SiriusBlack

Well, we have eliminated pretty much everything else and are now thinking it is a fuel pressure issue despite the new pump. When we raise the fuel pressure it just barely keeps it from dying when idling alone not in gear. There is probably still gunk and varnish in the lines and the injectors despite my cleaning them. So I plan to pull the injectors again and install new, plus give the lines another cleaning. Now my question is this, I know that injectors from a nissan 280ZX are direct bolt in and have almost double the flow capacity. I planned to run them when I finally switch to a megasquirt ecu for tuning purposes. What I need to know now is if the stock ecu can properly manage the nissan injectors, can I get the nissan ones now and run them without the megasquirt?

@Step-a-toe It has no problem whatsoever revving in P or N, no hesitation or anything. It wanders at idle and dies once put into gear.

We were thinking the same thing, why the hell would my resistances go up with the key on? The factory manual troubleshooting guide said to run these tests with the key on, so I assume the battery and everything else needs to be hooked up.

Following the factory manual troubleshooting we suspect it may be a faulty electrical ground. We tested resistance from one of connectors on the engine side, to body ground and got 0.03 ohms with the key off. Key on that went to 2.00 ohms.

The knock sensor has been disconnected while running before. I did it to test, made no difference. I'd still like to have it working properly, as a knock sensor is good to have on a turbo vehicle. Any idea how I might go about fixing the voltage to it? And of course I still haven't managed to solve the actual running issues, so I'd still like suggestions. Only other thing I really have left to try is replacing the coolant thermosensor connector.

If your talking about the date the car was made, the plate on the door says It was made in late December of 86. I ran more tests today, I replaced the knock sensor plug with one from a donor car. It measured 5 volts with key on engine off. Then when idling at temp, it idled at about 1000 rpm and measured 3 volts at idle, not 1.7. I also got around to checking the coolant thermosensor plug, it is corroded beyond belief and somewhat damaged. I'm going to see if I can replace that as well.

@Ionstorm66 That's what i thought. I had read an article somewhere that had said that was the case. However several people have said otherwise. I can put a link here to the discussion if you like.

I actually have another discussion I'm part of that discusses just that. I don't know if it has a 3 or 4 speed. My shop and owners manuals disagree. I figured I'd count the shifts once it was running right, but i can't get it to do that.

@Rampage that sort of makes sense. Except that doesn't really explain the wandering idle when not in gear. It wanders in idle and P,N occasionally dipping low enough in the wanders to make the engine die.

Mine must be a series one, as it has the white connector with no mate by the coil.

I need a new knock sensor connector for my 87 XT. Does anyone know where i can get a new plug or harness? As far as I know the sensor itself is fine, I just need the connector.

Well, I put the car in D mode today. With the green jumper connected. I followed the instructions in my shop manual step by step. As far as the ECU is concerned the car is fine. The diagnostic covers the TPS so apparently it's fine. I suspect it may be my knock sensor, the wires are very frayed and that sensor controls ignition timing. Anyone know where i can get a new connector or whole new harness? Otherwise I'm still at a loss. Any other suggestions?

On the XT the ECU is mounted in the trunk, just forward of the trunk lid. I will definitely check my TPS, as I recall mine has a rectangle connector, that probably goes into the wiring harness with the 2 large round connectors.

I'll be sure to check that too. Also, it was suggested that I see if I can get the car to tell me what's wrong with the diagnostic codes. It doesn't have the ECS light on the dash lit up, but how do I get the ECU to spit out codes?

My coolant temp sensor appears to be fine. It was the knock sensor that has frayed wires. I replaced the PCV valve and cleaned the egr valve. Double checked my vacuum lines again. Still no luck. I'm going to put a fuel pressure gauge on next and check that. In the meantime any other suggestions would be great.

I am still running tests. I finished cleaning the egr valve, but haven't run it yet. I still need to block the PCV valve and test. The plug that runs to my coolant temperature activated sensor behind the intake manifold has its wires frayed right next to the plug. Does anyone know if I can acquire a new plug for that anywhere? Also will it hurt anything to just delete the egr solenoid valve that's under the intake plenum?

