Ok guys, got a weird one. AS you all know, still trying to diagnose why my 3S-GE generally lacks guts. Been investigating different sparkplugs. A few weeks ago, I changed the TPS to see if hat helped. No difference. So i was running NGK BCPR5ES-11, the recommended NGK plug for my car, only not platinum. I gapped it down to 0.044 inch, and the motor proceeeded to start to miss randomnly. Ok I thought, just grab some new plugs. This time I got given the BCPR5EY-11, what my Haynes manual says is the right plug for a 1991 4A-FE engine. The performance seemed to increase noticeably, not great, but noticeably. Funny, because this is apparently the wrong plug! So I want to know, whats the difference between these plugs if they all sit in the same thread and all look the same? Is it simply the gap? Should I gap these plugs down to 0.044 inch if they arent already? Should I run the old set that was reccomended? Is there a performance diff to be had? Should I just buy the platinum plugs its meant to run? Theres meant to be no change in performance.... Basically, am I missing out on power because of the plugs? Im considering just buying a set of the platinums to make sure....
Close the gap in see if it runs better, old car, old coil. It doesn't matter weather you buy copper, platinum or iridium, you should not be able to decipher a performance difference between them. something else is wrong. Possibly in the ignition system. Why did you change the TPS?
Im trying to find out if there is a difference, not saying I have experienced one. Changed TPS trying to diagnose a performance issue, it generally just lacks power all through the rev range. Only old ignition component left is the coil. I still have to change the Fuel filter and check my TPS, after that im out of ideas. What gap should I run? 0.044inch? The gap on my old plugs was bigger tahan that, so i closed it down to that. should i gap it lower still?
the gap wont have such a huge affect. I think it might be a good idea to start anothe thread and list very specifily what the problem is, and thing like the black some at that rpm range, ect. ect. then list everything you have tryed and their effect on the motor, your diagnostic results ect. maybe if we see all the pieces of the puzzel at once we can put it together. I wish you were closer and could come by and try out all the spare parts I have tilly ou fix the problem. I haVe a new dizzy if you find its related to the problem
They should be pre-gapped. And the only difference between the normal and platinum ones, is platinum ones last longer. So just get the same NGK plug code without the p on the end.
replacing parts is not diagnosis. Diagnosis is testing components to find the fault. Since you seem to want to fix this yourself, go get a Toyota BGB for your car, and Test the components that are causing the fault based on your educated decision or the flow chart in the service manual. There is no guessing to repairing vehicles, so changing random things like fuel filter, TPS, spark plugs, is only going to fix something if your lucky. First start with a good visual inspection, followed by checking for trouble codes, Then you need to get into Air Fuel and Spark testing, none of which involves replacing anything. for example testing the TPS involves removing the connector and checking the resistance created by the potentiometer at various positions. then going to the computer and checking that the readings there are accurate to. This eliminates the TPS and its wiring for faults. Good luck
hum never thought of that, at one point he mentioned black smoke, or smoke in general under ahrd acceleration, I think he thoug it had to do with a rich a/f but it might have just been steam in cold temp. Cat woul dbe a good suspect to examine
Been through pretty much everything Klue, good advice but im alot further along. Only thing I hadnt tested was TPS, simply swapped it to see if it helped since I hadnt found how to test it yet. I have located it in my MANUAL (Yes I have one....) though and will test it soon. Exhaust has always sounded a bit odd, perhaps you could be onto something. How could I test that though Mafix? Fuel filter I suspect as sometimes when cold the car is hard to start, as in it will start, then idle at about 500rpm for a few secs then go to normal cold idle. Once it started then died straight away. I will also find how to test the coil resistance. Just to clarify, the problem is a complete lack of performance at all rpm, the car will make ok power as in it will roast the tires if launched at 3000rpm, just struggles to build up revs. Does so smoothly, but slowly.... So we have at the moment: Test TPS Test coil Possibilty of exhaust blockage Fuel filter (maybe) And also I have suspected the ECU since RYe mentioned somewhere he had a dodgy one... Igntion system bar the coil is all new, new air filter, AFM has been checked and trouble codes cleared-replaced an oxy sensor.
BTW I have a new fuel filter, just havent got around to changing it. The hard starting issue cold could be the coil I think. Also, I need to go through and double check the timing belt and cam timing, though its probably fine...
I reckon the next thing to check the is the exhaust like said. What if your engine has major problems, and your just wasting your time on nothing? :?
Engine doesnt use a drop of oil, which stays spotless, coolant remains spotless and doesnt go anywhere, and the motor has compression tested with excellent figures. Its something else....Does smell slightly, and smoke slightly as it passes about 4-4.5K rpm...
hum could be hard to test, you could unbolt the y pipe, and have the ehnust leave straight out the headers Thats what Id try. you wont have max power that way, but it would bypass a clogged cat.t-vis is still a possibility. You can wire it free up to test if its working, just run the t-vis wire to a ground, and put a switch between, so when you hit the switch it connects it with ground and BAM, t-vis
what you need to do to test the exhaust is to measure the pressure between the exhaust ports and cat. I don't know if they make a tool for this, but i made one my self pretty easily. Im in trinidad right now or else i would get you some pics. But basically you need to take a peice of metal, cut it accordingly to fit on the o2 sensor(precat) spot, and get a hose going to a pressure gauge(i use an old boost gauge). Ill have to check my text books when i get home but i dont think you should see over 1psi. You want to do this with the cat warmed up, and at various rpms. Just be careful that you dont melt the host, like me
Sounds interesting Klue, i thijk I understand what you mean. Might also be an option like Ant1 said to just unbolt it at the Y pipe and drive it haha. In any case, I did take slight offence to your statement about replacing parts instead of testing. Everything I changed was for a reason, and the TPS was just a quick check to see if it helped. The leads, cap rotor etc were done because the leads were destroyed, as was the cap. Air filter was because my car had a pod filter, when i changed back to the box, i was using the filter that came in the box from the wreckers and it was pretty stuffed. Fuel filter I am doing because I dont know when its been done, and would like to know a fresh one is there. Just thought I should clear that up, I have spent alot of time trying to diagnose whats up with this car, thank you very much for your help, Alot of people here are out of ideas, you seem to have a few fresh ones!
Ok, am ready to do a whole bunch of testing on the components. The car hasnt been in action as the taillights quit, and the battery has also decided to call it a day with the weather cooling down in Adelaide, its raining too. Finally! Anyway, have to wait for the weather to clear up, then work will start again on the celica....
