1992 5.0 Mustang GT - bad jerks & idle

[AgPete139]

Very unusual driving shudders & idle


Hey guys,

I've had a problem with my 1992 5.0L Mustang GT for the past couple months... (please read)

• At idle 800 rpm, my engine suddenly drops to 200 rpm every 6 seconds.
  
• When I am cruising in 5th gear @ 2000 rpm @ 70 mph, the entire car randomly shakes and shudders violently (the entire car wants to lurch forward/stop/fwd/stop). Hard to predict. It happens in every gear, & is RPM related).
  
• Hard acceleration past 2000+ rpm makes it barely noticeable.
  
• Sometimes I am forced to bog the engine just to avoid jerking.
  

I've read quite a few threads (& I hate reading reposts), but I'm stumped.


Recent maintenance:

• Cleaned IAC / TBV solenoid.
• Expanded & contracted the 10-pins Salt & Pepper Shaker connectors
• Expanded & contracted the 3-pins EGR connector
• Cleaned MAF
• Cleaned Throttle Body
• Set Throttle Position (TPS) to 0.91V (it exceeds 2.7V @ WOT)
• Reset Base Idle
• New spark plugs gapped @ 0.054"
• Flushed coolant system / radiator / heating
• Replaced harmonic balancer/dampener/damper (shimmy, rubber worn, 1 month ago)
• New heater core (leaking, 4 months ago)
• Fuel filter (clogged, 6 months ago)
• Oil change (1 month ago)
• New starter (bad, 2 months ago)

Other notes:

• I do not have fuel pressure gauge installed, and I am unsure how to test the EGR.
• A small amount of moisture exits my tailpipes, but that's normal.
• My #2 cylinder spark plug was slightly more whiter/gray than the others, but I have since regapped. There is a small amount of rust on that part of the fuel rail, but nothing even major. (It's a Texas car.)
• I did not notice a change in idle with propane in the engine bay (same theory as using carb cleaner to test for seal or vacuum leaks).

Please someone help. I am getting tired of this! Thanks in advance!

Pete

 

[kimcrwbr1]

at an idle hook the egr up to manifold vacuum or a vacuum pump if it dies it is working. take a long vacuum hose put it up to your ear and search around all connections and gaskets on the throttle body, manifold be careful of moving parts you can sometime find a leak like that listen for any hissing. have you checked for codes there are a few mustang forums that are mustang specific might get help in one of those

 

[AgPete139]

Rotor & points appear to be in good condition and making contact. Gave them a quick brushing anyways.

It turns out, there was a black 1/8" OD vacuum hard line that was broken. I decided to replace the other brittle hoses while I was there...




She still seems to stutter/hiccup. although not as severe as before. I checked the vacuum tree by the brake booster, & the A/C vacuum lines are fine.



3 vacuum fittings behind intake manifold (middle was replaced):

Vacuum connection (passenger side):

1.) What is the hose connection that the red & green hoses connect to?

2.) Are these large openings/fittings supposed to be exposed?



What else can it be? Why does it still shudder?



Peter

 

[The purple one]

I had a 88 LX 5.0 Many moons ago . It would die when you would push in the clutch some times (It would pop start when you let out the chutch) My chevy 1500 2002 would also stall sometimes when I pushed in the clutch too. For me it was a bad conection at the batt. The looked clean but after I cleaned them they were both fine. Can not hurt and it will not cost you anything

 

[feellnfroggy]

The red green vacuum hoses are the same as the red green hoses on the 92 2.3 rangers. Chekc the tech section. #2 without seeing the egnine bay i couldnt really tell you. Chekc out moddedmustangs.com, 3.8mustang.com, v6power.net, motorsportmustangs.com, and mustangheaven.com isnt a blog site but its a voting site like we have for TRS and it will list all the top 100 mustang sites. There are about 12 more mustang sites that I used to frequent when I had mine, But I cant remember all that.

Also a haynes manual will do wonders.

 

[AgPete139]

It still jerks, and I got my codes re-pulled yesterday. I swear, there was no other code besides Code 11 from 3 weeks ago. (Maybe the mechanic didn't pull them right?)

