Temprature - is this normal? - Page 3 - Alfa Romeo Bulletin Board & Forums
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post #31 of 103 (permalink) Old 07-21-2019, 01:58 PM
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Hot, hotter...hard to say...if the car never overheats maybe you are OK. Adjust the thermostat switches to come on earlier. For comparison, yesterday I drove down the Brigantine (Jersey Shore). 95 degrees and humidity. Highway temp surely well over 105. When I was in stop in go it was up around 200. 3.0. Aftermarket fans fastened through stock good radiator. AC on max

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post #32 of 103 (permalink) Old 07-21-2019, 04:33 PM
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You are way too lean if your AFr gauge is accurate. Running lean = running hot.

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post #33 of 103 (permalink) Old 07-21-2019, 05:52 PM
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Yup, way too lean if the gauge is correct. But I think something else is also going on. Generally, a increase of coolant temperature at speed is indicative of obstructed flow of coolant or air through the rad.
First thing to check is for exhaust leaks; which can affect the gauge reading.
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post #34 of 103 (permalink) Old 07-21-2019, 06:38 PM
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Here in the San Francisco Bay Area it gets into the 90's a few times a year My 76 Alfetta GT (with re-cored radiator) rarely gets over 180 even with the AC running in hot weather.
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post #35 of 103 (permalink) Old 07-21-2019, 07:24 PM
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Gepetto, I agree the A/F ratio, if accurate is waaay off. I think you are fixin' to burn valves unless you get that AFM off there, restore the mixture to that which the ECU controls, and be happy. The engine is running hot because the numbers indicate the culprit.

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post #36 of 103 (permalink) Old 07-22-2019, 12:00 PM Thread Starter
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I agree that if my AMF gauge is accurate, the engine is running too lean. The average should be around 14.7, with somewhere near 13 on WOT. And as it is now, under part throttle, I'm going up to 19! The AFM gauge is currently reading off one bank of cylinders (passenger side bank), with the O2 sensor for the computer on the opposite bank. I doubt it makes any difference, but maybe it could. The radiator was re-cored a couple years ago and it was tested recently and passed with flying colors...

I ordered a rebuilt AFM from VickAuto. Apparently, they are rebuilt by a Bosch certified re-builder to original factory specs. (Also, FYI, they apparently can rebuild L-Jet computers, too, to factory specs.) I hope that cures the problem. I am running out of counterclockwise "clicks" to adjust the internals of the AFM that's currently on the car. Me thinks the current AFM is all screwed up beyond repair....I hope it's not the actual computer itself that is going on the fritz. I try to console myself that if it was, it wouldn't hold 14.0 on WOT.

The other ideas I've had are 1) it's the headers that are somehow causing this, as the rest of the car is basically stock and/or 2) there's a vacuum leak somewhere after the AFM that is causing unmeasured/un-metered air to enter the combustion chamber.
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post #37 of 103 (permalink) Old 07-22-2019, 02:30 PM
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Could you have a leak upstream of the sensor?

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post #38 of 103 (permalink) Old 07-23-2019, 04:50 AM Thread Starter
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Quote:
Originally Posted by alfaparticle View Post
Could you have a leak upstream of the sensor?
Which sensor?
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post #39 of 103 (permalink) Old 07-23-2019, 09:36 PM
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Which sensor?
A leak upstream of the Wideband A/F sensor. This would probably cause a false lean condition throughout the RPM/load range, though. Since your AFRs seem to be reasonable at higher loads, I would agree that something is amiss. The key here is that the factory throttle switch is present to allow for "open loop" running conditions during high load and ignore the feedback from the signal generated by the factory oxygen sensor.

Before you replace the AFM, try running the car with the FACTORY oxygen sensor disconnected (NOT the aftermarket wideband sensor!). Then drive it as you normally do and note if the A/R ratio changes---this rules out either a biased O2 sensor causing running issues or a functional O2 sensor masking actual lean running conditions. If the change is not drastic, then a replacement AFM is not a bad idea (though I would do more testing, but I also work on cars for a living ).

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Last edited by cda951; 07-23-2019 at 09:40 PM.
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post #40 of 103 (permalink) Old 07-24-2019, 08:20 AM Thread Starter
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I hadn't considered that. The O2 sensor itself is new, but I suppose there could be a leak somewhere in the exhaust pipes upstream of it. I'll give it a shot disconnecting the O2 sensor - it should run richer than normal that way, correct?

I'm always happy to do testing if it means getting to the right answer
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post #41 of 103 (permalink) Old 07-24-2019, 08:59 PM
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I'll give it a shot disconnecting the O2 sensor - it should run richer than normal that way, correct?
Not necessarily----this is a common misconception about oxygen sensor-equipped cars of this era, that open loop is somehow "richer" and/or the ECU uses a completely different injection map than in closed loop mode. Neither of these conceptions are true, and I will attempt to explain why.

