DIS or coil pack?

[pete315]

was driving my 93 ATX. has been running great. not a sputter from start to 7 grand. 30,000 on plugs/wires. new timing belt/CPS/cam sensor about 6 months ago. was driving today. came to a red light with car running great. when I went to take off, it was stumbling all over. had a bad miss. feels like 2 cylinders went out completely. It has to be the coil pack or DIS module. how do you know which one it is? I have no check engine light ( yes, the light does work). if it's the coil which I am leaning towards, does the unit come out in one piece or is there separate packs for each or a pair of cylinders?

 

[pete315]

well I looked at the coil. I now see it's one unit. I also see that after doing a search, it might be the DIS module. would a bad DIS module **** 2 cylinders? DIS module is at least double the price of the coil pack. I checked the ground wire of the back tube of the intake and it's there and looks good.

 

[rubydist]

You have a number of possibilities with the symptoms you describe. It could be the dis or coil, it could be bad wires or plugs, it could be a bad tps and/or mafs. All of those are likely candidates.

Pull at least the front 3 plug wires off and see if there is oil in the plug wells. That will short out plugs and make it run crappy - either all the time or under load.

If you have a multimeter, put it on the tps and measure the resistance as you move the throttle from closed to open. The resistance should track pretty linear with motion and cannot have any 'hitch' in the value.

Normally, a bad coil pack will throw the cel. Most of the time, a bad dis will throw the cel. So, until you get the light on, look at the other items that were mentioned first. Of course, when the cel comes on, pull the codes and see what its complaining about.

 

[luigisho]

well I looked at the coil. I now see it's one unit. I also see that after doing a search, it might be the DIS module. would a bad DIS module **** 2 cylinders? DIS module is at least double the price of the coil pack. I checked the ground wire of the back tube of the intake and it's there and looks good.

The coil pack has 3 internal coils each of which fire 2 cylinders. I would echo looking for oil and fouled wires and plugs first. If you're not sure how to trouble shoot there are a few members in your area and you could always swap in know working parts before you commit to a purchase. You could always have a tech trouble shoot for a fee.

 

[Lorenr]

Missfire starting from a stop

Every time I hear about this, I immediately think about the idle air bypass valve. I think that they rarely throw a code. It is cheap and easy to remove an clean it. Cheap easy things are best to start with.

:wave:

 

[hawkeye18]

The idle air bypass valve only affects engine operation at idle. If the engine is acting fine during idle, the IAC is not to blame.

Having one wire short to ground through oil will take out 2 cylinders; that's just how the system works. So will losing a coil on either the coil pack or the DIS, but those two will almost always set off the light, as they have a dedicated diagnostic monitor.

I will reiterate that 90% of engine-stumbling-with-load issues are caused by either plugs, wires, or both. Check those first.

 

[93rev2sev]

if money is really tight, reach out to some local members. maybe someone can bring you a known good dis or coil pack to test with. I think that those are both possible culprits.

Is this an intermittant problem or has it become constant?

 

[pete315]

I did plugs/wires/valve covers and plug seals 30K ago. I wanted to double check if oil got into the plugs wells. I pulled all 3 front plug wires off, completely dry inside. I'm sure backs are the same. all 6 plugs wires are pushed on tight. it is a constant now. like some flipped a switch. running great all day,stopped at a light with a smooth idle, when to take off and I felt it right away. I was hoping to get the CEL but it did not come on which I thought was weird. 99.9 % sure it's either the DIS or coil pack. I hope I didn't foul up those 2 plugs that bad. I had to drive home about 4 miles running on 4 cylinders. hopefully after I fix car and with a couple of wide open throttles it will clear them out.

 

[shotime1994]

Even if there is no cel on you can have codes. I had the same problem and it was my coil

 

[shotyme92]

You can have the DIS checked at the auto parts store to see if its showing anything there. I also had something a little similar happen to me like this recently, ended up being fuel pump was kinda going out.

 

[GreenPlus]

Yep, fuel pump is a possibility, try checking the fuel pressure on the rail. You can also check you spark plug wires with an ohm meter. If i remember correctly normal values are resistance of 10,000 to 15,000 ohms per foot of length. Did you pull out the spark plugs and look at them? Like was stated previously, the coil pack usually sets off codes, but you can check the spark by taking both wires off the same coilpack, running them to spark testers and running the car. Just do the 2 off the same coil at a time. Good luck ~Will

 

[91 SHO Black]

the exact same thing happend to me. while the engine running hit the front of engine side of dis with a test light to check for signal. that will tell youif its firing. chances are that your dis is bad. and there not cheap. when mine went out it was and on and off problem sometimes it would run great like nothing was wrong and then in a flash with no worning or reason it would fall on its face. if you have those same simptoms then i can almost promise that its your DIS.

 

[91 SHO Black]

i tested everything and labbored over it for 2 weeks before i bought a DIS for like 300 bucks. if you have any other questions i'd be glad to tell ya what ever i can. that one can be a pain to diag. but testing the dis directly was the way i finally got it. don't worry your test light will not pull to much current.

 

[Eric VerValin]

He's got a DIS and coil in the mail... I'm curious to hear which it was..

 

[91 SHO Black]

its the DIS, i got 5.00 on it

 

[pete315]

well, I first put he used DIS module on and I still got it running rough. so I changed the coil pack, same thing. I was removing one wire at a time from the coil pack. each time I remove a wire, I saw a good spark jumping from the coil pack to the disconnected wire. the rpm's dropped very noticeably when I removed 4 out of the 6 wires. the right upper and right middle wire removed did not change rpm's much. I guess I'll pull those plugs and take a look. I guess I'll have to remove the intake to get out those plugs. is there a short cut I can take instead of removing entire intake?

 

[93rev2sev]

yeah there's a shortcut...don't remove the intake.

Remove the little knick knacks on the firewall, the little black canister on the back of the intake (12mm) and the rear drivers intake support bracket.

Plenty of room.

 

[pete315]

well, I just removed the intake. I pulled out the passenger back plug, found a couple of drops of oil on my socket. when I pulled wire off middle back plug, the boot was covered in oil. drivers back was dry. for some reason the middle plug seal was letting oil in. the plug hole was not filled with oil like the last time I did them, but I guess it was just enough oil to short out that plug. I know, I should have listened to all the post that said it's probably a bad plug oil seal or bad wire. the front bank is totally dry. I will change all the plugs and change that rear valve cover gasket and plug seals. what do you think would cause that one oil seal to leak? do you think if I wipe down the ignition wire real well it will be good? I hate to invest in another set of wires for this car. I was hoping to reuse the valve cover gasket and just replace the oil seals. I think I will also reuse the intake gaskets.

 

[pete315]

I just checked the valve cover gasket, the seals still looks pliable and intact. From underneath the valve over, I can see that oil was getting into the middle and right inside plug wells. the drivers side is still clean and was dry.

 

[Eric VerValin]

Well.... that kinda sucks to hear... I would imagine if you sprayed brake cleaner or ether up in there... using that straw... you could blow that old crap outta there... but it won't be "perfect" and it wouldn't hurt to try..

And if that one was the only one leaking... are you sure the bolts had bottomed out against the "stop" ? The spec's are pretty low, not really sure what they are, I just kinda do mine by feel... it will definately hit a point where it gets hard.. thats where I stop..




Another thing you might try.... I think those are some sort of rubber... and if you soak rubber in gasoline... they tend to swell.. Try reusing a gas tank seal and you'll know what I'm talking about.. This is just a theory however... If you clean it up, it'll at least run ok for a little while until you get some new seals... in the meantime wait it out and see what happens, maybe that VC just wasn't tight enough...