1994 Mark viii idle issue

BigUziLinc

LVC Member
Joined
Dec 28, 2023
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Location
Vancouver, B.C., Canada
Hi everyone,

I have an issue with my mark viii where the car idles very rough at 500rpm where the whole car sways side to side and has a loping idle that goes up and down ~50rpm. Also on the first start the car will rev up to 2k rpm and then stall, the second start it will struggle but will manage to keep the car running until it warms up to operating temp and then will stall. Once I start it again and leave it by itself it’ll idle with the above mentioned issue.

Once the car is warm and I go WOT it rev hangs ~1000rpm and then it starts to idle normally and very smoothly at ~650rpm but after a minute there’s a thud and the idle drops to 500rpm and becomes very rough with the whole loping issue again.

This problem only started happening after having changed the IAC, maf, tps sensor, spark plugs, wires and coils with new ones. Prior to changing the parts the car would idle fine but a bit higher at around 650 rpm but would have a jerk of rpm and if I wasn’t pressing the brakes hard enough nudge the car forwards while idling at traffic lights.

I have replaced the spark plugs with new warranty ones and they are gapped to the factory spec, have thrusted with old coils and wires and the issue persists. I get no check engine lights but using a obd 1 scanner I get DTC that say lean mixture.

Sorry for the long write up and any help would be appreciated to help find what’s going on.
 

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