98 Tahoe cold acceleration stutter

[jde99]

98 Tahoe with a 5.7 “sputters” when accelerating only when engine is cold. “Sputter” symptoms feel like engine or transmission is skipping or jumping erratically. This only occurs when engine is cold and when accelerating. Engine idle feels okay and it starts fine. Runs great after about 10 miles of driving and engine gets warm. Originally, sputter was only felt only during acceleration from 1st to 2nd but now “sputter” is getting worse and is felt up through 2nd gear. Problem seems to be worse after truck sits a couple of days. I already installed new fuel pump and intake gasket fairly recently (not related to this problem). Intake gasket problem did cause antifreeze to leak through exhaust system, so I’m thinking the cats might be internally rusted causing back pressure and backfiring through throttle body which could be a “sputter” symptom. My only other thought based on reading other forums is the spider injectors. Question: could blocked cats or internal fuel leak be the culprit for cold/acceleration problem if all is well after everything is warmed up? Any help would be greatly appreciated.

[777stickman]

Welcome to AF. After reading your post several times I have some suggestions and thoughts.

1. Need to check for active and history codes. If any, post back code numbers only.
2. Need to check the ECT sensor. This will need a diagnostic scan tool (not a code reader). If the ECT is sending a signal to the VCM that the Engine Coolant Temp is not at ambient temp when cold, this may cause your trouble.
3. My experience with CAT's is if they're plugged up you will experience a loss of power and an increase in engine temp regardless if the motors' hot or cold. Since it runs fine when warm, I would not suspect the CAT's.

[jde99]

No check engine lights. Checked ECT this morning: 5 V at connector, 2.4 kOhm at cold, 1.04 kOhm after enginge was warmer. Measurements check according to chart, but I did not verify whole range. To eliminate possible open/short throughout entire range, will replace with new tonight (only $13). Will reply results tomorrow. Thanks for the advice, I truley appreciate.

[jde99]

No check engine lights. Checked ECT this morning: 5 V at connector, 2.4 kOhm at cold, 1.04 kOhm after enginge was warmer. Measurements check according to chart, but I did not verify whole range. To eliminate possible open/short throughout entire range, will replace with new tonight (only $13). Will reply results tomorrow. Thanks for the advice, I truley appreciate.

[jde99]

No check engine lights. Checked ECT this morning: 5 V at connector, 2.4 kOhm at cold, 1.04 kOhm after enginge was warmer. Measurements check according to chart, but I did not verify whole range. To eliminate possible open/short throughout entire range, will replace with new tonight (only $13). Will reply results tomorrow. Thanks for the advice, I truley appreciate.

[jde99]

Replaced the ECT sensor with new. Also, removed inspected and cleaned the EGR while I was under the hood. I still got the stuttering this morning during the drive into work. I plan to rent the fuel pressure test kit tonight and check the fuel pressure. I wouldn't think this is an issue though because all is fine once the truck warms up. Any other thoughts? My last plan is to drop off at dealer and have them diagnose it after it sits overnight. Just would like to do all the obvious easy fixes before going this route.

[j cAT]

Originally Posted by jde99

Replaced the ECT sensor with new. Also, removed inspected and cleaned the EGR while I was under the hood. I still got the stuttering this morning during the drive into work. I plan to rent the fuel pressure test kit tonight and check the fuel pressure. I wouldn't think this is an issue though because all is fine once the truck warms up. Any other thoughts? My last plan is to drop off at dealer and have them diagnose it after it sits overnight. Just would like to do all the obvious easy fixes before going this route.

I would check distributor for bearing failure...this is common with your issues...poor spark cold with be greater issue ...then as the bearing gets worse it will run poorly at warmer temp...

plugs/plug wires/cap/rotor all can be defective or part of the problem ..check this out with resistance of plug wires cap/rotor carbon deposits/distributor rotor lateral play...etc....

[jde99]

Thanks for the distributor advise. I pulled one from the bone yard for $30 and reused my old cap and rotor. The pick up coil and main distributor were replaced. The old distributor gear was significantly worn. I haven't had the problem in the last two days so I think the problem was resolved. THANKS AGAIN.

[j cAT]

Originally Posted by jde99

Thanks for the distributor advise. I pulled one from the bone yard for $30 and reused my old cap and rotor. The pick up coil and main distributor were replaced. The old distributor gear was significantly worn. I haven't had the problem in the last two days so I think the problem was resolved. THANKS AGAIN.

thats a good cheap fix ...good luck with your repair ..

thanks for your posting with your results..