PATHRIDER Posted October 26, 2009 Share Posted October 26, 2009 Howzit going guys...Few questions here that you guys might have an answer for me first is my radiator/water pump...eversince I did my timing belt about a few years back Ive been topping off my radiator about once a month..Id say a couple of quarts.. I dont see any leak anywhere though but I do smell that coolant smell all the time ...I dont think the coolant is going to my engine block because I just did my oil change and theres no sign of water/oil mixing together.Im puzzled on this one Second is cold start ..It takes a while for my motor to warm up... I would say I have to let it run atleast 5-10 mins in the morning even in the summer time for it not to backfire on me BUT ONCE IT WARMS UP IT DRIVES FINE..ANY IDEAS GUYS? Thanks Link to comment Share on other sites More sharing options...
nismothunder Posted October 26, 2009 Share Posted October 26, 2009 Could the ratiator be rusted and its causeing the fluid to be forced into the over flow bottle and leaking from there?Could also be leaking from the heater coil. Back firing- I dont I really any thing to add to this,but my 95 would do this on cold mornings and it was caused by the rotor ir dizzy cap(I replaced both) Link to comment Share on other sites More sharing options...
Precise1 Posted October 26, 2009 Share Posted October 26, 2009 You obviously do have a coolant leak, just a small one. You will have to look much more closely or have it pressure tested. Something is wrong. Your truck shouldn't backfire because it is cold. Have you checked the ECU codes? Look for vacuum leaks also... B Link to comment Share on other sites More sharing options...
PATHRIDER Posted October 26, 2009 Author Share Posted October 26, 2009 (edited) Thanks for the quick reply guys Im going to do a thorough check sometimes this week om the radiator and water pump..I got a feeling that its the water pump..My overflow bottle is always at level. The backfiring started when I messed with my rotor..Could it be that the rotor wasnt put back in right? but I was thinking that if it wasnt put back right my pathy would run like crap all the time..Dids a tune up just a couple of months ago I did the ecu check about a year ago and no error codes...whats the best way to check for vacuum leaks B ? Edited October 26, 2009 by PATHRIDER Link to comment Share on other sites More sharing options...
nismothunder Posted October 26, 2009 Share Posted October 26, 2009 It would be kinda hard to not put it in right since you have to use a screw to reattach it,but you may have amoved it some,But I think you would of noticed that.It could be that theres a build up on it though. Link to comment Share on other sites More sharing options...
PATHRIDER Posted October 26, 2009 Author Share Posted October 26, 2009 It would be kinda hard to not put it in right since you have to use a screw to reattach it,but you may have amoved it some,But I think you would of noticed that.It could be that theres a build up on it though. well its kinda like putting a tbelt on..itll go in but my concern is if I have the pistons lined up when I slide it back in Link to comment Share on other sites More sharing options...
Terrano1992 Posted October 26, 2009 Share Posted October 26, 2009 whats the best way to check for vacuum leaks? Spray "Carb cleaner" or "Easy start" fluid to suspected areas when engine working at idle. RPM will rise when you spray to a leak point. Be careful - both fluids are EXTREMELY flammable! Don't spray too much and have a fire extinguisher at hand... Do you have backfire through the intake, or through the exhaust? In second case - probably you have faulty engine coolant temp sensor, not a vacuum leak. Link to comment Share on other sites More sharing options...
Indigent Posted October 26, 2009 Share Posted October 26, 2009 (edited) X2 on what Terrano1992 said. Backfire is almost always caused when your thermostat is not functioning properly. Edited October 26, 2009 by Indigent Link to comment Share on other sites More sharing options...
Precise1 Posted October 26, 2009 Share Posted October 26, 2009 I did the ecu check about a year ago and no error codes...whats the best way to check for vacuum leaks B ? It can't hurt to check them again. I prefer WD-40, but someone said brake cleaner because it dries so quickly and without residue. Basically any flammable aerosol you can spray around your vacuum system while the engine is running. To test a connection or hose, spray it and if the isle surges, there is a vacuum leak; it is drawing in the vapor... B Link to comment Share on other sites More sharing options...
87BeachCruiser Posted October 26, 2009 Share Posted October 26, 2009 I don't understand this: "Backfire is almost always caused when your thermostat is not functioning properly." Just got a new t-stat (along with t-belt, water pump, etc.) on my new (to me) 87 Pathfinder and now it runs like crap. I have a long list of things to look at before I blame the thermostat though... Link to comment Share on other sites More sharing options...
