Advice needed on hesitation

Case 7230 · 04-21-2008, 10:57 AM

Truck is `92 K1500, 350TBI, 4sp auto, 121000mls. Truck had been sitting for about 5 weeks. As always it started easily and ran smooth. Drove it for about 10mls., stopped it and left it for about 30mins. and started on way home. Initially it was running good then after about 5mls. it started to hesitate really bad on acceleration. Back off and it ran good again. Got it home and checked plugs, all good color. Fitted a new fuel filter and drove it for about 20mls with no problem other than I noticed the idle speed dropped to about 300rpm, but very smooth. Left it for 30min switched off and then took it for another drive. Hesitation under acceleration from the word go. Any ideas. I`m thinking ign.coil but would appreciate any input. Forgot to say that there is no light on and only code stored is 12

Chevy_Finatic79 · 04-22-2008, 03:27 PM

double check for a loose vacuum line/hose it sounds like a low vacuum problem

gmctrucks · 04-23-2008, 02:21 AM

Maybe TPS or bad gas try Lucas gas additive read directions first.

Case 7230 · 04-23-2008, 06:35 AM

Thanks guys. I should have said in my original post that I put around 10gal. of new gas in it with a can of Cyclo Fuel Injector Cleaner. Made no dirrerence but I have not run it all thru the truck yet. I should have thought of Lucas, used it before in a diesel and did a great job. What gets me is that it only happens after the hot engine has been sitting for about half hour (getting hotter?). Runs at 150 degrees under normal running, well that is what the stock gauge says. I will certainly check the vacuum hoses and will report back if and when I solve the problem. Thanks again for your replies.

03chevy · 04-23-2008, 06:37 AM

have you looked into these?

1Inspect Fuel Filter Clogged or dirty fuel filter

2Inspect Wireset Damaged, worn, or deteriorating spark plug or coil wire(s).

3Inspect Spark Plug Fouled, damaged or broken spark plug(s).

4Inspect Fuel System Pressure Incorrect fuel pressure being delivered to carburetor or fuel injection system.

5Inspect Fuel Pump Improperly functioning fuel pump or circuits.

6Inspect Ignition Timing Incorrectly adjusted engine timing.

7Inspect Throttle Position Sensor Faulty throttle position sensor or throttle position sensor circuit.

8Inspect Fuel Tank Contaminated fuel from rusted or deteriorated fuel tank.

9Inspect Air Cleaner Temperature Sensor Damaged or faulty air cleaner temperature sensor or air cleaner temperature sensor circuit.

10Inspect Accelerator Pump Diaphragm Damaged or faulty fuel injection accelerator pump diaphragm.

11Inspect Mass Air Flow Sensor Improperly connected or faulty mass air flow sensor.

12Inspect Oxygen Sensor Damaged or faulty oxygen sensor or circuit.

13Inspect Fuel Injector Plugged, dirty or poorly connected fuel injector.

Case 7230 · 04-23-2008, 10:42 AM

Thanks for reply. I`m thinking along the lines of No.2. May replace wires and see.

Case 7230 · 05-17-2008, 05:35 AM

As promised I am posting back on fix for odd hesitation. Turned out that a new oxygen sensor solved the problem.

04-21-2008, 10:57 AM	#1
Case 7230 Senior Member Join Date: Dec 2007 Posts: 521	Advice needed on hesitation Truck is `92 K1500, 350TBI, 4sp auto, 121000mls. Truck had been sitting for about 5 weeks. As always it started easily and ran smooth. Drove it for about 10mls., stopped it and left it for about 30mins. and started on way home. Initially it was running good then after about 5mls. it started to hesitate really bad on acceleration. Back off and it ran good again. Got it home and checked plugs, all good color. Fitted a new fuel filter and drove it for about 20mls with no problem other than I noticed the idle speed dropped to about 300rpm, but very smooth. Left it for 30min switched off and then took it for another drive. Hesitation under acceleration from the word go. Any ideas. I`m thinking ign.coil but would appreciate any input. Forgot to say that there is no light on and only code stored is 12 Last edited by Case 7230; 04-21-2008 at 02:10 PM. Reason: add info

04-22-2008, 03:27 PM	#2
Chevy_Finatic79 Senior Member Join Date: Mar 2008 Location: Lincoln NE Posts: 478	double check for a loose vacuum line/hose it sounds like a low vacuum problem __________________ "She's gonna Freak when she see's my wheels" 85' Chevy C-10 Longbox (Rat) TBI 327 Cu.In./THM350 90' Chevy Suburban 4x4 TBI 350 Cu.In./700R4 http://www.truckforum.org/forums/truck-pictures-176.htm

04-23-2008, 06:37 AM	#5
03chevy Senior Member Join Date: Dec 2006 Location: jax,fl Posts: 1,185	have you looked into these? 1Inspect Fuel Filter Clogged or dirty fuel filter 2Inspect Wireset Damaged, worn, or deteriorating spark plug or coil wire(s). 3Inspect Spark Plug Fouled, damaged or broken spark plug(s). 4Inspect Fuel System Pressure Incorrect fuel pressure being delivered to carburetor or fuel injection system. 5Inspect Fuel Pump Improperly functioning fuel pump or circuits. 6Inspect Ignition Timing Incorrectly adjusted engine timing. 7Inspect Throttle Position Sensor Faulty throttle position sensor or throttle position sensor circuit. 8Inspect Fuel Tank Contaminated fuel from rusted or deteriorated fuel tank. 9Inspect Air Cleaner Temperature Sensor Damaged or faulty air cleaner temperature sensor or air cleaner temperature sensor circuit. 10Inspect Accelerator Pump Diaphragm Damaged or faulty fuel injection accelerator pump diaphragm. 11Inspect Mass Air Flow Sensor Improperly connected or faulty mass air flow sensor. 12Inspect Oxygen Sensor Damaged or faulty oxygen sensor or circuit. 13Inspect Fuel Injector Plugged, dirty or poorly connected fuel injector. __________________ A dirty mind is a terrible thing to waste!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Miss or hesitation?	spacoli	Toyota Truck Forum	4	01-07-2007 12:10 AM
18" Rim advice needed	V-max	GMC Truck Forum	3	11-13-2006 09:41 PM
88 chevy hesitation	chevy_202	Chevy Truck Forum	2	11-10-2006 09:29 AM
18x9" Rim advice needed	V-max	Introductions	0	10-02-2006 02:35 AM
2002 chevy hesitation	mario.adame	Introductions	1	09-29-2006 07:49 AM

04-23-2008, 02:21 AM	#3
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 3,946	Maybe TPS or bad gas try Lucas gas additive read directions first.

04-23-2008, 06:35 AM	#4
Case 7230 Senior Member Join Date: Dec 2007 Posts: 521	Thanks guys. I should have said in my original post that I put around 10gal. of new gas in it with a can of Cyclo Fuel Injector Cleaner. Made no dirrerence but I have not run it all thru the truck yet. I should have thought of Lucas, used it before in a diesel and did a great job. What gets me is that it only happens after the hot engine has been sitting for about half hour (getting hotter?). Runs at 150 degrees under normal running, well that is what the stock gauge says. I will certainly check the vacuum hoses and will report back if and when I solve the problem. Thanks again for your replies.

04-23-2008, 10:42 AM	#6
Case 7230 Senior Member Join Date: Dec 2007 Posts: 521	Thanks for reply. I`m thinking along the lines of No.2. May replace wires and see.

05-17-2008, 05:35 AM	#7
Case 7230 Senior Member Join Date: Dec 2007 Posts: 521	As promised I am posting back on fix for odd hesitation. Turned out that a new oxygen sensor solved the problem.