Idle Problems

[Deep]

I have a 1987 Eddie Bauer with a 302 5.0 EFI Bronco. Recently I have developed a issue with the engine surging at idle. I have replaced the EGR and ECV valve. I have replaced the IDLE BYPASS VALVE, replaced the OXYGEN SENSOR. Replaced the DISTRIBUTOR CAP and ROTOR and performed a TUNE-UP. Symptoms are...Engine fires right up with no issue, after about a minute or two the idle drops and the engine begins to surge. Once the engine is warm, this goes away, until I shut the ignition off and restart. The truck runs fine without surging, and this is a initial startup idle problem. I have checked the coil and I have a Jacobs Ignition and these items both check out just fine. I need some direction here, could this be a MAP Sensor issue?

Thanks for any help.

 

[BroncoJoe19]

Hi and Yes.. IT could be a MAP sensor issue, or your TPS, OR a vacuum leak.

A surging idle is very typical of a vacuum leak.

First thing is check for vacuum leaks, and repair any you may find.

Then pull DTC codes.

IF you don't know how to pull codes, we can help you with that.

Good luck.

joe

 

[BroncoJoe19]

Oh.. and I hope that your tune-up included a new air filter /emoticons/[email protected] 2x" width="20" height="20" />

 

[Jeep'nBronco]

I have been having the same problems. I went through nearly every vacume line and replaced them. my next guess was the MAP so I say try it before you go through you lines cause dear lord Ford needs to cut down on the vacume crap haha

 

[cj_92Bronco]

check the voltage on your IAC too

 

[BroncoJoe19]

I have been having the same problems. I went through nearly every vacume line and replaced them. my next guess was the MAP so I say try it before you go through you lines cause dear lord Ford needs to cut down on the vacume crap haha

Another member wrote in another thread about how to check for vacuum leaks...

take a can of carb cleaner and spray where the intakes meet each other, lower meets head, and all vacuum lines. The idle will change when you spray where it is leaking.

This is a much easier method than replacing all of the hoses.

Ofcourse you can just replace parts until you find the right one, but me personally I prefer to only replace the broken ones.

Replaceing the MAP is a five minute job, the TPS an hour or two depending upon how dirty your throttle body is (how long it takes to clean it) and if you don't have to go get replacement screws for your TPS after you mess them up trying to get them out, like I did. Note: you'll need a digital voltmeter and a set of straight pins to adjust the TPS when installing it.

Then after you replace both parts, and if it still surges, then you can always go back and look for vacuum leaks.

BTW... if you do check for codes without looking for vacuum leaks, and you get a bad MAP code, one of the causes for that code is a vacuum leak.

I guess you can figure out what I would do first?

joe

 

[Deep]

Hi and Yes.. IT could be a MAP sensor issue, or your TPS, OR a vacuum leak.
A surging idle is very typical of a vacuum leak.

First thing is check for vacuum leaks, and repair any you may find.

Then pull DTC codes.

IF you don't know how to pull codes, we can help you with that.

Good luck.

joe

Not sure how to pull the codes........I did change the Air Filter, PCV Valve and I have checked all the vacuum lines....Forgot to mention that when I have made a drive with the truck and place it in park the idle rpm's are up to 1300 -1400 rpms.

 

[BroncoJoe19]

Not sure how to pull the codes........I did change the Air Filter, PCV Valve and I have checked all the vacuum lines....Forgot to mention that when I have made a drive with the truck and place it in park the idle rpm's are up to 1300 -1400 rpms.

Here you go... lots of reading...

http://broncozone.com/forums/index.php?sho...1&hl=codes#

 

[BroncoJoe19]

Here you go... lots of reading...http://broncozone.com/forums/index.php?sho...1&hl=codes#

I noted that there is an error on this page that has not been corrected.

http://fordfuelinjection.com/?p=13

However using the diagram on the page do this to prepare for the test.

Check your coolant level.

make a little jumper wire, all you need is about 4 inches to connect Signal Return, and Self Test Input (STI)

Start the truck and let it warm to operating temp.

Turn the engine off and wait 10 seconds.

Place your jumper wire to connect Signal Return, and Self Test Input (STI)

Get into the driver's seat

Follow the directions on this page starting with #5... (get into the driver's seat)

http://fordfuelinjection.com/?p=13

 

[BroncoJoe19]

I just found a great article on how to test for codes.

http://www.fordfuelinjection.com/files/self_test.pdf

This will be of particualr interest to those with 1984 through 1988 models, but is also excellent for those up to the 1995 models.

