85wrx Posted January 27, 2015 Report Share Posted January 27, 2015 (edited) I recently purchased a AE71 with 4AGE 100kw conversion. Wiring on the conversion was average to say the least which I have since rewired. Air temp sensor wasn't connected now connected, thermistor for cold start injector wasn't connected either now connected. All holes in the throttle body on the air filter side were filled with silicon and the throttle body had no idle adjustment. All sorted with a second hand throttle body. The issue I am having is the car seems to have a flat spot under light acceleration from 1500-2000 thru to 3000-3500rpm then acceleration hits hard. Try and push the throttle thru the flat spot and it will hit hard. Seems dangerous in the wet. Also whilst holding steady speed in all gears below between 2000 and 3000rpm, the car seems to be lurching back and forwards not holding a constant speed. I have noticed that when the car is cold these don't seem to happen. It only seems to start when the car is reaching normal operating temperature. I have changed the following items: * Compete set of brand new spark plug leads inc coil lead (car died on a test drive. turned out to be a coil lead) * New spark plugs platinum tipped BKR6EP-8 set at 0.8 mm * Brand new TPS. Set throttle body and TPS as per manual with feeler gauges and particular resistance readings * Swapped computers with no change. * Swapped coils with no change. * Set the ignition timing to either 10 deg btdc and 15 deg btdc no change. Tried to setup up with shorting terminals in diagnostic connector but it made no difference. * New fuel filters * I have also checked and there are no codes using CEL. I am sort of leaning towards either the water temperature sensor as it seems to happen when warm or the distributor. I disconnected the water temperature sensor and took I for a drive and it didn't make a difference. I am starting to run out of ideas. Anyone got any ideas?? It is starting to annoy me. Edited January 27, 2015 by 85wrx Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted January 27, 2015 Report Share Posted January 27, 2015 I have noticed that when the car is cold these don't seem to happen. Seeing it will be rich during cold start, it suggests the problem is that it is lean when warm. Lurching also suggsts it is lean, so check for air leaks on the inlet side again... Can you have the mixture checked when running, either on a dyno or with a mixture display meter that hooks into the oxy sensor. If you're in a capitol city see if you can borrow a mixture meter for an afternoon off someone. If it is lean and no leaks, then chase the sensors. Water temp, air temp, injector cycle, whatever else it reads before deciding how much fuel to inject. Also check the fuel rail pressure, as the cycle time might be OK but the fuel volume low if the pressure isn't there. Anyway, first is mixture. Did it do this before you connected the thermistor?? Maybe it was running a cold start cycle permanently. Quote Link to comment Share on other sites More sharing options...
oldeskewltoy Posted January 27, 2015 Report Share Posted January 27, 2015 What management are you running?? There are some in the USA who have experienced a similar type problem when running a 100kw(smallport right?), on the earlier type TVIS (largeport) management. Quote Link to comment Share on other sites More sharing options...
ke70dave Posted January 27, 2015 Report Share Posted January 27, 2015 Hows your fuel pump? Quote Link to comment Share on other sites More sharing options...
85wrx Posted January 27, 2015 Author Report Share Posted January 27, 2015 (edited) I have double checked for vacuum leaks. Fitted new hoses, sealed around throttle cable bracket where they have put 2 bolts thru from the inside of the manifold to hold it. Only thing I haven't checked is if there is an inlet manifold gasket fitted. When I got it, I don't remember it having this issue. Air temp sensor wasn't connected either. Thermistor might have just been a broken wire on the plug from memory. I am positive that the spare computer I got from a wrecked 1992 SX Corolla with same motor part numbers of computers are both the same 89661-12420. The fuel pump is brand new. Redone that system a well. The old setup was really dodgy. I have also replaced the distributor cap and rotor button. Not sure if I am going to be able to check fuel pressure or air fuel mixture. Could it also possibly be the oxygen sensor? Edited January 28, 2015 by 85wrx Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted January 28, 2015 Report Share Posted January 28, 2015 Unlikely... You could disconnect it and try. I hooked a mixture display up to our SR20 recently and found the oxy sensor wasn't working at all. A new sensor read correctly but didn't change the performance of the motor in any noticeable way. Check around the inlet gasket for leaks with an aerosol of 'engine start' or some oil, or listen with a plastic hose in one ear. That would be important to sort out, but a pain if you had to take it off to check and re-seal. A dyno run might be the only way to check the mixture under load. Quote Link to comment Share on other sites More sharing options...
