740 1990 starts and shuts down

Stetson · Post by **Stetson** » 04 Jun 2019, 09:11

Hi,
I just got my hands on a mint condition 740. It's got B230F LH2.4 and I can't figure out what's bugging it. It starts up fine but won't stay running. Just bogs down immediately when the revs come down to idle.

Here's a small video of me trying to start it: https://www.dropbox.com/s/8p7qo8nrnz5qx ... 6.mp4?dl=0

I checked for any fault codes and there aren't any. I've already changed the MAF and the TPS. Didn't change it's behavior.

Any suggestions on what to try next? I'd really like to get this old lady back on the road since it's in such a good shape and with very low mileage.

E: When the MAF is unplugged I can keep it running if I pump the throttle and keep the revs up. After the engine gets warm it idles but very roughly.

93Regina · Post by **93Regina** » 10 Jun 2019, 19:02

Pull plug off CTS (Coolant Temperature Sensor)....if outside air temperature is around 60°F (15 C), it should start fine.

Do a fuel pressure test on fuel rail...there is a port for it....

dm635 · Post by **dm635** » 16 Jun 2019, 05:34

I had a problem on my '91 740 where it would start just fine, but nearly die after that making it undrivable. I replaced/swapped all the electrical spare parts I have. It ended up being the FPR. Fuel pressure regulator.
Not saying this is your problem, just my own experience on my 740.

Stetson · Post by **Stetson** » 19 Jun 2019, 08:19

I just changed the FPR. Didn't help.

I also tried unplugging the coolant temperature sensor. I can get it running just as I could when unplugging the MAF. Although the outside temperature is about 24c and not around 15.

Post by **matthew1** » 19 Jun 2019, 08:25

Could be fuel delivery, plugged cat. converter, air filter, air intake generally, bad spark plugs. I don’t know a lot about red blocks, but given what you’ve tried, I’d look at those next.

93Regina · Post by **93Regina** » 19 Jun 2019, 14:54

Stetson wrote: ↑19 Jun 2019, 08:19 I also tried

Once moving, does engine run fine?

Stetson · Post by **Stetson** » 19 Jun 2019, 15:05

No it does not run fine. It barely stays idling with the coolant temperature sensor or MAF unplugged and if I touch the gas pedal it stalls immediately.

93Regina · Post by **93Regina** » 19 Jun 2019, 20:09

Stetson wrote: ↑19 Jun 2019, 15:05No it does not run fine.

Back to the basics....Timing belt Check...see this post