Missing and running rough.

[PhankinsTT]

I have a 91 Twin Turbo that is missing. I have the problem chased down to I believe what is the Number 5 spark plug in the car. The coil pack was replaced but it did not stop the car from missing. I can have the coil pack completely unplugged on that spark plug and it makes no difference as to how the car runs, even when I plug the pack back in. I changed the coil pack out with the Number 2 pack and it works on that Number 2 plug. The coil pack is getting fire because I used a test light to see if it was getting juice. What would be the next thing that I could look at to find the cause of this problem.

Thanks.

[evildky]

you are off to a good start, you ahve verified that you have a non functioning cylinder, now we find otu why, you swapped the COP around so you know it's not the problem, you can swap the spark plug to see if it's the plug, you can lay the cop and plug on top of the manifold and crank the engine to see is it spaks (pull the fuel pump fuse first), if no spark then it's likely the PTU, if you ahve spark then fuel is the liely issue, ohm the ijector, shoudl be 12-14 ohms

[PhankinsTT]

I have done some searching and found out about a PTU recall that my car is available for. I will be having this done in the next week, but the PTU that is currently in the car is a mitsubishi, which I'm not certain but I believe I read is the replacement for the ones that went bad. Also the spark plug is brand new, I replaced the plugs first as I was hoping that would alleviate the missing. I plan on Ohming the injector tonight when I get home. Do you have any tips on how to get to the injector. Do I just remove the logo plate that sits ontop of the plenum and it should be underneath. Also do you think I would benefit from doing the ECU diagnostic? I've had this car since 96 and kept it all stock. It has set up for about 7 years now. It only has 105k miles on it. Now that I'm no longer in school and have some free time i'm interested in getting it back into good working order. Everything is all stock as well with no aftermarket components besides having K&N air filters that mimic the stock air filters. I'm really glad there is a lot of information about this car on the internet now.
Thanks again for the help.

[CrazedZ32Owner]

if im not mistaken you have to pull the plenum off to get to the injectors

[evildky]

it's never a bad idea to check the ecu for codes

all the ptu's are mitsubishi, they make most electronic's for most cars, if yours has the adapter harness then yours has had th recall cone already, even the new one could have a dead channel

to ohm the injectors you just unplug the electrical connector fomr the injector and measure impeadance across the contacts, you won't need to remove the plenum unless you actually replace an injector

[PhankinsTT]

The ECU code was 55. When I ran the O2 sensor test. On the right side the engine light did not light up until I got it up to about 3k rpm and then dropped it down to 2k again for testing. As for the PTU, the wires that lead to the PTU are very long and have boxes on them where the wires go into one side and come out the other. It does not look like the boxes can be separated. There is some corrosion some of the wires going into one of the boxes, this is also the box that the rubber protector on it has dry rotted off. I could not get to the injector because there is part of what appears to be the fuel line running over the top of it. Since I had not drained my fuel line I didn't feel like unconnecting stuff and getting gas all over the place. Any tips on getting to the #5 injector? Also most all of the hard plastic connectors on my injectors will break if you move them just a little. Will that cause a problem?

Thanks again.

[evildky]

you cna unplug all of the injectors without removing openign any fuel lines, just takes a pick and patience

and it sounds liek you have the replacement PTU, the early one has 4 bolts that go thogh the ptu body, the new style has a metal bracket on the back that the screws go through, honestly it doesn't matter which one you have what matters is if you get spark out the #5 lead, like I said hook up the cop and plug, lay it on the manifold and crank the engine either it sparks or it don't

old style PTU


new style and adapter harness