QuestionQUESTION: Hi Linda,
Idle pulses 1100-1300rpm after reaching temp.This first started when spraying carb cleaner onto throttle plate 2 wks ago; sometimes it is 1800-2000rpm. I have done the following:
clean mass air sensor w/CRC mass air cleaner;
replaced all small vacuum lines;
removed throttle body, thoroughly cleaned, including ISC motor,pintle and seat;
replaced coolant temp sensor;
removed cold air valve, and lapped the plastic taper to the seat[w/diamond compound]until I got a good seal.[I think initially getting carb cleaner into this area probably broke up some carbon deposits, not allowing a good seal.]You can see the spring inthe throttle-body bore.
I am NOT getting a "check engine"light whatsoever. The car starts fine cold, a 1400 rpm idle, but once up to temp, the surging @ idle begins. The bypass air screw is turned all the way in, and any amt of back out increases rpm. If I unplug the single-wire idle position switch, the pulsing stops, but yields a 1500rpm idle. I have a Haynes Manual[#68030-2097], but have yet to do any of the electrical tests yet. This is the first time in the 17 yrs I've had the car[196000 miles]that the FI system has gone awry.I can't help but think something is amiss w/ the cold idle valve. I don't know how to check/adjust that, as Haynes doesn't mention anything[to my knowledge].I did read Kelly's response[10/12/07 :'91 plymouth laser idle problem], but don't understand what he means about using a scan tool to ensure the isc motor is at "15 counts", nor do I quite follow about the cold air valve fails to open. I need to know how the cold air valve works, and how to adjust it, as I re-installed the threaded spring cap/seat approx where it was initially. I thank you in advance for any help/suggestions. [I do need to get a digital multi-tester-any recommends here?] Your brother in Christ, Dick
ANSWER: Dick: I would say that spraying carb cleaner into or onto the throttle plate, took care of the sensor that is in that throttle plate. I don't think that you can really clean those sensors and re-use them. I mean think at the years that sensor has done its job and then someone comes along and sprays carb cleaner on it. I have had more people write in of late saying they have saved money, just cleaned the sensor and then are re-using it. I know those sensors are costly but still cleaning them? I wonder if the Throttle postion sensor is not weak or needs to be replaced. This would show up as a unstable idle because the computer thinks the throttle is moving. But look Dick, your car is the right year for those bad computers. Mitsubishi farmed out the building of their computes to another company. That company did not build very good ones, a piece with time will start to leak into the computer and it will kill off the computer. It shows up in different ways, but one of the ways would be surging idle. But then that cleaning spray is just not good for those sensors. You need to have your car coded, yes I know no check engine light. But sometimes the computer never bothers to put one of those on. If your car has one of those bad computers, the computer thinks everything is working just fine. And goes out to a coffee break a lot. lol. I know some people think you can somehow turn the key in the car and it will give you counts or something. I have never been able to understand any of that. I would get that digital multi-tester or a scan tool for your year of car. Sears sells some nice one but not to costly. If you are going to keep this car, then that scan tool will come in down the road. I would be doing some scans and see what kind of readings you get. But I really wonder if you shouldn't replace that Throttle Position Sensor and maybe the Intake Air Temperature sensor, this one tells the computer of the temp of the engine; if the sensor is bad the computer would not be picking up on the engine getting up to the warmer temp. But are you sitting down? Those sensors are costly, I have replaced them from junked cars so maybe cleaning them is a ok way of doing that. Because some of those sensors are very costly, I mean I was working on a car and the sensors were more than the car was worth in the blue book. So I found a junked car same year, model and engine; got those. So there is an idea for you. But coded the car first and see what the computer tells you. Oh keep me posted as I am wondering just what a carb cleaner does to these cars. I got to say I wish the cars still had carbs and they had not got into these computers as well as all those sensors. Thee hour is late and so if I think of something else or visiting with other people on Monday; I might write you with more ideas. But for right now, I would get that car coded and see what kind of readings you get. You might have to take the parts that you got that cleaner on, off and just clean them really well. I know these sensors are very touchy as to what touchs them. Hope this helps and God bless: Linda
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QUESTION: Thanks for the reply.
Several points:There is no sensor on the throttle plate. The only sensor I cleaned was the mass air sensor in the air cleaner housing after the surging began, which was recommended by a local shop. The CRC product is made specifically for that reason, but cleaning it did not help the surging problem.
The haynes book says to check codes by connecting an analog multi-tester to terminals 1 and 12, located on a plug under the dash, next to the fuse box on the lower left-hand kick panel, and count the "sweeps" of the needle. I did this and got just one "sweep", which, according to Haynes,indicated normal op conditions. I am open to any help, and will do some tests for ohms and voltages as soon as I get a digital multi-tester. Still curious as to how the cold air mass valve works, and how it is adjusted. One other thing I forgot to mention: there is an audible clicking from the rt side of the dash [where the ECU is located]now when I turn on the ignition- never had that before. Thanks and God bless, Dick
AnswerDick: Why not try replacing that mass air sensor with another one say from a junked car. See if that helps. You need to have that computer checked as that clicking noise it that computer and if you can hear that; you have one of those bad computers. I would say all your problems is because the computer thinks there is a problem or more when in fact it is the computer its self. That cold air mass valve is again controled by that computer. I am not sure if you can adjusted it and again I will check around to see what I can find out. I am sorry I thought you said the car was a 1991 year but I see this morning it is 1990 year. Opps on my part. Still think all your problems are in that computer, you know on line here there are companies that will clean and rebuild that computer. Or else you can buy a new one. But you have to get the right computer for your car, year, model and engine. I have had people write in to say their computer is bad, so they got one out of a Ford and made it work. But now the car will not start, oh I wonder why?? But I am sure you know better than that. Again I will try to do some checking and get back to you. If you like you could write to me at oppedal50@yahool.com but that is up to you. I am on my lunch break and better get going. But I will check into this. Again hope this helps and God bless: Linda
