Stumble/skip when accelerate

Big-Stable · Mar 13, 2007

ok, I removed a great running 302 out of our 89 hatch and replaced it with a 351 out of a 94 lightning. It is a stock short block, trickflow r intake, port matched heads, 170 or 190 lph pump, 24# inj, pro flow 24# maf, a9l eec (I also have a 93 cobra eec, it runs worse with it), bbk adj fuel pressure regulator, bbk shortys, off road h pipe.

It idles well, but has a stumble (Skip) when you mash the gas. It has all new wires, plugs, cap, rbutton. f pressure is set at 40 when ideling, when you give it gas it goes up to about 44 or so.

The egr is not hooked up, the trick flow intake has no provisions for it, neither are any of my 02 sensors, when you drive it it does not have the power it should & the check engine light comes on.

ANY ideas?????

John

jrichker · Mar 13, 2007

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is less than $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/p-7208-equus-digital-ford-code-reader-3145.aspx– It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

KcMstang · Mar 13, 2007

Since his EGR valve isn't being used on the car wouldn't he need to have a chip to tell the computer that??? I was having the same problem and threw on a EGR vacuum solonoid and my problem was fixed.

BK_CAULEY · Mar 13, 2007

Big-Stable said:
The egr is not hooked up, the trick flow intake has no provisions for it, neither are any of my 02 sensors, when you drive it it does not have the power it should & the check engine light comes on.

ANY ideas?????

John

this might have something to do with it.

302RollinHard · Mar 13, 2007

You are flying blind my friend. You need your 02's hooked up and functional.

Big-Stable · Mar 13, 2007

I have been told i could plug the egr valve in even ho its not functional & leave the vacuum line off & it will read closed & have no egr issues, is that correct?

BK_CAULEY · Mar 13, 2007

Big-Stable said:
I have been told i could plug the egr valve in even ho its not functional & leave the vacuum line off & it will read closed & have no egr issues, is that correct?

when the computer go's into Open Loop the O2's input is not used, and the engine runs on tables. closed loops is when it is reading. and if its just running off tables its not supporting all of your mods (bigger injectors and such) the computer is programmed for the factory stuff and since its running open loop and not getting the tabled fuel and air delivery its not gonna run right.

JChalfan · Mar 13, 2007

302RollinHard said:
You are flying blind my friend. You need your 02's hooked up and functional.

Seriously though, you NEED those O2 sensors hooked up. On a bone stock 5.0 you could probably run ok (not good, just drivable) with no 02's. Like BK said, it's running off tables, not listening to any of your sensors.

You can get by without an EGR, I believe it will run a little lean at part throttle. You can get a chip burned which will take care of that. But you absolutely must have your O2's hooked up.

Big-Stable · Mar 13, 2007

ok, that confused me a little. closed loop or open loop, what causes each, and what should I do to begin to try to fix my problem..

John

Big-Stable · Mar 13, 2007

& as soon as i get home, I will hook those o2 sensors up, the wiring is there, but they were not hooked up when i did the swap.. so i didnt worry about it, but I will do that, but what else should I do....

BK_CAULEY · Mar 13, 2007

Big-Stable said:
ok, that confused me a little. closed loop or open loop, what causes each, and what should I do to begin to try to fix my problem..

John

open loop- runs off tables. causes could be an unplugged or damaged mass air oxygen or other sensor.

open loop-its making adjustents and calibrations according to how rich or lean its running(o2's) or how much air its getting (mass air) and so on..
its usung its adaptive learning.

and as far as what to do. hook them o2's up. if that doesnt fix the problem pull codes and use JRICHKERS checklist.

Stumble/skip when accelerate

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