PATHRIDER Posted October 27, 2009 Author Share Posted October 27, 2009 Thanks for the reply guys. Im going to try to check my thermostat tomorrow. it could be leaking coolant there also...im also going to check for vacuum leaks ..it does backfire on the exhaust Terrano.What I have noticed for some time now on my temp gauge is it doesnt even pass the mid mark.Could this still be the prob? shouldnt it overheat if the thermostat is faulty? Another thing I noticed is that when I get it to the right temp where its not backfiring it only takes about half hour for it to be cold again..like when I drive to the grocery store and do a little bit of shopping when I get back in the truck and fire it up the temp gauge is all the way down again Another thing to check is that coolant temp sensor ..Would that show on the ecu code if its faulty? Link to comment Share on other sites More sharing options...
GrimGreg Posted October 27, 2009 Share Posted October 27, 2009 Another thing to check is that coolant temp sensor ..Would that show on the ecu code if its faulty? Probably not, the ECU just reads the temp sensor as a binary figure, off or on. Once the coolent hits a certain temp the sensor will switch and the ECU will reduce the fuel. If the sensor is bad, it doesn't switch, and the ECU just keeps dumping extra fuel thinking the engine is still cold. Link to comment Share on other sites More sharing options...
PATHRIDER Posted October 27, 2009 Author Share Posted October 27, 2009 Probably not, the ECU just reads the temp sensor as a binary figure, off or on. Once the coolent hits a certain temp the sensor will switch and the ECU will reduce the fuel. If the sensor is bad, it doesn't switch, and the ECU just keeps dumping extra fuel thinking the engine is still cold. Gotcha..This does makes sense.how hard is it to replace the sensor? Im thinking might as well replace it if I change the thermostat and this time Im using a rtv silicone..I got a strong feeling that its leaking around the thermostat since I was in a rush to finish it up and didnt use any..I just relied on the gasket..Thanks greg Link to comment Share on other sites More sharing options...
GrimGreg Posted October 27, 2009 Share Posted October 27, 2009 Gotcha..This does makes sense.how hard is it to replace the sensor? Im thinking might as well replace it if I change the thermostat and this time Im using a rtv silicone..I got a strong feeling that its leaking around the thermostat since I was in a rush to finish it up and didnt use any..I just relied on the gasket..Thanks greg The temp sensor is just above the thermostat, there are 2, one for the guage and one for the ECU. I would double check the water pump, when mine was leaking, it wasn't easily noticable. Also, check the short pipe above the thermostat, it's a pain to replace, but a real pain if it fails. Link to comment Share on other sites More sharing options...
PATHRIDER Posted October 27, 2009 Author Share Posted October 27, 2009 Thanks greg... I hope its not that little pipe behind the tbelt cover...I replaced that when I did my tbelt few years back. Ill check around that also on the sensor, how can I tell if the one for the ecu or gauge is bad? I would assume that the one for the gauge is still working coz its still reading temp Link to comment Share on other sites More sharing options...
87BeachCruiser Posted October 27, 2009 Share Posted October 27, 2009 Ahh I see the answer to my question, I wasn't thinking quite right. Sorry for jumping in on your thread. Link to comment Share on other sites More sharing options...
Terrano1992 Posted October 27, 2009 Share Posted October 27, 2009 the ECU just reads the temp sensor as a binary figure, off or on. You are not right. ECU reads sensor as analog value and selects corresponding "fuel map" (i.e. amount of additional fuel) depending on coolant temperature. So, if sensor reading is way over "cold" (abnormally increased resistance of overall circuit, i.e. sensor and wire harness, due to a sensor/connectors/harness fault), incorrect fuel map (way too rich air/fuel ratio) will be selected, and exhaust backfire will be a result. Sensor replacement is easy task (on cold engine, of course). Unscrew old sensor, put a small amount of RTV silicone to a new sensor thread, screw in and moderately tighten. Link to comment Share on other sites More sharing options...
Terrano1992 Posted October 27, 2009 Share Posted October 27, 2009 shouldnt it overheat if the thermostat is faulty? Bad thermostat can be half-open when engine is cold and full-open when hot. In this case, engine will not overheat, but engine warming will be "lazy"... Link to comment Share on other sites More sharing options...
