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Discussion Starter #1
Yes, this is a dumb question, but my truck feels like it's running lean. I have a 1990 Bronco XLT with 5.8 EFI and an E4OD and it is running SPEED DENSITY. I'm not throwing any lean or rich codes, but after I replaced the intake manifold (old one was cracked) with an Edelbrock 3881 Performer truck intake, it's got serious hesitation on acceleration and what feels like no kick-down gear at all at highway speed when you floor it. Here's what I'm running:

  • Stock 351w (about 5,000 miles on rebuild, only difference is flat top pistons with a little more compression)
  • Stock heads/Cam
  • Edelbrock 3881 Performer truck intake
  • Stock throttle body
  • Shorty headers
  • Bassani Y-pipe and exhaust
  • Accel 19 lb injectors
Truck is running only one code in KOER, code 44 (for thermactor, so don't think that's doing it). Timing is 10 degrees, plugs are good, wires are new. No vacuum leaks, idles fine and even. Honestly, the only problem is on the freeway, pressing the go pedal doesn't go. I know the speed density programming is "dumb" on how much fuel is being fed the engine vs. air, and I've read that the intake manifold was very restrictive and the Edelbrock is a huge improvement. I'm wondering if the 19 lb injectors are not keeping up with the new intake and I could replace them with 21lb or 21lb injectors, but I also know the fuel/air mixture EFI programming is set for 19 lb injectors, so obviously I'm hesitant to change them to something bigger unless someone else has tried it and it works.

I really appreciate any help.
 

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Hi someguy,
Have you contacted and asked Edelbrock about this?
They can most likely tell you a lot more than anyone here since they designed the intake.

Have you checked the health of everything else? Is your catalytic converter flowing well? Etc.
 

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Discussion Starter #3
Hi someguy,
Have you contacted and asked Edelbrock about this?
They can most likely tell you a lot more than anyone here since they designed the intake.

Have you checked the health of everything else? Is your catalytic converter flowing well? Etc.
Thanks, good suggestion. I emailed Edelbrock as well. Will update this post with the answer.

FYI, exhaust is in new condition (shorty headers to 3" exhaust), engine is basically new (rebuilt), runs good, except for no kickdown or passing power.
 

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aka: kemicalburns
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what size tires are you running?
 

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if i remember correctly, @BigBlue 94 had a speed density setup with more mods than you. i don't remember reading that he had to change injectors, though.
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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Oh yea, I had heads, cam, eddy intake, long tube headers, higher compression, etc all running on the factory injection system. Injectors had never been cleaned or rebuilt at 140k miles. No major issues to speak of.

I would guess that you fudded up the kickdown cable when reinstalling the intake. Might just need adjusted. I'm more of a manual transmission guy so I'm not keen on them there fancy automated shifting gearboxes.
 
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no no no dont change injectors without tuning. you will just make it start up rich and when the o2 sensors finally lean it back, it will throw rich codes. 19lb injectors are good up to ~260HP which your not near at with just an intake.

his E4OD doesn't have kickdown cable. however it could be a sensor. dont go replacing every sensor all at once either or you will never know what fixed it. i would start by getting a multimeter and testing each sensor, theres not as many as people think either. mainly i would check the throttle position sensor, especially if its not kicking down under hard acceleration. there are threads about how to test, replace and even modify the TPS so it has the right voltage. could also check the MAP, ECT, ACT, O2 sensors.

im guessing you pulled the distributor? did you pull the SPOUT when you set the timing? is the SPOUT back in? does the rubber of the harmonic balancer look in bad shape that it could have spun?
 

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Discussion Starter #8
Thanks, guys. These are good thoughts.

1. I'm running 35's with 4.56 gearing.

2. The SPOUT is in, distrubutor is only a couple years old, and the balancer is fine (just rebuilt the motor). No codes being thrown for either transmission sensor or TPS, but I'll check the TPS. Basically, you floor it, the motor slowly revs up like it doesn't have any vacuum, and the transmission doesn't kick down. My first theory was that I could be running lean, but it's not surging like there's a misfire or throwing a code, just accelerating VERY slowly. It's kind of disconcerting to floor it at 45 to merge onto the freeway, and the engine slowly spools up. Only EEC code I'm getting is 44 (right side thermactor).

One vacuum question though, I hold vacuum at idle and when the engine is turned off, but I can hear a hiss when I turn the motor off like vacuum leaking out. I was thinking it was the brake booster (the brakes have been soft), could that be related?
 

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Given the description, I agree with what others have mentioned; look elsewhere for your problem.

Larger injectors are only going to help on the top end when your motor leans out, not at the bottom end you are experiencing.

You have addressed the front end with a freer flowing intake and the backend with a freer flowing exhaust, however your heads (and cam) are the limiting factor now. You will be fine with the #19 injectors.

