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Car Forum / Nissan / Nissan Cars / August 2006Bad gas mileage, popping noises out of exhaust sometimes when engine is hot, loud exhaust
Vehicle: 1986 Nissan Pulsar NX Canadian Model One of the problems i have is bad gas mileage, between 9 MPG to 13 MPG ish. That kinda sucks. New distributor cap, rotor, spark plug, plug wires, carburetor fully rebuilt and refurbished, tightened up power steering and replaced alternator belt. I notice that the car is louder than what a car should be (bought it used). and, the idle is unsteady when the car warms up (jumping around 875 - 1000). The engine is also unsteady and sounds like it misfires when hot in park or neutral (around 1200RPM) no load on the engine. Put it in gear it drops to about 875 and jumps around. I turned the idle up to that speed because it will just stall out if i didn't raise it up. So can a bad muffler cause this? I also noticed that when parked close to the house or a wall or beside another car, there seems like an exhaust noise is coming out from under the car and reflecting off the wall. So exhaust leak is possible, and i've heard that an engine needs backpressure to operate efficiently. Could anything like this be the probelm? EGR valve maybe? When was the last time the catalytic converter was changed? Maybe it is plugged up. Just a speculative thought, not based on any automotive knowledge, but something I was told the other day by an owner with an older car. don't have a catylic converter on this car. > When was the last time the catalytic converter was changed? Maybe it is > plugged up. > Just a speculative thought, not based on any automotive knowledge, but > something I was told the other day by an owner with an older car. > Vehicle: 1986 Nissan Pulsar NX Canadian Model > [quoted text clipped - 17 lines] > > Could anything like this be the probelm? EGR valve maybe? I'd guess your emissions system has problems and you're running in open loop mode (rich and retarded, kinda like Paris Hilton :). You need to check the error codes. no computer. this car is carbureted (suprisingly for an 86). just a basic emissions system. also, just about all the vaccum lines has been replaced. > > Vehicle: 1986 Nissan Pulsar NX Canadian Model > > [quoted text clipped - 21 lines] > loop mode (rich and retarded, kinda like Paris Hilton :). You need to > check the error codes. It doesn't (or ever had) an O2 sensor? > no computer. this car is carbureted (suprisingly for an 86). just a > basic emissions system. also, just about all the vaccum lines has been [quoted text clipped - 24 lines] >> loop mode (rich and retarded, kinda like Paris Hilton :). You need to >> check the error codes. nope. no O2 sensor. So this is probably a really basic problem i have. Tonight it started stumbling around 3000RPM, if i gave it a bit more gas, it would clear out. > It doesn't (or ever had) an O2 sensor? > [quoted text clipped - 26 lines] > >> loop mode (rich and retarded, kinda like Paris Hilton :). You need to > >> check the error codes. > no computer. this car is carbureted (suprisingly for an 86). just a > basic emissions system. also, just about all the vaccum lines has been > replaced. Are you sure? I had an 86 Mustang (2.3L 4 banger) that had a carb and a computer. Most cars around that time period had feedback carbs, which were basically electronic controlled carburators. Also, you most definitely do have a catalytic converter - they have been required since the late 70's. Double check your exhaust mainfold and all pipes for leaks - a clogged muffler or converter could increase back pressure and make exhaust gasses come out where they shouldn't (joints, etc). absolutely no computer, and the only electronic thing on the carb is the choke and the anti-diesel solenoid (which i removed because it was sticking). the only feedback carburetor was made in california for this year, possibly the 50 states, but not in canada. Same thing for the catalytic convertor. Only thing i have is the main muffler and the after muffler. Since theres no O2 sensor, an exhaust leak wouldn't make it run rough at idle or get bad mileage would it? I also forgot to mention sometimes when i come to a stop it stalls out, so i turn the idle up, and its ok, then maybe a couple of days later, the idle goes extremely high, then i have to turn it back down. is this also a sign with a sticky egr valve? > > no computer. this car is carbureted (suprisingly for an 86). just a > > basic emissions system. also, just about all the vaccum lines has been [quoted text clipped - 9 lines] > muffler or converter could increase back pressure and make exhaust > gasses come out where they shouldn't (joints, etc). new info: i tested the valve today with vaccum from my mouth, and it closes right away, doesn't stay open for 30 seconds like the book says. instance close. also, i started the motor and accelerated it a bit. the valve opens up like its suppost to, then closes right when you return the throttle to a slow speed. sounds shot doesn't it? but this wouldn't be an idle problem, unless its not closing fully? gas mileage problem? on the air care smog test it only fails Carbon Monoxide (CO) 8.56%? isn't this a rich condition, then a lean? The NOx is way too low (127) instead of 1348. For idle i got 0.16 for CO, but thats with a 1200RPM idle. The other one above is a driving test, about 40kp/h. > absolutely