back with yet another question on this 5.0

Topic: back with yet another question on this 5.0 (Read 2011 times) previous topic - next topic

back with yet another question on this 5.0

November 08, 2006, 02:35:45 PM

Ok Ive been messing with this engine for a bit since about may and Im about ready to just have someone else fix it. I have a problem with the fuel mixture on this thing. The computer is out of an 88 cougar 5.0 so its speed density. the engine was a 302 SO CFI engine . Here's what all has been changed on it as far as engine components.
HO intake from a 90 mustang
HO throttle body and EGR from the same car
stock lower intake
Cold air induction kit for a mustang
stock HO injectors

Now for the problem.
The car had around 3/4's of a tank of gas in. It was a little over 3/4's.
I started the car at a friends house drove on the highway obeying the speed limit and everything not reving the engine high or stomping on the gas or anything just normal driving for roughly 75 miles. I parked at my house. The next day I went out with the timing light and bumped the timing slightly higher to try and get a little more power out of it. It was only a degree or two higher not alot.
Timing the car took maybe 5-10 minutes at the most where the car sat and idled. I drove around the block to test it and pulled back in the drive way. I ran in the house for about a minute and came back out and started to leave. I got a half a block and the car was out of gas.
During timing it and testing after I burned 3/8's of a tank of gas.
I pulled the codes and the driver side O2 sensor is bad as well as my emissions stuff came back as not working. Other then that it checked out ok. that was with both tests key off and car running.
I had figured it was the O2 sensor causing it but then was told by a couple people that it shouldnt make that much of a difference.
I was also told to check my map sensor which I had already done with 3 or 4 different sensors.
Im just lost on what it could be . Someone please help before I kill the car.

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Reply #1 – November 08, 2006, 03:21:29 PM

have you tried dialing in your TPS or have you tried a different one in it? I had pretty much the same problem a few months ago and it ended up being a tps problem. also check to make sure all of the wires going into the tps are making connection. I had one pull out and it made my car run like dog shiznit. give this a try.

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Reply #2 – November 08, 2006, 05:12:13 PM

You have a fuel mixture problem because you're running 19 pound injectors on a computer setup for 14 pound injectors while not adjusting you're fuel pressure to compensate for the larger injectors. Get yourself an AFPR and turn the pressure down to about 28-30 PSI with the vacuum line disconnected. You're running way to rich. Especially at idle and low rpm's.

Oh, and the SO and HO share the same exact lower intake.

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Reply #3 – November 08, 2006, 06:27:46 PM

88turbo That was a thought but I wasnt sure if that would cause this. I think I'm going to check the connections on it and run a voltage test on it to double check it and make sure its right.

Paul Flockhart I didn't even think about that when I hooked it up that makes alot of sense though. a question on the AFPR. Im guessing thats adjustable fuel pressure regulator, the question is. If thats what that is would I be ahead to go ahead and update to a computer that runs 19 lb injectors?
I know it would probably require a MAF sensor and updating the harness, but I was eventually going to update to Mass Air anyway so I can upgrade the engine better. If so which computer do I want to look for? I see all kinds of them on ebay all the time. It has an auto tranny in it but Im wanting to eventually switch to a T5.
oh and yeah I know the lowers are the same. I just added that to the list as it was changed when the CFI went bye bye.

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Reply #4 – November 08, 2006, 09:49:50 PM

You could change to a 19 lb/hr computer (HO speed density) but you would need a HO cam. Being the motor is out of a CFI car you have a flat tappet cam. I'm not sure what flat tappet cam is like a HO roller cam but if you could find one you could do the swap.

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Reply #5 – November 08, 2006, 11:45:42 PM

thats a thought Im trying to do it without taking the motor back apart, or without buying parts that I wouldnt be swapping over to my other block when I get it to the point of using it. my other blocks a roller block and I dont want to stick a flat tappet cam in it. Does like the A9L for instance require an HO camshaft since the main difference is the firing order ?

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Reply #6 – November 09, 2006, 09:11:49 AM

Your engine block is set up for a flat tappet cam. To use a hydraulic roller cam with your current block you would need to use a retrofit type hydraulic roller cam and lifters, which is about the same price as a new roller block from Summit. Since you already have a roller block it's not at all cost effective to do a cam/computer upgrade on your current setup that is in the car. The 86-88 Mustang HO 5.0 was indeed backed up by a speed density computer as well as all 5.0 HO equipped Lincoln Mark VII's. Running larger than 19 pound injectors is not a problem with the speed density computers so long as you have:

1. An engine combo that could benefit from larger injectors
2. A cam that provides a good amount of vacuum
3. A way to tune your fuel pressure/injectors (an AFPR)

With your current setup I would install the AFPR, set the pressure and be done with it while you put your project motor together in preparation for the impending swap. Whichever way you go computer-wise with the new one (speed density or mass air) you can use the AFPR on that as well. Consider it a sound investment.

