Loading up on bottom end

[Steves LX]

Why is my car loading up on the bottom end? If I am following cars in traffic and just holding staedy at low RPMs say either in 2nd or 3rd gear and I get a little bit of a clearing to speed up as soon as I go to accelerate the car acts like it loaded up and then you will get a backfire or 2 that is coming from up in the headers somewhere and it will take off. Now I have noticed that while cruising down the HYWY every once in a while at a lower speed(55-60 MPH) in 5th gear it will start to give a slight buck back and forth and a pop from the exhaust sounds like its up in the headers when it pops. But like I said its mostly while driving super slow and being behind traffic. If I just tromp the pedal it runs great. New plugs, wires, TFI is good, cap and rotor look fine, new O2's, I eliminated my coil with another one and it still did this. I pulled more timing also with no changes. I am running 14 initial and 40 PSI fuel. This is a brand new motor I just put in 2 weeks ago. I didn't have this issue with my old motor. The changes that were made were 306, GT-40Y heads, and Trick Flow street heat upper and lower. Everything else stayed the same. My old motor was a 302 with GT40P's and a Edelbrock performer upper and lower. Check my sig for what my new combo is.

[mustang8998]

Did you have the old combo tuned, with the SCT chip? If so, I'd think you need to re-tune it. 14* initial seems a bit much, for a tuned chip.

[YouGotJunk]

Try backing off the fuel pressure a little bit. Sounds like to me it's loading up a little. I would try backing it down to around 35 or so and see if it helps any. Goodluck!

[ibstrokin]

You can run a vacuum gauge in the car and watch what the vacuum is doing while this happens.

[Steves LX]

Try backing off the fuel pressure a little bit. Sounds like to me it's loading up a little. I would try backing it down to around 35 or so and see if it helps any. Goodluck!

I thought about doing that. But the thought came to mind so if I do that and it runs good like that, great excellent. But now what happens when I go to spray the car and have to add more fuel. I'm back to the same problem again and even more dangerous now if it decides to start doing this dumb shit while spraying it.

Jeff I am not running the chip so no need to worry there.

[graysonracin]

tps sensor?

[Black Horse]

Pull a plug to see if its loaded or real black.....you might have to run a hotter plug too

[MFIELD]

TPS X2

Thats what I was thinking. Maybe has a dead spot in it. I think you can test them with a meter and slowly rotate the throttle and watch to see if it fluctuates or drops in and out. I believe it should gradually change voltage.

[ibstrokin]

As far as testing the tps, you want to take a ohm meter and test the sweep. If you are using a digital ohm meter, as you go through a sweep( tps unplugged, someone in the car steadily pressing the gas pedal) if the meter goes to infinity at any point through the sweep, it needs replaced. You will want to do this slowly.

[Stangman]

Steve, if it is your TPS again... stop buying them from Advance Auto!!

Go to Smyths and get the STANDARD SELECT brand, or Pep Boys and get a Borg-Warner SELECT brand. I've never had an issue with either of those products, and I used to sell PLENTY of the Borg-Warner SELECT products when I worked at Pep Boys (Up-sell :bigthumb )

the GP SORENSEN brand looks very chinsy compared to those 2 products

AND could it be the 1 step colder plug you were telling me about?

[Steves LX]

Steve, if it is your TPS again... stop buying them from Advance Auto!!

Go to Smyths and get the STANDARD SELECT brand, or Pep Boys and get a Borg-Warner SELECT brand. I've never had an issue with either of those products, and I used to sell PLENTY of the Borg-Warner SELECT products when I worked at Pep Boys (Up-sell :bigthumb )

the GP SORENSEN brand looks very chinsy compared to those 2 products

AND could it be the 1 step colder plug you were telling me about?

No its neither of those two. I actually got my last 2 TPS sensors from Smyth. Its been doing this even with the normal heat range plugs in there. I'm starting to wonder if my computer isn't acting up. Beyond that minute issue the car runs greatI couldn't ask for no more but it's still not right that its doing this little issue on the bottom end.

[YouGotJunk]

No its neither of those two. I actually got my last 2 TPS sensors from Smyth. Its been doing this even with the normal heat range plugs in there. I'm starting to wonder if my computer isn't acting up. Beyond that minute issue the car runs greatI couldn't ask for no more but it's still not right that its doing this little issue on the bottom end.

