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Item Posts    Sort Order

Why doesn't my combo work?

 
mc302stang
New User
Posts: 34
Joined: 06/08
Posted: 05/31/13 12:39 PM

•1989 Mustang with BOSS 302 Shortblock, Tremec T-56 6-spd, and 3:55 gears:
Mahle Forged 4032 Aluminum Alloy Pistons with Ring Set. 4.00" bore Flat top w/ 1.60" compression height.  Yields a 9.0:1 (nominal) compression ratio w/ a 64cc combustion chamber.Pistons have generous valve reliefs that work with most inline valve heads. Ring set is 1.5mm compression, 1.5mm second, 3mm oil ring. Eagle 4340 Chromoly Forged Steel 6-bolt crank. Eagle 5140 Forged Steel I-beam Connecting Rods with ARP capscrew bolts. Splayed 4-bolt main on 2, 3, 4, main caps, 2-bolt main on first and fifth main caps. High Tensile Strength Diesel Grade Cast Iron 4.125"bore capacity, finished at 3.990" to 3.995" rough bore 8.2" deck height, finished at 8.200" plus .010" to .015" Maximum recommended stroke 3.400" Main bearing bores finished to low limit. Finished lifter bores. Revised oiling and cooling system passageways. Siamese bore with drilled coolant crossover holes Increased bulkhead material. Threaded core and galley plugs (straight thread port plugs with O-ring)

Trick Flow Twisted Wedge heads (street), Edelbrock performer II intake, E-303 cam, 1:6 rr, 42 lb injectors, MSD Dist, ignition box, Vortec Super Charger SC1(3-5 lbs boost),Ford PMS computer, 1-3/4" headers, 2.5" exhaust, and 75mm throttle body. About 400 rwhp.

Problem: car idles great, runs great with your foot in it, no vacuum leaks, but try to just drive around and it lurches or surges or whatever you call it. Feels like it cuts out when you try to maintain a certain speed. Supposedly, it is tuned (3x) and it still behaves this way. Can anybody tell me why?  

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jmardlin
New User
Posts: 7
Joined: 05/13
Posted: 06/01/13 10:18 AM

It sounds like you have a part throttle issue with it being too lean. This will cause the surge at light load you are describing. I have had the same problem with holley carbs with the idle feed restrictors too small or partially plugged. It would idle good, run great when you were hard on the throttle but surge and buck real bad at light throttle. What is your fuel pressure set to at idle and full throttle. It may be to low.  

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mc302stang
New User
Posts: 34
Joined: 06/08
Posted: 06/08/13 08:30 AM

According to the gauge, it is about 29-30 lbs. at idle, but something weird happened when I gave it some gas. The pressure dropped a couple of lbs. Shouldn't it go up?  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 06/08/13 10:27 AM

check the fuel pressure with the engine off..   should be 38 or 39PSI engine off..

when you cycle the key on.. the fuel pressure should come up INSTANTLY...  not take a while to come up.. i am talking less than a second..

how old is the fuel filter back by the tank????

is the fuel pump noisy...  there is a way to turn the fuel pump on via the EECIV test port..

if you run a test lead to the port #926 and the other end is grounded.. when the key turns on the fuel pump relay will cycle on..

Dlc Eeciv Zpse2a607e9



one additional thing for right now...

do you have a digital volt meter?????

get the engine running. turn the headlights on...

set digital volt meter and set to 20 volts DC..

1.. test battery post to battery post...  14.1 to 14.8 volts is expected..

2.. test negative battery post to the engine block.. 0.04 volts DC max...

3. test negative battery post to the body...  0.02 volts DC MAX

4. test engine block to the firewall... 0.02 volts DC max is expected..

this test takes less than 2 minutes including the time to open the hood and start the engine..

if tests 2, 3 or 4 come up with more voltage than 4/100 or 2/100ths of a volt .. you have a bad ground..

why.. because any fuel injected car will NOT RUN properly if there is a difference in the voltages on various parts ... same on the ground side..


you would not believe the difference is how this ranger truck ran.. when i moved the ground wire on the firewall from the wiper mounting stud to the proper stud... be sure to slide the image to the right to view the red circle on the wrong place..  test 4 had 0.8 volts.. after the move it had 0.01. exactly as expected...

2001Rangerfirewallgroundstrap  

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mc302stang
New User
Posts: 34
Joined: 06/08
Posted: 06/08/13 03:02 PM

Both fuel pumps are new and yes I hear them run when I turn the key. I will check the grounding issue out. Considering everything that has been done, there could be something hooked up wrong. Thanks for the walk through on checking the voltage and ground.  