Indigent Posted October 27, 2009 Share Posted October 27, 2009 (edited) Also, if you look in the FSM, EF&EC Diagnostic Procedure 21 "Backfire through exhaust", the ONLY cause listed is the coolant temp sensor. There are three items that often get confused in relation to engine temperature: 1. The mechanical thermostat that physically opens and closes based on coolant temperature. This has no electrical connection whatsoever. 2. The coolant temperature sensor, which is typically the one with the yellow connector and has 2 wires. Its resistance is proportional to temperature, which affects the voltage sensed at the ECU, as Terrano1992 pointed out. 3. The one wire sensor that drives the temperature needle in the dash cluster. All three are completely independent of each other. So if your dash needle is working, that doesn't necessarily mean your ECU is getting the right temperature reading. It is possible for the coolant temp sensor to be just fine, but the wiring may be corroded. Pull the plug off of it and clean it up, as it doesn't seal very well from the elements. Edited October 27, 2009 by Indigent Link to comment Share on other sites More sharing options...
PATHRIDER Posted October 28, 2009 Author Share Posted October 28, 2009 Thank you so much guys..Im going to tackle the temp sensor / thermostat tomorrow...Im going to start off by cleaning the plug ..hope thats just the problem..if not then ill have to get a new temp sensor.Id could be that both the sensor and thermostat is bad. What would you guys suggest if after cleaning the plug for the sensor doesnt do the trick..Do i replace the sensor and hope it cures the backfiring problem and replace the thermostat too for that lazy warming? Link to comment Share on other sites More sharing options...
Terrano1992 Posted October 28, 2009 Share Posted October 28, 2009 What would you guys suggest if after cleaning the plug for the sensor doesnt do the trick..Do i replace the sensor and hope it cures the backfiring problem and replace the thermostat too for that lazy warming? Measure sensor resistance with ohmmeter first. It should be 2100-2900 Ohm at 68 deg.F, 680-1000 Ohm at 122F and 300-330 Ohm at 176F. Then check sensor harness, as described in 1994 FSM, pages EF&EC-86..87. Replace sensor when you're sure that the sensor wiring and connectors have no faults. Link to comment Share on other sites More sharing options...
PATHRIDER Posted October 28, 2009 Author Share Posted October 28, 2009 Measure sensor resistance with ohmmeter first. It should be 2100-2900 Ohm at 68 deg.F, 680-1000 Ohm at 122F and 300-330 Ohm at 176F. Then check sensor harness, as described in 1994 FSM, pages EF&EC-86..87. Replace sensor when you're sure that the sensor wiring and connectors have no faults. Thanks again...good thing I downloaded the fsm the other day..im going to do some reading tonight Link to comment Share on other sites More sharing options...
carwilef7 Posted October 28, 2009 Share Posted October 28, 2009 (edited) Definitely take some time to read that Coolant Temp Sensor under a variety of conditions - preferably with a meter that will go into Megohms. Mine was causing an intermittent flooding condition - it read okay cold or after a half hour, but after the truck had been off for 5-10 minutes, it would SOMETIMES go to 12 megs! Only figured out the problem when it started doing it consistently, and it drove me crazy for a couple months. The computer was assuming that the temp was like absolute zero and throwing a buttload of fuel at it. Mine is a '97, but I would assume, since the temp/resistance range that Terrano 1992 quotes are the same as for mine, that it's possible yours could do the same sort of thing. $30 part at autozone or advance. Edited October 28, 2009 by carwilef7 Link to comment Share on other sites More sharing options...
Kingman Posted October 28, 2009 Share Posted October 28, 2009 Oh man, I had this ECU Coolant Temp Sensor go out on me on my old '87... it played tricks on me for months, randomly acting up and disabling the rig then clearing right up as if nothing happened. Then wham, one extremely cold day it completely went haywire and dumped a half a tank of gas through my engine in 14 miles. I think the sensor was giving 120 ohms of resistance when it got to the shop that tested it. It killed my cat and the thing was barely running, if it ever did start while the sensor was malfunctioning. It was the cause of quite a few tows, so many that the tow truck driver knew my name and rig. Link to comment Share on other sites More sharing options...
carwilef7 Posted October 28, 2009 Share Posted October 28, 2009 AND it never sets a code either, even tho it's supposed to! Damn, Kingman... sorry you had such bad luck. Link to comment Share on other sites More sharing options...
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