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Discussion Starter #1
Hi, I have a 1988 2.3L Stang that is having some "issues" and I am tired of searching all over the internet, so I decided to ask myself and see if anyone can help.

My basic problems are that:

A. as soon as I start the car (right now) it will idle at 1000 RPMs for about 5 to 10 seconds, however, after that allotted timespan it will randomly rev up to about 2500 to 3000 RPMs. Then after about 1 or 2 minutes it will idle back down to about 1500 RPMs. Then you drive it around for a bit. When you shift back into Neutral it revs right back to 3000 RPMs again.

B. My car is getting terrible gas milage for a 2.3L. I have read numerous threads (even some on this forum) that say they average 350 to 400 miles a tank. Well with gas prices the way they are I would love that, however, at my current state I am coasting into gas stations at 230 and thats completely driving as relaxed as a granny or something. I am averaging 16 MPGs at my very best and that is rather annoying. (to tell the truth when I hit 230 miles that last time I was overjoyed that I got that much out of it, I normally get about 14 MPGs and barley hit 200 miles)

Now there are some obvious problems with the car, but here is what I DO know.

I bought the car off eBay 2 years ago from some guy who I can guarantee did not do routine maintenance.

The car leeks a lot of water out of the exhaust (my dad says that it is condensation, but if you ask me it shouldn't still be doing it after an hour of driving) so it could have a blown or leaky head gasket

It is an automatic, and I will be willing to bet that the fluids have never been changed

It has 113,360 miles on it as of today (plus or minus some)

The timing belt did break on it last year so I had to fix that (that was fun)

Has new spark plug wires, a new rotor, and a really clean (shockingly) air filter (probably the only things going for it)


Now I am not made of money, and do not have a mountain of tools at my "immediate" disposal, but if I do need some special tool to check something I should be able to get ahold of it form my uncles garage

many thanks in advanced :)
 

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The first problem, i am not much help with, but the 2nd is most likely 35 bucks. You say you arent made of money but that will be the best 35 you ever spend on that car. Buy a new Oxygen Sensor
 

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Discussion Starter #3
Well, I know I said I am not made of money, but I have several hundred bucks so thats real within my reach ;)

Now a quick question. I know where the IAC is located at (cleaned it out a lot recently) but where is the O2 sensor located at? I am pretty good with locating stuff if I have a general direction to start in ;) I'll take a guess and say that it may be the plug that is located underneath the IAC.
 

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Discussion Starter #5 (Edited)
Borrow/Rent a compression tester. It will tell you if you have a blown Head gasket.
Well, compression testers (or at least a decent screw in one) doesn't cost that much dose it? Guess I'll look one up now since I am not doing anything important in class and see how much it costs so I'll just buy one :)

Edit: I just found one at Autozone for about $20 so I'll swing over there after school and see if I can pick one up ;)

Edit 2: I just went and put a new O2 sensor on order... it will be here by tomorrow.
also, I just did a compression check and I got this
C1 = 117 psi C2 = 124psi C3 = 97psi C4 = 118psi

Thinking cylinder 3 is looking a bit suspicious
 

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#3 cyl sounds a little low but it's not going to give you the symptoms or the bad mpg you're talking about on the intro to this thread.

the first place always to check do a self test of the EEC - run your codes even if your check engine light is not on.

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

it's best to let your EEC do a little diagnostic work for you before you start tearing things apart and buying lots of un-needed parts.

chances are, one of your sensors is creating your problem
 

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Discussion Starter #7
#3 cyl sounds a little low but it's not going to give
the first place always to check do a self test of the EEC - run your codes even if your check engine light is not on.

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

it's best to let your EEC do a little diagnostic work for you before you start tearing things apart and buying lots of un-needed parts.

chances are, one of your sensors is creating your problem
Well I have pulled the codes, and I got a ton back (mostly dumb stuff like "idle speed is out of specified range" as if I couldn't tell that already)... it is a little late tonight though and the codes are in the back of my car, so I will through what I got up here tomorrow.
 

