Engine 1990 Fox wont rev over 3500 RPMS

[limp]

Drop the exhaust pipes off of the exhaust manifolds ( or headers) and see if this helps.. Many years ago a mechanic friend and I battled a similar problem and the DOUBLE walled exhaust pipe had collapsed internally and was plugging the exhaust gases..

 

[alex.sweitzer]

You should be in the low 30s at idle. Do you still have the stock fuel pressure regulator with the vacuum line connected? At 50psi across the board you are way to rich.

Car has a BBK adjustable Regulator, dialed back pressure to mid 30s then down to 30 at idle, still no luck... it still smells rich when it hits 3k RPM

 

[AydenTv]

your having fuel to air ratio issues.. had the same problem with after market cold akr intake but getting too much air had to idke is up then the engine air would mess uo the maf reading.. had to build a air damn.. you shoukd make sure you get the right amount and i do believe if you unplug maf sensor your car should stall.. also id do codes and cylinder test.. imo i woukd try to get fuel oressure down to 40 psi at wot.. make sure tps at wot isnt going over 4.75.. and make sure your maf sensor is clean.. i bet its running pig rich

 

[AydenTv]

also dona base idle reset

 

[Trogdor]

I had a similar issue and it turned out to be that the START SIGNAL IN (#4 in the picture above) was getting 12V while the car was running. This wire is only supposed to have 12V while cranking to keep the timing set so that the car is easier to start.

To fist diagnose this I hooked up my timing light, started the car and checked the timing at idle with the SPOUT IN. The I revved up the engine and noticed that the timing would not change, it would stay at the same degree. I then probed the START SIGNAL IN wire with the car running and saw that ti was still receiving 12V. As a temporary fix I cut it from the connector leaving enough wire to splice it back once I found the issue and temporarily spliced it in with the little wire on the solenoid that is next to the battery. I still have not started looking for where my issue is as the car has been doing fine since, but when I do my HCI swap I'll have a look. Hope this helps!

 

[Mustang5L5]

kk you gonna send me over gaskets and permatex.. and fr im not a mechanic im not gonna take apart anything i know if i take apart i have the possibility of ruining the car

no permatex needed. All you need is a flashlight. Your IDing parts, not rebuilding the engine. You want to know why you have a non-HO firing order, then your gonna have to help us out because we can’t see your engine.

all you’ve been asked at this point to do is look at the engine and identify part numbers and snap a few pics. Then we can tell you “yes, that is correct for your car” or “no, that shouldn’t be like that”. They will provide clues that might get to the bottom of this once and for all.

we get you can’t tear an engine apart. That’s fine, but you gotta understand we can’t figure out what’s wrong with the car without being there to see a few things. We need more info, and much of that info you can provide doesn’t require anything more than flashlight and camera. You’ll even learn why we are asking the questions we are asking along the way.

I can’t speak much for FB, but you have decades of cumulative Fox experience in this forum and guys who can rebuild a 302 blind and identify motor components that should and should not be there. It’s not the first time we’ve played this game.

 

[AydenTv]

no permatex needed. All you need is a flashlight. Your IDing parts, not rebuilding the engine. You want to know why you have a non-HO firing order, then your gonna have to help us out because we can’t see your engine.

all you’ve been asked at this point to do is look at the engine and identify part numbers and snap a few pics. Then we can tell you “yes, that is correct for your car” or “no, that shouldn’t be like that”. They will provide clues that might get to the bottom of this once and for all.

we get you can’t tear an engine apart. That’s fine, but you gotta understand we can’t figure out what’s wrong with the car without being there to see a few things. We need more info, and much of that info you can provide doesn’t require anything more than flashlight and camera. You’ll even learn why we are asking the questions we are asking along the way.

idk if i mentioned it here but i do know it says 10 0n valve cover driver side corneron the front and it has an A9p ECM and on the Distributor it has E7AE which E is 80s 7 87 AE i think is for a F150 also noticed it says 80 mustang on driveshaft.. the headlight harness has fog light and air bag connectors.. but the gauge cluster A and B connectors are wired light the 87 to 89 ones.. fuel pump relay is under driver seat like the 89 should.. and here are some random parts numbers

also had a bunch of spare parts that came with it another a9p ecm (thats all i know bout it) and was told a 87 harness with speed density
.