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Reply #7 – November 09, 2006, 12:06:57 PM

I agree with what Paul says on the FPR... If you have acess to a HO Speed densety EEC, I'd think it would run reasonably well as is...

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Reply #8 – November 09, 2006, 02:06:45 PM

ok on the FPR any brands I should steer away from? I think I'm going to go ahead and put one on it like paul says no matter what else I stick on it.
Had another question come up though would putting 14lb injectors in it for now cure the problem as well? and if so what size injectors did the 302SO setup have in it forgot the name of the setup thats on it. its been awhile since Ive actually had to use technical terms on it but it has the lower and upper intake like I have.
If theyre the 14lb I found a set where all I have to do is pay shipping.
We're not totally sure if its an HO or an SO motor but its complete.
The HO motor should have HO casted into the intake under the plenum plate shouldnt it?
the guy said he's pretty sure its the SO but he's a chevy guy and I cant remember what year the mustang started coming with the HO. the bottom of the motors fried due to the addition of a 200 HP NOS kit added to it with no updates to the bottom of the engine. The guy said anything off of it I want let him know and its mine for the price of shipping. So I'm going to end up with some extra parts either way the engine turns out to be if nothing else so I can mess around with polishing and practice porting a little. as well as parts to use so I dont have to take one engine apart to finish the other one.
Thanks for all the help on this guys and sorry about the long drawn out stories or the rambling Im just excited about my new find as well as severly frustrated with the car at the same time

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Reply #9 – November 09, 2006, 03:59:03 PM

I've been using the Holley Adj FPR for about 5 years with no problems, there are others that are maybe better but they are pricey. The Crane unit used to be junk...

All SEFI Fuel Injected Stangs were HO('86-up)... No Exceptions... Prior years were carb'd, exc for the '84-'85 CFI automatics.

The original HO Inj are orange(Stang, LSC Lincoln, trucks, '91-'93 Bird/Coug, 4.6s begnning '91 and so on). SO Inj are white... Most common use of the 14lb were any 5.0 '86-'91, other than the above mentioned. NA 2.3 Stangs also used them as well as some of the V6s(Dunno which ones, I walk a wide path around those things)...

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Reply #10 – November 09, 2006, 11:23:29 PM

Quote from: Master_xzavior;112530

Had another question come up though would putting 14lb injectors in it for now cure the problem as well?

It should, since the SO computer is making all its calculations based on the assumption that the engine has 14lb injectors.

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Reply #11 – November 10, 2006, 01:22:23 AM

ok so going by what turbocoupe50 posted Id be somewhat safe to assume that the engine my friends got is a HO. which would be a good thing part wise. provided the cam is good I could be a step closer to having my parts to assemble the other engine. I know I stand a chance at having to replace parts sooner but if the parts are free to start then Im pretty much just spending extra time. The guy told me he thought it was an E303 cam he thought. If thats the case it should be a roller cam correct?
Another question is the roller block I have has the rotating assembly in it yet Im not sure exactly what year it is its 90-92 but it was in a pickup. it has taller lifter holes in it as well as the holes drilled and tapped for the spider and lifter bars. the pistons are dished, not flat or relief cut. Does anyone happen to know are these just regular dished cast pistons or are the the better forged pistons they put in the HO's?
The engine had the E7 heads same as an HO on it as well. The on difference I could tell from looking at it with the top half off was the use of a regular hydraulic cam which looks funny because the lifters sit alot lower in the bores. either way on the pistons it should make using a larger cam more possible without clearance issues.

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Reply #12 – November 10, 2006, 05:33:17 PM

E303's are roller cams. The truck blocks came with non-roller cams, but the blocks are machined to be roller cam ready as you've already stated by your observations.

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Reply #13 – November 10, 2006, 09:13:29 PM

Ok update on the whole thing. If things go as planned I should have the stuff to build close to a stock HO. the only part I'm not sure on is the pistons construction material or compression. Im getting basically everything on an HO minus the block, heads, crank, rods, and pistons. mainly because they damaged one of the pistons. If everythings in good shape I should be set to go as far as the engine is concerned.
On top of it all the guy found the computer out of the car sitting on top of the motor when he went out to check the parts. It's from an 88 stang GT. I know it was around there when they were just starting to put mass air on the stangs so I stand a chance of it being speed density or mass air. Either way it will run the engine set up without having to add the extra FPR and stuff, I may end up having to find a MAF meter though.
So from the sounds of it if all goes well I'll have what I need to get it mechanically sound soon.

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Reply #14 – November 11, 2006, 10:34:35 AM

Unless it was a Calif car, it's SD....