wildmaninid Posted April 27, 2013 Report Share Posted April 27, 2013 I am having some mixture issues with my truck. 1977 620 with a 1990 240sx ka24e engine. I do have the EGR removed from the intake (I hope that won't matter). I have noticed an increase in fuel consumption lately, and that the exhaust smells very thick and rich, especially at a warm idle (weird, you would think as it was warming up that would be the case more so than when warm) and when I pull up to a stoplight you can really smell it, sort of makes your eyes water. The engine was rebuilt when before I installed it 7,000 miles ago (3400 of those were a cross country drive). The truck has brand new cap, rotor, NGK plugs and NGK wires. So far I have replaced the obvious: Air Intake Temperature sensor, Coolant temperature sensor and I installed a new Denso Oxygen sensor, yet I am still having this issue. I wonder if the MAF sensor would have anything to do with it? I don't have my service manual for the engine, or I would be right on top of checking voltages and whatnot. The truck runs strong, Idles good (although sometimes when coming back down to idle from driving the idle "hunts around" up and down about 3-4 times before it idles). I was getting 27-30 on the hiway when I first installed it back in 2011, but now am lucky to get 20. Anyone have any ideas/experience etc? Thanks a million. Quote Link to comment
jesusno2 Posted April 27, 2013 Report Share Posted April 27, 2013 You have any codes? O2 sensor failure? coolant temp faliure? if you look into the 89 FSM its way more indepth than the 1990 FSM. it goes through the steps to check all of it. has it always hunted for idle? Quote Link to comment
wildmaninid Posted April 27, 2013 Author Report Share Posted April 27, 2013 It doesn't always do it, no. It's just a once an awhile thing. I have already checked the ECU for codes to no avail. Quote Link to comment
jesusno2 Posted April 27, 2013 Report Share Posted April 27, 2013 It has throw a code. code 55 means all is good in mode 3. Mode 1 will test the O2 signal, mode 2 will test the fuel mixture ratio. You could have a TPS outta whack etc just go through the motions testing the sensors adjusting what needs adjusted make sure your IACV and your aux air regulator are working properly. Quote Link to comment
wildmaninid Posted April 28, 2013 Author Report Share Posted April 28, 2013 So I went through the engine off stored code diagnostic (mode 3) and got codes 13 and 14. 14 is irrelevant (speed sensor signal) with the swap, but 13 is for coolant temp sensor. I replaced that yesterday morning. I went ahead and deleted the codes and will then go through the engine running diagnostic to see whats going on. If I still get the code 13, I will need to check the harness, maybe I missed a wire during the swap, but I don't think so since this running rich is a new development....... Quote Link to comment
Farmer Joe Posted April 28, 2013 Report Share Posted April 28, 2013 pretty sure it should be the temp sensor. makes sense since its acting like it still closed loop, even after it up to temp.. 1 Quote Link to comment
wildmaninid Posted April 28, 2013 Author Report Share Posted April 28, 2013 I am going to go drive today and see whats up. Quote Link to comment
wildmaninid Posted April 29, 2013 Author Report Share Posted April 29, 2013 So I drove the truck yesterday evening and after work today I re checked the codes. Code 14 was still there and code 13 was gone. I warmed the truck up and got it into closed loop and ran test 2 which is mixture monitoring. Computer indicated mixture was within spec. Rigged up a mirror system and put it in mode 5 (real time monitor) and drove around. No codes were showing. Truck exhaust still smells a little rich but not nearly as bad as it was. Going to fill up and check mileage this weekend. Thanks for the help. 1 Quote Link to comment
MikeRL411 Posted April 30, 2013 Report Share Posted April 30, 2013 Have you checked your fuel injectors? My '90 240SX had similar fuel smell symptoms which turned out to be a defective fuel injector. Replaced, no more fuel smell, better gas mileage. Good luck, hope it's as simple as this. Quote Link to comment
wildmaninid Posted April 30, 2013 Author Report Share Posted April 30, 2013 Were you getting a raw fuel smell with the injector? Like from underhood? (I have had bad o-rings on injectors before) Today's drive produced no more codes, but there seems to still be something off about it. Quote Link to comment
MikeRL411 Posted April 30, 2013 Report Share Posted April 30, 2013 Were you getting a raw fuel smell with the injector? Like from underhood? (I have had bad o-rings on injectors before) Today's drive produced no more codes, but there seems to still be something off about it. Yes Quote Link to comment
wildmaninid Posted April 30, 2013 Author Report Share Posted April 30, 2013 I don't seem to be getting any smell/vapor from underhood, but I am definitely having a very thick. rich smelling tailpipe. Rock Auto has brand new injectors for 38$ apiece.....might have to get some just becuz. Quote Link to comment
h190 Posted April 30, 2013 Report Share Posted April 30, 2013 SORRRY TRIPLE POST. Quote Link to comment
h190 Posted April 30, 2013 Report Share Posted April 30, 2013 Sorry double post. Quote Link to comment
wildmaninid Posted April 30, 2013 Author Report Share Posted April 30, 2013 It was actually only a double post, you overwrote your original comment. I changed the oil yesterday, so no worries there. I checked the plugs this morning and they look like like they are firing good, all a nice, even light brown. I do not have consult. Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.