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Discussion Starter #8 (Edited)
Ok, here is what I got from my codes when I ran them...

ER
21 Coolant temperature sensor out of specified range
23 Throttle position sensor out of specified range
35 EGR pressure feedback, regulator circuit
13 Normal idle not within specified range
87 fuel pump circuit
74 Break on/off ground circuit fault
12 Idle speed control out of specified range
22 MAP sensor out of specified range
18 SPOUT circuit open
77 Throttle "goose" test not preformed

KOEO

12 Idle speed control out of specified range
23 Throttle position sensor out of specified range
33 Canister or EGR valve not operating properly
13 Normal idle speed not within specified range
84 EGR control circuit
22 MAP sensor out of specified range
74 Break ground circuit on/off fault

Now I did these tests about 5 times just to make sure I got everything correctly, however some things still baffled me, like in the ER test the codes 74 and 12 came up twice, and 13 came up 3 times. Also on the KOEO test the codes 13 and 33 came up twice. Another thing... I don't even think I should get the number 12 code in the KOEO test... I don't even think that it is possible!!! Is my car just that screwed up?

Also, just got my O2 sensor and am about to install it once my engine is cold enough for me to touch again. Also, where is it located? Is it on the throttle body or somewhere else? As far as I can work out it is but I am not 100% positive.

Edit: Well I have learned its location. It is on the Headers just above the Cat. Unfortunately for me, it is frozen in place. Supposedly (after doing some research) you need to heat it beyond belief to get it out... this is gonna be fun.
 

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well the codes point to looking at your coolant temp sensor, your map sensor, your tps sensor, and your egr valve and solenoids.

time to get out the old volt meter and start back probing some sensors.

Ford Fuel Injection Sensors

and as far as O2 sensor, make sure you do it with the motor and manifolds cold. Once the exhaust manifold starts to heat up, you'll have problems with stuck sensors, stripped threads, cracking manifolds etc....
 

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Discussion Starter #10 (Edited)
well the codes point to looking at your coolant temp sensor, your map sensor, your tps sensor, and your egr valve and solenoids.

time to get out the old volt meter and start back probing some sensors.

Ford Fuel Injection Sensors

and as far as O2 sensor, make sure you do it with the motor and manifolds cold. Once the exhaust manifold starts to heat up, you'll have problems with stuck sensors, stripped threads, cracking manifolds etc....
Well, I got the old O2 sensor out probably due to the fact that I covered it in PB Blaster and let it sit for about 2 hours... I didn't use any heat at all even though I thought I would need it so we are all good in that department ;)

As for installing the new O2 sensor... it fit like a glove and works like a dream, however now when I start it it revs up to 2000 RPMs and idles there steady as a rock. When I shift into gear however it drops down to 1000 RPMs (probably due to that being the RPM that the tranny engages at and nothing to do with the actual engine what-so-ever) Also it still has its fits just like I described in my first post, however, now it revs from 2000 to 3000 instead of from 1000 to 2000.

On the plus side the engine seems to be running a fair bit smoother :)

Now as of the MAP sensor and all that other stuff, I guess I will start checking that out tomorrow... will post my findings probably about 8 PM.
Oh and thanks for all the links zonker! They are a great help!
 

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you can check the egr valve by unhooking the vacuum tube and checking if there is suction. If theres suction on the tube you have a good egr valve but if not u have to replace it. I dont think there very expensive so u should be good. I wish I could explain better lol.
 

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Discussion Starter #12
you can check the egr valve by unhooking the vacuum tube and checking if there is suction. If theres suction on the tube you have a good egr valve but if not u have to replace it. I dont think there very expensive so u should be good. I wish I could explain better lol.
How much suction are we talking about? Cause I pulled it off today and put my finger over the tube. The suction I felt is about the equivalent as a feather landing on your hand which is almost nothing. I could feel no suction at all unless I put my finger directly on the tube and then I could feel the slightest of a pull... but not much.

