engine surging


mcollier101
05-25-2013, 12:22 AM
I have a 99 Grand Am GT 3400. Just starting doing this, when you start the engine, it starts surging rhythmically as if you are pushing on the accelerator and letting off. When I put it in gear, I have to have the brake firmly pushed down as it lurches forward severely. I haven't driven it far, but it seems once you get going it runs fine. Any ideas?

Tech II
05-25-2013, 10:37 AM
Sounds like a vacuum leak.......also pull the vac line off the fuel pressure regulator and see if there is fuel in the line.....

Scan for codes....

mcollier101
05-25-2013, 06:28 PM
I checked vacuum and found one off. Did not solve the problem. I removed the fuel pressure regulator expecting some gas to come out of the line but none did. I replaced the regulator with a new one. I restarted and had the same problem, I did however feel the fuel line was empty and might take a few moments to get back up to snuff. I let it run and after about a minute and a half, all went smooth and the check engine light went out. Took it for a test drive and all seems okay. I do wonder if there isn't an underlying problem (perhaps a fuel pump). For now it seems okay, thanks for the advise.

SleepyHead98
05-25-2013, 07:15 PM
I wouldnt think so (Fuel problem and what not). I would think it would either be vac leak or sensor. Usually IAC (Idle air control). TPS could cause a problem too. But usually a code will be thrown for those.

Im not really surprised the surge went away after a while, once the computer relearned how to act once you plugged the hose back in.

Add your comment to this topic!