Ford Bronco Hard start after sitting ? Also exhaust question - Page 2 - Ford Bronco Forum
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post #21 of 101 (permalink) Old 01-19-2017, 04:02 PM Thread Starter
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Ok, So Whenever it is hard to start I notice that the tach jumps to 2000 rpm's while cranking(Sometimes). Could this be an ignition problem?
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post #22 of 101 (permalink) Old 01-19-2017, 09:31 PM
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The tach signal comes from the ICM, the schematic are below. My best guess is that the ground signal that charges the primary side of the coil is oscillating rapidly (rather than going to ground once for each plug firing event).
Normally, the PIP signal from the hall effect switch in the distributor goes to the PCM, the PCM generates the SPOUT signal which in conjunction with the PIP commands the ICM to send the COIL signal (pin 5) to ground. (SPOUT is to modify the timing of the COIL signal.)
The tach signal (going to page 60-5, w/pk wire) is decoded by a solid state circuit in the tachometer into RPMs.
So, lots of tach signals at 2000 RPM, should be a lot less at cranking speed (about 250 RPM).
So, a failing hall effect (PIP) circuit making the PCM think the engine is turning 2000 RPM could be the reason, or the PCM misreading the PIP signal and sending the coil signals at a 2000 RPM rate (and not synchronized with the engine).
You could pull the SPOUT plug and see if the PCM is confusing the ICM. After that, fixing the PIP generator in the distributor if it is broke, or replacing the ICM with the correct (black) ICM. Pull the PCM and look for leaking capacitors, you could be seeing an early PCM failure that will get worse.


1996 Ford Bronco '94 EVTM picture | SuperMotors.net


http://www.supermotors.net/registry/media/921714

Sorry about the slow response of SuperMotors, but it's not my fault, have patience and it will eventually load.

Good Luck

"The simplest solution is usually the best solution" - Occam's Razor

"The significant problems we face cannot be solved at the same level of thinking we were at when we created them." - Albert Einstein
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post #23 of 101 (permalink) Old 01-19-2017, 10:24 PM Thread Starter
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Wow man thank you. This info will definitely help me out. Also I noticed it more when I got the timing chain replaced the shop who replaced set the timing properly. So maybe the pip is giving out ? Once this beast gets started it runs like a clock when I'm sitting at a stop light it's so smooth you can't even feel that the truck is on. Also could a bad pip cause random chugging for just a second. Ill check for codes and see if the computer has "seen" anything odd? Also when I got the truck there was a gray ICM in there so I replaced that with the proper black one. Also I cleaned the heatsink and applied thermal paste.
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post #24 of 101 (permalink) Old 01-19-2017, 11:33 PM
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You could visually check the PIP generator (hall effect switch) by removing the distributor cap, then the rotor, then the shutter wheel (black thing with square notches held on by two screws). The hall effect switch works by sensing the changing magnetic properties as the shutter wheel interrupts the magnetic field between the two poles of the hall effect switch.
Clean out any crap you find in the bottom of the distributor.
There was an anecdotal post about the shutter wheel becoming magnetized (somehow) and that affected the function of the hall effect switch. While (if) you have the shutter wheel off, see if it will pick up a steel straight pin or paper clip. Demagnetizing it, if it has become somehow magnetized, will probably be a problem. Bulk magnetic tape erasers are as scarce as hen's teeth, but there is a possibility that a pad type cordless phone charger might demagnetize it, they have been known to demagnetize the stripe on magnetic credit cards.

One other thing, your truck (if it has the original motor) has roller tappets, this means your need a steel distributor drive gear. That info is important if you buy a new distributor. I bought one for my Bronco (years ago) from NPD. It wasn't too expensive, but the core charge was a bunch (IIRC about $80.)

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post #25 of 101 (permalink) Old 01-20-2017, 12:30 AM Thread Starter
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Ill try to check those two things when I can I'm at school now so time is limited. Also one more thing there is a small gap between the cap and the body of the dizzy could moisture be getting in there.

EDIT: the small gap was a shadow ...... sorry :/

ALSO i do notice that when I disconnect the battery its starts better but then after a while it goes back to the long crank time.
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post #26 of 101 (permalink) Old 01-20-2017, 01:21 AM
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The cap is not watertight if that's what you're referring to. If it is the correct cap, then it is fitting as tight as it should.