no computer, and the only electronic thing on the carb is > the choke and the anti-diesel solenoid (which i removed because it was [quoted text clipped - 22 lines] > > muffler or converter could increase back pressure and make exhaust > > gasses come out where they shouldn't (joints, etc). > absolutely no computer, and the only electronic thing on the carb is > the choke and the anti-diesel solenoid (which i removed because it was [quoted text clipped - 3 lines] > after muffler. Since theres no O2 sensor, an exhaust leak wouldn't make > it run rough at idle or get bad mileage would it? Wow - regulations must have been quite different or Canada! A plugged exhaust would cause some of these symptoms - If you can stand the noise, try driving with the exhaust disconnected for a mile or so and see if it works. > I also forgot to mention sometimes when i come to a stop it stalls out, > so i turn the idle up, and its ok, then maybe a couple of days later, > the idle goes extremely high, then i have to turn it back down. is this > also a sign with a sticky egr valve? Could be - IIRC the EGR system can play hell with the mixture, which will play hell with idling and such. Have you disconnected the vaccuum line to the EGR valve when it's running well? I thought this message died off ;) >Wow - regulations must have been quite different or Canada! I looked online here and compared it to canada: http://www.smogcheck.ca.gov/ftp/pdfdocs/asm_ph43.pdf California HC: 63.2, Canada: 314 California CO: 0.64%, Canada: 2.41% California NOx: 850, Canada, 3390 In canada they calculate the ratings from the engine size (in litres) and the curb weight and year of the vehicle. very nicely set i will say. > A plugged exhaust would cause some of these symptoms - If you can stand > the noise, try driving with the exhaust disconnected for a mile or so > and see if it works. I'll try that someday in september or october, its better to do that after school at my school's shop > Could be - IIRC the EGR system can play hell with the mixture, which > will play hell with idling and such. Have you disconnected the vaccuum > line to the EGR valve when it's running well? Well its never really run well, i've been able to get the idle down to about 800 on a good day, but it still jumps around. I tested the egr and it does hold vaccum now (for a long time with vaccum pressure), doesn't seem to be sticking (i moved the diaphragm up and down) and when i move it up when it does idle it stumbles and stalls out. seems like the egr is working perfect. I've heard to plug the egr vaccum line and see if it improves. Could this be a fuel pump issue? heard that older pulsars and sentras had problems. I can get a new one for probably 60bucks, or i might just rent a pressure tester. On our emissions site (try it out for your vehicle and sompare the emissions regulations: www.aircare.ca) if the CO is extremely high (8.56%, max allowable 2.41%, previous results from 1993 to 1999 is between 0.5% and 0.26%.) it will probably mask a NOx problem on they're scanner (my NOx right now is 127, max allowable is 3390, used to be from 1787 to 2655.) Could be why i'm getting 9 to 14 MPG instead of 26 to 30MPG. Any ideas? i forgot something else that recently started happening. man its late and i'm tired. Shop manual and emissions sticker under the hood says to set ignition timing to 5degrees after TDC with vaccum advance hosed plugged from distributor. Sometimes, around 3000rpm. switching into second or third gear, the motor will stumble a bit and i need to give it more gas to smooth it out, or take my foot off to shift it. its an automatic, but if i set it to 5 degrees Before tdc, it goes away, and it seems like fuel mileage is a bit better btdc than atdc. but atdc has a bit more power at higher rpms, btdc has a quicker response. does this unlock something? What kind of ignition system do you have on this car? Have you checked the timing? In point ignition system you need to check for the point gap and dwell angle. In some older electronic systems, you may need to check for the gap between the sender and the pick-up. Even in a carburated engine, there should be a compensation for the idle speed when in gear or when the a/c is turned on (if equipped with one). A defective exhaust would not cause this kind of problems in the kind of engine control you have. The idle speed hunting sounds like a vacuum problem. Was the carburator properly rebuilt? Are the gaskets at it's base new and seating on clean surfaces? Is it possible that you have an intake manifold leak? Yes, a defective EGR could cause this kind of problems. Good luck. > Vehicle: 1986 Nissan Pulsar NX Canadian Model > [quoted text clipped - 17 lines] > > Could anything like this be the probelm? EGR valve maybe? > What kind of ignition system do you have on this car? Just the stock ignition system. > Have you checked the timing? Yes, timing checked multiple times. Set to 5 ATDC like in the manual distributor vaccum advance hosed removed and plugged. > In point ignition system you need to check for the point gap and dwell > angle. In some older electronic systems, you may need to check for the > gap between the sender and the pick-up. No points in this car. Electronic Ignition. > Even in a carburated engine, there should be a compensation for the idle > speed when in gear or when the a/c is turned on (if equipped with one). Not too sure what you mean for