After Plenum/Knock Sensor Job...

[Meaux]

Gettin a code 21, 94Q45, 80K.

Well the slight knock at idle is gone, but I just dosen't feel right. Now I get a code 21, ignition circuit. Seems like all 8 ain't showin up.....This is what I did this AM.......

Got around to take a test drive this morning. 94Q, 80K.

Started up, idle at 1200, cool.

Turn on A/C, went down the street @25mph.

Stopped, took a left onto a 55mph zone, car now felt like it was running on 4 cylinders, (vibrating like on square wheels) this continued for about a mile.

Stopped at the Bank for 10minutes, back in the car, startup fine. once back on the 55mph road, floored it @ 30mph, downshifted fine, upshifted fine till I lifted @ 90mph.

Got home, run diagnostic 2, got code 21...I guess that is because of the rough running...

Cleared the code, ran at 2000rpm...no load.

Now I get 5-5 code.

If I have a bad power transistor/coil whatever, wouldn't it stay bad?

Sounds like a bad connection to me. I pulled all 4 of the connections on the valve covers, shot contact cleaner in the plug connectors.

Make sense?

I had this rough running before I did the KS, but it only lasted about 3 minutes...and would go away for months, then come back...

What have ya'll done to correct a code 21?

[maxnix]

Gettin a code 21, 94Q45, 80K.

I pulled all 4 of the connections on the valve covers, shot contact cleaner in the plug connectors.

Make sense?

If you follow with high temperature dielectric grease.

Try posting in just the Mechanic's Forum as this is a mechanical problem.

[DAEDALUS]

If I have a bad power transistor/coil whatever, wouldn't it stay bad?

Sounds like a bad connection to me. I pulled all 4 of the connections on the valve covers, shot contact cleaner in the plug connectors.

Make sense?

Don't know about the transistors, but a bad coil can go bad gradually and intermittently. If you do have 2 or more cylinders going out at the same time, then most likely it's not a coil. Transistor is a possibility, though this would be the first time I've heard about it. I would doublecheck connections as you did. Hard to troubleshoot like that. This is a case where, given how cheap the parts can be, and how easy they are to swap, I'd attempt a swap on the transistors and go from there. But only after figuring out which one it was. A timing light would help--it's either bank 1 or it isn't. Or disconnect one of the front 2 injectors to see which one doesn't have an effect.

[Meaux]

Well, the heck with it...I can't get it to mess up now, so I'm gonna button this up.

It upshifts/downshifts normal, stumble is gone, it just don't sound right. At the tailpipe it has a slight "poop" to it.

Hell, I dropped a 10mm wrench down behind the IAC valve and can't get it out with a magnet...can't even see it...PITA cause I wasn't even using it.

As soon as I remount the ECM, and install the deco covers, it'll mess up again...but at least I'll know what to look at...

Thanks.....

[Meaux]

Well, as luck would have it, the rough running came back.

I unplugged the #1 injector, and it ran REALLY rough, then I unplugged #2, and that closley matches the condition, so I'm assuming my ignition problem is on the RH Passenger side...


Modified by Meaux at 4:33 PM 9/13/2005

[DAEDALUS]

? This is the Online Mechanic forum. If spark is what's missing then you need to get this fixed asap. Washing the oil off the cylinder walls with unburnt fuel will kill those cylinders, plus the fuel in the oil will wear on the journals. Have you done the basic continuity test on the transistor?

[Meaux]

The line: I posted this onthe "mechanic Forum" also, but seems that Forum isn't read as much......."

Well it is now, I got the forums confused...

Oh yes, I agree totally...I wish it would do it more often, then I'd have better luck finding the problem. Sometimes it will go for months without showing up...It only does for a short while...

By "basic continuity test on the transistor?", are you referring to checking the plugs on the transistor, and the wires back to the ECM? If there's a way to check the transistor itself, I haven't seen it in the FSM...Then again, I haven't read the whold thing...:-) It would be nice to check the transistor itself without having to wait for the symptom.

I reckon I better start printing pages out of the FSM and start from square one....

[DAEDALUS]

There are a couple tests given in the manual. One is on the component itself, testing continuity with regard to polarity. The other is to test on the vehicle (ignition circuit), looking for continuity through the harnesses. I fear that neither one will be very conclusive since an intermittent problem is more likely to pass under the negligible currents of the tester. Like a bad coil, consider a part swap here to be a cheaper and more certain test, as long as you know the part is good.Again, you're sure this is affecting more than one cylinder? Makes a huge difference in the order of suspects.

[Meaux]

DAE asks, "Again, you're sure this is affecting more than one cylinder? "

Hummm, Now that you've asked that question, I'm assuming that if the transistor is bad, then more than one cylinder wouldn't be getting spark? (If not all 4 on that side) Half of a bad transistor wouldn't work,would it?

So, if it is only one cylinder, the transistor is most likely OK, and the individual coil is at fault. (Assuming the wiring and connectors check out fine)

I can't tell if it's just one or two.

Would a spark plug show a clue? (Appearance) I'm guessin that a spark plug wouldn't throw a code 21. Has to be wiring, or bad coil, unless a transistor can be half bad...

Thanks....

[DAEDALUS]

If it's only one cylinder then you need to look at the injector (ohm test) or coil. A bad transistor could affect a single cylinder, but go with the odds. Have yet to hear of a transistor failing.

[Meaux]

I did an ohm test on the injectors when it was in pieces and they all showed ok. (12)

When I unplugged the 2 injectors, I got injector code 51....

I reckon I'll start on the wiring checks tomorrow. The problem won't show up anymore...Geeze.... If I didn't like the car so much, I'd dump it...:-)

Thanks.....

[DAEDALUS]

A power balance test would tell you for certain if it's one cylinder or more.

[Meaux]

Well I went this morning and couldn't get the problem to show up, so I thought before I get into ohming all these dang wires, I'll give it the old wiggle test.

I wiggled everything under the hood. No cigar. When I wiggled the harness to the ECM the problem came back. Checked the code and got a 21. Took the harness off and found a crack in the female side near the bolt. Superglued the crack shut, reinstalled and wiggle wiggle, the problem didn't come back. Got the 5-5 code and put the ECM back in it's place. Been fine for the last few hours.

I do hear an exhaust leak right under the drivers door, just to make my day...

Puttin on the ornament covers, and drive it...If I don't have a problem in the next month...I reckon that was it...

Thanks......

[DAEDALUS]

That's a first! Maybe a bit too much torque on it at some point in time.

[Meaux]

You ain't kidding. I think you have to "try" to do that. Unreal amount.

Funny though, it didn't seem that tight when I removed it.......

Now I have to find this pootin exhaust leak...

[RobertsnewQ]

Those connectors are fussy, but that's the first broken one I've heard of. Probably someone got it on crooked and then forced it with the bolt.

[maxnix]

Now I have to find this pootin exhaust leak...

Had one of those where the exhaust was perforated right before and after the catalytic converter so I could hear the exhaust valves close (click....click....click).

Couple of spot welds and for $10 good as new.