I have a 90 civic with a 1.5L engine, dual point throttle body injection system. It stalls out in the 1500 to 2000 rpm range, acts like it is not getting fuel. It started as just the occasional sputter, but has gotten worse. The fuel pressure is supposed to be 36psi, I tested and got 38. Pulled the vacume to the regulator and it went to 46. when I reved the engine, about the speed you need to go through a traffic light, it died out, at the same time fuel pressure spiked to 46 psi. Restart the engine and fuel psi is 35 psi runs good.

hold rpm's at 2000 and the engine hunts between 2000 and 1000 rpm, it dies off at 2000 like it is starved for fuel, drops to 1000 and then back to 2000. at 2000 rpm when the engine acts like it is starve for fuel the fuel pressure goes to 40, as it recovers at 1000 rpm the pressure is 38.

I'm thinking fuel pressure reglator, any thoughts?

 

Those numbers suggest the regulator is OK.

Have you changed the fuel filter yet?

As you rev up but don't let it stall, pressure should increase slightly due to less manifold vacuum (more vacuum brings the pressure down so the pressure difference across the injectors is always the same). If the flow is restricted it will drop. This all assumes you are measuring pressure after the filter of course.

 

Is the CEL ON? Is the ECU flashing a code?

Have you checked the ignition timing? Has the timing belt slipped?

 

When this problem first started about 3 mo. ago.pulling away from a stop the car would give a little cough, and then keep on going. It felt like water in the gas. dumped in heat, no help. Checked plugs, they were bad, replaced them and poured some seafoam down the intake. It ran better but the cough at intersections was still there. I also cleaned the rotor and distributor contacts.
At the start of this problem it was intermittent. you could go for a week and have no sputters. It slowly got to the point that it was sputtering everytime you pulled away from a stop.

I pulled the fuel filter and poured the gas into a bowl, it had a lot of rusty looking tiny particles, and some water.
I had gotten a load of bad gas, right in the middle of trying to solve the problem. spent a week trying to get the water out of the tank, finally pulled the tank and made sure it was clean and dry. Replaced the filter and thought my problem was over.

But no, still sputters.I figured out the way to get through intersections was to drop back to idle, where it would run good, and then try to rev again, by doing this I could get the revs above 2000 and then it would take off and run right.
I drove it like this for several days while waiting for a fuel pressure test adaptor to come in.
Yesterday it started to run rough above 2000 rpm also. and then would not run above an idle. Had it towed home, where I found that the test adaptor had arrived.

Checked the fuel pressure and the car seemed to be normal.
rev the engine and get a little bump in pressure, but mostly it stays around 35-36 psi, even at higher rpm it would bump up, for a second and then stay at 36. when it goes into fail mode the pressure would go to 38-40 with spikes to 46 when it started to really die off.

If this was a simple carb type engine I would suspect a blockage in the idle passage that controled the mid range rpm. I pulled the idle air control unit, and checked the screen, it was clean.

I have never had a CEL light, at the beginning of this, I had a O2 code, checked the connections,cleared the code, and it has not come back.

I plan on spending the dayworking on it, and will let you know whatI find

 

As the pressure is staying up, I'd move away from thinking it's a fuel problem. If you had a lot of water in the gas, it wouldn't idle either.

Check the timing as previously suggested. You might have a bad cap rotor or wires causing it to misfire badly under load. Or it could be a sensor problem those will usually set the CEL but not always. Make sure the hose from the manifold to the MAP sensor on the firewall is in place. Check the air filter, sometimes mice move in there and clog up the works badly.

 

I agree with everything mk says. Is it also possible that the fuel injectors are clogged due to the contaminated gas?

 

Ron makes a good point. One of the fuel injectors is for idling and the other for running. If that latter one is clogged it might do about what your car does.

 

No mouse nest in the air filter.

I pulled thefuel injectors today. the main injector was really cruddy looking, the secondary had a light film of crud. Put them in a seafoam bath for a couple of hours. Pulled the pressure regulator, just to see what the condition was, sucked on the vacume side. no gas in my mouth, and it held vacume.

Other than dirty injectors, the intake looked clean.
The fuel passage goes from inlet, tomain injector, to secondary, to relief valve, to tank. they are all large diameter, and looked clean. So blockage is not a problem.

After cleaning the injectors, I could tell that the screens were brighter looking, and there was a lot of crud in the pan.

Reinstalled the injectors, the car ran better, as in not stalling all the time, only at 1500-2000 rpm, like before,and then only when I hold it in that range. Otherwise it idles, and accelerates good.

 

Seems like you've made some good progress, but still not perfect. Maybe running some Seafoam through the gas tank and bake booster vacuum line would also help.

Have you already checked the ignition timing?

having another look at the plugs, wires, and distributor might also be a good idea.

 

i vote for a broken or missing or disconnected vaccume line. a car that old they are bound to be there.