I'm still thinking it's loading up. I had 30lb injectors in my car with h/c/i and if I was driving it around at low rpms it didn't run good at all and it would only idle for a few minutes unitl it loaded up to much then it would die. When I would get on it real hard or got up into the upper RPM's it would run perfect. I would try backing the FP off a little and see if it helps it. What kind of nitrous kit are you running...wet or dry?? I would try lower fuel pressure first...if it helps it..then worry about your nitrous tune later.

[Rick93coupe]

Check your grounds, I've seen some pretty strange stuff coming from the ground on the harness at the back of the intake.

[Stangman]

No its neither of those two. I actually got my last 2 TPS sensors from Smyth. Its been doing this even with the normal heat range plugs in there. I'm starting to wonder if my computer isn't acting up. Beyond that minute issue the car runs greatI couldn't ask for no more but it's still not right that its doing this little issue on the bottom end.

Get ahold of me later, I'll bring my A9L over, just so we can eliminate that from the equasion :bigthumb

[Timido]

As far as the Nitrous goes. If it is a wet kit tune the car to run the best on motor. Then pull 2 degress of timing per 50hp of shot. You are adding the extra fuel for the nitrous with the jetting in the fuel solinoid. If it is a dry kit do what the instructions say because I have never messed with a dry kit.

[quik lx]

If you have the ZEX kit, it richens up the fuel for you using vacuum from the backside of the soleniod. My fuel pressure pegs at 90PSI anytime the spray is on. So you really dont need to worry about FP off the bottle.

[Steves LX]

Yeah joe my kit is a dry kit which is identical to yours. I pulled some fuel out of it and drove it to work today and just like my luck goes it did nothing for it. It's still loading up and popping thru the headers. I tried to pull some more timing and it didn't like that either. This really sucks big time. I should've just kept my old motor in there with no oil pressure and ran it till it blew up. I didn't have any of these issues with it. I'd like to take it down to Craig and get it on the dyno but I don't know with the way its acting. It be nice if it acts up down there maybe we could figure it out together. But I think putting it under a load on the dyno and under a load on the street are differen't from one another so it will probably not act up down there.

[YouGotJunk]

Start checking for vaccum leaks...Unplug your mass air and see if it runs any better too. Your electronics on the mass air may need cleaned..If it runs better with the mass air unplugged...need to clean it or look into getting another one.

[Steves LX]

Start checking for vaccum leaks...Unplug your mass air and see if it runs any better too. Your electronics on the mass air may need cleaned..If it runs better with the mass air unplugged...need to clean it or look into getting another one.

I thought about unplugging that this morning on my way into work. I have to go out in a little bit and I will do that. I did however clean it just last week when I was trying to eliminate things. I even swapped it out and put a pro m on there that is calibrated for 24# injectors and low and behold it laughed at me and said F@@@ You I am still going to run like shit. I have hosed that whole engine compartment down with carb cleaner and brakleen with no change in the idle no stalling out or nothing. The damn car doesn't throw out any codes other than the typical EGR crap which I no longer have. I do know this I am getting to the point where I am starting to lose my patience with it and pretty soon I am just going to drop the fuel pressure way down jack the timeing way up and arm the nitrous and mash the pedal sitting still on the 2 step at 6200 RPM's and watch the fireworks go off. Then it will be one less headache I have to think about or deal with. I'll just go back to how it use to be, drive my truck and ride my moped with a fat chik on the back.:lol:

[Stangman]

Cant you harm a MAF sensor by cleaning it too much?? I had to replace the one in my '94 because I had cleaned it and then it went south on me and ran like shit all the sudden...

[Steves LX]

Cant you harm a MAF sensor by cleaning it too much?? I had to replace the one in my '94 because I had cleaned it and then it went south on me and ran like shit all the sudden...

Not sure if you can or not. But the other one I have is only a few months old and what the liklihood of having 2 differen't ones being bad? You never know with my luck though.

[Timido]

Start checking basic stuff. Compression test, Cylinder leak down test, Check you valve clearance rocker adjustment. Rule out the base engine can save you alot of time

[YouGotJunk]

Yeah you definately need to check your valves and stuff also...I'm guessing it does have an adjustable valvetrain???

