Engine Swap Problems: 302 to 302HO
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Engine Swap Problems: 302 to 302HO
Hey guys,
This is my first post here, so bear with me.
I recently blew the 302 out of my 1991 F-150. I picked up a 302HO out of a 1991 Mustang for next to nothing. Checked main and rod bearings, replaced oil pump, timing chain, and harmonic balancer. Everything looked good.
Installed the engine, reusing all my other parts.
Problem is, engine will not idle now. From a cold start, it will fire right up and idle at around 1500RPM. Once it begins to warm up, the RPMs drop to around 600 and stays running. Once I shift it into gear, it dies. If I fire it up with no throttle it will die immediately, or surge a few times, then die. After a few startup attempts, it will idle, however, everytime I shift into gear, it dies.
When I unplug the IAC there is no change in idle.
Does this sound like a computer problem with the new setup?
Or could something else gone bad at the same time (EGR, IAC, etc...).
Any input will be greatly appreciated.
Thanks
This is my first post here, so bear with me.
I recently blew the 302 out of my 1991 F-150. I picked up a 302HO out of a 1991 Mustang for next to nothing. Checked main and rod bearings, replaced oil pump, timing chain, and harmonic balancer. Everything looked good.
Installed the engine, reusing all my other parts.
Problem is, engine will not idle now. From a cold start, it will fire right up and idle at around 1500RPM. Once it begins to warm up, the RPMs drop to around 600 and stays running. Once I shift it into gear, it dies. If I fire it up with no throttle it will die immediately, or surge a few times, then die. After a few startup attempts, it will idle, however, everytime I shift into gear, it dies.
When I unplug the IAC there is no change in idle.
Does this sound like a computer problem with the new setup?
Or could something else gone bad at the same time (EGR, IAC, etc...).
Any input will be greatly appreciated.
Thanks
Lead Driver
Joined: Nov 2002
Posts: 9,557
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From: Concord, NC
Start out by pulling the codes from the computer to see if it is trying to tell you anything. If you've never pulled them before, there are instructions at http://fordfuelinjection.com. Let us know what codes you come up with and maybe that will tell us something. I would also make sure the idle air control valve is clean and is not sticking closed when the engine is warmed up. The idle speed should be set with the IAC unplugged, so that should be ok. It could also be that the cam is a little large for the stock truck computer, but usually that would cause a surging, unsteady idle.
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The believe 351 firing order. The truck runs smooth when I am driving, it only surges and stalls at idle. I think that if I had messed up the firing order it would run like crap throughout the entire throttle and rpm range.
Thanks
Thanks
Senior User
Joined: Jan 2004
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From: Illinois
bank fire injection
We did this in my buddys 92 f150 4x4 put a 95 ho motor in it. People argue me to this day but here goes... When you change firing order you should also change the injector firing order. Otherwise you are drawing fuel across the intake to charge the cyl in need of the fuel. His truck had codes (lean bank) etc. and would surge and die when putting it in gear. We changed the injector firing order and to this day some 30k miles later not a single problem. Better fuel mileage and runs perfect. I just used matching guage wire and the shrink wrap style butt connectors to do this but it made all the difference.
I would have to look at his truck to see which ones I swapped but after removing the upper intake it was a relatively easy fix.
I would have to look at his truck to see which ones I swapped but after removing the upper intake it was a relatively easy fix.
Lead Driver
Joined: Nov 2002
Posts: 9,557
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From: Concord, NC
The injectors are connected the same on both firing orders on the trucks, unless my haynes manual is wrong. Injectors 1-4-5-8 and 2-3-6-7 are grouped together on both firing orders. It might be possible that the injector banks might need to be swapped - swap pin 58 and 59 on the computer 60 pin plug - although I don't know if this would mess up anything or fix anything either. What exactly did you change on his '92?
Last edited by EPNCSU2006; Jan 14, 2005 at 10:11 AM.
Senior User
Joined: Sep 2003
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From: N.W. OHIO
Did you swap out the truck pcm for the HO pcm,If memory serves correctly fuel mapping and ignition settings are a little different.There could be other sensor issues to. I'm doin a 4.9 to 5.0 HO swap on my '94 , engine is out of a '90 MARK7 I picked up a 5.8 harness for it ,also figuring on using the '90 computer. I'd also like to supercharge it somewhere down the road.By the way mine is a 4X2. 