Code 84 - EGR vacuum solenoid circuit failure
Code 84 - EGR vacuum regulator circuit failure


So, there are 2 solenoids, an EVAP, and an EGR? + Charcoal canister, and other smog shit?

I hooked up the manifold vacuum hose to the EGR valve and the engine wanted to die, but did completely.

• 
  [*]If it does not completely die, is it still okay? How can you "clean" it if it's contaminated?
  
  [*]Which solenoid is bad, the one along the passenger fender or the one on the shock tower?
  

Yea, I posted this on Modded and there are a few different responses that I have gotten. I guess you could say that I'm double dipping, but I guess I'm partially loyal to my TRS for all the answers and my automotive needs.

I have the Chilton's manual, and I am just trying to isolate the problem from here.


Thanks again Purple & Froggy!


Peter

 

[AgPete139]

I directly routed the vacuum hose to the EGR so I could see if the EGR diaphragm+spring were moving freely. Under acceleration, the EGR reroutes the gas to keep manifold temps down (or is it the other way around?).

I've been spraying carb cleaner all around the upper intake manifold and parts of the lower manifold, but not a single rev / noise change. Hose-stethoscope has the same results.



Tested the EGR solenoid, and the connector. 12.05V from the "hot" wire terminal, and 41.5 ohms load across the solenoid itself (passenger sock tower).

Anyways, I replaced the ****er. The new solenoid has a 42.2 ohm, and the car is still misbehaving.

Still a harsh shudder. Not nearly as violent, but still sporadic and hard on the drivetrain.





UPDATE:

I took the EGR out, and sprayed it heavily with carb cleaner. The valve spring still works fine with normal resistance, the diaphragm is in tact, the carbon is cleaned out, and the engine will still want to die when the EGR (moves easily) is under a straight manifold vacuum (this tests the EGR function). There is a new EGR / TB gasket, and no other hissing or vacuum leaks. Carb cleaner spray does not reveal anything new.

Installed new EGR solenoid.

Took it the EGR position sensor, wiped it clean, rod moves freely, new o-ring and gasket sealer made to the EGR valve).

It is definitely NOT spark. New BW cap, BW rotor, BW 8mm ignition wires & ignition coil installed.


Any more expert advice? : I still have not been able to fix the problem, despite all the $ I've been throwing at it.


Thank you guys (& gals),

Peter

 

[shane96ranger]

Let me see if I can help

I'm a proud 15 year owner of an 89 GT, so I have a decent amount of experience with the Fox Stang; I've owned 3 total.
_____________________________________________________

Do you have any mods done to it? This info can help remedy the problem as well.

First off, it sounds more to me like a mass air sensor than anything. I know you said you cleaned it, but I would recheck that; most importantly the 2nd wire back, closest to the firewall. Do you have a K&N? I almost always have to clean my MAF sensor after I've cleaned and oiled my K&N.

I would look at the PCV valve as well. It's easy to miss on the back of the lower manifold and if it has come out of the bung then it can cause erratic driving.

I would also check the TPS sensor, it sounds like you know it's the green wire already. Check it sweeping, not just at idle and WOT.

Is your SPOUT connector in place and does it have clean contacts? Let me know if you need to know how to find that.

What is your timing set at?

It also sound like your injector in #2 may be culprit to a lean condition. I would check the ohm's vs. other injectors. I am assuming you have the 19lb. injectors still? I have 16 of them sitting in my shed if you need a new one for a good deal.

One other thing........the carb cleaner method is only good if the leak is really bad in my opinion. When my upper to lower was leaking it wasn't revving with carb cleaner. I found the leaks by mixing a solution of dish soap and water and spraying it out of a spray bottle. You'll want it to be good enough to blow bubbles with because that is exactly what happens when there is a leak. Use this on all of your vacuum hoses as well. It works awesome if you have the right mixture.

 

[shane96ranger]

Any luck fixing your Stang yet?

