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1990 bronco 5.0 v8 fullsize
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Discussion Starter #1
Here's my problem the engine will start but idles badly and will stall if I don't give it gas and when Iam driving it the engine will start to lose power and buck a little then die and some time it will start back up or I will have to give it some time to start back up. I checked for vacuum leaks and found none and did the smoke test too and still found nothing, I'll pull codes and post when I get off work. Any help would be appreciated, thanks.
 

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Yo Reynolds,
Welcome!
Pull codes and post them here later.

In meantime;
Unplug/test the IAC by SeattleFSB @ How to Clean and Test your IAC

Some no code usual suspects by Ford;
Vacuum leak, see my leak diagnosis link in post #11 @ Help with dtc codes and idle

Air filter, is it relatively clean?

Air inlet atop radiator support to filter box and to throttle body; look for obstruction; damaged tubing, openings in tubing, loose fit at throttle body or if at MAF sensor.

Fuel quality; Oxidized fuel often turns darker over time and may even smell sour. You can check stored gasoline by pouring some into a clear glass container and comparing it side-by-side with known fresh gasoline. If your old sample looks noticeably darker than the fresh gas, you have strong evidence the gas has gone bad.

Electrical connectors; inspect for corrosion, etc at coil, firewall, ICM, distributor, PCM, etc. especially those with broken locking tabs.

"Troubleshooting Fuel Injection Problems with a Noid Light;
Occasionally, you may have to troubleshoot a no-start condition, a misfiring or a bad fuel injector in a vehicle. A Fuel Injector Noid Light is one of those indispensable tools that will help you to diagnose the maladies affecting most of the fuel-injected vehicles on the road today. The Noid light test in conjunction with several others will help you find the root cause of the misfire or no-start that your vehicle may be experiencing." Read more @*Troubleshooting Fuel Injection Problems with a Noid Light - Apex Tool Company
Rent it @ some parts stores, especially mom and pop owned:*unplug one of the fuel injectors and plug the NOID light in. Then crank the engine and if the NOID light flashes the computer 7 grounding the injectors OK. But if you can smell raw gas at the tailpipe when you crank engine over."

Or, try this injector test; "...With eveything connected normally & the key in RUN, pierce the OTHER wire (not the Red one) on any ONE injector & tap it BRIEFLY to ground. Do you hear half the injectors click open & then closed? Put a finger on each one to feel which ones are working. If some of them don't open, repeat the test, holding the ground SLIGHTLY longer each time, but never more than 3 sec continuously...Repeat this for the 2nd bank of injectors (just one with a different color wire)..." by Steve

Here are the:
1990 Bronco Pre-Delivery Shop & Electrical & Vacuum Troubleshooting Manuals (EVTM), Partial by member Kingfish999 in Google Drive @ 1990 Ford Truck service manuals - Google Drive
&
1990 Ford Truck Emmisions Manual.pdf by Ford via member 90.CaliBronco in Google Drive @ 1990 Ford Truck Emmisions Manual.pdf

Suggest you download both for faster scrolling and to use the table of contents index.

1990 Ford Bronco Brochure by Ford via Dezo's Garage @ https://www.xr793.com/wp-content/uploads/2020/07/1990-Ford-Bronco.pdf

Register with VIN to see most Ford dealer maintenance/repairs done @ any dealership nation-wide @ Welcome to Ford Owner | Official Ford Owner Site

For any Bronco issues or to chat about it's planned modifications or build, it's better to post each seperately in Noobie Bronco Tech Questions. Flame free zone. This will get more attention and you can build up your post count to get into other sections such as Bronco and Ford Parts/Accessories that requires 75 non-padded posts to participate due to scammers who preyed on our members.

To save you time and for better responses, please fill out your Bronco info with location, year, engine size, transmission type, transfer case type (manual or electric shift), locking hub type (automatic or manual) info & major mods such as a Lift, etc. .
Bronco info is now able to be put under your user name.
Click your profile button in the top right and go to account settings.


On that first page, named Account Details, scroll down to "Vehicle Info" and type in up to 100 characters.

