Slight Hesitation on part throttle.

[dubbs693]

Hey guys, I am in desperate need of help.

I will try to explain the issue as best I can and list what parts I've thrown at the issue.

Under part throttle I get a slight hesitation in acceleration.. Basically the accel isn't smooth as it should be, It is a lot worse when the engine is cold, when warmed up the issue is still there just not as noticeable. Also the Idle is a bit lumpy cold or warm.. Fluctuates about 100-150 rpm when sitting. The lowest I can get the idle is 800...

I've replaced the TPS and adjusted it within spec.Replaced a clogged fuel filterSpark plugs, wires, cap, rotor.

I have 2 MAFs and when I switch btw both the issue doesn't change.

Changed out the O2 and noticed it was very white. ( I get about 26mpg mix of city and highway) Spark plugs look ok now though..

Its a KA24DE from a 91 240sx, the motor is freshly rebuilt, 20k miles on it.

Any input would be greatly appreciated. Thanks.

Edit - I check the grounds.. Replaced the battery negative ground to the intake mani with a 4 gauge wire.. Also changed the stranded wire ground off the engine with an 8gauge wire.. Sanded down all other grounds that I could see..

Modified by dubbs693 at 11:52 AM 5/15/2007
Modified by dubbs693 at 11:57 AM 5/15/2007

[dubbs693]

Whoa, too many responses.. Can't read them all.. Damn..

[rogoman]

Several things to check.- possible vacuum leak; use a vacuum gauge.- dirty air filter.- check fuel pressure; may be too low.- check ignition timing; should be 20.- dirty fuel injectors.

[dubbs693]

I checked all of the vacuum lines I could find, and didn't find anything wrong. Do you have a diagram I could use?

Air Filter is clean..

Fuel Pressure is good..

Ignition Timing is good.

Only thing left I guess is Injectors..

When it gets really hot outside and I get stuck in traffic for a little while my car refuses to accelerate at a normal pace. It runs VERY VERY SLOW, also hesitates really bad. Once I get some air on the radiator.. It's fine. I've changed out the Coolant temp sensor and the temp gauge seems fine.

Any ideas?

[dubbs693]

Thanks

[AWDB12wagon]

Try capping off your EGR...

[AWDB12wagon]

the egr vac line that is...

[rogoman]

Do an ECU code readout. There may be one or more fault codes set; if so, it could help you find the problem.

[dubbs693]

No ECU codes.. Comes back 5-5

I will try the egr capoff..