No, not my 68 vert.It"s got a carb.It's my 91 chevy truck.It's missing.I thought it was a plug or wire so I replaced the whole setup from dist. cap to plugs.still not right. I noticed most of the old plugs were carbon fouled. I took out a couple of the new ones after about five minutes and they are already soot black.Any HELP would be GREATLY appreciated.

Injectors leaking?

alan

Vacuum leak. Intake leak. Bad O2 sensor(s)....................


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very limited experience with these. Had one not too long ago, was idling high and running rich, with no check engine light. Turned out to be the base gasket under the TBI had rotted out, caused a large vacuum leak.

Thanks for info.I was out of town and wife had new water pump put on.I think it was over heated? Of course she denies this. No oil in water. No water in oil.Idles very rough.I will be checking gaskets tomorrow morning.Time to get the vert. out while the weather is perfect. Would the oxygen senser cause this when cold?. Any more ideas would be appr.Thanks

Just because the check engine light is not on dosnt mean there may not be a code stored in there.

If this started after the possibility of overheating, I would be checking the compression first. With a throttle body gasket leak the engine will idle high as Jim stated, but you should also hear a sucking sound coming from the area. You can spray some carb cleaner around the base of the throttle body being careful not to spray directly into the throttle body and see if the idle changes. If the idle changes you have a vacuum leak. A stuck open EGR valve will cause an internal vacuum leak and cause a rough idle and a rich condition but usually will not affect idle as much as an external leak will. An 02 sensor will not cause a problem cold because the ecm is in open loop. A leaking injector is a possibility as well as a leaking or stuck fuel pressure regulator. A bad MAP sensor can cause a rich condition as well as a bad coolant temperature sensor. It would also be a good idea to check that the fuel pressure is within specifications. I don't work on too many of these any more so my memory is a little rusty, but if I think of anything else I'll let you know.

I'll be checking the compression in the morning along with the other stuff and report in. Man what a nice ride today in the 68 vert.Thanks guys.

Old rocker touched on what I was thinking. However, I'm not sure if your EFI is throttle body or an injector per cylinder setup. If it's the later, pull the vacuum line off the fuel pressure regulator. It should be located at the return end of the fuel rail (on a multi-port setup at least). If you see wet fuel, your pressure regulator diaphram has ruptured and it'll run rich as a pig. You might even see that the fuel fowled plugs are downstream from where the regulator gets it's vacuum from.

Your truck is TBI, I believe, and the TBI to adapter gasket fails alot, so does the EGR valve, all have been suggested earlier and good places to start looking.

Check to make sure the two-wire coolant sensor has not fallen off or broken. It tells the ECM how cold and ECM richens the mixture, as if the choke is on.

My suggestions are to be checked after you checked others' suggestions first.
Ignition coil could be faulty as well as a low output alternator.

.... If you see wet fuel, your pressure regulator diaphram has ruptured and it'll run rich as a pig. You might even see that the fuel fowled plugs are downstream from where the regulator gets it's vacuum from.


Yeah, the fuel pressure regulator is a real good possibility. There should be a place on the fuel line to attach a pressure gauge, you may need to go to a local shop, but they should have the gauge. Attach gauge, then run engine briefly, then stop engine and pressure should hold steady. If pressure falls off rapidly, it's most always the fuel pressure regulator.

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The engine for this year was throttle body. The pressure regulator is in the throttle body. For some reason GM didn't see a reason to add a port for fuel pressure testing. I have an apparatus that takes the place of the fuel filter and has a port to install a gauge for testing purposes. You should have around 13psi., but this is not a constant fuel system so it will leak pressure down even if there is no problem with the pressure regulator.

Up date.Pulled no.1 plug checked compression,60 and carboned up. No.3 0 and antifreeze in cylinder.No5 same.Did not even go any further. It must of been overheated and blown head gaskets or cracked cylinder etc.I guess i got another project on the list of a million things to do.Sure glad I'm retiring in two months.Thank you guys for all the input.

You definitely got a project there. Good luck.

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