Something tells me you are talking about more of a suction than that :(
 

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had more or less same issues as you with my 93 vert

this is what i did...and made a hugh difference...runs great for last year

-cleaned throttle body
-cleaned mass air flow sensor (dont believe yours would have)
-changed oxyen sensor (was pulling check engine code for this)
-changed erg sensor (not just egr)
-cleaned IAC (i found using seafoam and q-tip worked well)
-used seafoam (used 1/3 can threw vacuum line)...pour slowly and keep engine revs about 2000-2500 (i did threw brake booster vacuum line,and put a small funnel into line and poured slowly...1/3 can in about 4-5 min) turn off engine,let sit for a good 10 min,then drive it for 15-20 min like you "stole it"
 

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Discussion Starter #14
Is this Seafoam stuff like really good cleaner or something? It keeps popping up where ever I go. Maby I'll buy a can of that stuff after school today. Chances are I am gonna have to clean mostly everything in this engine.
 

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Discussion Starter #15 (Edited)
well the codes point to looking at your coolant temp sensor, your map sensor, your tps sensor, and your egr valve and solenoids.

time to get out the old volt meter and start back probing some sensors.
Well, I just started checking the sensors on the Stang... I will be reporting back periodically as I test voltage on each sensor/solenoid

Many edits later...

MAP Sensor
green wire = 2.60 volts
orange wire = 5.12 volts
black wire = 0.06 volts

ECT Sensor
green wire = 1.20 volts (mind you the car has only been sitting for a good hour so the temp might still be around 110 F)
black wire = 0.16 volts

TPS
closed throtle (idle)_________WOT
green wire = 3.28 volts______4.60 volts
orange wire = 5.12 volts_____same
black wire = 0.06 volts______same

EGR
brown/green wire = 0.53 volts
yellowish wire = 5.11 volts
black wire = 0.06 volts

IAC (cause I was suspicious of it)
red wire = 12.45 volts???
white/light blue wire = 12.45 volts??? (short maby?)

this is what I have so far... not really sure what else to test (nor do I even know what voltages I am looking for in these tests) I basically just stuck the black probe in the negative terminal on the battery and let the red probe test the wires in case that makes any difference in these results. All of this was done with the engine off and (for the MAP) vacuum line unplugged from the tree, not the sensor itself (didn't want the wind to potentially mess up my results)
 

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Originally Posted by 00MustangGtPremium
you can check the egr valve by unhooking the vacuum tube and checking if there is suction. If theres suction on the tube you have a good egr valve but if not u have to replace it. I dont think there very expensive so u should be good. I wish I could explain better lol.

How much suction are we talking about? Cause I pulled it off today and put my finger over the tube. The suction I felt is about the equivalent as a feather landing on your hand which is almost nothing. I could feel no suction at all unless I put my finger directly on the tube and then I could feel the slightest of a pull... but not much.

Something tells me you are talking about more of a suction than that

Yea there should be more suction than that. I would get a new egr valve just to be safe. Like I said they are not very expensive and idk if u have a short in the iac because it should be protected on a circuit and the fuse would blow if the iac was shorting out.
 

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Discussion Starter #17 (Edited)
Originally Posted by
Yea there should be more suction than that. I would get a new egr valve just to be safe. Like I said they are not very expensive and idk if u have a short in the iac because it should be protected on a circuit and the fuse would blow if the iac was shorting out.
Well, i think your right... but just to be safe... you are talking about the suction coming from the black tube you pull off the EGR correct? I mean there is no suction coming from the EGR either, but just to be safe.

Also, why would the EGR being bad control how much suction is coming out of that tube? Dose that little black box on the passenger side of the car mounted to the back side of the strut mount have something to do with it and controls how much suction the EGR is getting? The only reason I ask that is because I noticed that the vacuum lines run through there and then go to the EGR.