 

[Mustang5L5]

idk if i mentioned it here but i do know it says 10 0n valve cover driver side corneron the front

Look on the opposite corner of the same head. The heads will have a letter on one corner and a number on the other. The number is an internal number from the foundry that identified the core used. The letter identifies the head.

T= E7TE (correct head for your car)
S = E6 head
R = E5 head.

everything else I’ve seen you post is 100% correct for a 1989 car.

Some close up engine bay shots would be helpful too. Get in close and just snap pics of details like injectors, throttle body, the head bolts, wiring etc.


You should probably make one thread and update that single thread vs having this info in multiple threads.

 

[AydenTv]

top spark plug in pic is the one autozone sold me for a 89 lx 5.0

 

[Mustang5L5]

Auto lite 25s were used on E7 heads. Would help to confirm that with the letter on the head.

E6SE is the proper part number for the lower intake manifold. Problem is the lower was used on the HO and non-HO. There may be a date code cast in the front.

injectors are correct 19#. They work with your ECU. What are the part numbers on the mass air flow meter??

so far everything looks originsl and correct.

 

[AydenTv]

Look on the opposite corner of the same head. The heads will have a letter on one corner and a number on the other. The number is an internal number from the foundry that identified the core used. The letter identifies the head.

T= E7TE (correct head for your car)
S = E6 head
R = E5 head.

everything else I’ve seen you post is 100% correct for a 1989 car.

Some close up engine bay shots would be helpful too. Get in close and just snap pics of details like injectors, throttle body, the head bolts, wiring etc.


You should probably make one thread and update that single thread vs having this info in multiple threads.

thought T was bad but ill go now and take pics but you do mean i wont have to take apart valves tpo right lol i know the gaskets are like 10 bucks and i could do that in 10 days.. but need to know what distributor i can use for this motor cuz of it is a roller i have to have a steel gear and tappet is cast iron plus it does have a bad wobble that makes it buck and snatch on rough roads, there was quite a bit of oil in intake from pcv valveneed to change groument and all... need plugs wires.. ect sending unit prob act too as well as an air damn for hot air intake and research if that big cone filter fr isntoo biligbfor my mf the housing or injectors..

 

[Mustang5L5]

T is what you want to see. Those are the right heads.

your distributor is correct. There’s no reason to change it. Non-HO cams are also roller and would use the same dist. I highly doubt someone went through the effort of swapping in a old school flat-tappet cam. Doesn’t make sense given what I’ve seen so far. Most likely it would have an 86+ non-HO roller cam because it would be a direct swap. That’s IF the cam was swapped.

Everything You’ve posted so far is 100% correct for an original 5.0 HO. I haven’t even seen signs of the motor being apart just yet.

best way to confirm is in fact to pull a VC off. But I’d hold off on that for now.

 

[Mustang5L5]

Here’s the issue with the firing order and the A9P.

the A9P is sequential meaning it fires each individual injector when needed in order. The order matches the firing order of the cam. The ECU is programmed for the 1-3-7 firing order.

if you stick a non-HO cam in there, 4 of the 8 injectors are not firing at the right time. Car should run like dog crap. If it runs right with the 1-5-4 firing order, then the injector wires may have been switched to accomplish this.

two ways that could be done. One is rewire the injector harness, which you should see evidence off, and #2 is someone repinned the ECU. That would be easy to check as you can just confirm if two wires are located in the right spot on the ECU.

but again...it makes no sense for someone to swap in a non-HO cam, unless the engine blew up and someone grabbed a cheap 86+ Non-HO short block. They could install that, bolt all the Mustang specific parts on, and swap four wires at the ECU and it would run.

