jcslocum

I have been chasing the cold start roughness/shaking and have yet to solve it. So, I'm looking for more input from the group.

Here's what is going on and what we have done already:

Cold start seems to be OK as far as the engine firing. Maybe 8-10 seconds of cranking and then she fires. Once fired the engine runs quite rough and will almost stall then catch almost stall shake and then will finally begin to smooth out and run on idle at about 900-1000 RPM. Once running the idle is very steady and the engine runs great.

We have replaced or fixed the following:

All vacuum hoses under the manifold. DME Temp sender, air filter, spark plugs, cap, rotor, etc....

Throttle body was cleaned and the idle valve was also cleaned.

There doesn't seem to be a cold start injector to clean or replace.

Can you all give me some input on what to persue next??? Is the ISV fully responsible for cold start management of the idle?? I have a used one to swap out but it's in a crappy place and tough to do.

Grandpa#3

Still sounds as if the Idle Speed Control is giving you problems.

http://www.clarks-garage.com/shop-manual/fuel-21.htm

http://www.clarks-garage.com/shop-manual/fuel-08.htm

Cheers,
Larry

pnbell

Just a note: 8-10 seconds of cranking seems awfully long. Mine is like -maybe- a second or two, even after a week of sitting.

I just mention that; as maybe there is a fuel priming/pressure issue. On cold start an engine wants more fuel to run; so if it isn't getting enough fuel, it would run rough.

You drive motorcycles - I assume from your Signature- and might be familiar with this issue when starting a motorcycle with the choke. Too much air and the bike won't start, or runs rough.

MichaelK

I had a hard time starting cold until I replaced the fuel filter. As soon as I did that the car transformed in terms of starting and running noticeably better throughout the RPM range.

Have you tried a shot of starter fluid? Not as a solution necessarily but if it catches immediately on a shot of starter fluid you probably have a fuel delivery issue as mentioned above by pnbell.

PeteL

The two times I have had this problem it was the fuel pressure regulator.

jcslocum

I'll replace the fuel regulator and the ISV and let you know what the result is.

Thanks for the help!

black944 turbo

Please let us know what you find.

CyCloNe!

Ya I'm going with the ISV as well, thats what mine was then it got worse over time where I would stall out on idle... pull out a multimeter and check the resistance and voltage on all your sensors and fuel pump... that's how I usually find stuff.