Ned help Bad! Bucks, vaccum prob, timing issues.. at my wits end.

Mike86Stang

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Here's the story.. put a mark VII motor in swapped in a e-cam ran w stock heads for awhile. Always been really sluggish/ low on power. valve seals started leaking so i got some GT-40ps and an explorer intake and swapped that in with some 30s and maf. Didn't wana run, tuned it best i could bucked in gear, black smoke on hard accel. Swapped out the 30's for stock 19's and meter, issue was still there. Felt like it was loading up on fuel< bucking in gear and generally running like crap.

With timing set @ 14 btdc, car doesn't want to idle, wants to stall, bucks in gear seems really sluggish and lacks power in a big way. It only pulls about 10" of vac in this tune.

If i jack up the base timing to 22* btdc it has great power, sounds/accelerates the way it should but it still bucks in gear. pulls between 16-18" of vac in this tune.

I cant get it to stop bucking no matter where i put the timing, fuel pressure, idle speed, or tps setting.

PLEASE Help!
Mike


86 GT -302 GT40p heads, Explorer Intake, aeromotive fpr, 255lph pump, 75mm maf, long tubes, off road h, mac cat back, 4.10s, e-303 cam.:nonono:
 
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RatStang

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Swap a stock MAF in and see what it does. My guess is that your meter/computer/injector combo have everything running way rich.

Pull codes
 

Mike86Stang

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Sorry forgot to mention codes are as follows

31- EGR (Disconnected)
96-Thermactor Air Bypass (Disconnected since no provision for it on P heads)
95-Thermactor Air Diverter (Disconnected since no provision for it on P heads)
27- VSS (Never installed from Maf Conversion)
 

RatStang

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Damn... you should be getting a code for 02 sensors.... unless... it is stuck and staying in open loop?


Bucking is often a sign of a mixture that is either way to lean or moderately to more rich. With your description of other symptoms (blue/black smoke, having to advance timing), I'm guessing that you're running very rich.


Do the ether test. Try and pinpoint any potential vac leaks. Reset the EEC, Reset timing with a timing light, check balancer for any signs of deterioration, check ALL spark-plug wires for sign of deterioration, check cap and rotor.

If all that is good plus whatever someone else suggests that I've forgotten... get it on a dyno and let the tuner play with it for a while.
 

Mike86Stang

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Well there in lies a lot of the problems.. I went a step further to pin point vac leaks and borrowed a friends "Smoke Pro" ( Smoke Pro® Offical Site - Redline Detection - EVAP Smoke Machine ) and there are no vacuum leaks. Plugs wires cap rotor are all new when i did the swap 2 weeks ago. Bosch plugs msd cap rotor napa pro gold wires ( really nice ) but ill check them again, and i always set timing with a light. I reset the eec, did the relearn procedures, checked the balancer.. no wiggle no wobble rubber looks in good shape. Although i know that doesn't necessarily mean anything the outer shell could have spun.
 

RatStang

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It sounds to me like you've covered all the bases. It's gotta be down to tune then.

Have you looked hard at the throttle linkage? There's nothing preventing the throttle blade from completely closing or causing it to hang open, is there? I've had that happen before. The throttle blade was ever so slightly, hanging up on the 90* elbow I had installed on the throttle body. Barely noticeable but made a HUGE difference.
 

Mustang5L5

i'm familiar with penetration
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How did you install the cam? Straight up? Dot to dot? Did you degree it?

Verify 351 firing order and then perform a cylinder balance test to make sure all cylinders are firing evenly and there aren't major misfires.
 

jrichker

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Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about
1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 9 for everything OK, or the number of the failing cylinder such as 2 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure

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. You watch the flashing test lamp or Check Engine Light and count the flashes.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

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. You watch the flashing test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical





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.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.



The STI has a gray connector shell and a white/red wire. It comes from the same
bundle of wires as the self test connector.



WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.

Do a compression test on all the cylinders.
Take special note of any cylinder that shows up as weak in the cylinder balance test. Low compression on one of these cylinders rules out the injectors as being the most likely cause of the problem. Look at cylinders that fail the cylinder balance test but have good compression. These cylinders either have a bad injector, bad spark plug or spark plug wire. Move the wire and then the spark plug to another cylinder and run the cylinder balance test again. If it follows the moved wire or spark plug, you have found the problem. If the same cylinder fails the test again,
the injector is bad. If different cylinders fail the cylinder balance test, you have ignition problems or wiring problems in the 10 pin black & white electrical connectors located by the EGR.

How to do a compression test:
Only use a compression tester with a screw in adapter for the spark plug hole. The other type leaks too much to get an accurate reading. Your local auto parts store may have a compression tester to rent. If you do mechanic work on your own car on a regular basis, it would be a good tool to add to your collection.

With the engine warmed up, remove all spark plugs and prop the throttle wide open, crank the engine until it the gage reading stops increasing. On a cold engine, it will be hard to tell what's good & what's not. Some of the recent posts have numbers ranging from 140-170 psi. If the compression is low, squirt some oil in the cylinder and do it again – if it comes up, the rings are worn. There should be no more than 10% difference between cylinders. Use a blow down
leak test (puts compressed air inside cylinders) on cylinders that have more than 10% difference.

See the link to my site for details on how to build your own blow down type compression tester.
 

Mike86Stang

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have you verified the HO firing order?
Yes, i verified it, Even went back over the wires and the injector harness to see if i somehow swapped one. It all checks out.

How did you install the cam? Straight up? Dot to dot? Did you degree it?

Verify 351 firing order and then perform a cylinder balance test to make sure all cylinders are firing evenly and there aren't major misfires.
I installed the cam dot to dot, straight up.. didn't advance or retard it since i have a standard timing set. I'll have to try the balance test when i get home tonight.

As far as the throttle linkage i double checked it and its not hanging up or anything. :shrug:
 
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