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Misfire, Rough Idle After Tuneup


glenmore
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Now I've gone and done it. The car (1990, 160m) had been running perfectly but I decided to do some routine maintenance before my daughter took the car up north for a few months. I put in new caps and rotors. The old ones were cracked but worked fine. Put in new plugs (Denso PK20R11 ND), old ones looked just fine. And new wires, the originals were still in there marked 1989. Two vacuum lines broke off this small brass sensor so I had to replace that. In the emissions part of the manual it is referred to as the EVAP BVSV. While I had the coolant drained I finally got around to replacing a leaking heater control valve at the firewall.

I start the car and it sounds fine with the initial warmup RPMs at about 1000. After a minute or two the RPMs drop to 500 as it usually does, but then it starts missing or misfiring, and then the engine stuggles to keep from choking off.

I checked all the wiring layout, made sure all the wires were fully connected. Did not tear all the way back down to check the caps and rotors. Checked all the hoses that had to be reconnected. Earlier I did spritz the air flow sensor with special MAS cleaner. It seems like a vacuum problem.

Any suggestions guys?

Thanks,

glenmore

1990 LS400

1991 300CE

2000 C280

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Now I've gone and done it. The car (1990, 160m) had been running perfectly but I decided to do some routine maintenance before my daughter took the car up north for a few months. I put in new caps and rotors. The old ones were cracked but worked fine. Put in new plugs (Denso PK20R11 ND), old ones looked just fine. And new wires, the originals were still in there marked 1989. Two vacuum lines broke off this small brass sensor so I had to replace that. In the emissions part of the manual it is referred to as the EVAP BVSV. While I had the coolant drained I finally got around to replacing a leaking heater control valve at the firewall.

I start the car and it sounds fine with the initial warmup RPMs at about 1000. After a minute or two the RPMs drop to 500 as it usually does, but then it starts missing or misfiring, and then the engine stuggles to keep from choking off.

I checked all the wiring layout, made sure all the wires were fully connected. Did not tear all the way back down to check the caps and rotors. Checked all the hoses that had to be reconnected. Earlier I did spritz the air flow sensor with special MAS cleaner. It seems like a vacuum problem.

Any suggestions guys?

Thanks,

glenmore

1990 LS400

1991 300CE

2000 C280

My quick guess is either some of the wires or spark plugs are not attached right or even d.o.a try putting the originals back.

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Update. Turns out I probably did all my repairs correctly. What I probably did improperly was spritz the air flow meter with too much MAS cleaner. I took the car in to my indie after another day of rechecking everything that I had done, but by then the car was running near perfect. No stalling or RPM hunting. The RPMs seemed a bit low at 400, IIRC it was usually around 500 at idle before. I spritzed the air meter twice. I think I may have turned it upside down at one point. FWIW the indie said never to spray cleaner in a Japanese air meter. They are different than US type air meters. If you check the cost of a new air meter, you want to be very careful around this part. I just drove the car home on the freeway and gave it a good blast. The RPMs are back to about 500 now and all seems well.

Thanks,

glenmore

1990 LS400

1991 300CE

2000 C280

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