@Step-a-toe in order to be sure I have the right part this time, where is the PCV valve?

It now has a new fuel pump and new damper. I also removed and thoroughly cleaned the injectors.

Warm to operating temp in park. Put foot on brake, no change just wanders the 200rpm like in park. I shift to drive or reverse, engine immediately begins to struggle then dies without throttle added. If I add throttle it runs as it should. If it needs to idle while in gear, like at a stop light the engine struggles then dies.

@Ionstorm66 As far as I can tell, there is no oil in the intake. It does die when warmed up, stays fairly steady in RPMs but struggles and dies the moment you put it in gear.

I am trying to fix an insanely irritating idle problem on my 87 XT. EA82T engine MPFI. Its the one that sat for 17 after my dad fixed the heads and I recently got running. When it idles it wanders by about 200 RPM either way. The main big issue is that when it is in gear (Auto Tranny) it dies if you don't feather the throttle, as you can imagine that would make in town driving a pain. I have checked all the vacuum lines to the best of my knowledge. Scoured the shop manuals i have for the 86 year. Cleaned the idle air screw and the EGR air bypass solenoid as I originally thought it was the IAC valve. I have tested and replaced the vac line to the tranny from the intake manifold. And replaced the vac hoses from the pressure ports on the front of the throttle body. I cleaned the main throttle butterfly as it was suggested that that being dirty could cause this issue. I have triple checked the timing both valve and ignition. The only other thing i can think of it might be is the Aux Air Valve on top of the thermostat housing. I had pulled the electrical plug from it when it was idleing cold and it made no difference. It was my under standing that if you do that when its idling cold there is supposed to be a major idle change? I sort of suspect that it has to be a vac leak somewhere, because the engine gets kinda hot despite an upgraded cooling system and new thermostat. I have been beating my head against the wall about this problem for almost a month. If any of you can help me I would be forever grateful.

I have triple checked my timing, both valve and ignition. I will double check my disty. I also talked to someone that suggested that if my main throttle butterfly is dirty, it can mess with how it closes. I'll try cleaning it thoroughly and see if that helps.

I'm thinking it's most likely the Idle Air Control valve that's causing my problem. Can anyone tell me where it is? I know where the EGR solenoid valve, the Aux air valve on top of the thermostat housing and the fast idle solenoid for the AC is. I just can't seem to find the IAC valve, only post i found that came close to telling me said it was under the power steering resevoir and difficult to get to. However i looked and there doesn't appear to be anything resembling a valve there. Please help, this is driving me nuts! lol

Well, I just got done fiddling with it some more. I tested both of those air valves for leaks and they didn't have any. I tested and replaced the vac line from the manifold to the tranny, with no result. I noticed that if I turned the air valve screw on the turbo side in increments of quarter turns it made small changes to the idle speed. I got it to idle a bit longer when in gear, but the moment I put it in gear the engine struggles for probably 30 seconds then dies without increasing the throttle. I also removed and cleaned the turbo side screw and cleaned it. So once again I'm out of ideas, it's truly baffling. Some research I've done seems to suggest it could be a dirty or faulty IAC valve. Anyone know if that might be my problem? Also I have a general idea, but where is it located? Any other suggestions would be great.

Well, I tested the air valve. Blocked both sides off and ran it, didn't make a lick of difference. I thought that it might have a bad brake booster that was causing a vacuum leak, since the engine seemed to struggle when the brakes are applied. I tested that too though and it passed, not to mention I was fiddling with it today and as long as the car was in park applying the brakes didn't make it die. Putting it in gear (auto transmission) made it die without pressing on the throttle. It also gets kinda hot sometimes despite an upgraded cooling system, which makes me suspect a vacuum leak as well. Now that I eliminated both the booster and the valve I'm really rather stumped. Any help would be greatly appreciated. PS my digital fuel gauge doesn't work either, it says the tank is empty all the time.