were replaced recently with professionally rebuilt ones from a well known UK supplier.
 

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This may be considered a "bodge" so take it or leave it. My needs are the opposite of yours. My L-Jet is too lean to make best power and I have a way of cheating it. I have a variable resistor ( a pot) wired in series with the coolant temperature sender. The control knob is in the console and easy to adjust while driving. I have a wideband AFR in the car and I can clearly see the effect on the mixture when I adjust the knob. You could do something similar with a pot wired in parallel with the sender. This would tell the ECU that the engine is hotter than it really is and it will lean the mixture. I would suggest a 5k or 10k pot.

I live in a state with no emissions tests (and no equivalent of the MOT) but my son drives old cars in an emissions state. He pours a can of magic brew into his gas tank and gets the engine hot before he takes the car in for a test. Maybe there is a similar product in the UK but I expect that methanol or ethanol would work. It is important the the motor is hot when you get it tested.
 

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But Mad North-Northwest
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Wait, did you replace the coolant temperature sensor (CTS) or thermo time switch (TTS)? The TTS will affect ease of starting. The CTS is what would cause hot running problems and that's what you should check.

You need to slow down and be systematic here, and also clearer about what you've checked. There are four connectors at the thermostat housing at the front of the engine:

1) TTS: Bosch-type connector
2) CTS: Bosch-type connector
3) Temperature gauge sender: two spade connectors
4) Cold temp retard sender: single wire, should be cut and the wire from the harness taped so it doesn't ground on anything

Stuff to check:
-If you disconnect the CTS, the sensor should measure 2-3K Ohms at room temperature and 250-400 Ohms warmed up
-Make sure someone didn't swap the connectors between the CTS and the TTS. The CTS wires should be BROWN and BLACK. TTS is GRAY/GREEN and LIGHT BLUE.


For your rear brake problem, my guess is you didn't set the pad clearances correctly. If you don't get this right when you install pads the rear brakes will never work right. Once you know how to do it it's fairly easy, but it's tricky the first few times. Do a search and you'll find some procedures on this.
 

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Discussion Starter #19
I have always thought that something went back incorrectly. The car was awesome until the valve/head crash. It has not run since then, and the local Alfa specialist (nice guy, I respect him and he is respected in the Midlands) has all but given up. It was left to me to get it running.

As you say, the single wire cold retard sensor is disconnected. Not sure where it has gone. Perhaps I should check it is not shorting somewhere, or put on someplace it does not belong. I replaced the middle sensor (Bosch 0 280 130 023) pointing to the radiator. I haven't checked the CTS for resistance, but the new part improved starting, idling and running.

For the price of a sensor, I will replace the TTS. Do you have a test for it?

The reason I added my booster problem is it is defective but can't see it affecting the over fueling. The booster is defective. Easiest check is to put your foot on brake pedal and start the car. The pedal should sink a bit, mine stays firm.

Thanks.
 

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But Mad North-Northwest
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Okay, that is the CTS you replaced, so that's good. Check that you have the right plugs in the right places: that one you swapped should have the connector with brown and black wires to it.

There's a test for the TTS at the link below. If the car starts okay I wouldn't mess with it: it's only energized when the starter is cranking.

L-jetronic Fuel Injection Technical Troubleshooting Article
 
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