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164S dies frequently when throttle is closed

1274 Views 11 Replies 5 Participants Last post by  MrT
like when approaching stop signs. Not most of the time, but frequently enough to be a nuisance. It could be a hazard if steering effort is needed because the P.S. pump is not driven.

This happens when putting the car into neutral approaching a stop, and closing the throttle. The car gets an EPROM failure occasionally which lights up the CE light, but it has an aftermarket chip (not Squadra). The CE light is not correlated with the stalling.

I've thought of the idle control valve as a culprit, but haven't really done any troubleshooting. I hope you all collectively can help me knock this out in short order. It's on my wife's newly rebuilt (5k mile) '92 164S with 75K plus the recent 5K miles.

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Pull codes and see what you get if AFM code comes up. It is really probably idle actuator sticking. Don't ask me the logic of that but I have seen it happen before. Remove and clean IAC and see what happens.
The car died just as I drove it into the driveway before starting this thread. I restarted it and parked it. After your question I went and checked it. Unfortunately, I decided to start it to see whether the CE light was on. It was. Then I stopped and re-started it, and the CE light turned off. This is the kind of behavior I've seen with it: alternate starts get the CE light (but not rigorously alternating). Then I pulled the codes, and even though the CE was off when running, it gave me a 1251 code:

1-2-5-1: RAM/EPROM memory of control unit is not operating normally. Replace Motronlc control unit Sll
Michael, the 1251 code is because you have the aftermarket chip. If you turn the key on and let all of the idiot lights lash, then try and start the car, the CEL should stay on with the chip you have. If you do a quick start from when you enter the key, it should stay off. I would remove that chip and go back to stock...
Sean, I'm planning to do just that using the chip from my son's defunct '92S. I just haven't gotten there yet. Your observation explains, however, why I find that turning the car off/on fairly quickly makes the CE light stay off. I hadn't noticed the association with quick key insertion/starting. The car takes a few cranks to get going. All of our 164s are that way. This chip was put in by the P.P.O. and the P.O. told me very little about it other than that the swap had been done. I do not have the original chip, or it would have been undone already.
Michael, you probably had the same chip I had in my 92 164S. I believe it was one of those cheapie ebay ones sold by some italian-sounding make. They usually make the CEL go on, but why you can bypass it by moving the key quickly, i don't know. That technique helped me scrape past the smog test.
I had those symtoms do to a bad throttle position sensor on our 164LS. Fixed that and our problem went away.
I guess the Alfa Ricambi and e-bay copies of it from what others on this board have said are known to throw the CEL. I recently installed the Squarda chip on Friday. I do not have enough time to tell from the seat of the pants if the improvements are that great. I do know the RPM limit is higher. Hopefully in a week or so I will re-dyno the car with the chip and see what performance differences actually exist.
The name given to me by the P.O. wasn't Alfa Ricambi, nor was it Squadra. I don't remember it just now, but it will probably become irrelevant after I put the other ECU in place.
Well, I measured the throttle position sensor behavior, and it reads closed when it is supposed to read closed, and when the throttle is opened anything like a degree (just about the minimum I can perceive), it goes open with an audible "click." The S.C.S. (Suspension Control System?) sensor on the throttle was broken, so I replaced it even though it probably has nothing to do with the running of the engine. I used DeOxit on both sensor sockets and verified their operation.

On the test drive, as I was turning in to the parking lot of the grocery store, the engine stalled. I was still moving, so I let out the clutch to restart the engine and parked the car. I turned off the switch and turned it back on to try to extract codes. However, I held the button in too long and apparently entered the injector test mode. I have never figured out how to use these "mode B" tests for the injectors, idle air actuator, and "evaporation solenoid valve" described in

Does anyone else? But I digress... I got a 1411 code and thought I was onto something until I looked up the meaning on the page. Oh, well. Maybe next time. I fiddled with the system w/o starting the car, trying to clear the "codes" and get back to 4-4-4-4 condition. I got the venerable 1251 RAM code again. So I'm back where I started. Which is to say, I maybe should have pulled the idle control valve and cleaned it to start with.

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I got the venerable 1251 RAM code again. So I'm back where I started. Which is to say, I maybe should have pulled the idle control valve and cleaned it to start with.


Don't you have a spare stock S ECU in wrecked S you can swap into this problem child?
yep. It belongs to George.

Sean, I'm planning to do just that using the chip from my son's defunct '92S. I just haven't gotten there yet.
I'm just slow, bro'. Sorry 'bout that. But Steve's memory works and is correct.

I had this dream of getting a Squadra chip, but I opted not to do so beacuse of $ out of pocket. When the Squadra chip (for $200 donation to alfabb) came up some weeks ago, I inquired early on, but chickened out because I had the salvaged ECU as a back-up. I think Andrew Garcia opted for that chip, and I hope it does him well. I thought I'd probably go back to stock for Claudia's car, as her driving plans aren't likely to involve much extra tire wear.

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