 

[bobbywalter]

get a moates quarter horse and shitcan all that silly vacuum bullshit.....brake booster and fp reg. will all that will be needed when your done.


with some time it will run better then ever. hell if you tune it right you can dump the o2's as well.....those bastards are expensive too every 30-40 k.....or alot more often if you race.

 

[shane96ranger]

That all depends. Some people like me need to drive their car on the street. There's no way my car would pass State & Smog without that stuff in place. Plus the factory ECU relies on that stuff for proper air/fuel ratio and timing.

But if you really wanted to go that far, custom ECU's can be made. I guess it depends where you are and who you have to impress with it =).

 

[AgPete139]

I'm a proud 15 year owner of an 89 GT, so I have a decent amount of experience with the Fox Stang; I've owned 3 total.
_____________________________________________________

Do you have any mods done to it? This info can help remedy the problem as well.

First off, it sounds more to me like a mass air sensor than anything. I know you said you cleaned it, but I would recheck that; most importantly the 2nd wire back, closest to the firewall. Do you have a K&N? I almost always have to clean my MAF sensor after I've cleaned and oiled my K&N.

I would look at the PCV valve as well. It's easy to miss on the back of the lower manifold and if it has come out of the bung then it can cause erratic driving.

I would also check the TPS sensor, it sounds like you know it's the green wire already. Check it sweeping, not just at idle and WOT.

Is your SPOUT connector in place and does it have clean contacts? Let me know if you need to know how to find that.

What is your timing set at?

It also sound like your injector in #2 may be culprit to a lean condition. I would check the ohm's vs. other injectors. I am assuming you have the 19lb. injectors still? I have 16 of them sitting in my shed if you need a new one for a good deal.

One other thing........the carb cleaner method is only good if the leak is really bad in my opinion. When my upper to lower was leaking it wasn't revving with carb cleaner. I found the leaks by mixing a solution of dish soap and water and spraying it out of a spray bottle. You'll want it to be good enough to blow bubbles with because that is exactly what happens when there is a leak. Use this on all of your vacuum hoses as well. It works awesome if you have the right mixture.

I have since taken it to 2 separate full-time mechanics and 2 friends' friends who know what they are talking about, and have asked a couple other of my car friends (no gurus, more like novice enthusiasts). Still, no change.


I ave repulled the codes on more than one occasion. There are no codes. KOEO & KOER both show no codes. The only one is a Code 11: System Pass.

Thanks for your concern, but I need my emissions here in Houston. I'd rather not just take off emissions parts, and she's not really raced. Spirited street driving and the local 1/8 mi once in a blue moon (last was perhaps a year ago).

Resetting base idle does not do anything. Here are more parts that have been tested:

• New Remanufactured O'Reilly's MAF sensor + housing (it's an assembly)
• Last night, I changed the fuel filter (wasn't clogged). (Last change was July, but it can't hurt.)
• New TFI module. Old module was on average ~1800 ohms over. No change.
• We (me & a 5.0 guy) checked my SPOUT connector. No difference. Same conditions apply when it is completely unplugged.
• Rechecked timing. Timing still set @ 12 degrees.
• Took out PCV, shook it, and it rattles. I cleaned it w/ carb cleaner before replacing anyways, as well as the pickup screen. There appears to be no loss of air back there.
• I've tried using other batteries I have sitting around (still good charge).
• Jiggling the harness & wires produces no change.
• Pinned the green & black TPS, and there is no voltage sweep across the board.

I'm beginning to think the lean #2 could have been caused by a bad spark from the wires/distributor (before those parts were replaced). Yes, stock 19#/hr injectors.

Problem has gotten worse. I cannot drive over 30 mph (which is 4-5th gear @ idle/slight gas).

The tach jumps from 0 rpm to 1200 rpm all the time, yet randomly.

It happens when it's hot, cold, & at all rpm (& after I disconnect the battery). WOT sometimes allows it to open up and it briefly acts normal in the upper rpm limits.

