Did a search, so I'll try again for help. Idles perfect at about 6, starts off smooth until I get to 40 mph, 4th gear, then the car wants to surge and buck if I just drive steady. When I accelerate up to 50 mph, smooths out perfect. As long as I am accelerating, it does not surge.

Cleaned the IAC, heard mention of cleaning the MAF, any other thoughts?
Richard

 

any mods?

 

Sorry, a good question - it has a chip, don't know which one, came with it, and Flowmasters. No K&N, all else appears stock. Automatic. 110,000 miles.

 

It could possibly be from the chip...my car does the same thing...its because of the EGR flow, but my problem is because of the aftermarket heads i have on it. After i got it dyno tuned it reduced the bucking considerably but it still does it if i hold steady just like your description. If you want to give it a shot you can disconnect the vaccum line on the EGR valve and block it off, your check engine light will eventually come on but if it changes the bucking at all you could have the same flow problems that i had...but considering our mod list is considerably different anything is possible...

Keep in mind this is just a suggestion related to mods....a regular driveability concern could still be possible at 110k that could be fixed with a simple tune up even. Go through the regular checklist for tune up items if you havent already done any of them first, and you could always try that EGR vaccum line and see if that makes a difference.

 

Great advice, will give it a try this weekend, the EGR idea and I will pull some plugs and see how worn they look as well. thanks

 

could be a tps sensor or iac. id check the tps first. i had the same problem, as long as i was accelerating i was fine but once i started to cruise it buck and buck. turned out to be the tps

 

Sounds like the DPFE (Delta Pressure Feedback EGR) sensor on the EGR system has gone bad, (although that usually gives a code) like previousle said take of the vaccuume line to the EGR, plug it and see if the surging goes away. If that dosen't seem to fix it try the TPS

 

I am a weekend mechanic, so please clarify, plug the HOSE and the EGR? Or just the HOSE? thanks again

 

just plug the end of the vacuum hose once removed from the EGR valve. as far as the DPFE sensor going, im almost positive that sensor is only there to monitor the fact that there is indeed flow or no flow, at least thats how it used to be on some older models, and every instance we've come across that was a DPFE always set a MIL code, even if it was for the high temp hoses it still set a code

 

OK guys, finally got around to plugging the EGR hose and it seems to have helped considerably. Please tell me what I just did and WHY it worked! I need to learn.
Richard