[Steves LX]

No it still has bolt down rockers. I did find a vacum leak earlier tonight on the vacum tree on the manifold. I fixed that and drove trhe car and low and behold its still acting up. I hooked my nitrous up today and pulled some timing out. I set it at 10 degrees initial and it really didn't like that. It really ran like dog shit on the bottom end. Popping and bucking like crazy but if I kept my foot in it from right off the get go in 1st gear on up it ran alright. I can do a compression check but hell this motor is fresh. It's only been running for 2 weeks now. The heads are brand new. I'm starting to wonder if my pick up coil in the distributor isn't going south on me. Not sure if it would do something like this or not.

[Stangman]

It's weird how its only in the low end and under load, when I was riding with you today during the nitrous runs, it felt like it had plenty of power on the top side...

[12seclx]

Hope you figure it out soon... If things don't work out on the spray, you may have to make peace with the current dirty dozen running order... :lol:

[babiixoxbritty]

ive had a few similar situations. the first time it was the maf, it was supposed to be calibrated for 30s, but after replacing everything else i could think of, i tried a new pro m and it fixed it. its sometimes hard to tell if the car has had a tune on it, mine didnt. another time, it was my distributor, it would pop and crackle at low rpms but would clear up after you mashed the throttle, it wasnt the tfi, it was an internal problem. i see alot of fulie cars that suffer from the violent rock at low rpms when runnin 30 pounders and a good size cam. i guess it just takes a good tune, if i had to bet i would say maf problem but its kind of hard to guess not knowin all the specs. good luck hope, i can give ya some ideas.

[Steves LX]

Well here's the latest news on this thing. I have swapped out computers with a buddy, changed MAF's,new pick up coil, differn't TFI module, new cap and rotor, new O2 sensors, new wires, new plugs, differn't coil, pulled codes, vacum test and nothing has changed at all. Something I did notice is the car runs great when you first start it up and drive it. This popping thru the intake and lugging doesn't start until you drive for about a mile or two. And then it starts doing it and even then its only at certain low RPM's and not all the time. But it happens more than it doesn't. Its like as soon as the car starts to initially warm up. The only thing I have yet to do is a compression test which I intend to do tonight. I would certainly hope I don't have a bad valve seat or a valve sticking on brand new heads out of the box. I have been thinking about it and the car was running half way decent before it started doing this and I replaced the O2 sensors and it went away for the most part and then it suddenly reappeared a week or so later. I got no O2 sensor codes when I pulled codes. So after the compression test tonight if all my cylinders come back pretty close to one another I will be at a loss for whats causing this. I guess I will start Ohming out every single pin on the computer harness and looking for continuity issues.:mad:

[Steves LX]

Hope you figure it out soon... If things don't work out on the spray, you may have to make peace with the current dirty dozen running order... :lol:

:flipoff::lol:

[Stangman]

I guess I will start Ohming out every single pin on the computer harness and looking for continuity issues.:mad:

I guess we wont be hearing from you in a week... you'll be knee-deep in wiring!!

I dont know how up to it you are or if my harness is even any good either, but what if we sorta slap my wiring harness in it half-assed and see if that changes anything?

[Steves LX]

I guess we wont be hearing from you in a week... you'll be knee-deep in wiring!!

I dont know how up to it you are or if my harness is even any good either, but what if we sorta slap my wiring harness in it half-assed and see if that changes anything?

We could try. Right now I'm desperate to get this thing right. I also need to put a fuel pump in my truck.

[kennebellcobra]

If it runs fine when it first starts it's probably because it's still in open loop then when it switches to closed loop is probably what causes it to run bad which is usually a fuel problem or a sensor giving wrong info. You could try and unplug the o2's and that should keep it in open loop and see how it runs.

[12seclx]

:flipoff::lol:

:lol: I couldn't help it man... Gotta tell ya, drove the car yesterday and it feels really stout... I haven't even put the other rockers on yet... I can't imagine that new clutch disk made a difference in power/ET but we shall see next week! :eek:

[Stangman]

I also need to put a fuel pump in my truck.

Gimme a call later

[Steves LX]

Not sure what happen today between leaving the shop at 10:00 this morning and driving maybe 6 miles and parking it for an hour. Butr when I got back in it and started driving it everything was acting right. The car has more power than I have ever felt it have. Its been running like a scalded dog all day and night now. So your guess is as good as mine. I 'aint touching it now. I just hope it stays this way. I'm not exaggerating either. The other night when it was still acting up I put 125 shot to it. And if the same car would have been lined up next to it now I would have walked away thats how much stronger this thing feels now. :dunno:

[Stangman]

I think it's called "Possession"



:D