this one. Idle smoothens out a bit more when in gear, and i don't have a/c. > A defective exhaust would not cause this kind of problems in the kind of > engine control you have. Ok, but it sounds loud anyway, so i might get a new muffler. > The idle speed hunting sounds like a vacuum problem. The only vaccum lines i didn't replace (because I ran out) was vaccum advance and the charcoal canistor to the carburetor. I should go buy some more. > Was the carburator properly rebuilt? Are the gaskets at it's base new > and seating on clean surfaces? First kit i put in was the wrong one, second one makes it run a lot better. Soaked and cleaned. The intake base gaskets are new and the old ones were scraped off. > Is it possible that you have an intake manifold leak? How would i check this? > Yes, a defective EGR could cause this kind of problems. And how could i check or repair the EGR? > Good luck. Thanks. > > Vehicle: 1986 Nissan Pulsar NX Canadian Model > > [quoted text clipped - 17 lines] > > > > Could anything like this be the probelm? EGR valve maybe? I had a UK Nissan Sunny of this vintage with just an old fashioned carb setup, and I seem to remember diaphragms splitting causing all sorts of wierd problems once the mileage got to about 110000m. These were external to the main body of the carb on mine, and weren't meant to be repairable but I bodged them very successfully by hacksawing a few slits in the fold-over rim so that I could peel them back and open the diaphragm case up. I used bicycle puncture repair rubber sheet to fix it, probably an old inner tube would have done. They lasted another 70000m before I sold it. It's easy to test the diaphragm is OK or not by attaching a tube to it so that you can suck on it and see the diaphragm operate the plunger on the other side. To know if you have a manifold gasket leak you should drop some fuel or light oil betweent the manifold and the head (or engine block) and see if it gets sucked in. It is not always easy to find. What about the float level in the carbs? The canister lines should not be a cause for hunting. Another possibility is that you have low compression in the engine. Measure it. If the idle speed drops too much when shifting in gear, the drop could be an indication of a lean mixture, due to vacuum leaks or improper adjustment, improper timing or low compression or other mechanical issues. Some EGRs can be manually opened, by pushing the diaphragm with your fingers. Others you need to open using a vacuum pump. If you open it and there is no change in the idle speed, then you know you have a problem. The most you can do to most EGRs is to clean them. If it is defective, you would need to replace it. Another possibility is that you have low compression in the engine. Measure it. You could also have problems with the valve timing. You may inspect the timing physically by looking at the crankshaft timing marks and the opening and closing of the valves, or you can use a vacuum gauge and analyze the readings using the info that comes with the gauge or by visiting: http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm http://www.secondchancegarage.com/public/186.cfm Besides poor mileage could be due to wheel alignment, tire pressures, transmission slipage, etc etc. Good luck >>What kind of ignition system do you have on this car? > [quoted text clipped - 68 lines] >>> >>>Could anything like this be the probelm? EGR valve maybe? > To know if you have a manifold gasket leak you should drop some fuel or > light oil betweent the manifold and the head (or engine block) and see > if it gets sucked in. It is not always easy to find. will check out later. wouldn't it cause it to be lean,not rich like my mixture > What about the float level in the carbs? float level is perfect, line up right in the center of the window on the carb > Another possibility is that you have low compression in the engine. > Measure it. don't have a gauge. will try to rent one > If the idle speed drops too much when shifting in gear, the drop could > be an indication of a lean mixture, due to vacuum leaks or improper > adjustment, improper timing or low compression or other mechanical issues. Its an automatic, pretty much anything below 1000rpm will cause it to stall out. now theres a loud screech noise when i start the motor, it goes away within about 10 seconds, and the rpms are unstable and want to stall out, maybe a bit of backfire. i'm going to change the timing belt. > Some EGRs can be manually opened, by pushing the diaphragm with your > fingers. Others you need to open using a vacuum pump. If you open it > and there is no change in the idle speed, then you know you have a > problem. The most you can do to most EGRs is to clean them. If it is > defective, you would need to replace it. Already did that. Idle speed changed, so i know its working. > Another possibility is that you have low compression in the engine. > Measure it. Will try to rent the gauge. > You could also have problems with the valve timing. You may inspect the > timing physically by looking at the crankshaft timing marks and the > opening and closing of the valves, or you can use a vacuum gauge and > analyze the readings using the info that comes with the gauge or by > visiting: I gotta change the timing belt and timing tensioner anyway, because i believe the belt might be slipping, because it screeches (all the drivebelts have been