ke70dave Posted January 28, 2015 Report Share Posted January 28, 2015 (edited) Got the check engine light hooked up? Might be time to look for codes. Unplug the 02 sensor and see if it helps. I ran a smallport with no 02 sensor for years and it was happy enough. A stuffed one pligged in might cause issues. Edited January 28, 2015 by ke70dave Quote Link to comment Share on other sites More sharing options...
85wrx Posted January 28, 2015 Author Report Share Posted January 28, 2015 Might have to try that around the manifold. Got a check engine light hooked up. Only code it is throwing is for the vehicle speed sensor 42. Unsure whether that would be causing it?? Is there any way to connect a vehicle speed sensor into an AE71?? Quote Link to comment Share on other sites More sharing options...
B.L.Z.BUB Posted January 28, 2015 Report Share Posted January 28, 2015 The speed sensor code won't make your car run bad or put it into limp mode. It'll just throw a code. Quote Link to comment Share on other sites More sharing options...
snot35 Posted January 28, 2015 Report Share Posted January 28, 2015 I was going to say O2 sensor as well, sounds like things are occurring closed loop ranges. Does it feel fine under wide open throttle? Regarding the speed sensor, the speedo in the dash cluster has an output that plugs into the ECU to provide the speed. You'd have to transplant a speedo from a twin cam corolla or work out some other way of generating a signal. I'm pretty sure many people have run without speed input to the ECU without any problems. Quote Link to comment Share on other sites More sharing options...
ke70dave Posted January 28, 2015 Report Share Posted January 28, 2015 Have you ever had it running properly? Getting the Injectors cleaned might help. Youve basically replaced everything else:s Quote Link to comment Share on other sites More sharing options...
lexsmaz Posted January 28, 2015 Report Share Posted January 28, 2015 (edited) It does sound like its running lean, strange though that it comes good up top though as if it's running lean it should get worse the harder you push it ... Also i haven't done it for many years now but the last engine coolant temp sensor I disconnected with the motor running it went full rich & stalled & you said it seemed fine, makes you wonder if its getting an accurate signal ?? the one I tested wasn't a 4AGE though .. Edited January 28, 2015 by lexsmaz Quote Link to comment Share on other sites More sharing options...
85wrx Posted January 28, 2015 Author Report Share Posted January 28, 2015 (edited) It feels fine once it gets past the flat spot. If you give it a boot full thru all gears no hesitation, no lurching, no flat spot. It is only when you go gentle on the throttle an ease the acceleration. Only had it 5 months. Wasn't running 100% perfect when I got it. Wanted a hobby car. Trying to sort out all the little things I didn't like about it. Retuning it to a reliable car. I have not had it running perfectly since I purchased it. Edited January 28, 2015 by 85wrx Quote Link to comment Share on other sites More sharing options...
ke70dave Posted January 28, 2015 Report Share Posted January 28, 2015 (edited) Id get the injectors tested and cleaned if you don't knoe their history, a mobile guy shouldnt charge you more than $140ish. My 4age was spluttering amd carrying on and it was just dirty injectors. Perhaos in your case the injectors work ok with long opening duration but light duties they start to spray funny and don't deliver fuel properly? Just guessing really..... Edited January 28, 2015 by ke70dave Quote Link to comment Share on other sites More sharing options...
Samwich Posted January 28, 2015 Report Share Posted January 28, 2015 Similar issue happened with my SR. Ending up giving it a hiding cause i was pissed at it. 14psi maxing out gears, Been fine ever since (Could have had water in my fuel lines... have 0 idea haha) Quote Link to comment Share on other sites More sharing options...
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