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Discussion Starter #1
Hi,

I am getting really tired of this thing, my favorite truck is just falling apart. So far in the past *MONTH*:

Rotted oil pan, leaking 1qt/day - FIXED (what a job!)
Hydraulic brake line ruptured - FIXED (replaced EVERYTHING, bleeding the ABS was fun, thank goodness I found the rotunda tool)
Rear shock housings cracked - FIXED (replaced with bilstein's)
Alarm module shorted out - FIXED (replaced with cool new viper smartstart)

Two major problem remain, cant figure out either one:

1. Detonates under heavy loads - Wide open throttle or up a hill, towing etc. It is kinda random, does not happen all the time, but happens enough to have me concerned. I'm thinking injectors, but not sure.

2. Stalls at idle - This is new, but REALLY bad, when sitting at a light, engine idle drops from around 650-700 to 500 then just stalls. Does not happen all the time, buts its REALLY annoying. Seems to only happen in gear, in park/neutral idle is slightly higher, but seems fine. Normally I would say vacuum leak, etc, but can't find anything, entire ignition system was replaced like 2yrs ago (mostly MSD components).

This is a factory MASS AIR 94 fullsize 302, E4OD. As you can see from above, I'm getting tired. Please help.

Thanks
Brian
 

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I had the same issue as #2. Never got around to diagnosing, but through the course of my own upgrades I replaced the coil, wires, rotor, cap, and plugs, and cleaned the IAC. I don't have the problem anymore and I'm assuming it was the IAC that did it.
 

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Discussion Starter #3
I'll assume you are referring to the stalling problem and not the pinging problem. I'll change the IAC if that will fix it, aftermarket is under $50. Also do MAF trucks have an IAC or is it only on SD? Some other info: When it is idleing above 500rpm it runs very smooth no shaking/misfiring. It accelerates off idle fine.
 

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The Anti Yam!
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Discussion Starter #5
1. Check for codes.
http://www.fordfuelinjection.com/?p=13
Remember, you will get 3-digit codes, not 2-digit.

I have a scanner, I'll pull codes later, no check engine light, as of last week there were no codes (111)

2. With it idling, pull the IAC plug.
Did the idle drop?

Will check later and get back to you.

3. What is the reference voltage on the TPS?
http://www.fordfuelinjection.com/index.php?p=30
Reference voltage or signal voltage? The reference voltage should never change, it should be a fixed 5V. The signal voltage output should vary between ground and Vref. What should the signal voltage be at idle? I am kind of confused about idle adjustment on EFI. Technically the idle speed is controlled by the PCM in terms of how much fuel it will deliver. the adjustment screw basically sets how much the throttle body is open at idle so this basically sets air/fuel mix. From my experience if you try to increase idle screw adjustment at throttle body, it will work for a few minutes until the computer adapts and turns it down.

For the stalling (needs to be fixed asap), my first guesses would be IAC (if it has one), TPS, MAF, maybe even injectors (if programmed pulse width is not actually delivering enough fuel), but in a MAF vehcile this should be compensated for automatically, the only time it should be a problem is wide open throttle.

Also as for the pinging/detonation under load problem, I can offer another useful piece of info, the problem is NOT in the long block, I blew up the last motor at 150k (long story), and the problem existed in that motor as well, seems to be getting worse. But a new longblock and problem is still there. Thats what was leading me toward injectors.
 

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The Anti Yam!
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Discussion Starter #7
Havent pulled codes or pulled plug on IAC yet. Will have answer in approx 4-5hrs. I may just pick up an IAC on my way and try it, they are not really expensive.

As far as setting the idle screw, how do you do it properly? I think someone messed with it when replacing the motor last year as the original paint/glue is scraped away.

Another thing I want to check before replacing injectors is base timing, I've never done it before, I assume you need to just pull the SPOUT and shine a timing light on the balancer? It should be 12deg? I don't remeber seeing a timing arrow/mark on the engine or the balancer, I'll look closer later.

The wierd thing is the problems don't agree with each other, the pinging/detonation sounds like timing too far advanced, the stalling at idle sounds like too far retarded, therefore the problems must be unrelated. I know the pinigng problem has been around for a while, the stalling is new.
 

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Discussion Starter #8
Okie Update time:

1. No codes (KOEO and KOER)

2. I didn't pull the cable from the IAC, but I just replaced it (picked up another on my way home, it was cheap enough), I didn't want to clean it and if it didn't work, not be sure.

I pulled the old IAC and inspected it, it was pretty black, but no thick deposits, just lot of carbon.

