Hey guys,

I made a thread about this a few months back. For about a year and a half now, my car has been hesitating under load. When it first started, it would only do it when I first started climbing a steep hill or tried to accelerate quickly. The car would jump between 1600-1800 rpms for a few seconds, and then surge up to 2400 rpms and be fine the remainder of the hill/load.

Well, it's gotten worse over time. When the car is cold, it is hard to start. I have to turn the key for about 10 seconds before the engine starts to rumble a little bit. Then I have to give the car gas or it will die. Then as it's idling, it cycles between about 800rpm and 1200rpm until it settles down at 750rpm. The car started hesitating under throttle loads that used to be okay over the course of this year, so I knew I couldn't ignore the issue anymore.

I've been troubleshooting this problem for a while. In August I tested the fuel pressure and found out the fuel pressure regulator was bad. So last weekend I put in a new fuel pressure regulator diaphragm and new fuel injectors from south bay. It really didn't do anything, though. The car runs better in the over-2500 rpm range, but the hesitation issue at the lower rpms is much more pronounced. The car was hard to start before this, but it's even harder to start now when its cold.

It also really doesn't like to start accelerating at all now. Unless I REALLY baby the throttle, it will hesitate all over the sub-2000rpm range, until it finally stops and surges up to about 3000rpms. Once the car gets past about 2500rpm, it runs fine, which seems really odd.

Tonight I put in a new ignition coil thinking that may have been the issue. No luck though, and it's still running as bad as ever. While I was installing the new coil I found a vacuum leak and put in a new hose in case that was the issue. I'm stumped and have no idea where to go from here. The car is hard to start when it's cold, but it fires right up when it's warm. The car almost dies backing out of my garage and when entering my garage. It hesitates and sometimes feels like it's going to die when I first start off, but it runs like a champ once its past 2500rpm. Plugs and wires have about 10k miles on them since I replaced them three years ago. What in the hell could this be?

 

Does it hold fuel pressure? Drive it with the gauge tapped to the windshield, does the pressure drop below 35 psi under load?
Check the tps & map sensors. Do a resistence check on the cts when hot & cold. Check the ecm grounds.

 

Alright, I'll try some of that out tomorrow. What is the cts? I don't think I have enough hose on my fuel pressure gauge to tape it somewhere I could see it while driving.

 

Cts is the coolant temp sensor, if its reading wrong it could make it run rich/lean, causing hard starting.

 

I was able to get some log files in tunerpro RT from the car and I posted over in the ecm forum to see if they could tell me if the car was running correctly or not.