Hi all,
After recently buying my '94 Suburban 5.7 TBI I decided to do a bunch of maintenance.
So I did and now it stutters / hesitates / runs rough and almost dies when I take off. All the problems are at low rpm, on the highway I don't really feel any problem.
Here's what I changed:
Engine Oil & Filter (5W-30)
Transmission Oil & Filter (basic pan drop) (Lucas transmission conditioner added)
Coolant flush & replace. Added 1 bottle water wetter

Installed new 180 degree thermostat (is this too cold?)

Front and Rear differential fluid replaced
Fuel filter
MSD 8406 Cap and Rotor kit
MSD 5562 Street Spark Fire Plug Wire Set
Spark Plugs (AC Delco #1 Rapdifire)
PCV valve (AC Delco CV774C)
EGR valve (9109 Engine Mgmt)
Seafoam treatment
Air Filter

The old cap and rotor looked pretty bad so I was all excited expecting a much better running truck but instead now I have this low rpm problem.
My new thermostat is a 180 instead of 192, could that be the problem?

Thoughts?

Thanks in advance,
Dan

 

AHHHH SEAFOAM!!! Thats evil stuff. DONT USE IT!

This sounds like ignition. Replace one thing at a time with your old. First do the cap, then rotor, then wires, etc. Try that and see.

 

Thanks. The thing is, the old stuff was pretty corroded plus my mechanic friend who was helping me has likely already disposed of these parts.

Second thoughts?

Oh, and I gapped the new plugs at .035 - that's what it said in the engine bay.

Thanks,
Dan

 

Are the AC Rapidfire plugs the ones that are called out for your particular engine?

 

Yes, there is the standard plug and the rapidfire that I can use from AC Delco. Both are considered good replacement plugs, also if I am to believe the many people who use them on these engines.

 

I would think it would be a crossed plug wire almost 100% sure. It is for sure a ignition problem I would check the firing order and plug wires to make sure none have touched anything hot and burned through and are arching anywhere also. Also make sure the rotor is on correctly and not loose.

 

So.... based on eeeeeverything I have read in aaaaaal the threads I became very suspicious of the EGR system.
I had replaced the EGR valve already and so didn't expect it to be the problem at first but then I did a simple test by unplugging the power to the egr solenoid.... Problem fixed....
I will still have to run it down to see if I got a defective egr valve or the solenoid is bad, or it didn't get power blah blah... but.. it's the EGR system.
For others who are having this problem, the signs are stumbling around 1000-1500 rpm range or there about. Idle was fine and so was cruising a highway speed. Sounded and felt like a mix of missing and running rich. Symptoms were particularly noticeable on take-off and idle would sometimes drop ultra low when getting off the gas.

Thanks to all for responding, now I'll do some searching on EGR troubleshooting....

Dan

 

First, try cleaning the throttle body. I've had the same problem at least twice after disconnecting or replacing the battery in my '03 Avalanche. It ran fine while driving, but would stutter and almost stall out at a red light, or when starting from a stop.

Both times, the advice from my father-in-law (who is a retired GM plant mechanic and still current shop mechanic) and from my regular mechanic was "Clean the throttle body". Both times it fixed the issue.