[Tanker27th]

I have built the engine in my car and have finally worked most of the problems out but I am having trouble at crusing speeds. As lond as I am at wide open throttle the cuns great, but when I am staying at a certain speed its struggling pretty bad. It is jumping and hopping like there are fuel issues or something I really dont know it just isnt right and its drivin me crazy! Can anyone help me??

[1931 steve]

What year, make, and model is the 5.0 in?

Steve

[xntrik]

Your tertiary fetzer module is staticly arcing to the pudromh terminal.

[ap72]

Originally Posted by xntrik

Your tertiary fetzer module is staticly arcing to the pudromh terminal.

Figures that'd be it- damn Fords

[xntrik]

LOL, LOL, OK let's give him a couple days to give us some information, and then we can see if we can actually solve his problem.

[Tanker27th]

Thanx for all the help guys yall are great! or not. it is a 1989 5.0 liter that has been bored .030 over, this makes it 306 ci(if your wondering). It has a E-303 camshaft with 1.7 ratio roller rockers, a cobra intake stock injectors and MAF sensor. The heads are stock but have 1.94 intake and 1.64 exhaust valves installed, they are also port matched to the intake. The computer is a A9P a LX 5.0 computer. ??? I dont know what im talkin about or thats what you think obviously. Oh yeah and this is in a Mustang which is a ford.

[Siggy_Freud]

No need to get tweeked. But in order to give you a solid answer more information was needed. More information would still be helpful. Are there any engine codes? Was the chip in the computer updated for the new cam and any modifications you did? Is it only at a certain throttle position? Does it pop or make any noises? Can you be more descriptive as to what its doing at cruise?

The more info you provide the more detailed we can get with possible solutions.

[Tanker27th]

Yeah sorry about that I was a little lit. But anyways, I still have the factory computer A9P. I was wondering if I needed like a Cobra computer or would it be better to get a custom chip from somewhere?? The only code it is sending is one for the EGR valve not opening properly, this shouldnt matter though cuz I have no smog on my car.

[Siggy_Freud]

Do you mean that you have the EGR blocked off? Unless the EGR is disabled via computer as well, it is still going to affect your engines performance a bit. The engine is going to adjust fuel and timing because its still going to be commanding the EGR to open under certain conditions. I would recommend finding someone locally (who is reputable) to datalog and burn you a chip that is truly customized for your setup.

Beyond that, you need some sort of scanner to know what the various sensors are doing. If we knew that, we might be able to provide more information. If its only acting up at a certain throttle position (that might happen to be where you tend to cruise at) Id suspect a flat spot in the Throttle position sensor. But thats really shooting in the dark because I dont know much at all about what is going on with the electronics.

Like I said before, unless the EGR is completely blocked and told never to open via the ECM, it is still going to have an affect on how the engine runs. When I retrofitted a TPI onto my 66 GMC, I had to block the EGR, and then tell the computer only to open it above 280 degrees F. Since my engine never gets that high, it never opens and thus doesn't affect my mixture.

Also keep in mind that the smog pump/AIR system are seperate from EGR functioning.

Dylan.

[xntrik]

Most have the A9L computer. I have never seen an EGR problem with them. Is yours an AOD trans?

Removing the EGR on these Mustang engines is inconsequential. Ford Motorsports sells the harness set up for street rods with the A9L and Ford says just ignore the EGR and canister plugs. All it does is NOT advance the timing as much under light load and coast conditions for smog/ those times the EGR is open.

My car the entire EGR plate is not there, I have the TB directly on the intake manifold. No problems.

NO chips are needed with an A9L computer unless you are way-way up the modification list. (added= the A9L takes a E cam fine, no alterations needed)

You say stock injectors and Cobra intake. Cobra has 24# injectors, regular HO has 19#. Are you calibrated for that?
What about the mass air meter? Is it matched to the injectors?
What are your 2 fuel pressure readings?

I'd look to the TPS as he suggested.
Maybe an ignition crossfire between wires. Seen it happen under only certain load conditions.

Also I would look inside that distributor cap. You need a stock type cap that has the anti-flashover ridges. Many of the after market caps that are so pretty and expensive do not have sufficient anti-flashover ridges like the factory cap. All that hype about brass terminals is BS. Compare aftermarket caps to the stock Motorcraft caps and you will easily see the difference in the ridges.

Another thing is that some of the aftermarket rotors have a shorter contact finger that makes the gap to the cap terminals too wide. Stick with stock Motorcraft stuff and all will be OK.

5.0 fuelie guy here.

added: One more thing. The two 10-pin connectors at the rear of the upper intake plenum are prone to get loose and make bad connections. Check them and hold the two halves tightly together with a wire tie. Be sure there is no corrosion in the connections and fill the plugs with silicone grease to keep out water. Do this on all connections on a FORD.

[Tanker27th]

My car has an A9P computer, im not sure if that is cuz it was a AOD (before I swapped it over) or because it is an LX. My intake is a cobra intake but I used the stock injectors and mass air sensor because I knew that I couldnt replace one or the other I would have to replace both and well funds got very low. So now im working with what I got. I will try new plug wires and cap and rotor, might as well. The wires I have need replaced anyways. Thanx guys!

[farna]

You can put in 24# injectors without changing the MAF. You won't get the full benefit from the larger injectors is all. The computer will adjust the pulse length for the injectors -- shorter pulse for 24# vs 19#. If you're running a little lean during cruise bigger injectors will help. You may need a little more fuel due to the cam, size, and slight compression change. I'm assuming you put a new O2 sensor in? That will affect mid range cruise as well as the TPS. Check all the sensors, one out of spec will throw everything else off.

You can't put a bigger MAF on without bigger injectors -- that will cause a lean condition since the stock injectors couldn't keep up -- but at WOT or high cruise speeds, should be able to keep up at mid range cruise.

[Arrowhead]

check your throttle position sensor to make sure there are no dead spots on it - common problem.

[xntrik]

A9P should work OK. I am told that is an AT computer regardless of body style LX or GT.

You still need to check your idle and wide open fuel pressures. Either one out of spec can make you low to mid-range lean.

Do the checks before you go chasing your tail and wasting money on parts.

O2 sensors will compensate for 24# injectors at closed loop only (running with O2 operation), but OL will be rich if fuel pressures are at spec.