Could this be a charging problem? The alternator died about 1.5-2 years ago. Could it be a connection on the back? I wiggled the wires, but there was no change in sputtering. I was wondering since the upper rad hose is so close to it. My lights & accessories work fine and don't dim, unless of the course the rpm drops to 0-100 rpm.

The mustang guy guaranteed that it is not O2 sensors. I don't think that O2 sensors would FUBAR the car that much, and plus there are no engine codes for it.

I am going to see my best friend's coworker who owns 3 Four-eyes (one is a GT Pace car w/ Recaros, ~85-86) and has owned a couple Foxes. Hopefully he can finally do a complete/full vacuum test, and check fuel pressure @ 38-42 psi. He thinks maybe injectors or pump. Leaving in 5 minutes...

Damn, this girl is really misbehaving and pissing me off!

Thanks everyone & Shane. Anymore input is appreciated.

Peter

 

[shane96ranger]

In my entire 15 years of owning my 89 GT I have had the check engine light come on twice (once for EGR position sensor, the other for a bad O2 sensor). It's really an awesome system, just bad at telling you what's wrong when something is wrong.

I agree with your friend, the O2 sensor wouldn't do this on an EEC-IV car.

Anyway, something you wrote caught my eye. You say the tach jumps from 0 rpm to 1800 rpm. Is the motor revving with it? If not, I'm pointing the finger at a bad ground or a bum ignition coil. Have you ever had the heads off of the car? The reason I ask is there is a very crucial ground wire that is connected on the back (by the firewall) of the drivers side head. This grounds the entire engine harness if I remember correctly. If this has a bad connection or not hooked up, I think this is your issue. My wire is orange in color with a brass ring connector. It is located pretty close to the emissions pipe that connects to both heads. The other reason I think this is a pretty good possibility is the SPOUT not doing any changes plugged vs. not plugged in.

However, your alternator could also be playing a role, but not likely. I bought a bad one from Autozone years ago that made my car wig out. My gauge was bouncing though. They gave me a replacement that had bad bearings in it and it seized, so I bought a used one which worked much better for about 6 years. Last August I replaced that with a 140 amp off of a 2001 V6. This was in part to Ford's terrible connector they used on the stock alternator. Be sure to check your harness (the one that has the 2 charge wires which are black with an orange stripe) for being burnt. If yours is burnt let me know, I may have one in my parts collection.

I doubt you'll find it to be the pump, it flat won't run at all when that dies. What you've said convinces me it's electrical.

******Now that I'm thinking about it, that ground wire for the engine harness MAY be connected with one of the bolts for the emissions pipe. So if that pipe has been messed with, that's a possibility as well. I don't have the pipe anymore because I have GT-40P heads or I would go look for you.******

 

[bobbywalter]

That all depends. Some people like me need to drive their car on the street. There's no way my car would pass State & Smog without that stuff in place. Plus the factory ECU relies on that stuff for proper air/fuel ratio and timing.

But if you really wanted to go that far, custom ECU's can be made. I guess it depends where you are and who you have to impress with it =).

you can leave all the emmissions componants in place and just turn them off with the Q/H....you can completely mod the system to perfection....it is a custom ecu at that point.....not impressing anybody, just dialing in the car better for your application verse some generic meet all oem tune.



a fuel pump will certainly lay down and cause erratic behaviour exactly as described.....especially if the connector is corroded.

i do agree that between a bad ground or pip is highly likely. but a sticky egr has potential as well. may just have some capacitor leakage starting on the board or some other damage within the old ass ecm.

i know i would need to have it and drive it to find out what the issue could be, and that if i could find it.

 

[shane96ranger]

Hey AgPete139, I have some information on your car that may be helpful. There is a guy with the handle TMOSS on www.allfordmustangs.com who has gone through and done pinouts on ECU's for Mustangs.

Your 92 ECU specifically is at: http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Lots of other info here, like alternator wiring: http://www.veryuseful.com/mustang/tech/engine/

This is the ground wire I think you should is #19 in this pic: http://www.veryuseful.com/mustang/tech/engine/images/mustangEngineHarness.gif

You may want to join over there and talk to TMOSS, he is a genius.

Let me know how it turns out!