I replaced the IAC and started the truck back up, fine when cold (high idle), but when it warms up and goes closed loop and idle drops, thats when problems start. Once truck heated up idle dropped to like 650 I then shifted in and out of gear and the truck stalled.

I then thought about it, and disconnected the battery for 10 mins to clear the keepalive memory in the PCM. Reconnected battery and started truck, once truck warmed back up, had lousy idle, then seemed to get better (learn routine). I then took it for a 15 mile drive (10miles hwy, 5mi streets stop and go), no stalls. I am not sure if the IAC was bad, or it just needed a ECM relearn, but it seems to be better now, cautiously optimistic at this point.

As far as TPS Idle position goes, I was too lazy to break out the DMM, but since I had the scanner connected, I did a data scan of the TPS, closed throttle is about 1.15v, skinny pedal to floor is 4.85v. Nice linear response in between never jumps around.

As far as the detonation issue goes. It still seems to be there, only happens (intermittently) under heavy power output conditions (uphill, hard acceleration, etc). Usually the easiest way to reproduce it is to "snap" the throttle in park/neutral. You can usually hear it while motor is revving. Or on an incline, try to accerate hard. As an experiment at idle, I pulled the SPOUT connector and tried snapping the throttle, it did not happen in this case. Granted I probably backed out 20degrees of timing (went from computer control to fixed base timing), but it seemed to get rid of the issue. So there are a few ways to look at it.

#1 Lean fuel condition - My gut feeling is injectors, not outputting the "expected" amount of fuel for a given pulse width which throws off the tuning tables in the PCM. By the way, how many people know Ford Racing recently discontinued the M-9593-C302 19lb/hr EV1 injectors??? They seem really hard to come by lately.

#2 Timing problem - If the base timing is too far advanced, anything the computer thinks its supposed to add will be that far off. I have no clue how to check/set the base timing on this thing. First question is, if the motor is idleing/running good at idle and midband (no backfire or rough idle), can you essentially skip most of the parts of setting base timing, ie seating the distributor in correct position, checking the relationship between the markings on the balancer and actual #1 piston position at TDC with both valves closed, etc and just go straight to timing light adjustment?? I don't know how to do the timing light adjustment with this, I have access to one, and I can clip it to #1 wire, and point at harmonic balancer, but I can't find any reference mark/needle/arrow on the block. Ive seen pictures of the 302 that has this bracket on right side of motor next to water pump, but can't find it on mine. I put a piece of white vinyl tape at 10 degrees BTC on the balancer (this is where it should be set to right?).

As an alternative, since it sounds like its really close, should I just "blindly" adjust it a little? I just don't want to mask another real problem (ie lean fuel) and sacrifice power by backing out timing. If I wanted to move it, looking down on the top of the motor, will turning the distributor clockwise advance or retard the timing?

Thanks
 

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not to hijack but I have the same stalling problem, I have a Haynes and a Chiltons manual. I cant find IAC and would like to try and track down my issue.
Okay, so what is it?
 

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Discussion Starter #10
Look on the side of the throttle body closest to the center of the motor, solenoid looking thing with a 2 pin plug going into it, small black plastic cap sticking out the side.
 

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will do. so I can possibly find it in a manual what does IAC stand for? I'm betting its something very common and I am just not getting it, everyone else is like AIC this and AIC that haha


EDIT: okay, I found it. It came off my parts bronco. It appears to be brand new, I will take a look and see if there is any corrosion on the connection tomorrow when it is light out. Thanks
 

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The Anti Yam!
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, closed throttle is about 1.15v,
Thats a little high, adjust the TPS (Not the throttle screw) to .9 and see where that gets you.

Then pull the IAC plug with it idling, it should either die, or idle way down.

I run a little cushion on my base idle by manually adjusting the throttle set screw to force a base idle of 600rpm, then adjust the TPS to read .9 at that setting.

Gacknar said:
1. Start engine, and run it until it has reached operating temperature.

2. Unplug the IAC, if the truck dies when you unplug the IAC then turn the idle stop screw one turn, and try to start the truck. Continue doing this step until you get the truck to idle with the IAC unplugged.

3. Now with the truck idling with the IAC unplugged adjust the idle stop screw to where the truck is idling at 400-600 rpms. I personally set all mine to 600rpm.

4. Reconnect the IAC, the idle should bump up slightly.

5. Check the voltage on the TPS
http://fordfuelinjection.com/index.php?p=30
It should be between .90 and .99 volts. If it is not, wallow out the mounting screw holes so that you can turn it to where it reads between those two numbers.