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mc302stang
New User
Posts: 34
Joined: 06/08
Posted: 06/09/13 10:46 AM

Yikes, numbers were all over the place (not steady) when I checked the voltage on 2,3,& 4. Well, must be some place in the engine compartment I would think since it ran fine before the swap.  

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mc302stang
New User
Posts: 34
Joined: 06/08
Posted: 06/19/13 12:55 PM

Ok, discovered some corroded (battery & computer grounds),loose wires, and loose connectors. Ignition coil wire where it was spliced into was loose so I fixed that. Car seems to be running fine now. I also ran an extra 4 gauge wire from the block to the frame for grounding purposes. Working on going thru rest of the wires to make sure connections are all good. Found the problem with trunk release and fixed that too. Still not sure why the cruise control is not working, need to pull the switches and dig in the fender to see if anything is amiss. Fuses are all good. There is no draw on the battery and I do not appear to have any more ground issues but will check wires anyway as a precaution.  

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oamo111
New User
Posts: 8
Joined: 08/13
Posted: 08/15/13 07:46 AM

Dude i am also go through the same problem my combo is also not working but this information is very helpful for me specially..Thanks for great sharing..


Authorized Dealeres  

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mc302stang
New User
Posts: 34
Joined: 06/08
Posted: 09/01/13 07:35 AM

Wondering if it is a temperature thing...Ran like a dream when it was 74 degrees out. Smooth, not a single hiccup. Once it got into the 80's, there were a few hiccups here and there. But when it is in the 90's not so well. So I am going to use some heat wrap tape on the intake pipes and plug some holes so it is not sucking air from the engine compartment. I may pull the intake off and wrap the fuel lines. The other option is to set the pms to add more fuel when the coolant temp gets to a certain temp (yet to be determined- bump it by 1% until it runs better in the heat). I can adjust it on the fly so I can tweak as I drive. I just need to set up another profile so I can just switch back and forth for hot days & cold days. Let you know how it goes.  

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mc302stang
New User
Posts: 34
Joined: 06/08
Posted: 09/01/13 07:39 AM

Almost forgot, Cruise control switches checked fine. Need to check the dump valve, assembly, and then the servo & diaphram inside the fender. Ugh, not looking forward to taking the fender off. Actually, not looking forward to putting it back on.  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 09/01/13 08:41 AM

do you have a 192F thermostat installed??????

once the engine comes up to temp... if your radiator and cooling fans are sized and working properly.. the engine should be at a stable temp... somewhere between 195 and 220F...

you might want to check the fuel pressure... replace the fuel filter..

the fuel pump is grounded to the back of the car...  and is the reason i wanted you to check the grounds at the front.. Smile

they should take about 7 amps of power to spin the pump with the engine running...

you might be able to build some test leads... that allow you to unplug the inertia switch and plug the digital volt meter leads into that connector with the leads in the 15 amp DC location in the meter.. to allow you to monitor the amp draw of the fuel pump... for testing..

i am taking that this engine had a new engine coolant temp sensor installed.. and a new wiring harness with it...

do you have an INFRARED temp gun??? so you can monitor the actual temps of the various parts of the engine and cooling system...


electric fans or belt driven thermostatic fan???

with the belt driven fan.. the originals on these rotated in the OTHER DIRECTION from a normal fan.. depending on the year...  i have found several mustangs with the incorrect fan on them..  where the fan was actually blowing forward thru the radiator...

and if you have electric fans...  i have found the big wires to the fans to have a broken number of strands at the ground connector near the core support.. that limited the amount of current that could pass thru.. so the fan would not run at design speed...

please verify the charging system voltage with the engine running.. and the electric fans running if equipped...

you can also run a voltage drop test on the electric fans while they are running...

positive battery post to the positive wire into the fan motor..  as close to the motor as possible..

negative battery post to the negative wire going into the fan motor..

post results..

post some pictures.. try photobucket or another image hosting site.. post links here..  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 09/01/13 08:45 AM

Icon Quotemc302stang:
Almost forgot, Cruise control switches checked fine. Need to check the dump valve, assembly, and then the servo & diaphram inside the fender. Ugh, not looking forward to taking the fender off. Actually, not looking forward to putting it back on.

this cruise control takes the trouble shooting section of the repair manual to follow the testing path...

how is the CC servo cable attached to the throttle linkage????  

got pictures???

Fordcruisecontroldiagnosis Zpsfd3e92ae

i don't know if this will help or not... its for a slightly different model ford.. but it does give you areas to check...

Ford 89 Wiring Diagram Cruise Control Zps445fa78a  

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