Bronco Forum - Full Size Ford Bronco Forum banner

1 - 20 of 83 Posts

·
Registered
Joined
·
633 Posts
Discussion Starter #1
Just got a new '93 since a drunk rear ended mine a month ago in front of the house and totalled it. My question is, it idles ok and runs at speed ok but when it drives from a stop, it wants to misfire for about 5 seconds and then it smooths out and runs strong but pings bad under power. The engine is original and appears to be all intact as far as all the factory EFI equipment. No CEL and no idle issues. Timing is correct. I'm wondering if the knock sensor is not working and could cause this or where would you start first?
 

·
Registered
Joined
·
649 Posts
Pull codes. You probably have some even if CEL is not on.

Check fuel pressure/filter, and check compression since you will be doing a tuneup anyway since you just got it.

Seafoam it and see if the pinging goes away.
 

·
Premium Member
Joined
·
10,000 Posts
This assumes your BKO has any or all of these sensors, IAC, TPS and ECT are for fuel management at "cold start" and during normal operation.

Did you actually "pull codes" from the vehicle computer for diagnosis....initially I would more be inclined to look at the IAC =" idle air control valve" located on the right side of the throttle body which can be removed and cleaned inside using TB cleaner and re-install which might solve the irratic idle issue. "search" for IAC - How To....


TPS = throttle position sensor located on the bottom of the TB, it's voltage driven and controls "blade angle" there are 2 styles of TPS, the older style actually adjusts for setting using a mulitmeter, the newer style is "plug & play" voltage setting is automatic when re-connected..."search" TPS for How to

ECT = engine cooling temp sensor located in the lower intake manifold in an "octagonal tree" between the FI plenum and the distributor.. test the wiring and look at the condition of the sensor...if you don't know how old it is I would replace it, around $30.00 or so..

There are a number of test procedures in the "Haynes Repair Manual" for all of the sensors using a multimeter, probing wires for voltage level and ohms resistance that indicates whether to replace or not..

Additional Help source:

www.fordfuelinjection.com ~ FREE, pulling codes and test connectors, code numbers and fault explanations
www.broncolinks.com

Good Luck ~
 

·
Registered
Joined
·
633 Posts
Discussion Starter #4
Yeah I am familiar with all of the components and have general knowledge of how they work together, but hearing that there could be codes even with no CEL was a good place to start as I thought if there was a code, CEL would bo lit. This is not OBD2, anyone have a quick link to procedures to pull codes from pre OBD2?
 

·
Registered
Joined
·
649 Posts
Yeah I am familiar with all of the components and have general knowledge of how they work together, but hearing that there could be codes even with no CEL was a good place to start as I thought if there was a code, CEL would bo lit. This is not OBD2, anyone have a quick link to procedures to pull codes from pre OBD2?
http://fordfuelinjection.com/?p=13

Here you go. There is probably a tech writeup on this forum also.

I also recommended testing the fuel pressure because that would not throw a code (AFAIK)
 

·
Premium Member
Joined
·
10,000 Posts
X2 on FPR......

Ford Code Readers with diagnostic book are currently $29.99 + tax at Kragen/O'Reillys, this device just plugs into the OEM test connectors located on the right inside fender off the harness behind the battery area..mine are red/tan ....this is expalined on FFI.com but make sure the batteries are fresh or it won't trigger the computer or give accurate info properly....

There is a "plusing" technique (free) but IMO it's real a slow PITA way .....it's your call....

Good Luck ~ :thumbup
 

·
Registered
Joined
·
633 Posts
Discussion Starter #7
http://fordfuelinjection.com/?p=13

Here you go. There is probably a tech writeup on this forum also.

I also recommended testing the fuel pressure because that would not throw a code (AFAIK)

X2 on FPR......

Ford Code Readers with diagnostic book are currently $29.99 + tax at Kragen/O'Reillys, this device just plugs into the OEM test connectors located on the right inside fender off the harness behind the battery area..mine are red/tan ....this is expalined on FFI.com but make sure the batteries are fresh or it won't trigger the computer or give accurate info properly....

There is a "plusing" technique (free) but IMO it's real a slow PITA way .....it's your call....

Good Luck ~ :thumbup
Thanks!! I will try to find the device, otherwise I'll go through the PITA way. It didn't look that difficult, just tedious.
 

·
Premium Member
Joined
·
10,000 Posts
There is a "schreader valve" on the fuel rail towards the front, drivers side which looks like a air tire stem and you press the center for a quick check on FP, otherwise you will need a fuel pressure guage to test for PSI, guage costs a little more or borrow one if you can....FPR are easy to replace....small upside down hex screws...


Good Luck ~ :thumbup
 

·
Registered
Joined
·
633 Posts
Discussion Starter #10
The only code its showing is 5-3-8. Book says its insufficient RPM change when WOT test performed, cylinders out of balance. Guess a compression test is next.
 

·
Registered
Joined
·
649 Posts
The only code its showing is 5-3-8. Book says its insufficient RPM change when WOT test performed, cylinders out of balance. Guess a compression test is next.
Did you run the test with the engine running?
 

·
Registered
Joined
·
633 Posts
Discussion Starter #13
Did you run the test with the engine running?
Yes, all tests performed as the book instructed. I am not new to this just not to vehicles this old that are EFI. Haven't had time to do compression check or check fuel pressure, plugs, etc. I have only had a few minutes each day for about a week to do small things. I am going under the assumption these things are ok for the time being. Compression, fule pressure and spark will be checked this weekend.
 

