Okay, so here is the latest update: The car (86 IROC 305 TPI auto) has been acting really goofy. The car was missing at idle, off idle and at low speeds (35-45) cruising down the freeway it ran like a dream, smooth as glass. When you stand on it from 70 it pulls smooth, but it gains RPM pretty slow and doesn't pull really hard. I was getting code 13, 22, 24, 32, 36, 46 (I think that was all of them). The plugs looked good on all of the cylinders except #3 which was black (carbon & fuel, not oil) and every cyl had 210 psi and very slow leakdown. There were a lot of issues, so I pulled everything down to the lifter valley. I resealed the intake, changed the egr, resealed all of the runners and plenum, reset the base timing, changed the o2 sensor, all new plugs, new wires (new hall-effect, module, cap and rotor about a year ago), new IAC, and cleaned the throttle body. I did some other things too, but they wouldn't effect performance (belts, hoses, etc). I put it all back together and it runs, but I still have the same problem but it is also REALLY rich now. All of the codes are gone except 36 (maf burnoff) but I haven't had a chance to drive it yet to see if the other codes resurface. To set the IAC I just put it in, started the car let it get to operating temp and shut it off (that is what the book said) I set the TPS to .55 volts and it dropped to .53 with the car running. I tapped into the TPS to read voltage and on one of the wires it read 4.39 volts (I think at about 1000-1500 RPM) and like 4.98 if I tapped into another set of the three wires. Am I doing this right? I checked the voltage and settings about three more times and nothing moved around, so my settings are holding. In playing with it last night we swapped in a module that we thought was good, but the car actually ran a little worse. I also plan on checking spark a little better, but I hooked the timing light to the plug wires and everything seemed fine on the pass side (2,4,6 & 8 cyls) with a nice consistent repetitive flash, but I tried two of the wires on the drivers side (3 and 7) the flash of the light was a bit odd, it would be like flash, flash, flash, pause, flash, pause, flash, flash, pause, flash, pause, flash, flash, flash. Very erratic! What could cause this? The super rich condition makes me think injectors, but the erratic flashing makes me think ignition. Intermittant ignition would also cause the rich smell as when the cylinder finally did fire it had 2-3 times the fuel in it that it should. Does this sound right? what could cause the erratic ignition pattern though? With new wires and plugs and similar behaviors before puting them on, it makes me hesitant to think it could be plugs or wires. Could it be the module? what about cap and rotor? If it was either of these though wouldn't there be an issue on every cylinder and not just a few on the same bank of cylinders? Could it be the ECM? If it was a bad ECM, would it still be able to recognize that the issues that threw the codes earlier had been fixed (remember there were 6 codes before the repairs and only one after)? I love driving the car when it runs right, but I am about to drop a match in the tank and walk away. Please help, I am flat out of ideas. Thanks for taking the time to read my ramblings and take a few moments to respond!

 

Since you replaced the plugs and wires, I'd say to finish the tune-up with a cap and rotor. Inspect/replace the fuel filter. Check fuel press and fuel press decay rate. Sounds like you may have a leaking inj. The fuel press decay rate test will check that.

 

Thanks for the info. How do I go about checking the fuel pressure decay rate? I have a hi press gauge and show 46 or 48 psi as I recall, how will I know what the decay rate is? How will I know how it compares to acceptable standards? Thanks in advance for any info you can provide.

 

It should hold pressure for AT LEAST 10 minutes (a couple psi drop is normal), If it holds the first 10 minutes, remove the pump relay and turn the car off, come back in 30 minutes and check the pressure, then check it again after an hour. Is it still showing pressure? Should be in the 20's for a nice tight system.
Don't forget to hook the relay back up after done testing.

 

Which one is the fuel pump relay on an 86 IROC? What I am thinking is that the thing is just dumping fuel as the car is running. Will the pressure bleeding off too fast indicate bad injectors? Bottom line, I need a surefire way to diagnose the problem. At $180 for a MAF, $200-$300 for injectors, $100 for an ECM, every part is way too expensive to just throw at the car in an attempt to fix the problem. I have no problem throwing another $100-$200 at the car, but I want that to fix the problem. I just don't want to spend another $600 on parts that don't fix teh problem and cannot be returned to the parts store. Do you guys know of any test methods that can be used to verify the function of these parts in such a way that they can be completely ruled out as a source of the problem? Thanks again for any help you can offer!

 

couple more things, do I leave the ignition switch on while testing for fuel pressure drop? I wouldn't think so as the pump would just recharge the system. Your thoughts?

Also, in my first post, I mentioned an intermittant flashing of the timing light on known problem cylinders. The code that the system threw was a 36 which is traditionally listed as the maf burnoff. I saw on the code listing on this site that it could also be a "fault in direct ignition system" or "missing pulses in Electronic Spark Timing signal". First question, what is the direct ignition system, is this the coil, module, hall effect, etc? Secondly, what is the Electronic Spark Timing signal, is this a signal from the hall effect or from the electronic spark control module mounted on the fire wall? This kind of sounds as if it might be the heart of the problem, any ideas on how to test these two systems? Of course the possible source of the code is listed, but not how to fix the problem once it shows up. Any ideas? Thanks again!!!

 

Since you said you are having a problem with intermittent spark loss I would first replace the cap and rotor, module and coil. Not trying to just replace parts but since the spark is a documented problem you should go for that first. -John

 

First, the pump won't recharge the fuel system unless the key has been off for 10 seconds or more. Prime the pump and check the pressure (the part about disconnecting the relay you can ignore if you don't have an electrical fuel pressure guage) watch the pressure for 10 minutes, if it holds come back in 30 minutes and check it again, if it is good check it in another 30 minutes. If it is showng pressure in the teens-20's after an hour you have a good tight system. If it dumps pressure within the first 10 minutes you'll need to isolate which component is leaking (injectors, regulator, pump/pulsator).

For the code 36, you don't have a "direct ignition system"
for your application it is "MAF Burn off function fault". To troubleshoot this I would get a new relay and replace it. Even if it doesn't fix the problem it is a good idea to have a spare relay for the MAF system (power and burnoff's are interchangeable). If it doesn't fix the problem you'll need to do come wire chasing (checking voltages on MAF wiring)