Now, having said all that, I'll buck conventional wisdom and say there is a time and place for larger injectors and an SD ECU...

3 months ago I dropped a stroked 347 in my '93 XLT. Running a Bassani exhaust similar to you, but retained the stock TB and intake (that's more a 302 vs 351 thing - you've done the right thing replacing your intake). Running GT40 heads and 1:7 rockers though with a relatively mild cam - all on the SD ECU with #24 injectors.

The key is the components were matched to work with one another specifically for bottom end torque and, oddly enough, better fuel mileage - it wasn't a matter of simply putting in the "best" part, but the best combination of parts to meet my goals.

I know there is potential there as well with a proper tune and even more if converted to MAF with a more aggressive cam stuck in it.
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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95 5.8L MAF XLT, Hedman Shorties/MF SS Y & Muff, E4OD, Man hubs, KYB Quads, 31x10.5x15, 301K miles
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If your Trans isn't kicking down to a lower gear and staying in the gear it is in you are not going anywhere fast!!!!! Fix the Trans problem "FIRST" and then go from there. The performance from your your engine isn't going to be earth shattering from the "Changes" you made, sorry to say, so just understand that. If you want a Major noticeable change in performance from this engine you need a Head and Cam change that are Matched and then match all the rest of the components accordingly so they all play together well. Start with Basics and go from there, get everything working correctly first, then start Tweaking what you have.

BTW as a side note: you said you upped the compression with Flat top pistons; how much? 5.8's run fine on 87 octane with stock compression and 10degs of timing if your compression is too high then 10degs of timing on 87 octane might be TOO much unless you are running 91/92/93 octane and then that might not be enough, again depending on the compression ratio you are at now.

Good luck, I hope "WE" (FSB) are helping you get this straightened out!
 

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aka: kemicalburns
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Anything new regarding the transmission? Perhaps your TB isn't opening up all the way when you smash on the skinny peddle.

being a 90 year model i am not sure if you have a PSOM that would need calibrated for the new tire size. is the Rear ABS sensor still in place along with the Tone ring? we have seen/hurd of the tone ring being left off after a gear swap by folks.
 

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Anything new regarding the transmission? Perhaps your TB isn't opening up all the way when you smash on the skinny peddle.

being a 90 year model i am not sure if you have a PSOM that would need calibrated for the new tire size. is the Rear ABS sensor still in place along with the Tone ring? we have seen/hurd of the tone ring being left off after a gear swap by folks.
there is no PSOM. the rear axle still has the tone ring ans sensor but it is only for ABS. jsut like older trucks it still uses the speedometer cable in the back of the transfer case. it has a electronic sensor the cable goes into and the speedometer gear attaches to in which it gets the signal from, older trucks used the signal for cruise control. he would have to replace the speedometer gear to adjsut the speedo. but since it is with driveshaft speed instead of ring gear speed, gear ratio does affect the forumla. without doing the math, the stock speedometer gear is probably relativly close to what he needs as 4.56 and 35" is about the same as 28" and 3.55. tho im sure it still reads abit off. at some point he might want to change the gear as they are pretty cheap and easy to do.

just want to verify, you did remove the SPOUT when you set the timing correct? if you left it inwhen you set timing then it is gonna be a good amount off.

the no kickdown to me screams TPS or MAP. there both important in determining engine load and when the engine needs to do what. at WOT, it should kick down so i would say TPS first

did you replace the throttle body along with the intake or remove the TPS? if so the TPS tabs might not have grabbed the shaft of the throttle blades. you cant put the sensor straight on. you have to put it on and then rotate it into place so the tabs catch

you can always spray starting fluid or similar around the intake to check for vacuum leaks if your convinced its the issue. make sure no vacuum hoses are broken.
 

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Discussion Starter #14
Yes, this is a dumb question, but my truck feels like it's running lean. I have a 1990 Bronco XLT with 5.8 EFI and an E4OD and it is running SPEED DENSITY. I'm not throwing any lean or rich codes, but after I replaced the intake manifold (old one was cracked) with an Edelbrock 3881 Performer truck intake, it's got serious hesitation on acceleration and what feels like no kick-down gear at all at highway speed when you floor it. Here's what I'm running:

  • Stock 351w (about 5,000 miles on rebuild, only difference is flat top pistons with a little more compression)
  • Stock heads/Cam
  • Edelbrock 3881 Performer truck intake
  • Stock throttle body
  • Shorty headers
  • Bassani Y-pipe and exhaust
  • Accel 19 lb injectors
Truck is running only one code in KOER, code 44 (for thermactor, so don't think that's doing it). Timing is 10 degrees, plugs are good, wires are new. No vacuum leaks, idles fine and even. Honestly, the only problem is on the freeway, pressing the go pedal doesn't go. I know the speed density programming is "dumb" on how much fuel is being fed the engine vs. air, and I've read that the intake manifold was very restrictive and the Edelbrock is a huge improvement. I'm wondering if the 19 lb injectors are not keeping up with the new intake and I could replace them with 21lb or 21lb injectors, but I also know the fuel/air mixture EFI programming is set for 19 lb injectors, so obviously I'm hesitant to change them to something bigger unless someone else has tried it and it works.