Now you can simply enter your information in the text editor and click save.

Our Forum FAQs includes for example: How To Upload Images To Posts, How to Use Search and more tips!

➡See Baba Looey's Favorite FSB Links (lots and lots of tech links) ... includes such as, "Tailgate Window repair & troublehooting".

Try to find time to participate and vote in our current Full-Size of the Quarter Contest & later in the year, Full-Size of the Year Contest @ Voting
You will get ideas by those competing. Also see the prizes! They are awesome as compared to other sites' "contests"!
 

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Registered
1990 bronco 5.0 v8 fullsize
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5 Posts
Discussion Starter #3
I did the test and here's what I got

8
10
21
45
72
73
25
52

I know 52 pertains to the power steering there is no sensor on the power steering lines, but there is an connector there for one. why it's not there I don't know.

Thanks for the help. cheers.
 

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Yo Reynolds,
8 Not applicable, try test again. If you see this code again and/or different codes, pull EEC and inspect for leaky capacitors, burnt resistors, etc.
EEC IV PCM Removal up to & include 87- 91 COMPENDIUM "...Remove driver's inside kick panel adjacent to pedals. It comes out through cabin." by Seattle FSB; "Should be one small metal screw holding it. Just slide it out, but be careful w/ gasket for firewall. Don't mess it up, you can reuse it." by Darth_ted_82 H "To remove it first disconnect battery & get use 10 mm socket to unbolt the wiring harness "connector from inside the engine bay. Then pull plastic kick panel from inside cab & remove the retainer clip Remove it by lifting rear slightly & wiggling it out of the "pocket" ... the firewall rubber gasket will have a pretty good grip on the connector so it will take some persuasion to free. " "You have to unplug it under the hood very low on the fire wall (10 mm socket)."

EEC IV PCM in 85-86 Bronco is right under the dash just above the hump off to the right just a bit.

10 Cylinder #1 Failed Cylinder Balance Test. You don't have dynamic cylinder balance testing ability on a 1991 model Bronco. Bank-fired injectors do not allow for such provision. Try test again.

21 ECT out of self test range 0.3 to 3.7 volts. "... ECT is bad, engine not warmed up, bad thermostat, low coolant..Coolant is less than 50 deg F for KOEO, or less than 180 deg F for KOER, or greater than 250 deg F for either. If coolant temp is in proper range, suspect ECT sensor or it's connector/wiring..." read more
Source: by me at FSB 86 Bronco Need help pulling codes
Testing; "..."But due to its simplicity of design, the ECT is rarely at fault when problems occur. Before testing the ECT or any other EFI component perform a self-test, trouble codes received during test can be used as a diagnostic tool along with other indicators. To test an ECT sensor you will need a volt meter. You can test the ECT by back probing the harness while reading the voltage returning to the EEC. Or you can removing the connector completely and test the resistance between the 2 pins on the ECT..." READ MORE Source: by Ryan M at http://www.fuelinjectedford.com/images/eec04.gif

and to help testing on all codes; use these by Ryan

EEC IV Connector Pin Depiction Pic by Ryan M
& EEC IV PIN LEGEND @ Ford Fuel Injection

45 Thermactor secondary air is misdirected. Try vacuum leak test.
Thermactor air system inoperative-right side: "...The code 45/95 is an Air Management fault. These particular codes are used for the Thermactor Air Diverter (TAD)/Thermactor Air Bypass (TAB) valve system (Fig. 3). In following the diagnostic tree we were to first check for vacuum lines that could possibly be broken or disconnected. One line was found disconnected. One line was found disconnected. We also discovered that this particular vacuum line got its source vacuum at the same place the MAP sensor did. This leak, we believed, was the cause of the erratic readings that set the MAP sensor code 72. At this point the codes were cleared and the emissions were checked. The emissions were lower, but not good enough. And a code 95 was still present. We continued with the diagnostic tree and determined that the diverter valve was not at fault. We entered the output state check and cycled both the TAB and TAD solenoids on/off. They both worked correctly. Finally, we supplied vacuum to the solenoid to make sure that the vacuum did not leak down. The TAD solenoid would not hold vacuum. It slowly bled off. We replaced the solenoid. We then performed a KOEO and KOER test. No codes were present and emissions looked excellent. HCs were averaging about 97 to 112 ppm, and the CO was down around .2%. We concluded that the emissions readings were being affected by the vacuum bleeding off of the TAD solenoid. This allowed vacuum to be applied to the diverter valve at the TAD portion continuously. This resulted in the air always being diverted to the manifold before the oxygen sensor. The oxygen sensor would read lean, because of the extra oxygen, and therefore the computer would enrich the mixture. This is why the vehicle failed emissions..."
Source: by tomco-inc

