Rough idle in drive

[sunk]

I am troubleshooting my k5 (5.7L). While in park, it runs pretty smooth but when in drive it almost dies. When driving and coming to a stop it really almost dies. It will throw a code after about 10 minutes of driving or if I floor it.

i am leaning twards a vaccum leak but have not discovered it let. I have replaced the MAP sensor and O2 sensor.

any suggestions? Anyone have an obd 1 code reader?

[Chris]

Bad PCV? Fuel Filter? Too simple I suppose but I'd check that then search for the vacuum leak.

[sunk]

Shorted pins A and B on the Diagnostic port and counted the check engine codes. Found code 23 (VSS) no vehicle speed present during a road load decel. And code 44 (O2 lean exhaust indicated) o2 sensor voltage below .2v for 20 seconds.

not sure what the o2 code means, i just replaced the sensor. What would casue it to run lean?

what is the pcv chris?

[sunk]

After doing some reading i saw that the pcv is part of the vaccum system and those lines are pretty trashed, i suppose it wont be too expensive to just replace all of them.

i also saw that people suggest checking the fuel line pressure but i dont have a pressure gauge...yet

[Chris]

I'm not familiar with your motor Adam but if it's anything like my old truck be very careful replacing the lines. Lots of people pull them off and put new ones on incorrectly causing more issues.

Check the o2 sensor wires, probably a bad one causing the lean code, same with the speed sensor wire.

[dieseldoc]

contanuity test the wires then look for power....
you could have a bad ground in there somd pkace

[Brian]

If you have vacuum power brakes check that hose too. Being in drive and coming to a stop usually require brake pressure. If not the hose the internal diaphragm on the brake booster could be leaking vacuum.

[sunk]

i would not be happy if it was within the master cylinder (just one more thing). I have yet to remove and clean the EGR but im not holding out much hope for that since it seems to be working.

It is possible i damaged the wire from the o2 sensor during installation. My headers are really close to the firewall and i have had to clearance the wall but it is still close and the wire did not turn with the sensor while screwing it in.

i was also told to check the ground strap at the ba k of the block. Since the ecm and several other sensors are mounted to the intake the ground strap is crucial. I was not too concerned since it runs fine while in park. Easy enough test tho

[sunk]

My chilton does not have the vaccum line documented to the brake booster (no hydroboost)

[Brian]

The hose would typically be coming off the intake manifold and connect to the brake booster. I don't think it would be categorized as part of the emissions system.

[Robert B]

okay i have 3 ideas as yours should be like 99% the same as mine .
1--- the aformentioned o2 sensor wire grounding for bad reading.. also on this note did you reset the comp after putting in the new sensors ?? the comp should adjust but it may not be able to if the reading is too much of a difference
2--- also mentioned is a vacuum leak somewhere but may be many things so not alot of help there though if you would like a pic of the vacuum boost brake system hose routing i can do that for ya
3--- the injectors for the tbi may be dirty ( you can check the spray pattern at idle with a good flashlight) and when giving more gas they would open more and allow the fuel to be much more at a normal level and idle they would be barely open and dirt can block the fuel then easily ---- also on this note for the fuel pressure that was said its only a 12-13 psi system with 10 minimum and 15 max and if its under 10(or the minimum to open the jets) the vehicle will not run at all and you would notice a big loss in power and coughing and etc when giving it large amounts of gas then and it seems to run fine at higher rpm times

[Robert B]

took out my comment as i did not have all the facts i wanted :)

[sunk]

I think it was as simple as a messed up o2 sensor but i need to drive a bit more before deciding. Turns out i have been messing o2 sensors up since i installed the headers years ago. Every time i would screw it into the header i would cross thread it since there was no room next to the firewall. This would crush the fins on the sensor just a little bit.

solution? Hole saw! I still have to make a cover plate but at least it will be easier in the future...

[Chris]

Good to hear Adam!