"The simplest solution is usually the best solution" - Occam's Razor

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post #27 of 101 (permalink) Old 01-20-2017, 05:17 PM Thread Starter
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So I was reading up on the PCM and how it could have some bad caps. So my theory is this when the truck is cold it fires like it should but as soon as the PCM heats up the caps will malfunction thus making it hard start and the tach acts funny like mentioned above. I have see this happen to many electronics that have had old caps in them as soon as they heat up like all electronics do they will malfunction also I read that the lifespan of the PCM are about 15 - 20 years. So my plan is this I'm going to pull the computer and visually inspect the internals and see if there is any sign of bad and or leaking caps. I will keep you all posted and take some pictures when I have the time to tear into this thing.
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post #28 of 101 (permalink) Old 01-21-2017, 08:54 PM Thread Starter
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So an issue happen when I was on the off ramp of the highway today. When sitting at a red light the idle started to go up and down. There is no engine light so I might take it for a spin tomorrow and see if there is any codes stored. If there is no codes present could this have been fule pressure not venting properly after driving highway speeds ? Or maybe that the computer is starting to tell me that it needs replacing soon?

One thought that just popped into my head does the computer mess with the timing while starting if so when does it mess with it ?
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post #29 of 101 (permalink) Old 01-21-2017, 11:07 PM
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IIRC, the PCM holds the timing at base timing when starting, then advances it as soon as the engine starts. You can check this with a timing light.
When cranking the timing should be at base which is 10 (or whatever your emission sticker says). This info is useful as you can disable the coil, and crank the engine with the starter and check if the timing is set correctly. (Helpful if you had the distributor out or loosened it for some reason.)

Rereading your original post (#1) you said that when refueling, the pump would shut off before the tank was filled. Do you know if the fuel tank was ever replaced? The filler hose is supposed to prevent that and vent the tank as it is being filled. See:



http://www.supermotors.net/registry/media/285175

There is also a vent line coming from the fuel tank to the carbon canister in the engine compartment.
The PCM uses the signals from the HO2S sensors and diverts the secondary air to the convertor or vent it is as determined by the PCM. It may be difficult to achieve factory performance with the original systems changed, as the PCM may try to change the mixture based on the HO2S sensor, which would change based on the secondary air. The secondary air only is changed after the engine reaches full operating temperature.

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post #30 of 101 (permalink) Old 01-22-2017, 03:12 AM Thread Starter
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The Fuel tank was never changed I did have it removed to replace a fuel pump(whole assembly was changed). The timing chain was replaced by a shop and was timed oil changed along with the coolant. The new cat has no air inlet tube. So here is what I am thinking. It's either the tank valve on top of the gas tank and or the charcoal canister or the computer. Is there any way to test the charcoal canister and the vent valve ? If I take the vac line off the TB going to the solenoid it smells like gas. But it smells like gas after it hardstart not while its cranking.
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post #31 of 101 (permalink) Old 01-22-2017, 01:48 PM Thread Starter
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UPDATE: So I think I found the issue. When the cold hard starting happens the tach reads 900 rpm then 500 rpm and finally when it reads 200 rpm it starts. When the warm hard start happens the tach goes 2000 rpm 1000 rpm 900 rpm 500 rpm and then 200 rpm and then starts. Now when It starts in 2 seconds the truck only reads 200 rpm when cranking and it fires like it should. Also I have been smelling some odd smells when the rpms go to 2000 when hard starting kinda like a hot computer. So right now I'm leaning towards the computer again I do still need to open it up and verify it'll be extremely foolish of me to replace a 300$ part with out testing it first.
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post #32 of 101 (permalink) Old 01-23-2017, 02:08 AM Thread Starter
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Should I unplug the spout connector and see if the truck cranks like it should and if it starts faster with the spout unplugged. It means the issue could be with the ECM ?

Can I also remove the spout with the battery connected.
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post #33 of 101 (permalink) Old 01-24-2017, 01:10 AM Thread Starter
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Here is some video of what is going on.
this video you can see the tach go up to 500 RPM and then it evens out and then it starts but has a really rough idel.

Now this video when cranking the tach reads the proper 250 rpm and starts right up and idles smooth.

