Back-fire through intake

JBeezy53 · Jun 8, 2006

First off the car is a 65 Galaxy but with a EFI 5.0/AOD swap out of a 91 GT. Well atleast the harness and everything on the engine except the cam, it turned out to have the non-HO firing order so its not a roller. After doing the swap everything was fine except the car drives sluggish and back fires through the intake. It doesn't do it that much when its in park or nuetral but when driving it does it a lot and the car is a dog, no torque at all. My uncle put a A9L computer in it but from what I hear it doesn't work to well with an AOD. So we put in an AOD computer, 8GL or something like that and then a thunderbird computer. It actually drove best with the A9L. I pulled the codes and got 51, 85 and 87. This where we are at now, we've checked timing and firing order many times and a few other things and just can not figure out the back firing problem. So any real help is appreciated.

Bad92GT · Jun 8, 2006

well its mass air correct? the A9L isnt designed for the AOD.. neither is the 8GL.. you basically just dont have the computer correctly.. at the same time you have a serious lean problem.. thats basically running the car out of fuel.. mess with the timing, and fuel and see what happens

JBeezy53 · Jun 8, 2006

I also tried advancing and retarding the timing but that did not help. It has the stock regulator but a fuel pump that flows better than a stock 5.0's (77 or 85 lph something like that). The next thing I will try will be to check the fuel pressure and maybe take the adj. regulator off my car. But shouldn't the stock regulator keep the pressure low?

JBeezy53 · Jun 8, 2006

oops........didn't see your post Ironman. Well if its lean then I'll check the pressure tomorrow and I'll also get another computer, my uncle thought the 8GL was an AOD computer. Yeah it is mass air.

It also seemed to run better when the timing was retarded more than when it was advanced.

Deleted member 87397 · Jun 8, 2006

I think the A9P would be the best computer for you to be running with that combo, but you still might have isssus if it's a non-HO motor.

Hissing Cobra · Jun 8, 2006

My brother and I just finished reinstalling our 2nd camshaft/lifter set into my 306 last weekend. It was also backfiring through the intake manifold. The cause? A worn camshaft lobe and worn lifter. It was also a flat tappet camshaft (although a solid lifter unit and not a hydraulic lifter unit.)

Back in January, I blew a head gasket. While it was apart, I pulled the lifters out and couldn't get one our of the block - 7th one back on the passenger side.) After forcing it out, we noticed the burrs on the lifter and yanked the cam. Yup, it was going down.

We smoothed the lifter bore and reinstalled a brand new camshaft and lifter set. It was broken in and the oil/filter were changed. It ran good. The next day, it began backfiring through the intake and power dropped severely. I couldn't even idle it without it backfiring. We pulled the intake and lifters and the 3rd one back on the driver's side wouldn't come out. Yup, it was burred and the lobe on the brand new camshaft was wiped. It had less than 40 miles on it! WTF?

I've since read a very good article on flat tappet camshafts and their failures in the June 2006 issue of HOT ROD Magazine. It's a very good article and I advise you to read it. There's one engine builder that's quoted as saying that he's had more camshaft/lifter failures during the last 3 years, than he's had in the previous 30!

We've since reinstalled another brand new camshaft/lifter set and it's been great so far. If it fails again, I'll be saving up for a roller unit.

I would pull the intake and look at all of the lifters. If one or more don't come out, you probably have a camshaft that's gone bad.

Good luck!

JBeezy53 · Jun 8, 2006

Thanks Hissing Cobra. I keep telling my uncle to swap in a roller cam and lifters and get rid of the flat tappet one, this would be a good reason for him to do it this weekend.

Keep the ideas coming, I'm making a check list.

jrichker · Jun 9, 2006

The A9L or A9P will not work well with a non roller engine. The injector firing order is off sequence, you need to use the correct computer. See http://fordfuelinjection.com/index.php?p=92 for more information.

Code 51 Engine Coolant Temperature (ECT) sensor signal is/was too high -
Possible bad ECT sensor, or wiring. Possible missing signal ground –
black/wire wire broken or bad connection. With the power off, measure the
resistance between the black/white wire and battery ground. You should see
less than 1 ohm. Check the same black /white wire on the TPS and MAP
sensor. More than 1 ohm there and the wire is probably broken in the harness
between the engine and the computer. The 10 pin connectors pass the
black/white wire back to the computer, and can cause problems.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Voltages may be measured across the ECT by probing the connector from the rear.
Use care in doing it so that you don't damage the wiring or connector.

Here's the table :

68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61

Note that all resistance tests must be done with power off. Measuring resistance
with a circuit powered on will give false readings and possibly damage the meter.

Ohms measures at the computer with the computer disconnected, or at the sensor with
the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Code 85 - CANP solenoid - The Carbon Canister solenoid is inoperative. Check vacuum lines for leaks and cracks. Check electrical wiring for loose connections, damaged wiring and insulation. Check solenoid valve operation by grounding the gray/yellow wire to the solenoid and blowing through it.
The computer provides the ground for the solenoid. The red wire to the solenoid is always energized any time the ignition switch is in the run position.

Code 87 – fuel pump primary circuit failure. The fuel pump lost power while the engine was running. Check fuel pump relay, check inertia switch, wiring to/from inertia switch, red wire going to inertia switch for +12volts. Check the other side of inertia switch for +12 volts.

To help troubleshoot the 87 code, follow this link for a wiring diagram for 89-93 cars [urlhttp://www.autozone.com/servlet/UiBroker?ForwardPage=az/cds/en_us/0900823d/80/19/59/5a/0900823d8019595a.jsp [/url]

For 79-88 cars use, http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp

JBeezy53 · Jun 9, 2006

Thanks jricher, you always have a very good, detailed answer to most problems.

Back-fire through intake

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