I have an 89 GXL converted to Turbo. Engine rebuilt by me about 6000 miles ago. Running Supra fuel pump, ID 720 secondary injectors, front mount intercooler, and medium street port. Also using a Power FC. I have tried running stock ECU and AMF, but still has same problems.

Onto the problems. A few months ago started having some sporadic conditions I thought was ignition related. The car will randomly stutter, loose power, vacuum goes to near zero and will barely build boost. It almost feels like it is running on one rotor when it acts up. AFRs go very rich, about 10:1 according to my LC1. The plugs will foul out and it is very difficult to start after this happens. Haven't had a chance to check timing when this happens. The couple times I have been at a shop and had the computer hooked up, nothing goes wrong. Power is great when this isn't happening.

I have checked fuel pressure, holds steady at about 30-32. Checked voltage to leading coil when this happens and voltage is always 13.5 or greater. I have changed plugs and leading and trailing coils to no avail. Not sure where to go from here. Any ideas would be appreciated.

 

You may be losing power to one of your coils. Get a bed of nails lead for your multimeter and hook it up to the +12v connection on the coil packs. Then drive the car while watching that meter and see if you're losing something somewhere. It'll take a few drives, but that's what I'd do.

If you have a datalogging feature or even a streaming display, you can see if you're losing a signal from something, be it your crank signal (not likely based on your symptoms, but possible), coolant temp, etc. I'm not too familiar with the Power FC, but I can connect a laptop to my Megasquirt to watch all the parameters in real time, or datalog.

 

Yeah, I have checked the leading coil, need to verify what wire is the hot wire for the trailing. I am assuming there is only one for the pair, but need to verify. I do have the datalogit, but am waiting for an adapter for my laptop. I am not sure if I can check the crank angle sensor or not. I will post that up in the Power FC forum.

 

If your AFR's go super rich, it's probably not your crank signal dying out. Remember, it drives the injectors too.

 

angle sensor also controls spark advance in the control unit it should check out between 110 - 210 on your meter at all 4 pins in the angle sensor connector ..make sure all the pins are connecting proper and not pushed inside when I pulled my engine one pin showed green corrosion ...just a thought .

 

I will check the Crank Angle Sensor. Are they the same for turbo/non-turbo and s4/s5?

 

I think so but not sure .. check the pins at the coil plugs also make sure they are not pushed back or corroded ..also I didn't mean the AS controls the advance as much as if the AS isn't working proper neither will your advance .This ignition stuff kills me let us know what you find out .

 

try posting up on the Power FC section of this Forum.(under engine management)
I am wondering if 30 psi is too low for your Fuel.I am running 42 with an Rtek.

 

well it depends on where he is getting the number from. but i dont think he is having an issue here/ after lookin in the FSM that number seems fine

 

It seems pretty consistent with the pressure, and it was close enough to the FSM spec that I wasn't worried about it. I am going to try and catch the fuel pressure when it acts up and see if it is changing. Taken it into the shop twice and had fuel pressure, laptop, and timing light hooked up for an 1-2 hours each time and it didn't act up the whole time. As soon as I left it was acting up 5 minutes later.

 

You need a new license plate. EVLRX7

 

I seriously doubt it's got anything to with fuel pressure. If his AFR's are going really rich, it's probably ignition dropping out. CAS doesn't really drive anything, it's just a sensor. The ecu takes the input and modifies it based on the other parameters (coolant temp, MAP, air flow, intake temperature, etc). So it has to be either in the wiring, ECU, or a sensor. And you've already eliminated the ECU by swapping it out and experiencing the same issues. My money's on wiring.

Come to think of it, it is possible to have base engine problems too. Check compression, and try steaming the internals. I know it's been recently rebuilt, but if a seal is getting stuck from running too rich and getting held up by carbon, you'll experience these same problems.

 

Not quite sure how to steam internals. And I still have to check the voltage to the secondary coils. Is there a way to check that the ground is getting through good?

 

Suck water in a vacuum port once the engine's fully warmed up. Water turns to steam, steam removes the carbon. If there is any, that is.

Check ground the same way you check for power. Use a multimeter, red goes on a good known power source, black goes to the ground wire in question.

 

Given that the ground for the coils will be pulsing (my assumption), will a multimeter pick this up easily?

 

A DVOM with frequency, but the only real way to properly test it is to use an oscilloscope. Unfortunately they're pricey, and not many have one.

Here's what you'll be doing.

Take a look at the diagram. It's the 1989 GXL engine control diagram. At the top are the coils. The black/yellow wires are power. Use a bed of nails lead to tap into it (red lead) and clamp a black lead to ground. Drive around until the condition happens. When it does, see if the voltage goes away. Check it at EACH coil, and check it on the coil side of the connector.

The green/yellow on the leading is the pulsed ground. That's where you'll connect one lead to power, the other to that wire, set the voltmeter to freq. and drive it, see if freq. drops out when the condition exists. Do the same for the other coil. I'll have to figure out which wire's which, I'm trying to find an ECU pinout.

 

Finally got a log when the car messed up. Noticed the water temp reading went from 49c, to 175c, to -45c. When the water temp went back to a normal 52c the timing went back to normal as well. Could this be a bad temp sensor or more likely wiring? Could this be the cause of my problems? Just a change in timing due to the computer seeing the drastic temp changes?

 

Probably wiring. The pins in the coolant temp sensor like to pull out and it begins to make intermittent contact.

 

When the pins pull out, do they pull out of the sensor itself or the wiring harness? Does this require replacement of the sensor? I am trying to find how to test the sensor now in the FSM.

 

They pull out of the wiring. The sensor is just a thermistor, so it'll usually fail open, not intermittently. When you unplug the connector, peel back the insulation a little from the back and see if the pins are coming out.