RetroTA

I bought the car over a year ago with 42K and it ran great except it would sputter erraticaly at Idle and low RPM. I just flushed and serviced the cooling system witch was like brown mud water (Bars Stop Leak?) Or is this normal for a car needing a flush? Now at 47K it still does it. I replaced the Opti with new MSD Opti, New blaster coil, New plugs, Fuel filter, Fuel pressure is within Specs. Havent changed wires or fuel injectors yet. My concern is I might have a bad head gasket, or worse a cracked head causing antifreeze to enter the cylinder resulting in this symtom. Is there any way test for this condition. The car accually runs great but when I pull up to a stop light it runs a little rough and up to 1500 RPMs you can hear a slight sputtering out the exhaust. There is no white smoke and my coolant stays full and doesnt seem to be going any where. Could this be wires or fuel injectors or worse?

G-Sting

Have you cleaned the Throttle Body and IAC pintle lately? They seem to collect gunk on them after time and need cleaning at about 40K or so. It may be something else, but this may be something to rule out.

firemanjim

Check the threads on the spark plugs to see if the threads are rusty. I read somewhere here a bad head gasket causes rusty spark plug threads and dirty coolant.

RetroTA

The coolant was muddy brown before the flush? But I dont
recall rusty threads when changing the Plugs? Will look into
both these ideas, Keep ya posted.

Lichen

If the head is cracked or bad gasket, you should have water in the oil. Sounds like the previous owner may have put those stupid GM pellets in the cooling system. Flush, flush, flush.

RetroTA

Cleaned IAC and Trottle body.. Seems to idle a little smoother but still
sputters a little at idle, only after it warms up?

fxgrnd38

Try Seafoam, I've had great success with it. Just follow the directions. You'll be fine. A lot of guys don't trust this stuff, but it really works.

rick lambert

with SeaFoam, but I'd probably do a fuel pressure test to rule out leaky injector(s) and also ohm the injectors.

RetroTA

Seafoam? Ive heard bits and pieces about this stuff, I'll run a search on the fourm.

RetroTA

Fuel pressure holds all day at 42psi, put seafoam in with last fill-up.
injectors all ohm out between 12.9 & 13.1. Will keep ya posted

GeoffC4

Not sure this will help but check the EGR valve. I have 1995 with high miles. EGR valve opens during rich fuel conditions to reburn exhaust gas. If it sticks open just a bit, you could have sputtering at low PRM's - e.g. causing a bad vacuum leak from the exhaust. I had similar issue. changed out the entire fuel Tank Sending unit, fuel pump assembly and strainer, as well as fuel filter. I also tried the Seafoam. Turns out a shot of carb cleaner to the EGR valve fixed the prob pretty quick. Not sure that was the final fix, but I no longer have the problem. Pretty easy to replace if you need. Manual should show you how to test and repair/replace. glad it's gone, I was thinking about the ECM and Fuel Injectors next....

Bandit's C4

Holy thread resurrection, Batman!

sailorsteve

Well, so far, no one asked, so... is the service light on? Are there any stored codes?

The brown gunk in the coolant is likely from the factory SOP of using those pellets in the cooling system- IIRC there was an issue with porous heads... anyway, a compression test should diagnose a head gasket problem, and if there are combustion gases getting into the cooling system, I would expect to see bubbles in the coolant.

Cliff Harris

The original thread is from 2006. Forget it.

sailorsteve

Good catch, Cliff. I'll drop this thread from my watch list.