Acceleration hesitation (1 Viewer)

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Did your 02's throw any codes?
 
Does pulling the fpr vacuum hose increase fuel pressure by a few pounds? Im thinking if i pull the vacuum line and increase the pressure in the rail maybe it would help diagnose if my fuel pump is weak. Also, if one of the injectors is bad would it throw the cel? What about a spark plug and or wire, would a bad plug or wire throw the cel? If I powerbrake the truck it seems like one cylinder is missing, but I have no cel. The cel works as soon as i unhook the tps, so i know the cel works. The cel light is off at the moment and I cant seem to get a code with my problems...
 
The ECU does have the ability to tell when a cylinder is misfiring. Interesting why it isn't picking up your missing cylinder....
 
Just went through the same scenario, in a way.
no codes, but hesitation upon acceleration, to the ear sounded like a misfire... popped the hood and started tracing vacuum lines; one to left of the egr was no longer attached, reattached, good to go.
 
Ill double check the vacuum lines. However, the truck runs great for the first 6-7 minutes when cold.
Im going to try disconnecting both o2 sensors tomorrow and see if it changes anything. Ugh!
 
I went through this same thing- it's expensive and time consuming. One thing you may not have checked yet is the VSV. If it's plugged or inoperative it will give you a stutter without throwing any codes. Do a resistance test on your heated oxygen sensors as well to rule them out- the FSM has the value range listed and it takes 5 minutes to perform if the harness plugs are stubborn.

I changed my fuel filter, sock, spark plugs (a hairline crack in the porcelain will short the plug), cap& rotor, wires, TPS , thermostat, and most of the vacuum lines.

The other option is buy a used ECU (New is north of $2k , used ~$100). This is what mine turned out to be and it cured the issue.

Good luck!
 
Ill double check the vacuum lines. However, the truck runs great for the first 6-7 minutes when cold.
Im going to try disconnecting both o2 sensors tomorrow and see if it changes anything. Ugh!

I know you're frustrated but hopefully we can come up with a solution for your issues. generally speaking, the oxygen sensors shouldn't affect your engine in this fashion, ECU would definitely throw a code if something was amiss with your sensors.

did you check all your vacuum lines yet?
 
All the vacuum lines look good and intact, even the ones underneith the intake. I unplugged a spark plug wire and the mis was was a lot more severe then what I have been experiencing. I feel like the mis is partial and not a full on mis. Im trying to swap computers with someone in Denver to see if that helps. Im going to pull the plugs tomorrow and do some testing with the voltmeter on the wires and coil. Ill keep this updated....
 
Ive read up on unplugging the vacuum line to fpr will increase fuel pressure in the rail by a few pounds. I unhooked it and the problem still persists. I looked at the fuel filter and its nice and shiny black, so I believe the fuel filter is somewhat newer. I also replaced the pcv valve and vacuum hose to it and no change.
 
If you look at the vacuum diagram on the underside of your hood (mine is), there is a part called TVV (Thermal Vacuum Valve??) It's a "sensor" that is threaded into the side of the head. Below is a pic of where it is. I'd suggest testing it to the FSM, or bypassing it (brass tube), or plugging both directions (brass rod) and see what happens. Since it runs "great" cold, there's something that isn't working to let the ECU or vacuum system know it's warmed up when it is.

Or, maybe when the TVV actually *does* open, it tries to engage a function that is defective. What does the TVV connect to?

DSC_5800 (Medium).JPG
 
Makes sense if its function changes as it warms up. Ill give it the college try tomorrow and report back.

Is that your motor or a fancy piece of art in your living room!?
 
I cant find too much about the TVV, but its the same part on some 22RE's. What I understand is that once the motor warms up the valve opens and it lets the charcoal cannister vapors into the motor to burn again. The motor has to be at a certain temp in order to handle the richness of the extra fuel vapors. I checked the vacuum lines and the routing, but it doesnt seem to go directly to the canniater. Ill have to retrace them and see where they go, looks like under the intake somewhere. Ive disconnected the charcoal cannister with no solution to my problem, so if that really is what the tvv does then it doesnt fix my problem, but I need too see where those vacuum lines really go...
 
The two vacuum hoses that attatch to the vtt attatch underneith to the intake. I undid the vacuum hoses and drove home, 25miles, to see what would happen and its still the same sad story. Runs great cold and studders when warmed up.
 
FIXED!

Well I finally got some time to do some wrenching and pulled the throttle body, spark plugs, wires, and cap and rotor off. The tb egr port was clogged almost shut. I had to get a flat head screwdriver and chisel away at it to remove the carbon. I cleaned the tb royaly and made sure all of the vacuum ports were clean. I noticed the plugs were an Autolite Double Platinum and were gapped all over the place, but were all more than .032. The plugs also had some weird wear on the back of the curve like some bad arching.I replaced them with the oem Denso copper plugs and gapped to .032. I checked all the plug wires and they were all within the correct ohm readings per fsm. I put some diealtric grease on both ends of the spark plug wires. The cap and rotor didnt seem too bad at first look, but once I brushed up the contacts they were flaking metel, weird. I replaced the cap and rotor with the NAPA brand and they looked of good quality. The cap was actually made in Japan and looked identical to the Denso one I replaced. I fired it up and it ran great. I got it good and warm and did a load test with the brake and NO sputtering! Its a joy to drive again! The world can turn now. Its also worth mentioning I tested the tps and it tested fine with no dead spots. I also replaced a few hard vacuum lines that looked suspect.
 
FIXED!

Well I finally got some time to do some wrenching and pulled the throttle body, spark plugs, wires, and cap and rotor off. The tb egr port was clogged almost shut. I had to get a flat head screwdriver and chisel away at it to remove the carbon. I cleaned the tb royaly and made sure all of the vacuum ports were clean. I noticed the plugs were an Autolite Double Platinum and were gapped all over the place, but were all more than .032. The plugs also had some weird wear on the back of the curve like some bad arching.I replaced them with the oem Denso copper plugs and gapped to .032. I checked all the plug wires and they were all within the correct ohm readings per fsm. I put some diealtric grease on both ends of the spark plug wires. The cap and rotor didnt seem too bad at first look, but once I brushed up the contacts they were flaking metel, weird. I replaced the cap and rotor with the NAPA brand and they looked of good quality. The cap was actually made in Japan and looked identical to the Denso one I replaced. I fired it up and it ran great. I got it good and warm and did a load test with the brake and NO sputtering! Its a joy to drive again! The world can turn now. Its also worth mentioning I tested the tps and it tested fine with no dead spots. I also replaced a few hard vacuum lines that looked suspect.
 
Thanks for everyones help! Im not sure which part was the reason for my sputtering, but with no codes and no cel it was tough to narrow down. Thanks again for all the help guys! Hopefully I can meet up with some of you local guys soon.
 
Thanks for everyones help! Im not sure which part was the reason for my sputtering, but with no codes and no cel it was tough to narrow down. Thanks again for all the help guys! Hopefully I can meet up with some of you local guys soon.

Congrats mi amigo! Threads like these are very educational for all, including me! On your final posting, could you do a bulleted list of steps you tried to arrive at the final fix?
 

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