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d1staz
3rd June 2013, 05:32 PM
Car - ADM AE86

motor / part in question - 7AGE

problem - Engine running on 3 cylinders

occurs/started when (if applicable)- Driving

personal situation (if applicable)-

Ok, two weeks ago I was driving home and I started to hear a rattle so I pulled over and it seemed to be coming from around the exhaust cam. I kept driving then as I got round the corner from home the engine started vibrating and dropped a cylinder. I suspected bottom end bearing so I drained the oil and cut open the oil filter and found very fine metal. This made me think it was definitely bottom end cause I had my head fully rebuilt by a top mechanic 6 months earlier and had no problems with it. Pulled the sump off and bearings were stuffed. I had trouble finding a decent replacement short motor so I went 7age. Got a very low k's 7afe and got it all together. Fired it up and it has the same problem as before. Cylinder 3 wont fire and there is a rattle in the head. It has good compression in all cylinders and has spark. The rattle sounds like its coming from around the dizzy but I checked it out and it's fine. The valves looked ok when the head was off. I haven't dialed it the cams yet but they are close so I assumed it would run rough until I did. Not sure what else it could be?

Tore
3rd June 2013, 09:37 PM
Are all the injectors working properly?
I had a similar problem with a 20v, with weird rattling @ idle, when I revved it up a little bit the rattling disappeared (Bad alternator charging at idle)

You probably already did this but, doesnt hurt to double check: Check injector resistance (For 20v injectors its around 3.00 ohms) and voltage (12v with ignition on), for good measure check voltage at the battery when the engine is running, from my recollection the injectors need 12,8 volts or you`ll have a problem.

d1staz
4th June 2013, 09:51 AM
Never would have suspected the alternator but that may be it. The rattle goes away when revving. I think I'm running a camry alternator so I will check that out. I'm going over the injectors again today. Thanks for the help Tore.

Tore
4th June 2013, 05:48 PM
Never would have suspected the alternator but that may be it. The rattle goes away when revving. I think I'm running a camry alternator so I will check that out. I'm going over the injectors again today. Thanks for the help Tore.

Np, I started getting the same problem just weeks ago and I know how frustrating it is!

Another thing you could check is battery voltage with engine running, with engine @ idle you should have above 13 volts, if no go try recharging the battery and start the engine again, if it runs good enough then you have a likely culprit.

Problem could also be a low engine idle RPM so that the alternator can not provide the necessary voltage, seeing as the rattling goes away when you rev the engine, or your alternator belt might not be tightened enough.
But then again that is pure speculation on my part.

d1staz
14th June 2013, 11:05 PM
Ok, turns out the rattle was a broken valve spring
28712
Was surprising because there was very little difference in compression on that cylinder. Replaced them all and I still had a voltage drop at full throttle so we added a relay and everything is sweet.

Tore
16th June 2013, 12:26 AM
Ok, turns out the rattle was a broken valve spring
28712
Was surprising because there was very little difference in compression on that cylinder. Replaced them all and I still had a voltage drop at full throttle so we added a relay and everything is sweet.

Auch! Valve spring..
At least you got it fixed, praised be the 4AG-lord, good job!