Car idles like crap - a bit of knocking too

[Cobra]

Background: Car dies on my wife on the highway. I assume it was the alt. since it was acting up. I proceed to do other work on the car as well including changing the head gasket on my 88Lx, went to start it up and now it idles like crap.

It sounds like it's running on 2 cylinders or like the firing order is all messed up, the garage fills up with exhaust fumes and the engine finally dies. While it's trying to idle the engine shakes and even knocks a bit.

I checked the TDC on the compression stroke and the distributor to make sure it was pointing to #1 and that the firing order was okay. Checked the plug and wires and they all look okay. I thought perhaps it was bad gas so I continued to drain the tank by just running the pump and putting the fuel hose into a container. Well, gas flows out of the hose but it flows very slowly and not smoothly, almost like in slow pulses. I hooked up my fuel pressure gauge but the pressure doesn't even register. The book says the pressure should be 2 to 3.7 lbs. I changed the fuel pump 1.5 years ago.

So my questions are:

If the fuel pump is working very slowly, does this cause such rough idle? I thought the float in the carb would keep it from starving the engine. Wouldn't the engine idle normally until it was starved and then die?

Sorry for the long story,

Take care,
Dan

[VTEC_Inside]

Did you change the filterS when you changed the pump. Thats where I would start.

[Cobra]

Did you change the filterS when you changed the pump. Thats where I would start.

Yes. Both filters were changed and now I checked them as well for any obstructions.

Take care,
Dan

[Deadhead]

With the fuel pump, i would say replace that before doing anything else if it's not putting out the proper pressure. Your going to have to replace it anyway.... so just take it one step at a time.

otherwise....

are you getting spark to every cylinder? Was the car working ok before you were changing the head gasket?

Did you get cam gear aligned in the correct place?

How does your air filter look?

try cleaning out your carburator and see what that does.

[POS carb]

you shouldn't have gas fumes if it's a leanout condition (i.e. bad fuel pump)
While it is possible that your fuel pump is bad I think it more along the lines of an over rich condition...
Do you have a vacuum gauge?

[Cobra]

With the fuel pump, i would say replace that before doing anything else if it's not putting out the proper pressure. Your going to have to replace it anyway.... so just take it one step at a time.

otherwise....

are you getting spark to every cylinder? Was the car working ok before you were changing the head gasket?

Did you get cam gear aligned in the correct place?

How does your air filter look?

try cleaning out your carburator and see what that does.

Thanks DH,

True, about replacing but I have a feeling that it's not the problem since fuel does flow albeit slowly. Probably enough to fill the float tank.

Spark, yes.

Cam gear, yes, hence the distributor check

Filter is clean.

Carb cleaned a few months ago.


I'm still curious about the effects of low fuel pressure/flow on a carbed engine. I know for a fuelie it's a big deal.

Take care,
Dan

[Cobra]

you shouldn't have gas fumes if it's a leanout condition (i.e. bad fuel pump)
While it is possible that your fuel pump is bad I think it more along the lines of an over rich condition...
Do you have a vacuum gauge?


Yes I tend to agree, I will take a reading when I get home.

Take care,
Dan

[Cobra]

Okay did a vacuum test:

15 inches at start and quickly went down to 9 to 12 as the engine began to stumble and die. I did hear a slight whistle at the beginning which I didn't notice before. What should the normal vacuum reading be for this engine 88- 2L?

Take care,
Dan

[VTEC_Inside]

You should have at least 20. The higher the better.

My car idles fine and I'm getting about 20. Thats measured using my vacuum pump though and the guage is considerably smaller than a dedicated one.

[lostforawhile]

ok first of all you probably have a vaccume leak,second are you trying to test the fuel pump by turning on the key to see if fuel runs out? there is a safety relay behind the fuse box,that only allows the fuel pump to run if it detects ignition pulses from the coil. it runs for a couple of seconds,then shuts off.this is in case you run out of gas to get it back in the carb. the point of this is to keep you alive in an accident,if the engine stops the fuel shuts off. if you break a fuel line,the carb runs out of gas,the engine shuts off,and the fuel pump shuts down. there is a diagram in the book of how to run a jumper wire to bypass the relay for testing the pump. since my book was stolen,i can't help you on that. maby someone knows which two terminals it was?

[Cobra]

Thanks gentlemen for your responses. The problem may have been located.

I went out this evening to do a thorough check and found that the PCV valve had come disconnected from all the work I had done previously. Tough to see until I removed a bunch of stuff. While at it I re-tightened all the nuts on the bottom of the intake man. :banghead:

LFAW, to check the pump I jumped terminals 1 and 2 at the relay box as per manual and turned the key. I may have to revisit the pump issue once I get this idle under control.

Too cold to put everthing back together tonight but will check tomorrow.

Take care,
Dan