Edit: Just did a little research and the thing I am talking about is a the EGR Vacuum solenoid. Could that have possible gone bad?
 

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Well, I just started checking the sensors on the Stang... I will be reporting back periodically as I test voltage on each sensor/solenoid

Many edits later...

MAP Sensor
green wire = 2.60 volts
orange wire = 5.12 volts
black wire = 0.06 volts

ECT Sensor
green wire = 1.20 volts (mind you the car has only been sitting for a good hour so the temp might still be around 110 F)
black wire = 0.16 volts

TPS
closed throtle (idle)_________WOT
green wire = 3.28 volts______4.60 volts
orange wire = 5.12 volts_____same
black wire = 0.06 volts______same

EGR
brown/green wire = 0.53 volts
yellowish wire = 5.11 volts
black wire = 0.06 volts

IAC (cause I was suspicious of it)
red wire = 12.45 volts???
white/light blue wire = 12.45 volts??? (short maby?)

this is what I have so far... not really sure what else to test (nor do I even know what voltages I am looking for in these tests) I basically just stuck the black probe in the negative terminal on the battery and let the red probe test the wires in case that makes any difference in these results. All of this was done with the engine off and (for the MAP) vacuum line unplugged from the tree, not the sensor itself (didn't want the wind to potentially mess up my results)
Ok for the map sensor, that needs to be checked with the meter on the frequency setting check the Hertz at engine off, and at idle

ECT sensor needs to be checked with ohm setting, unplugged, and at many engine temperatures.

The TPS should have a range from .45 V to 4.5 V (based off your readings its bad)

Egr i know needs to be tested for voltage across a spectrum, it is a potentiometer like the TPS. Run the engine at 3000 rpm and then let off, see if it changes output voltage.

For the IAC, run the engine, unplug it and see if it idles down to about 500 rpm, if it does then check the resistance, i believe that it is a pulse width solinoid, if it has really low resistance it is shorted. It should have 12 v at both poles, one is power in, and the other is the ground wire that is controlled by the ECU and it will read 12 v with the engine off. If your car does not idle down, then your idle screw has been rammed in too far. back it off to 500 rpm with the IAC unhooked.
 

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Originally Posted by 00MustangGtPremium
Originally Posted by
Yea there should be more suction than that. I would get a new egr valve just to be safe. Like I said they are not very expensive and idk if u have a short in the iac because it should be protected on a circuit and the fuse would blow if the iac was shorting out.

Well, i think your right... but just to be safe... you are talking about the suction coming from the black tube you pull off the EGR correct? I mean there is no suction coming from the EGR either, but just to be safe.

Also, why would the EGR being bad control how much suction is coming out of that tube? Dose that little black box on the passenger side of the car mounted to the back side of the strut mount have something to do with it and controls how much suction the EGR is getting? The only reason I ask that is because I noticed that the vacuum lines run through there and then go to the EGR.

Edit: Just did a little research and the thing I am talking about is a the EGR Vacuum solenoid. Could that have possible gone bad?
Ive never had a problem with my egr valve but I know that if there isnt any suction coming from the egr valve means that its bad. And yes the black tube coming from the egr valve. I would do a voltage test like Mikel89us said and see what the numbers are before getting a new egr valve. I just read if the egr vacuum solenoid isnt working there will be little or no vacuum to the egr so yea it also could have gone bad.
 

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Discussion Starter #20
Ive never had a problem with my egr valve but I know that if there isnt any suction coming from the egr valve means that its bad. And yes the black tube coming from the egr valve. I would do a voltage test like Mikel89us said and see what the numbers are before getting a new egr valve. I just read if the egr vacuum solenoid isnt working there will be little or no vacuum to the egr so yea it also could have gone bad.
Well, I guess I am gonna have to do a little more testing... when it finnaly stops raining I will get back out there and do all this testing like the MAP sensor and stuff again corectally along with the EGR Vacuum solinoid.
 
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