Fixed the video's
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post #34 of 101 (permalink) Old 01-25-2017, 12:31 PM Thread Starter
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So I did a KOER test and got code 311 ? Now when I replaced my cats the exhaust shop replaced it with one that has no air tube in it could this cause my hard start issue. Or could this be a issue with the computer because the RPM's are still all over the place while cranking. PLS HELP
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post #35 of 101 (permalink) Old 01-25-2017, 12:46 PM Thread Starter
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Here is what the shop gave me https://www.napaonline.com/napa/en/p...708_0284566659 it says it dose not require a air tube ? Also yes the RPM's and still erratic and the computer does not seem to give me any codes should I just bring in to a shop and have them check it out ?
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post #36 of 101 (permalink) Old 01-27-2017, 04:49 PM Thread Starter
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So after taking it on the highway. My bronco chugs like in this video EXACTLY like this video

He said that he found a bad cap in his ECM here Bad ecu symptoms? - Ford Mustang Forums : Corral.net Mustang Forum

So right now I'm 98% sure that is it my ECM. I will keep you guys updated on this issue.
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post #37 of 101 (permalink) Old 01-27-2017, 05:23 PM
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Yo G,
Pull that ECM, aka EEC, PCM and look.
Give usthe name of the NAPA person who said that the cat doesn't need an AIR tube. The AIR Tube is in the y, as shown in this pic by rcracerx

The blue hose is supposed to be a High Temperature Silicone Hose piece.
...

311 koer Thermactor air system inoperative (right side)
"...The computer determined that for some reason the fresh air injection from the Thermactor system was not present. There are several components that make up this system. The initial component is the smog pump. The first checks I would make are the hoses and plumbing from the smog pump back to the diverter valve (behind the pass. cylinder head) and then on to the crossover pipe at the back of the heads and down to the catalytic converter. The check valves that are at the center of the cross over pipe and the top of the metal tube from the cat are often the culprits as they can and do snap in half as the get old. If the plumbing looks to be in good order we can discuss the slightly more complicated aspects of the system. The diverter valve also has two vacuum lines running to it. Make certain they are in place and intact. (Computer needs to be able to control the flow of fresh air by the Thermactor system)..."Source: by greystreak92

PCM Removal in 92 to 96 bossind @ Changing out the Bronco Computer ECU

See my partially recovered Bronco web site ...Will need to clean up dead links & add many more new links some day. Thanks to Mr. Schwim!
THANKS to ALL WHO SERVE!
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post #38 of 101 (permalink) Old 01-27-2017, 05:36 PM Thread Starter
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Ok so a shop said it did not need the air tube but this was 5 years ago. The shop is now out of business (no wonder). I'm currently at school and there is a orileys within walking distance and I used a mirror and got my code for the PCM. Now with the exhaust should I get a new cat or just weld the tube in before the cat.

Thank you so much for the info
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post #39 of 101 (permalink) Old 01-28-2017, 12:23 PM Thread Starter
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So I left my torx set at home. So even if I were to pull the ECM in the parking deck. I would not be able to open it up . Hopefully Itll get me home. Or I say **** it and replace the damn thing. Could I pull the spout and see if it starts better and my tach acts normal while cranking? If it was the PIP the computer would throw a code at least I would think.
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post #40 of 101 (permalink) Old 01-28-2017, 09:07 PM Thread Starter
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Quote:
Originally Posted by Mikey350 View Post
The tach signal comes from the ICM, the schematic are below. My best guess is that the ground signal that charges the primary side of the coil is oscillating rapidly (rather than going to ground once for each plug firing event).
Normally, the PIP signal from the hall effect switch in the distributor goes to the PCM, the PCM generates the SPOUT signal which in conjunction with the PIP commands the ICM to send the COIL signal (pin 5) to ground. (SPOUT is to modify the timing of the COIL signal.)
The tach signal (going to page 60-5, w/pk wire) is decoded by a solid state circuit in the tachometer into RPMs.
So, lots of tach signals at 2000 RPM, should be a lot less at cranking speed (about 250 RPM).
So, a failing hall effect (PIP) circuit making the PCM think the engine is turning 2000 RPM could be the reason, or the PCM misreading the PIP signal and sending the coil signals at a 2000 RPM rate (and not synchronized with the engine).
You could pull the SPOUT plug and see if the PCM is confusing the ICM. After that, fixing the PIP generator in the distributor if it is broke, or replacing the ICM with the correct (black) ICM. Pull the PCM and look for leaking capacitors, you could be seeing an early PCM failure that will get worse.


1996 Ford Bronco '94 EVTM picture | SuperMotors.net


1996 Ford Bronco '94 EVTM picture | SuperMotors.net

Sorry about the slow response of SuperMotors, but it's not my fault, have patience and it will eventually load.

Good Luck
So like could I just pull the spout and then see if it changes any thing and if it improves then its the computer ? Will it hurt my engine if I pull the spout?
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