changed) > http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm > http://www.secondchancegarage.com/public/186.cfm > > Besides poor mileage could be due to wheel alignment, tire pressures, > transmission slipage, etc etc. wouldn't be that. its even rich just sitting driving no where. you can smell it out of the exhaust. > Good luck > [quoted text clipped - 70 lines] > >>> > >>>Could anything like this be the probelm? EGR valve maybe? Sorry about the quality of my previous posting. I was too tired. I was not aware that the mixture was rich. The jumping around idle and the misfiring led me to believe that it was lean, my bad. Back firing is normaly a sign of timing problems (ignition or valve). Have you adjusted the mixture screw in the carburator? Does the idle respond to changes in this adjustment? Another possible cause for poor mileage would be an obstruction in the air intake system. Not being familiar with your vehicle, I cannot tell you specifics, but I have had cases of colapsing intake hoses or rubber seals that obstruct the flow of air causing the mentioned problems. Inspect the air intake system. A timing belt does not slip with a squeal, they slip and cause the engine to stall or damage internal components if in an interference engine. A timing belt off by a tooth or two will cause the kind of poor mileage and/or idling that you have. Replacing a timing belt is a job that requires lots of care to avoid expensive damage, and lots of cleanliness to assure that the belt lasts a long time. Not only the sprockets and idler need to be clean, but also the surrounding areas, so when you install the belt, it does not get any dirt on it. When replacing the timing belt also consider replacing the idlers and/or tensioner. If you replaced the drive belts, and you still hear a squeal it could be that the belt tension is low, that oil or water is dripping on one of the belts. Yesterday I was working on an Isuzu, and the squeal was caused by a slipping harmonic balancer (crankshaft pulley), the two parts of which had separated. Check the cylinder compression and the intake manifold vacuum readings. These can tell you lots. Good luck >>To know if you have a manifold gasket leak you should drop some fuel or >>light oil betweent the manifold and the head (or engine block) and see [quoted text clipped - 129 lines] >>>>> >>>>>Could anything like this be the probelm? EGR valve maybe? > Have you adjusted the mixture screw in the carburator? Does the idle > respond to changes in this adjustment? yep i've adjusted the mixture screw, the kit said 4 turns from seating. i've played around with it and it doesn't respond to much if not anything. from what i see, its the same when the mixture screw is all the way in (lean) and most of the way out. it doesn't seem to change. my nissan factory manual says the throttle screw controls the idle speed and the mixture screw only controls mixture during idle. maybe i got a blocked idle jet. > Another possible cause for poor mileage would be an obstruction in the > air intake system. Not being familiar with your vehicle, I cannot tell > you specifics, but I have had cases of colapsing intake hoses or rubber > seals that obstruct the flow of air causing the mentioned problems. > Inspect the air intake system. just an air filter on top of the carburetor, and an air injection valve that runs from the air cleaner to the exhaust manifold. basicallly it sens secondary air to the exhaust manifold to reduce CO and HC emissions in exhaust gases. so nothing special, just a round air filter in a case on top of the carb. the center of the air filter is the choke valve, then it runs down to the intake. > A timing belt does not slip with a squeal, they slip and cause the > engine to stall or damage internal components if in an interference [quoted text clipped - 4 lines] > sprockets and idler need to be clean, but also the surrounding areas, so > when you install the belt, it does not get any dirt on it. well when that squealing noise is on the rpms drop about 100 - 200 RPM. i'm planning to do the timing belt this week. it seems that the tensioner might be the squealing part. but the weird thing is it goes away after i rev the engine up a bit, but usually comes on at low engine speeds, (like 1200 rpm or lower) > When replacing the timing belt also consider replacing the idlers and/or > tensioner. no idler pulleys because no air conditioning but i'm replacing the tensioner anyway > If you replaced the drive belts, and you still hear a squeal it could be > that the belt tension is low, that oil or water is dripping on one of > the belts. Yesterday I was working on an Isuzu, and the squeal was > caused by a slipping harmonic balancer (crankshaft pulley), the two > parts of which had separated. doesn't seem to be any liquid on the belts, and they're nice and tight (push down on them they only drop about 1/4 in. to 1/2 in (in range with the new belt tensions in my manual. > Check the cylinder compression and the intake manifold vacuum readings. > These can tell you lots. i'll try to find a compression tester. > Good luck Thanks ! > >>To know if you have a manifold gasket leak you should drop some fuel or > >>light oil betweent the manifold and the head (or engine block) and see [quoted text clipped - 129 lines] > >>>>> > >>>>>Could anything like this be the probelm? EGR valve maybe? |
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