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Car Forum / Nissan / Nissan Cars / June 2007Carbureted 1987 E16S Sentra Won't Idle
Well, after 333,000 good miles my 1987 E16S Sentra has developed a very unstable idle. It started out as occasional stalling during warm- up. It got worse and began a rolling idle (rpm up and down) when cold and during warm up with more frequent stalling during warm up. Now there is always a rolling idle whether cold, warming up or hot. Once warmed up it will sometimes idle at very high rpm and sometimes it will not idle at all but flat out stall as soon as the clutch pedal is depressed. The carb primary and secondary are fine as once you get past idle it runs great. Also, it is an idle speed problem and not an idle mixture problem as there is no black smoke and the plugs look fine. There is an idle speed control actuator which operates on vacuum providee by a vacuum control modulator (VCM). Due to the rolling idle I suspected the VCM, so I tested it per the factory service manual and it checks out OK. The voltage (12v) and the vacuum (2" Hg to 3" Hg) are within specs. There are two small air filters that filter outside air to the VCM and the idle speed control actuator and they are not clogged. So I'm now thinking that the idle speed control actuator itself is going bad. Has anybody had any experience repairing/replacing this part? Can it be replaced without removing the carb from the manifold? Anybody know of where one might be able to buy one short of a junk yard (likely to be in worse shape than mine). I'll appreciate any advice. Thanks in advance. Al years ago, i noticed a similar carb anomaly (different brand vehicle). on my carb, if you unplugged the connector on the throttle position switch and raised the engine speed above 2300 rpm, the engine speed would fluctuate. this was a feature of the deceleration fuel cut system. does your carb have a throttle position switch? > years ago, i noticed a similar carb anomaly (different brand vehicle). > on my carb, if you unplugged the connector on the throttle [quoted text clipped - 3 lines] > > does your carb have a throttle position switch? Many thanks for your thoughts. Unfortunately, there isn't a throttle position switch. It's an electronically controlled carb. The ECM sends signals to various control modules based on various inputs. There's an idle speed control actuator, hence my suspicion that it might be at fault. I suppose I better check each and every electrical connection though. Thanks again. Al Withe age of the vehicle and no mention of carb repair I will guess that you have a leaky diaphragm within the carb. Especially woitht he wacky additives we have in the gas now Its possible and probable that all the rubber parts need replacement. -SP > Well, after 333,000 good miles my 1987 E16S Sentra has developed a > very unstable idle. It started out as occasional stalling during warm- [quoted text clipped - 22 lines] > be in worse shape than mine). I'll appreciate any advice. Thanks in > advance. Al On Jun 19, 5:00 pm, Speedy Pete <speedythetrash.p...@verizon.net> wrote: > Withe age of the vehicle and no mention of carb repair I will guess that > you have a leaky diaphragm within the carb. [quoted text clipped - 32 lines] > > - Show quoted text - Thanks for that idea. Indeed the carb is 100% original. Since it runs very well once past idle, my first thought was the idle speed control actuator. But there's no doubt that today gas ain't what it used to be. Al. Most of my carburetion experience was prior to all of the high-tech goodies (computerized crap) that was added on to cars past about the mid-70s or so. You will probably find that a bad idle will NOT necessarilly show up just by inspecting the spark plugs. Usually the engine idling time is very minor in comparisson with its road-speed operating time. That tends to burn-off any small amounts of carbon that may be acccumulating while the engine is idling too rich. An idle that is variable may signify you could have some loose bolts that mount the carb to the intake mani. My girlfriend had a problem once, where she had a franchised car dealer shop (aaargh!) do "repair work" and they screwed it up bad. They charged her $432 for what was a tune-up, plus they replaced a slightly leaking head gasket too and messed-up the whole deal. The engine would then NOT idle properly. I'd bought a $25.50 carb kit for her 86 Escort and went to replace some carb parts & set the float height. etc. etc. As soon as I took that carb off that intake manifold I found her trouble (in addition to her having a F-O-R-D). The lousy beggars who replaced that head gasket (which could probably have been tightened in 1 hour "free") had broken the OLD gasket that the carburetor SITS on - that's on top of the intake manifold! Those jerks had RE-USED to same busted old carb. gasket which had a 1/8 inch chunk missing altogether. Another case: 2 old biddies drive into a service station where I was working. They ask me to tell then why their old plymouth was running so bad -and why it didn't wanna start. I found the 2 nuts on the studs that hold the carb on the intake manifold so LOOSE you could see that 1-barrel Carter just a-dancing on top of the engine. It was so loose I couln't see who that old car even started. So I fixed that free for them (like a chump-idiot) and I recommended I could replace the 6 plags that were HORRIBLE just for the price of the plugs. Those dumb broads said "No" and just drove off! (Hey - is the phrase "two dumb broads" redundant?) > Well, after 333,000 good miles my 1987 E16S Sentra has developed a > very unstable idle. It started out as occasional