·
Registered
Joined
·
215 Posts
be sure to pull the spout connector at the dizzy before timing it, and the timing on bkos are at 13* Good luck.
 

·
Premium Member
Joined
·
10,000 Posts
I'd say timing at 13 degrees BTDC would be more for performance ignition and timing upgrade with a wider plug gap, check FSB member Sixlitre for his ignition & timing upgrade.thread...

My 86 302 EFI is OEM 10 degrees BTDC......look for the decal on the radiator core support on top it should be there or refer to the Haynes Manual OR www.broncolinks......


Good Luck ~ :thumbup
 

·
Registered
Joined
·
633 Posts
Discussion Starter #17
Update...Changed plugs and wires. Resistance in old wires (new according to PO) was nearly nothing. Plugs (also new according to PO) were gapped incorrectly, some at 40, some at 50 and one at 38. Timing is set at 13 degrees and plugs gapped at 50 for now. Drove vehicle warm for about 5 miles. WOT several times and no pinging and no misfiring. Stopped at a store for a drink for about 2 minutes and start her back up and now constant misfire. Didn't have time to check fuel pressure but I am assuming it is ok for now because it ran so well until I shut it off. Here's where I'm at a loss. I guess tomorrow I'll check fuel pressure and if that is ok, I assume it could be injectors? I do not believe EGR would cause this and it didn't present any codes except the one mentioned above. Thanks for your input.

BTW, I forgot..93 EB, 5.0, E4OD appears to be all stock and complete.
 

·
Premium Member
Joined
·
10,000 Posts
I'm still not seeing that you "pulled codes" from the computer and what faults are indicated....?
Start your diagnosis from there and if necessary perform KOEO and KOER tests for thorough, accurate results..

Make sure the spark plug wires are adequately spaced apart from one another or you may cause "cross -over arcing"....creating a miss...bad plugs and ignition components will do the same EVEN brand new ones.....PITA....lol lol...

My 86 302 EFI calls for .44 plug gap with OEM 10 degrees BTDC timing so I don't see how yours is any different, look on the core support for the OEM decal...check the Haynes Manual for stats.
The Sixlitre ignition and timng upgrade recommends a .55 plug gap using the least expensive Autolite plugs with a range of 12-13.5 degree BTDC timing..so you get more power out of the truck along with better gas mileage but it does suggest all new ingition components with a 48K coil and possibly new O2 sensor for best results.

A vacuum leak can cause a miss such as damaged plastic or rubber vacuum lines or code: 44 Thermactor Air Injection System "fault" indicating a vacuum leak somewhere in the emissions system anywhere from a single vacuum line, rubber hose or "check valve" perhaps the one on the exhaust cross over tube bolted to the cylinder heads ONLY if this applies to your year BKO.

In this case the leak causes air to sucked in changing the EGR air stream from up to down essentially going out the CAT instead of going thru the engine, ie: oxygen starvation, now giving the feeling there is a miss..

I'm not saying this is your specific issue but pulling codes, diagnosising and visually inspecting all vacumm lines should help narrow down the problem....

Good Luck ~
 

·
Registered
Joined
·
633 Posts
Discussion Starter #20
You might want to try doing a vacuum check too, as it can help diagnose many problems-- this is a very helpful site that i found through FSB posts. check out the "readings" section. http://www.secondchancegarage.com/public/186.cfm

hope that helps and you can figure out your problem here
I'm still not seeing that you "pulled codes" from the computer and what faults are indicated....?
Start your diagnosis from there and if necessary perform KOEO and KOER tests for thorough, accurate results..

Make sure the spark plug wires are adequately spaced apart from one another or you may cause "cross -over arcing"....creating a miss...bad plugs and ignition components will do the same EVEN brand new ones.....PITA....lol lol...

My 86 302 EFI calls for .44 plug gap with OEM 10 degrees BTDC timing so I don't see how yours is any different, look on the core support for the OEM decal...check the Haynes Manual for stats.
The Sixlitre ignition and timng upgrade recommends a .55 plug gap using the least expensive Autolite plugs with a range of 12-13.5 degree BTDC timing..so you get more power out of the truck along with better gas mileage but it does suggest all new ingition components with a 48K coil and possibly new O2 sensor for best results.

A vacuum leak can cause a miss such as damaged plastic or rubber vacuum lines or code: 44 Thermactor Air Injection System "fault" indicating a vacuum leak somewhere in the emissions system anywhere from a single vacuum line, rubber hose or "check valve" perhaps the one on the exhaust cross over tube bolted to the cylinder heads ONLY if this applies to your year BKO.

In this case the leak causes air to sucked in changing the EGR air stream from up to down essentially going out the CAT instead of going thru the engine, ie: oxygen starvation, now giving the feeling there is a miss..

I'm not saying this is your specific issue but pulling codes, diagnosising and visually inspecting all vacumm lines should help narrow down the problem....

Good Luck ~
As I said before, all vacuum lines (hard and soft) are intact and not leaking. As far as a manifold leak, unless the gasket is bad, which the ether (starting fluid sprayed all around the intake) is wrong, everything is ok with that part of it. Let's just say I have eliminated every problem with the mechanics of the engine except fuel pressure so far. Spark, compression and air delivery. The symptoms point to either a fuel delivery problem or an air delivery problem. My question now is...could a faulty EGR cause the same symptoms as I star the vehicle cold and it runs great until it reaches operating temp.
 
1 - 20 of 83 Posts
Top