TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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What would cause hesitation under initial throttle?
Alright, I have a weird issue in my '86 305 TPI Camaro. It fires right up (now that I replaced the fuel pump relay) every time and idles smooth and well. Engine sounds like it is running strong. No smoke on start up and it doesn't appear to be smoking at all under throttle either. However, whether warm or cold, if you give the engine quick throttle in my garage (as this car is not daily driving or anything so I haven't really checked this in gear) the engine bogs for a second than accelerates. Now it smells rich, but for the most part it is usually cold as I don't normally let it run long enough to really get up to temp. nor do I drive it. A couple times though I have let it warm up pretty well and it gets a bit better but it is still there.
Now I have replaced the spark plugs, any bad wires, cap and rotor. I also changed the oil and filter as well as the air filters and that fuel pump relay. I imagine the car had old fuel in it as it sat for a long time before I recently got it I can imagine by the looks of everything when I picked it up.
Now, I have since run about 4 gallons of clean new fuel through it and haven't replaced the fuel filter yet, but I was just wondering if anyone had any other ideas of what it could possibly be sure fire that they have run into in the past or know to be a fix for this general problem almost every time before I just start replacing everything maintenance related as I am trying to sell the car and just wanted it to be a decent runner right off the bat for whoever gets it so they don't have to do all that initial maintenance stuff that tends to cost a bit if none of it has been done. Basically, I want the car to be able to run decent enough for someone to be able buy it and not have to spend another $200 on engine/drive line stuff right away and can get to working on the other project aspects...however, I don't want to spend too much replacing things that don't necessarily need to be replaced either if you know what I mean :-p
Re: What would cause hesitation under initial throttle?
Not yet, I need to though. Would that cause it to fall on its face under initial hard throttle though but still fire right up and idle fine? That is what's throwing me off a bit here. No throttle response and it seems to get a bit better when the car is warm.
Re: What would cause hesitation under initial throttle?
I have an intermittent check engine light, but I cant get the codes to flash using the methods that usually work bridging the connectors on the plug under the dash. It's weird because it was always coming on when cold and staying on until I got the engine warm, turned it off, and restarted before it would go away. After I replaced the fuel pump relay, it seems to be gone...though I doubt that has anything to do with the light...just weird. I was thinking about replacing the TPS, but I think its like 30-40 bucks...and what would you clean the MAF with? I don't want to damage it with too harsh a chemical.
Re: What would cause hesitation under initial throttle?
ok in your first post, it says you never let it get up to operating temperature. simple mistake, for the car runs rich until it is at operating temperature because it is in open loop... once it heats up the computer goes into closed loop and runs leaner, hence why it doesnt smell as rich when it warms up.
how bad of a "bog" do you get when you punch the throttle in park?
Re: What would cause hesitation under initial throttle?
It falls on its face for about a half second to a second, then revs up from there. I pretty much assumed the rich smell was just due to not letting it run up to temp. but maybe once, but thought I would mention it anyway just in case. I've had it up to temp. a few times, but just not the temp. as if I had been running on the road for more than 20 minutes.
Re: What would cause hesitation under initial throttle?
I'm trying to help a friend with a LT1 in 55 Chevy right now with the same problem. He has replaced Optispark, all wires, O2 sensors, I've deleted EGR, smog, cannister, VATS, etc from ECM, and it still does it.
We haven't been able to find answer either.
If I get clue, I'll post it also.
Re: What would cause hesitation under initial throttle?
i did this on my 88 gta decarbonzie the engine i used sea foam bought it from auto zone and a small piece of vacuum hose i hooked it up to near the throttle plates as i can and let the engine suck it in but dont let it suck it and kill the motor if it starts to die pull it out of the liquid running ruff is ok that means it is working and most likely u will be seeing white smoke out the tail pipe after the can was empty turn off engine let it set for 10 to 15 mins start it and rev it up till there is no more carbon smoke ( alot of white smoke ) ( a side note make sure you are in a place with a lot of ventlation i wasnt in to well of one and filled my repair shop with it had to leave the place it smells like a engine running to rich and white smoke every where)