New Spark Plugs, now check engine light!

[turbo55]

So I recently got my first E30, an 87 325is. Engine was running alright without issues (other than a pretty loud ticking, even after a valve adjustment). For good measure, I changed the plugs (all 6) to ZGR5A NGKs. The NGK website said they're a 0.028" gap, but when I got them they were more like 0.031", so I gapped them to the 0.028" (also the owner's manual says 0.027 + 004").

The problem is, now when I fire the engine up I get a check engine light on. It seems to be idling fine but if I give it some revs, it revs up fine but then it shudders for a sec after when it comes back to idle.

I poked around online a bit and it seems that it could be dirty/corroded contacts between the plugs and the plug wires, so I was going to try to clean the wire contacts a bit and maybe put a little Permatex dielectric grease on there. But I'm also wondering if the symptoms I'm having could have to do with the gaps at all?

[jlevie]

Your problems have nothing to do with the plug gap or ignition system. The first suspects would be intake leaks and/or an aged/bad O2 sensor (replacement interval is every 100k.

[3vilE30]

Ummm if I recall 87 and older didn't have a CEL, just the check light in the middle. Have you tried tapping the breaks anything on the overhead check panel?

[turbo55]

You're right, I meant the central CHECK light in the middle. No I forgot to look at the overhead panel, still new to e30s and forget it's there. Will check it out next time I turn it on, doing tie rods now so I'm waiting to finish those first.

Yeah it does kind of sound like a sensor thing but I just know that before spark plug change, good. After spark plug change, bad. Would have to be quite a coincidence...

[anokES]

could be because of the valve adjustment. Did you replace your valve gasket? You could have a leak there.

[turbo55]

Yes I replaced it with a Victor Reinz one, the old one was leaking like a sieve, the PO (or the PO before that) had pinched a piece of conduit under the cover which didn't exactly make for the best seal.
Although it did take me two attempts to get the valve cove back on cuz I snapped one of the studs when torquing it down (to spec) so I had to take it off the next day to put a new stud in. I did run the car after the valve adjustment briefly and there were no issues then. If I get to troubleshooting that tonight I'll have more info to report back...

[turbo55]

Alright finally got some dielectric grease yesterday, put that on the spark plug wires, no better. I might try to back to the 'last known good configuration' and put the old ones back in, if it's still happening maybe there's an air leak so maybe I'll change the VC gasket again. Also I'm thinking of checking the resistance of the spark plug wires to see if any are bad?

[Cephas]

What light is on in the check panel? It is located above your head in the center of the headliner by the windshield.

[MR 325]

Ummm if I recall 87 and older didn't have a CEL, just the check light in the middle. Have you tried tapping the breaks anything on the overhead check panel?

87 325i/iS cars use Motronic 1.1 and DO have a check engine light.

[MR 325]

Alright finally got some dielectric grease yesterday, put that on the spark plug wires, no better. I might try to back to the 'last known good configuration' and put the old ones back in, if it's still happening maybe there's an air leak so maybe I'll change the VC gasket again. Also I'm thinking of checking the resistance of the spark plug wires to see if any are bad?

Just to double check, did you unscrew and remove the tips from the new spark plugs before installing them?

[turbo55]

Yes, it's the central CHECK light that's on. Yes, I did unscrew the tips, after spending 5 minutes trying to get the #1 wire to go on.
I didn't have any time this weekend to work on the car so nothing new. I will check the overhead panel next time I work on this issue. Then I'll probably take out just the #1 plug and put the old one back just in case I was too rough with it and something inside is busted. Then I'll put all the old ones back in.
Someone also told me to not overlook the wires as they seriously degrade over time... I'm pretty sure mine are stock.

[agent]

If the "check" light between your speedometer and tachometer is flashing, it is not the same as a "check engine" light. The "check" light means "check the overhead panel" as there will be an LED illuminated there alerting you to the issue. It could be as simple as low washer fluid.

[turbo55]

You guys were right, the 'brake light' light is on on the overhead. I guess the check light has nothing to do with the plugs then. But the low idle for a sec after reving is still there. I got some more troubleshooting to do...