6. If you had to adjust the TPS, then unplug your IAC again and make sure the idle is where you left it.

7. If it is then your golden, if not then repeat the steps until it is
As far as your pre detonation issues, I believe you said you had your timing set to 12btc, factory is 10btc. Back it down to 10 and see what happens.
 

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Discussion Starter #13
Since I cannot find a timing pointer on the block, is there any other way to verify base timing. Right now, the stalling at idle seems to have stopped from IAC replacement + PCM Relearn, has not done it since and idle is nice and low 650 in gear 850 in neutral when running closed loop. As for the TPS anything in the 800mv to 1.20v is considered "within spec" for closed throttle and the computer will learn around it, since it seems to be working, I don't want to mess with it a lot. I wonder if the TPS has not been moved, can I assume its "correct" and the idle screw is wrong, and simply back out the idle screw until TPS reads 900mv at closed throttle as opposed to adjusting the TPS to an "unknown" throttle body idle position?

The detonation issue has been driving me crazy, I cannot find any rhyme or reason to it, it sometimes does it when its hot, sometimes right from a cold start if you take off too hard (or even snap the throttle in park), it will do it. Its intermittent. If it was base timing I would expect it to be reproducible under certain circumstances (ie Hot air intake charge temp, etc). The only consistant thing is that it does it under high output conditions. This is what keeps leading me back towards injectors, and one other thing as well. Probably 5yrs ago I had a problem where you had to excessively crank the engine to start it, turned out to be an injector leakdown issue. I replaced the injectors with 8 "rebuilt/remanufactured/cleaned/etc" oem injectors (they were the 4 hole nozzle type). Shortly (1 month) after that, the knocking problem started, but VERY intermittently, hardly ever in fact. For a while I was running higher octane fuel, and it went away, it has gotten progressively worse since. Thats why I'm suspicious of the injectors in this thing. Thats right I've been dealing with this for years, only lately has it gotten bad to the point I'm worred about burning pistons.

I am afraid of aftermarket/racing injectors (ie Accel, venom, etc), and suspicious of "cleaned/rebuilt" injectors. I cannot afford new OEM injectors (ford quoted me like $104ea for the ford part number). How about the M-9593-C302 from Ford Racing Performance Parts, how close are these to the OEM? They appear to be discontinued as of very recently, but theres still some floating around out there.

Any other thoughts?
 

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There are a couple of good threads here on rebuilding the injectors.

If you can't find the timing mark, just mark the distributor, loosen the retaining bolt and just play with the timing and see if that helps.
 

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Discussion Starter #16
I know FRPP is owned by ford, was not sure if the FRPP ones are any different from the actual OEM part number that sells for 3x to 4x the price.

Also it is a great thing I decided to change the injectors, not necessarily because they were bad, but because I otherwise never would have realized some lazy SOB left half of the plenum bolts missing when they were R&R'ing the motor (so glad I being it to a "pro" for a job like that)! Not sure if thats the whole problem or not, but I'm sure it was contributing to a nasty vacuum leak. I'm impressed it was running as well as it was. Still not convinced it was the whole problem though, as the old motor was doing it too. I'll have the injectors tomorrow, just got a head start on pulling it apart today. The plenum is a sludge mess, any ideas? I know sandblasing/abrasives is a nono for intake parts. How about the Gunk stuff you use on a chassis let it soak and hose it off? Any other ideas? Also now I need that damn hard to find bolt that has a hex allen type head that is special because standard ones wont fit that tight spot in the middle of the plenum, any idea where to get that one? Or for that matter a whole set?
 

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Discussion Starter #17
ARGH! New Problem. I put the whole thing back together last night. Put the new injectors in, BTW- The brand new ford racing packed ones are the pin type pintile, not the 4 hole style. Now the problem is it is NEVER switching to low idle, stays above 1000 consistantly, no check engine light, I went over the vaccuum lines and it looks like everythings connected. At 2am last night, I was too tired to troubleshoot further. While I had it apart, I did clean out the throttle body and the plenum, both were full of sludge, in the plentum, the EGR port area was probably reduced by 50% from the sludge. Did a degreaser and hose job several times, got it pretty clean, and cleaned the throttle body by hand. Now whats going on?!?!?

I guess later I'll connect the scanner, and see what the EGR position is reading as well as TPS value at closed throttle, and see if the EFI ever goes closed loop. Its running very nice/smooth, but cannot get it to drop to low idle, starts at around 1300rpm and drops to around 1100. If its EGR related you will usually get a check engine light after 5 mins of operation when engine warms up.
 
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