 

[Mustang5L5]

Here’s another idea. Can you get your hands on a borescope inspection camera? Rent or borrow?

pull a spark plug and use it to look at the top of the Pistons.

this is what you should see:

correct Pistons for your car should have 4 valve reliefs.


here is the wrong piston. No valve reliefs. This is evidence it’s a non-HO short block




you’ll need one of these. Not saying to buy one, but see if someone has one you can borrow. It will give you another clue as to what is going on.

Advance Auto Parts - Down for Maintenance

 

[Mustang5L5]

Here’s the last thing you can check for now.



like stated. If there is a 1-5-4 cam in the car, the injector wiring would need to have been changed to fire at the right time. It’s either cut and spliced out at the car, or repinned at the ECU.

not sure how good you are at elevtrical troubleshooting, but you can pull the computer connector and look at the pins and see if the wire colors match up.

for example, injector 3 is the Brown wire with yellow stripe, and should be in pin 12 on the ECU. Injector 5 is tan with light blue stripe and in pin 14. If those are swapped, that’s a big clue.

If not, then you might want to test continuity from the wire at the ECU. One wire should do it. Test injector 3. Easy way to do it to prob pin 12 on the ECU connector to the brown/tab wire on injector 3. You might need a piece of wire if your meter won’t reach. If it rings out, the injector order is wired the right way for a 1-3-7 firing order.



that should be plenty to keep you busy. Let us know what is in your scope of ability to do and not able to do.

also, pictures of MAF part number as well as the throttle body and general wiring pics woukd help spot something out of place.

 

[AydenTv]

alright here is everything i know or for fact.. Vin and title comes back to a 89 lx 5.0 convertible.. it has 8.8 positraction rear end, Aod transmission, 140mph 1989 140mph Speedometer, Take Autolite 25s (GT40 spark plugs, it has Mickey Thompson Valve Covers, My firing order is 15426378, Previous owner had a parts car and gave me alot of expensive stuff.. like harness, a9p ECM another MAF, etc.. Came with a C and L Cold Air Intake sittining engine bay.. Spout was gone when i drove it back (took the one from other harness) and vacumm lines was a mess... i have changed the tps, fuel filter deleted emissions and all vac lines besides Fpr Brake Booster and PCV which all hoses i replaced... i poured seafoam intake take and alot of injector cleaners so far.. and just got new plugs... the temp guage and fuel guage dont work and as far as the 154 firing order that is with me finding tdc on compression stroke.. ive tried 137 and even restabbed the dirstributor 3 times and following yt videos on how to make sure the window thing lines up.. ohh and i have a mystery oil leak but i think36 its my rear end oil and gonna by a drivetrain o ring, the rear end differential gasket and 90w 175 gear oil.. along with intake gaskets valve cover gasket and after i buy me a cheap honda for a daily tear this thing apart..lol any help or clues willm go along way

 

[Mustang5L5]

S = E6 heads.

Those are not the heads that should be on an 89 5.0 mustang. Now it’s looking like the long block was swapped out for an non-HO 5.0 at some point. E6 heads did come on the 1986 mustang 5.0 HO but with the 137 firing order

154 firing order plus E6 heads are a very strong indicator of this. Not what you want to hear, but at least you now have an answer.

that also means that the injector harness was rewired either at the manifold, or repinned at the ECU.

 

[Mustang5L5]

Also, autolite 25s are not the correct spark plug for E6SE heads. They use an Autolite 2546.

the E7TE which is what you should have used an autolite 25.

did that spark plug even fit right??

 

[AydenTv]

Also, autolite 25s are not the correct spark plug for E6SE heads. They use an Autolite 2546.

the E7TE which is what you should have used an autolite 25.

did that spark plug even fit right??

w

 

[AydenTv]

i asked for 89 lx 5.0 spark plugs and they gave me the top ones..i am now using autolite 25s..