I really appreciate any help.
Ok, short version is I fixed it. It was the throttle position sensor, and now it runs great. But instinct was right, it was running lean, but sensor was at fault all along.

Long version:

1. Started with the "thereafter inoperative" code. Tracked problem down to air bypass valve on passenger side of block, vacuum valve not actuating. Replaced bypass valve and re-tested. Thereafter now operative, but idled had and three code 13, "RPM out of range, low."

2. Ok, now we're getting somewhere, sounds like the IAC. Tried to test, lost patience and just replaced it for $20. That wasn't it, still throws code 1 3.

3. Sounded lean, pulled spark plug and read it lean. Ok, tested fuel pressure, came up 31 psi, on low side of 30-45 normal range. Replaced filter. Nope. Replaced regukator, even though it tested ok. Nope. Replaced fuel pump (been meaning to replace generic pump I'd used before anyway.). Nope. Same fuel pressure, same code, no effect.

4. Ok, if it's lean, maybe the TPS? Pulled throttle body off, and there was a puddle of oil right behind lower bore. Now we're getting somewhere. Pulled pcv, and it was bad, replaced. Replaced TPS, checked no codes!

Drove it, lockdown works great, idle is smooth, plenty of power.

Long answer is: Bad PCV blew oil into throttle body, seeped into the TPS at bottom, sensor went bad.

Thanks for humoring me, you guys were very helpful in getting me thinking.
 

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Discussion Starter #15
Ok, short version is I fixed it. It was the throttle position sensor, and now it runs great. But instinct was right, it was running lean, but sensor was at fault all along.

Long version:

1. Started with the "thereafter inoperative" code. Tracked problem down to air bypass valve on passenger side of block, vacuum valve not actuating. Replaced bypass valve and re-tested. Thereafter now operative, but idled had and three code 13, "RPM out of range, low."

2. Ok, now we're getting somewhere, sounds like the IAC. Tried to test, lost patience and just replaced it for $20. That wasn't it, still throws code 1 3.

3. Sounded lean, pulled spark plug and read it lean. Ok, tested fuel pressure, came up 31 psi, on low side of 30-45 normal range. Replaced filter. Nope. Replaced regukator, even though it tested ok. Nope. Replaced fuel pump (been meaning to replace generic pump I'd used before anyway.). Nope. Same fuel pressure, same code, no effect.

4. Ok, if it's lean, maybe the TPS? Pulled throttle body off, and there was a puddle of oil right behind lower bore. Now we're getting somewhere. Pulled pcv, and it was bad, replaced. Replaced TPS, checked no codes!

Drove it, lockdown works great, idle is smooth, plenty of power.

Long answer is: Bad PCV blew oil into throttle body, seeped into the TPS at bottom, sensor went bad.

Thanks for humoring me, you guys were very helpful in getting me thinking.
Hah, autocorrect. "Thermactor inoperative" and "kickdown!
 

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Discussion Starter #16
Also, I heard back from Edelbrock, and 19 lb injectors work just fine with the Edelbrock Performer 3881 truck intake. Here's what they said:

When Edelbrock Developed the Intake Manifold and used our Performer Cylinder Heads with a Twin Throttle Body and back in the day Edelbrock Headers, we used the Stock Injectors, so honestly, we do not feel it is running lean,
 

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called it, if you would have tested the TPS like i said twice would have saved you a good amount of effort and time

if your PCV valve was bad (not sucking), then the oil from crankcase pressure would go through the breather to the air filter box before the air filter. your air filter would be drenched, this is a common issue with old engines with bad blowby so check that out

im not buyin your theory. the throttle shaft is pretty sealed going thrugh the body. it has to be or it would cause a constant vacuum leak. for oil residue to build up enough from the PCV to somehow leak through and damage the TPS is not something realistic. if so then you need a new TB. no im not saying to go buy a new TB.

as said the 19 injectors can handle up to 260hp. stock engine makes around 210hp new. a new intake is not going to add 50hp
 

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if your PCV valve was bad (not sucking), then the oil from crankcase pressure would go through the breather to the air filter box before the air filter. your air filter would be drenched, this is a common issue with old engines with bad blowby so check that out
Know that one well! So bad, installed an air/oil separator between the block and air intake. Was pulling 4-6oz of oil at every tank full-up. :-0

The first time I called my engine builder and mentioned the blow by he agreed it was common, but his explanation was interesting and ties back to the topic...

He claimed it was common for an injector to get plugged leaning a cylinder out causing excessive heat and eventual scarring of the cylinder wall. Thus bad blow by...



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