72 Insufficient MAP change during Dynamic Response Test, try test again.
DTC 72 indicates that the MAP sensor output did not change enough during the Dynamic Response Test.
Possible causes:
-- System failed to detect partial WOT.
-- MAP sensor vacuum supply hose improper routing, blockage and/or linkage.
-- Damaged MAP sensor.
l Rerun Engine Running Self-Test. Be sure a complete WOT is performed during the Dynamic Response portion of the test by RLA

73 TPS senor did not exceed 25% rotation during Dynamic Response Test, try test again.


25 Knock not sensed during dynamic test, try test again.

52 Power steering pressure switch always open or closed, iggie for now.
 

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1990 bronco 5.0 v8 fullsize
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Discussion Starter #5
Okay ran the test again
8
45
72
73
25
52

I will be doing more work on the bronco, also what did this go to?
167590
167591
 

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Yo Reynold,
On the hose, Guessing;
167600

Smog pump...
 

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1990 bronco 5.0 v8 fullsize
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Discussion Starter #7
0kay bottom panel left side passenger side the tube goes nowhere on my Bronco it was broken off when I got it but it seems to have a vacuum leak there and where the pedles ar at I found a three whire harines not connected too anything.
 

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0kay bottom panel left side passenger side the tube goes nowhere on my Bronco it was broken off when I got it but it seems to have a vacuum leak there and where the pedles ar at I found a three whire harines not connected too anything.
The hose you are pointing to is an intake tube to the smog pump... it is going to be vacuum because the smog pump pumps fresh air into the catalytic converter.
As for the wiring harness plug, I’ll look at mine in the morning. I don’t remember seeing it... although it might go to the clutch pedal.
 

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Yo Reynolds,
Either replace the resistors or replace the EEC.
EEC IV PCM Removal up to & include 87- 91 COMPENDIUM "...Remove driver's inside kick panel adjacent to pedals. It comes out through cabin." by Seattle FSB; "Should be one small metal screw holding it. Just slide it out, but be careful w/ gasket for firewall. Don't mess it up, you can reuse it." by Darth_ted_82 H "To remove it first disconnect battery & get use 10 mm socket to unbolt the wiring harness "connector from inside the engine bay. Then pull plastic kick panel from inside cab & remove the retainer clip Remove it by lifting rear slightly & wiggling it out of the "pocket" ... the firewall rubber gasket will have a pretty good grip on the connector so it will take some persuasion to free. " "You have to unplug it under the hood very low on the fire wall (10 mm socket)."

Member jermil01 wrote, "I've used G7 Computers @ How Does This Work? in the past..good company and responsive. If your EEC has a faulty capacitor or resistor as is the case with most of them it's usually fixable as long as the board isn't damaged, but they need to have to be able to determine that. A while back I had a spare EEC I was going to send to them to have checked out, before I did, I snapped a pic of the board it had scorch mark. They said not to bother that the board was probably shot.."
Member gedebohls wrote, " i went with sending my ecu to G7 computers in Canandaigua, NY, the reason i went this way is because i send them my unit, i get my unit checked out 100% and they will then fix as needed. I like this bc I will know for sure if my ECU is or was bad, etc, and I get my ECU back fixed. the cost is $225 plus shipping one way, if nothing is wrong with my ECU i get 100% refund.
 
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