stalling during warm- [quoted text clipped - 22 lines] > be in worse shape than mine). I'll appreciate any advice. Thanks in > advance. Al > Most of my carburetion experience was prior to all of the high-tech goodies > (computerized crap) that was added on to cars past about the mid-70s or so. [quoted text clipped - 56 lines] > > - Show quoted text - Thanks for the ideas - and the laughs. I also run an old Rambler American and the puny one barrel carb works loose on the manifold every so often and starts popping. The thing is held on with screws, not bolts! So your advice is well taken. I'll try tightening things as well as putting a vacuum gauge on the manifold. The rolling idle, when it will idle, is indeed suspicious. So watching the vacuum carefully might reveal something. You're right that these fancy carbs are a far cry from the old Rochesters I grew up with. You need a PhD in engineering to read the carb section of the factory service manual. Thanks again. Al You might want to put some Loc-Tite on those carburetor screws. That ought to keep them from working loose. But be SURE that you DON'T use the kind of Loc-Tite that is *permanent*! I had a '64 Rambler that my dad bought new & gave to me. Like an idiot, I sold that car because I had a couple other cars at the time. I should have abandoned the 2 other Plymouths I had & KEPT that Rambler! At that time I was young and stupid (more so) so I got rid of the decent Rambler. Our family dog had piddled in the back on the floor and it seeped into the carpet. This got to stinking a bit which "irked" me so the car got sold. What a moron! >> Most of my carburetion experience was prior to all of the high-tech >> goodies [quoted text clipped - 77 lines] > in engineering to read the carb section of the factory service > manual. Thanks again. Al > I had a '64 Rambler that my dad bought new & gave to me. Like an idiot, I > sold that car because I had a couple other cars at the time. I should have [quoted text clipped - 3 lines] > carpet. This got to stinking a bit which "irked" me so the car got sold. > What a moron! My dad bought a '64 Rambler American wagon. The six cylinder was 195 cu. in. (as I recall). It had a non-synchronized 3-speed transmission with the shifter on the column. The throw was quite long. It was the car on which I learned how to drive a manual transmission. The floorboards eventually rotted out. A friend who worked at a sheet metal shop gave me some 36" square galvanized sheet of a very heavy gauge. My brother and I bent those sheets into new floor panels and pop riveted them in place. We sealed the edges with silicone or rubberized caulk. After the repair the metal thickness and sturdiness of the floorboards was probably better than original. I seem to rememebr those cars had an enclosed driveshaft. Eventually the engine was running very badly. We took the head off and found a gasket had blown between #3 and #4 cylinder. Instead of just relacing the gasket we had a valve job done on the head and installed it again. Those engines had some cool features. The intake manifold could be taken apart. There was a top cover that could be opened up and the main part of the intake was part of the cast head. The carburetor was a Rochester, I think. It was a single barrel and in retrospect probably pretty simple. But, I remember the way it was attached was a lot different than the later GM cars I drove and worked on with V-8's with the Quadrajets. Once we had to put a new wire on the starter motor. We ran the wire on the wrong side of the steering column and the wire soon shorted. It was the first time I knew a car battery could instantly melt copper, as there were drops on the street when it happened. The car was passed on first to my brother, then to me, then to a younger sister. I don't remember when the family finally got rid of it but the body was in pretty bad shape at the time. The front fenders we susceptible to rusting. Yes, if I had a place to have stored the car and wored on it it would have been a good one to keep due to it's simplicity of design. I had not thought about that car in a long while until reading your post. Mark on 6/28/2007 8:16 PM Mark Fields said the following: >> I had a '64 Rambler that my dad bought new & gave to me. Like an idiot, I >> sold that car because I had a couple other cars at the time. I should have [quoted text clipped - 46 lines] > > Beep, Beep, Beep, Beep. His horn went Beep, Beep, Beep! "Beep Beep". The Playmates 1958.  SignatureBill In Hamptonburgh, NY To email, remove the double zeroes after @ Years ago my 1985 S-10 pickup also had an very *unstable* idle. At that point I didn't know about READING the engine trouble CODE - so on a hunch I changed the throttle-body fuel injector. This gave the truck more power, but the idle was still terrible and kept changing a whole lot & died at stop signs, etc. Finally I found how to read that trouble code = On Board Diagnostic = "OBD". I only had to connect a short piece of wire between two terminals on the socket where the diagnotic computer plugs in & the Check Engine light gave a flashing code readout, over and over. That code showed that the MAP sensor (manifold air pressure) was BAD. Replaced the MAP module (which was easy) and the truck idled real good. The book telling that was found at a Pep Boys store & cost about $13. > Well, after 333,000 good miles my 1987 E16S Sentra has developed a > very unstable idle. It started out as occasional stalling during warm- [quoted text clipped - 22 lines] > be in worse shape than mine). I'll appreciate any advice. Thanks in > advance. Al |
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