"Open loop" means that the system is ignoring the voltage signal generated by the oxygen sensor. In these Alfas and other Bosch EFI cars of this era, this only occurs under two conditions. The first is before the engine has reached full operating temperature (because the engine needs a richer air/fuel mixture due to fuel condensation, etc, and the oxygen sensor takes a while to warm up, especially in the early cars with non-heated O2 sensors). The second open loop condition is if the full-load contact of the throttle switch is closed; the base injection map is tuned to have a richer A/F mixture in this region to control combustion chamber temps and stave off detonation, and if closed loop feedback were allowed in this high-load region, the engine would likely hesitate and surge as the system attempted to drive the mixture lean. Well, there is a third way to achieve open loop, and that is by unplugging the O2 sensor .

If your engine is perfectly tuned and has no vacuum leaks and all of the injection system components are in spec, unplugging the O2 sensor will not make a drastic difference in how the engine runs---the injection map is tuned to provide near-stoichiometric A/F ratios during idle and light load/cruise conditions anyway. The early single-wire cars tend to hunt a tiny bit at idle while in closed-loop mode, as the nature of the oxygen sensor composition is designed to alternately drive the system lean and rich in a sine-wave pattern to allow the three-way catalytic converter to achieve maximum effectiveness (lean to quell HC and CO emissions, then rich to reduce NOx, while averaging 14.7:1). Later Bosch systems have more advanced oxygen sensors and engine management and idle control valves to allow a smooth idle while doing the same.

Anyway, if your engine has vacuum leaks or anything else causing a general lean running trend, it will run leaner if you unplug the O2 sensor (vacuum leaks tend to be most prominent at idle/low engine speeds). Likewise, a dripping injector(s) or anything causing a rich condition will do the opposite. The oxygen sensors of this era tend to bias towards the rich side if/when they degrade, which is often only noticed during a state emissions test. Occasionally a sensor will be shorted or very far out of range, causing more extreme running issues, but I doubt this is the case based on your description.

Sorry for the long-winded explanation, but I hope that it clears up a few misconceptions!

Chris
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post #42 of 103 (permalink) Old 07-25-2019, 01:05 PM Thread Starter
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Originally Posted by cda951 View Post

Sorry for the long-winded explanation, but I hope that it clears up a few misconceptions!

Chris
Thanks for the explanation, Chris! Now I know what to look for! I'll try to get to this soon and report back with some results.

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post #43 of 103 (permalink) Old 07-25-2019, 07:56 PM
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Maybe I missed it in the discussion, but have you checked for adequate vacuum reading at idle? That could rule out a serious leak. Check at the intake plenum.

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post #44 of 103 (permalink) Old 07-30-2019, 10:22 AM Thread Starter
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Cool UPDATE: Partial solution

This weekend I disconnected the O2 sensor and drove the car around a little (highway and some "suburban" in Long Island). No real change in the readings on the A/F Ratio gauge. Temperature was not too high, but higher than I'd like. (I drove with A/C on; car has new, powerful SPAL twin cooling fans). I went to the mechanic and after scratching our heads thinking what could be the problem, we tried two things: increasing fuel pressure and checking to make sure the A/F Ratio gauge installed in the car was giving an accurate reading.

Increased pressure did make the car a slightly more responsive, but not enough that I thought it worth the extra risk that can come with increased pressure. Then, we decided to attach the professional A/F gauge my mechanic has to the back of the tailpipe (note: I have no cat), just to make sure the readings I was getting were correct. Doing the test twice in exactly the same way (with increased fuel pressure and with stock; with and without A/C on), it turns out I'm getting FALSE readings! The mechanic's gauge shows the car maintaining an average of 14.7 under normal cruising, about 11.0-11.3 on full throttle, and the standard "infinity" when coasting (the fuel cuts off when doing so).

The gauge installed in my car shows an average of about 18.5 under normal cruising, 12.5-12.7 at full throttle, and maxes out at 22.4 (gauge limited) under coasting. I was being deceived! By a brand new, properly calibrated gauge no less!

On the way home with the A/C on, the car was warmer than usual on the highway (almost at the line to the right center, as in previous picture posted; see picture here). Shutting the A/C off helped and the water temp decreased to about 180ish. I'm concerned because a) the car didn't do this when I first bought it - with A/C on highway it never went past 180 and b) I'm hesitant to take a longer highway trip with it out of fear of true overheating. Of note: the driver's side cooling fan stays on once the A/C is switched on, but the passenger side fan cycles on and off with temperature. Should maybe both of them be on at all times? Or, is this a sign that the old York compressor is on it's last legs (and generating more heat than the cooling system can cope with)?

Or am I worrying about nothing?

As always, a big thank you to you guys for your thoughts!
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Last edited by Gepetto; 07-30-2019 at 10:29 AM.
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post #45 of 103 (permalink) Old 07-30-2019, 12:46 PM
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Glad you got some accurate A/F ratio readings... at last! So much for your meter.

What was the ambient temp when you took this drive? Actually, my son's GTV 6 cycles between the reading you show and about 180 with the AC on, depending on whether it's cruising or idling. BTW-- It is normal for the one fan to run constantly with the AC engaged, also.
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