My '87 740 GLE wagon hasn't had sufficient power since I bought it. So far,
I've checked:

- fuel pressure- 30 lbs which seemed a bit low. Fuel pressure went way up when I pinched the return hose coming off of the regulator. I applied vacuum to the FPR with the engine running and the pressure dropped.

-Timing was off a bit, so I set it to 12 degrees BTC

-checked hose from AMM to throttle body and it was fine

The car doesn't miss and idles well. Starts on the first try. There just isn't much power at all. Also, the timing belt marks line up like they should.

I'd really appreciate advice with this. I'm sort of thinking that the fuel pump isn't putting out enough pressure.

Thanks,
Dave

Hey Fellas,

I think I'm going to cut the cat out of the exhuast system and clamp in a straight piece of pipe. I won't leave it like this permanently, but it will make it easier to diagnose what's wrong with the car.

Compression was great. It was around 170 across all four cylinders. I'll probably fix this wagon up as I need to sell my really nice 240 wagon (since it is worth more money and I'm broke now). I only have a few hundred in the 740 wagon.

Thanks,
Dave

You might try checking for exhaust backpressure using a vacuum gauge. At idle you should be reading around 15-17 inches. Make sure the ac is off and run it up to 2-3k rpms in neutral. The vacuum should remain the same. If it drops then you've got some exhaust backpressure somewhere.

Your pre pump in the tank could be bad.

Sorry, I forgot to post that the intank pump is running. I can hear it with the gas cap off.

Have you checked the vacuum line at the FPR, should be not gas or even a smell of gas..or,,,Plugged cat or AMM on its way out?
--
Post Back. That's whats makes this forum work.

Well, I'm not sure about the AMM. It is a used one that I put on the car. I may try to find another one that is known to be good. When I bought it, the car wouldn't rev up at all. I changed to the current AMM and that made it run.

I didn't smell or see gas at the FPR vacuum line. The plug right before the cat is also missing (where O2 sensor goes on some models). I'm not sure how to tell if the cat is plugged up.

Thanks,
Dave

Info learned by reading this BB, not personal experience:

Look at the exhaust ahead of the cat. Find what looks like a screw-in pipe plug. If that is removed, exhaust escaping there will reduce the need for flow thru the cat. If the car runs better that way, it is the cat plug that's hurting performance.

That's new tech, the old tech for lousy acceleration is a problem in dynamic spark advance. That's not the 12 degree static advance.

Use a timing light. When you can see the 12 degree static advance with the engine at idle, rev it up a bit. Open the throttle plate quickly but not very far. The timing should should jump quickly to a greater advance.

The ignition control module controls, but it needs certain inputs. One is manifold vacuum, which it gets via the little nylon hose from the intake manifold to the ICM. See that is is OK end to end. Well connected and has no holes.

Good Luck,

Bob

:>)

Hi Bob,

I checked the timing while revving the engine a little. It does advance. I didn't see an ignition module with a vacuum line on this 740. Are you thinking of the one like the 240's have?

The plug before the converter is already out. It was out when I got the car.

Thanks,
Dave

So your 740 has an ignition control module, but there is no vacuum hose to it? I am a 240 guy, and expected that a 740 would have that similarity. Wonder how the ICM gets input describing manifold vacuum?

Regarding the plug in the exhaust pipe: If it was out when you got the car, wonder why?

Good Luck,

Bob

:>)

Hi Bob,

The 740's don't have the ICM like the 240's do. I'm presuming that you're referring to the one mounted on the passenger side front fender well on the 200's.

Yeah, the converter may have been giving the previous owner a problem. I owned this car about 4 years ago and it had better power then. The converter that is on it now is an aftermarket job. It has been clamped into place. It looks like it has been on there for a while. Maybe an exhaust shop could tell me if it is plugged or not.

Thanks,
Dave