92 740. Multiple missfire. Now it's dead.

Ktackett1 · Post by **Ktackett1** » 30 Jan 2019, 18:46

Hey guys I'm a long time reader... First time poster..

I have a 1992 740. About two months ago it would run really rough on first start up... And would continue to run rough for about 40 mins of driving... Then like a light switch it would run perfect and take off. It would start running rough again if I came to s stop...

One night ileave work and it's running rough.. normal for me at this point. I hit the highway and it dies at about 50 or 60 mph.

Towed it to a shop. They replaced numerous things. One of their seasoned guys says it is not getting secondary fire. They replaced the coil... distributor... ignition module... And supposedly checked all associated relays. Any ideas guys

dj_v70 · Post by **dj_v70** » 30 Jan 2019, 20:16

Did you check for codes on your OBD1 computer.

Ktackett1 · Post by **Ktackett1** » 30 Jan 2019, 20:18

Yes I plugged in at every port and I get one one one saying there are no issues detected

Ktackett1 · Post by **Ktackett1** » 30 Jan 2019, 20:19

Before I wiped the codes about 2 months ago there was an oxygen sensor code from where I had it straight piped with no sensor and there was also an air intake temperature sensor code because I simply forgot to plug it back in apart from that it never triggered any other codes and is triggering no codes right now

dj_v70 · Post by **dj_v70** » 30 Jan 2019, 20:37

Either you misunderstood the mechanic or he is incompetent. If the car won’t start, the problem is no longer intermittent. And if so, it is easy to find for a mechanic.

1st prove whether it is primary or secondary. The mechanic puts a scope (or even a dwell meter) on negative coil terminal and checks for proper signal. No reason to replace ignition module if signal is there. I could walk you through checking coil, etc, but you either need to tow it to another mechanic or home to troubleshoot it.

Ktackett1 · Post by **Ktackett1** » 30 Jan 2019, 20:50

At this point I'm probably gonna have it towed to the house. Six people have touched it and the only one I trust says he has primary igition but no secondary ignition.

Ktackett1 · Post by **Ktackett1** » 06 Feb 2019, 10:52

It was the computer