Last edited by grampztoyz351; Jan 16, 2005 at 01:00 AM. Reason: more info
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dmelton.....why dont you just replace the iac? i think its only 20.00 and if there was no change its a good possibility it went bad.....ive had a couple go bad on me already..........hey im fixin to do the same swap in my 87 (5.0 to 5.0ho)...so whats the difference in power and torque? have you noticed a big difference while driving?
thanks
thanks
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Lead Driver
Joined: Nov 2002
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From: Concord, NC
^^ There are a couple of changes to the pin locations in the 60 pin plug between the car computers and the truck computers. Plus most of the car computers were sequential injection, which would require the injectors to be re-wired. It's not as simple as plug and play.
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Thank for all the responses.
grampztoyz351, I am using the truck's stock ecm. I have thought about going with the mustang ecm, but I haven't had a chance to sit down and figure out the wiring issues.
F-150Guy, the only differences I know of between the two are the roller cam and valve train, and the compression. 8.2:1 verses 9:1.
bob1987f, the IAC is $60.00 at AutoZone. I would love to know where I could pick one up for $20.00. I pulled it and cleaned it this weekend, and after installing it back on the truck, if I unplugged it, the truck would die. So, it must be working now.
I think I figured out my idling problem, but since I created a new problem in the mist of trying to fix it, I won't know for sure until tonight. The tube running from the EGR to the lower intake manifold had broken into two seperate pieces. Oh well, if it's not one thing, it's another.
Thanks again,
Dan
grampztoyz351, I am using the truck's stock ecm. I have thought about going with the mustang ecm, but I haven't had a chance to sit down and figure out the wiring issues.
F-150Guy, the only differences I know of between the two are the roller cam and valve train, and the compression. 8.2:1 verses 9:1.
bob1987f, the IAC is $60.00 at AutoZone. I would love to know where I could pick one up for $20.00. I pulled it and cleaned it this weekend, and after installing it back on the truck, if I unplugged it, the truck would die. So, it must be working now.
I think I figured out my idling problem, but since I created a new problem in the mist of trying to fix it, I won't know for sure until tonight. The tube running from the EGR to the lower intake manifold had broken into two seperate pieces. Oh well, if it's not one thing, it's another.
Thanks again,
Dan
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
Try setting the idle speed with the IAC unplugged. It shouldn't depend on the idle speed control to keep the truck running. Also check your tps voltages - closed throttle should be less than 1 V, around .8 - .9 Volts is good. If you then slowly open the throttle to full throttle (engine off, key on for all voltage checks) the voltage should smoothly increase to around 4.8V at full throttle. If you don't have these numbers, check the VREF for a constant 5V. If that is good, try adjusting the tps if only the idle voltage is wrong, or if there are skips and jumps in the voltage, you should replace the tps.
Senior User
Joined: Jan 2004
Posts: 174
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From: Illinois
bank fire
OK guys heres the beef. Ya know you cant just change the pins... You are swapping which side of the engine the injectors are firing. number 3 and number 5 need to be swapped along with number 4 and number 7 they are on different sides of the engine. The truck therefore has to draw fuel all they way across the intake. And it is really hard when the intake valve is closed on that cyl it is drawing from. causing a lean condition. And on the other hand causing fuel droplets to form and a rich condition when that cyl does fire. I wish I could draw a schematic on here. You would see where I was coming from. Not only that, drive a truck before the swap and after....
h.o.13726548
std 15426378
1 2 3 4 right bank
5 6 7 8 left bank. look at the 3-5 and the 7-4 locations! get my drift?
h.o.13726548
std 15426378
1 2 3 4 right bank
5 6 7 8 left bank. look at the 3-5 and the 7-4 locations! get my drift?
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From: Utah
So that creates basically a vaccum leak?
the HO does not have roller rockers.... only the Cobra version had roller rockers w/ a higher ratio..... 1.7 i think.
I thought that truck 5.0's had roller cams??? am i wrong?
the HO does not have roller rockers.... only the Cobra version had roller rockers w/ a higher ratio..... 1.7 i think.
I thought that truck 5.0's had roller cams??? am i wrong?