Manifold Vacuum Pressure

[Alfa33GC]

My father has an Alfa Romeo 90 Super, which has a 2.5 ltr V6 Engine, with jetronic fuel injection. It has a problem on transition from cold start, to normal operating temprature. It will start up from dead cold easily enough, but runs very badly untill it hits normal Running temprature. We have replaced all of the vacuum hoses, and the Aux. Air Valve. We have cleaned all of the electric connections, including earths but this hasn't improved anything.

The manifold vacuum has been checked, and appears to be low, around the 11 Bar of pressure (sorry for the lack of knowledge on proper measurement).
Would there be anyone out there who would be able to shed some light on how much pressure there should be in this manifold?.

[Duk]

11 Bar .
11 inch's of mercury
Or for a quick conversion is pretty close to 2 inch's of mercury for 1 psi (pound per square inch).
Most cars (unless they have a reasonable cam upgrade) tend to idle around the 14" mercury.
The Alfa v6 has pretty tame cams, so I would expect to see similar. Probably a fare bet you have a leak somewhere.
What is the idle speed like?
Read this if you haven't already done so L-Jetronic

[ToonRboy]

Did you replace the aux air device with a new one? Check to make sure it's operating correctly. I'd also check the coolant temp sensor & perform the thermo-time sensor and aux injector checks. Lastly, I had an issue similar to yours and didn't find the leak till I removed my plenum for powder-coating. Two of the intake runner couplings were cracked - one was 180* around! They are approx 42mm or 1 5/8" dia. I replaced mine with a suitable radiator hose cut down.

Good luck,

The Greg Gordon L-Jet troubleshooting page is a good place to start. See Duk link to L-Jetronic.

[Alfa33GC]

Sorry about the blunder about the lack of knowledge on the measurement, Damn apprentices!

With this 90, we had the vacuum measured by a supposed EFI Guru here in Brisbane, and he said it was running 11 inches of mercury when cold, and 13 inches when warm. We are a bit concerned when he said that there was no cold start injector on these cars , but he said it should be running between 19 and 21 inches, so basically we are just trying to check what it should be running. If they should be running 14, then 13 is pretty close to the money aye?

As for the rest, We have put in a new Aux air valve, and checked it before installing it into the car, All hoses have been replaced with Greg Gordons silicon hoses, (dad seems to think the car will look better with the purple hoses he has chosen to put on :P) The intake runner couplings are new and the AFM is known to be good, really that only leaves the thermo time sensor, and coolant time sensor doesnt it?

The idle speed of the car is normal and the car does run really well once the motor hits normal running temprature which leads him to think its not an air leak.

Thanks for the info on the vacuum pressure, any other suggestions or ideas will be gratefully recieved. (He wont listen to my suggestion of buying a 33 :P)

[Rookie ROX]

I'm not sure whether the 90 had it fitted like the 75 did, but you HAVE checked that ignition retard sensor isn't connected?

It's the only single wire (purple and white) connector on the left side of the thermostat housing. It will cause terrible running whilst cold, but the car will run perfectly when up at operating temps. I had very similar problems before I found out the sensor and the tech bulletin to disconnect it. Worth checking out anyway.

ROCK ON
R~R

[kredden]

Did you also check the o-ring in the manifold for the idle control (as per Greg's write up)?

Kevin

[tukilevu]

G'day all and thanks for all the replies. I am the proud owner of the Mighty Ninety, subject of this thread, and while we are on the subject - why isn't there a forum for 90's? Just as well I've got a 75 so I can sneak into this forum!

Anyway, I did check (as per Rookie R's post) the wire on the ignition retard sensor. I did know about this and have removed it twice and it keeps getting put back on - not sure who was the most recent guilty party. Anyway it is off now, taped up and zippy tied away out of sight. I haven't had a chance to see how it is running since I have disconnected it again but I know when I originally removed it, it did make a big difference.

I haven't worried too much about checking things that affect idle - it just isn't a problem. The vehicle just runs badly during the transition from cold to warm. The idle isn't the problem but it is how it performs under load. It won't accelerate cleanly, not that I ask any big questions of it until it is warm. My drive is quite steep and it struggles to get up there at all. When it is cold, it idles well, when it is warm it idles well, it even idles well while it is warming up. It is just when the motor is under load that there is a problem. Always an interesting experience getting through an intersection until it is completely warm!

Anyway thanks for all the responses. Will check the Thermo Time Sensor and Coolant Temp Sensor one night this week when No 1 Son can get a lend of a good quality multimeter from his work. If I still can't get to the cause of the problem, I'll be back for more suggestions.

Stephen.

[Rookie ROX]

If that sensor was reconnected, I'm going to be close to guaranteeing it will have solved your problems.

Bad idle, poor acceleration, dodgy emissions and just overall crap running until warm all comes down to that sensor and was exactly what I experienced. As soon as it was gone, she was perfect. In the end I took the sensor out completely and had a bung made and used it as a second, more accurate coolant temp sensor for my fan controller. Nobody is reconnecting that sucker!

I'd suggest checking how it runs first before (potentially) wasting time checking over other things.

ROCK ON
R~R

[ToonRboy]

Not exactly the same thing tukilevu, but I once owned a Mitsubishi Starion ESI-R that idled fine (cold or warm) but fell on it's face when under load Mitsubishi Starion - Wikipedia, the free encyclopedia. Turned out to be the secondary injector (that car only had two, 1-550cc and 1-1000cc). Anyhow, you seem to be saying that she runs fine when warm, so that would tend to indicate no problem with fuel system (injector condition & pressure) - so, I would concentrate on the cold running circuits (inputs to ECU for temperature). Also, it wouldn't hurt to check ignition - what spark plugs are you running and what gap (I only run Golden Lodge plugs which do not have adjustable gap) Alfa Romeo, Fiat and Lancia Spark Plugs ? Lastly, (and more remotely) there could be a small air leak in the intake system whose gap gets closed-up when warm.

Hope this helps,

[tukilevu]

Ignition retard sensor - poxed thing!

I finally got a bit of spare time this afternoon to take it out for a test drive and the old girl is flying again, well as much as a Mighty Ninety can and still maintain the dignity of a luxury vehicle.

Thanks everyone for your thoughts and advice.

Stephen

[GEOALFA]

Where is the ignition retard sensor located? I thing I have the same problem.

[tukilevu]

Have a look at Rookie ROX's post - he describes exactly where it is.

Also click the L Jetronic hyperlink in Duk's post, you have to wade through a bit of info but there is a very good description of what it is, and the problems it causes. Even better, there are good clear pictures. And a strong recommendation to disconnect it.

[Gubi]

Here's a pic from the 75/Milano TSB, but the 90 should look pretty much the same I would think.