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I have a problem with my car it hesitates at about 4500 rpm when cold and as it gets to operating tenperature it hesitates at any rpm, I changed the distributor spark plug and wires and air flow meter still the car hesitates any idea as to what the problem may be.
would air leaks cause hesitation or just bad idling, I also heard tat the tenperature may cause this problem any ideas.

When you say hesitates, do you mean that you are just crusing along and when you punch it to go faster the car has a heart attack and maybe goes slower for a sec then picks up?

If thats the case then it sounds like you are leaning out due to the "throttle pumps" not being high enough. When you suddenly change throttle position you are all of a sudden giving alot of extra air to the engine and this sudden change in air volume needs extra fuel since the injectors wouldent give enough so its programmed to increase fuel while the throttle is moving and then put it back to normal again as the position stops changing. When a car is cold, alot of extra fuel is being injected anyway since during warm up fuel dosent atomize properly and sticks to the walls of the chamber so youd be less likely to notice the problem since this extra fuel is covering it up.

I see in your sig that you have a bpt, so I guess you have the bpt ecu to go along with it? What wiring harness are you using? The reason Im asking is because this problem could be caused by the ecu not getting the throttle position sensor signal. Thats what the ecu uses to know when there has been a sudden change in throttle position and to add extra fuel.

If you wired in the engine yourself I would DEFINATELY check the wires to the tps and make sure its getting the voltage its supposed to, Heres what they all do if you have a 4 wire tps.

+5 Volt (RED / GREEN)
Throttle % (GREEN / WHITE)
Ground (BLACK / BROWN)
Idle Switch (RED / WHITE)

So youll want to make sure its getting voltage and then cross reference with a wiring diagram for the gtx ecu (if thats what you have) and make sure that the throttle % wire is going to the proper location on the ecu. I had the same problem with mine and some wiring fixed that right up.

Hope that helps.

Thanks franko I had an air leak that was causing the problem got it fixed today

Blast! I thought I had it figured out.. Ohh well, you got it fixed anyway.

Yep but you where right about it running lean

how did u determine it was a leak?
i am trying to figure why mine hesitates on throttle increases.

I just listened to the car and hear a whistle kind of sound and checked all the pipes, you could also use some sort of carb cleaner and spray it at the jionts or where u suspect the leak the idle will changed if it gets into the pipes.
One thing if you are using those cheap hose clamps use the t-bolts there are much better, i had a leak couldnt find it it was the clamps after i changed it no more leaks.