 

[Deep]

Thanks for the information...I used some carb/choke cleaner to look for vacuum leaks, and detected none.

I just found a great article on how to test for codes.http://www.fordfuelinjection.com/files/self_test.pdf

This will be of particualr interest to those with 1984 through 1988 models, but is also excellent for those up to the 1995 models.

 

[BroncoJoe19]

Thanks for the information...I used some carb/choke cleaner to look for vacuum leaks, and detected none.

That was painless enough eh?

I'm glad that you did, because if you didn't and it ended up being a vacuum leak, you'd be kickin youself in the place you normally sit.

The next step is to check for diagnostic codes.

I just found a great article on how to test for codes.

http://www.fordfuelinjection.com/files/self_test.pdf

This will be of particualr interest to those with 1984 through 1988 models, but is also excellent for those up to the 1995 models.

Let us know what you come up with.

joe

 

[KansasBronco]

my bet is on the Air bypass valve. as with age, and use the motor gets old in there. try changing it.... read my old thread!

 

[Deep]

my bet is on the Air bypass valve. as with age, and use the motor gets old in there. try changing it.... read my old thread!

Thanks for the suggestion.....I appreciate your time.

 

[Deep]

That was painless enough eh?I'm glad that you did, because if you didn't and it ended up being a vacuum leak, you'd be kickin youself in the place you normally sit.

The next step is to check for diagnostic codes.

I just found a great article on how to test for codes.

http://www.fordfuelinjection.com/files/self_test.pdf

This will be of particualr interest to those with 1984 through 1988 models, but is also excellent for those up to the 1995 models.

Let us know what you come up with.

joe

TPS was what was causing my problems....it is replaced and engine no longer surges. Only thing I have noticed is that my idle after a drive holds at about 1500 rpms. Prior to driving it is at 900 rpms and while driving when I am at a stop the engine purrs smoothly holding strong at 900 rpms. Not sure why the idle climbs to 1500 rpms when I place my bronco back into park??

 

[BroncoJoe19]

TPS was what was causing my problems....it is replaced and engine no longer surges. Only thing I have noticed is that my idle after a drive holds at about 1500 rpms. Prior to driving it is at 900 rpms and while driving when I am at a stop the engine purrs smoothly holding strong at 900 rpms. Not sure why the idle climbs to 1500 rpms when I place my bronco back into park??

If I am reading this correctly, when the engine is still relatively cold in PARK it idles at 900 rpm, but after you drive her and she is up to normal operating temp she idles in PARK at 1500 rpm.

It could still be a vacuum leak.

When you installed your TPS, did you adjust it with a voltmeter?

If not I have instruction on how to do that in a thread I can point you to.

Another thing that could contribute to / cause a high idle is timing.

I believe that the timeing should be 10 degrees BTDC

If you check it, you need to pull the SPOUT connector first.

 

[BroncoJoe19]

If I am reading this correctly, when the engine is still relatively cold in PARK it idles at 900 rpm, but after you drive her and she is up to normal operating temp she idles in PARK at 1500 rpm.
It could still be a vacuum leak.

When you installed your TPS, did you adjust it with a voltmeter?

If not I have instruction on how to do that in a thread I can point you to.

Another thing that could contribute to / cause a high idle is timing.

I believe that the timeing should be 10 degrees BTDC

If you check it, you need to pull the SPOUT connector first.

Here is the link to adjusting the TPS.

http://broncozone.com/forums/index.php?s=&...ost&p=72288

 

[Deep]

If I am reading this correctly, when the engine is still relatively cold in PARK it idles at 900 rpm, but after you drive her and she is up to normal operating temp she idles in PARK at 1500 rpm.
It could still be a vacuum leak.

When you installed your TPS, did you adjust it with a voltmeter?

If not I have instruction on how to do that in a thread I can point you to.

Another thing that could contribute to / cause a high idle is timing.

I believe that the timeing should be 10 degrees BTDC

If you check it, you need to pull the SPOUT connector first.

 

[Deep]

You are correct, when the engine is completely warmed up, it idles at 1500rpm. When I installed the TPS, I did nothing to adjust it and wasn't even aware I needed to(where do you adjust this, as it is held in place with two screws and has a solid body)..........so any info you provide regarding this will be appreciated. I have again checked for vacuum leaks and can find none. The MAP Sensor was replaced as well. I noted your timing that you mention. My Engine is a 302 with a 351 firing order, will this still be the same timing? Thanks again for your help.