HELP Engine issues after build!
Thread Starter
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Trailering
Joined: Mar 2025
Posts: 19
Likes: 1
Either the PCM has to be scaled for new injector size or that MAF meter. Tuning MAFs is weird, we used Pro M ones back in the stone age. There was another brand/style with different size sample tubes to deal with injector sizing.
Agreed, what heads did you buy? Ps also take a near impossible to find header now. I too would have seen if they actually sealed if ebay specials
Agreed, what heads did you buy? Ps also take a near impossible to find header now. I too would have seen if they actually sealed if ebay specials
As for the heads and headers here's the ones that I used:
Heads: https://ebay.us/m/RGyutD
Headers: https://ebay.us/m/UjGkvx
(for anyone curious, you will have to modify your Y pipe slightly to get it to fit correctly. Plus the supplied mounting studs will not work)
I love my chinese ebay specials 😉
But maybe it bit me in the *** this time...
Thread Starter
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Trailering
Joined: Mar 2025
Posts: 19
Likes: 1
Repinning the ECU was required as well as adding injector wires. They included very detailed and comprehensive instructions. Ive double and triple checked my work and I can verify that all the ECU wires are in the correct place.
Thread Starter
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Trailering
Joined: Mar 2025
Posts: 19
Likes: 1
Yeah I gapped them all to 0.044 per the manufacturer spec
Hotshot
Joined: Jul 2020
Posts: 10,401
Likes: 2,607
From: Near Salt Lake City
One thing at a time
You've made so many mods and some of the parts may not be up to snuff
I'd start back at the timing and whether the computer is controlling it okay and set the base time once more
I'd get a DU 30C for the distributor and a new Ford Motorcraft ignition module for it
You might want to put some of it back to "stock" until you get the drivability sorted out
You've made so many mods and some of the parts may not be up to snuff
I'd start back at the timing and whether the computer is controlling it okay and set the base time once more
I'd get a DU 30C for the distributor and a new Ford Motorcraft ignition module for it
You might want to put some of it back to "stock" until you get the drivability sorted out
Cargo Master
Joined: Mar 2007
Posts: 2,811
Likes: 1,023
We have all been down this road before. We tend to believe, it's nothing we have caused. One thing for certain, if you did everything right and everything is working right, it would be running fine. So, start with thinking that there is something wrong. I would start with thinking 'What did I screw up?'. I would not trust someone over the phone/internet telling me the ECU is the right one. I would get a second opinion and find a wiring diagram to confirm that the wiring matches your computer.
Hotshot
Joined: Jun 2015
Posts: 12,811
Likes: 2,431
I chose 24# to increase the power ceiling. The ecu doesnt need a tune for NA 24# injectors, it just needs a MAF thats calibrated for those injectors.
I didnt choose the MAF specifically to expand my options for cams, mostly for its improvements to mpgs and more capabilities for power adders, which allowed me to use that cam.
I used generic gt40 "style" aluminum heads. That use rocker studs which allowed me to use roller rockers which needed to he properly preloaded
The emissions delete was performed by capping off all unused vacuum ports, wiring in line resistors where needed, and capping off the egr ports. The Smog pump is still in pace but acts as an idler pulley pretty much. I had done the emissions delete a while before the engine build and it gave me no issues so I don't suspect anything in that regard is causing issues.
I didnt choose the MAF specifically to expand my options for cams, mostly for its improvements to mpgs and more capabilities for power adders, which allowed me to use that cam.
I used generic gt40 "style" aluminum heads. That use rocker studs which allowed me to use roller rockers which needed to he properly preloaded
The emissions delete was performed by capping off all unused vacuum ports, wiring in line resistors where needed, and capping off the egr ports. The Smog pump is still in pace but acts as an idler pulley pretty much. I had done the emissions delete a while before the engine build and it gave me no issues so I don't suspect anything in that regard is causing issues.
You didn’t need stud mounted rocker arms in order to use roller rockers. Back in 2017, I used Scorpion 1.72 roller rockers when I swapped cams and installed GT40 heads on the 302
It might not have turned on the check engine light but the computer is more than likely going to set codes from those resistors. The input from the EGR is a different value when it is open than when closed. There is no way for a resistor to do that.
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Cargo Master
Joined: Mar 2007
Posts: 2,811
Likes: 1,023
I spent a few minutes playing with injector sizes and MAF sensors calibrated to those injectors. The ignition timing changes with engine load and with a 'tuned MAF sensor' the ignition timing is not close to being right. I had to pitch the aftermarket MAF sensor and installed the stock MAF sensor. To save time, I just lowered the fuel pressure so the larger injectors delivered less fuel. I dealt with this for a decade. Eventually, I did put in the stock 19lb injectors and jacked up the fuel pressure back to stock.
Maybe a slight change injector size does not effect the ignition timing to cause problems, but larger ones with the tuned MAF sensor does. I would not go that route unless I could change the stock tune [Tweecer/Quarterhorse].
Maybe a slight change injector size does not effect the ignition timing to cause problems, but larger ones with the tuned MAF sensor does. I would not go that route unless I could change the stock tune [Tweecer/Quarterhorse].
Cargo Master
Joined: Mar 2002
Posts: 3,132
Likes: 218
From: W (BY GOD) V
They did not have any in stock ECU's at the time but I was in touch with Brian from Fiveology and I bought an approved junkyard ECU. I also replaced the capacitors in the ECU.
Thread Starter
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Trailering
Joined: Mar 2025
Posts: 19
Likes: 1
UPDATE
I was able to put a vacuum gauge on it again and it looks like im getting extremely low vacuum (0-5inhg) at lower rpms which leads me to believe I installed the cam incorrectly. Will update later when I'm able to pull the front cover and take a look.
I was able to put a vacuum gauge on it again and it looks like im getting extremely low vacuum (0-5inhg) at lower rpms which leads me to believe I installed the cam incorrectly. Will update later when I'm able to pull the front cover and take a look.
FTE Chapter Leader
Joined: May 2006
Posts: 12,336
Likes: 1,312
From: Central Mississippi
My guess is a cam lobe on an intake valve is been flattened. (no lift=no filling CC=lean burn=glowing manifolds)
If it were me, I'd put a dial gauge on a plate bolted to valve cover holes & check lift before trying to pull cam out.
If you find it, then you can just pull engine rather than fiddle-farting with pulling cam before doing the inevitable pull.
By the way, did you test the seal on these heads before install? (I.E., 120 psi compression)
Sorry dude, it's just looking like a cluster. Maybe you'll get lucky & the cam isn't flattened & the filter not full of metal.
If it were me, I'd put a dial gauge on a plate bolted to valve cover holes & check lift before trying to pull cam out.
If you find it, then you can just pull engine rather than fiddle-farting with pulling cam before doing the inevitable pull.
By the way, did you test the seal on these heads before install? (I.E., 120 psi compression)
Sorry dude, it's just looking like a cluster. Maybe you'll get lucky & the cam isn't flattened & the filter not full of metal.
Lead Driver
Joined: Sep 2002
Posts: 9,520
Likes: 2,028
From: North Texas
Yep, FMS kit here with a Pro M MAF, bought at Summit. I still rock 19s as basic 302HO with all bolt ons.
Interesting point about the PCM used perhaps beyond its ability to compensate. Even the HO MAF ones reach a limit where they need to be dialed in to work well.
Too many variables, but it happens.