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Need help/advice. Low idle/ stall upon acceleration

5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

Need help/advice. Low idle/ stall upon acceleration

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Old 09-18-2018, 05:32 PM
  #1  
HarshFyasko66
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Default Need help/advice. Low idle/ stall upon acceleration

New to this forum so I’m sorry if I posted in the wrong spot.

I will try to be as detailed as I can...

I have a 90 foxbody LX 302 with “slight mods” reason it is captioned is because the guy I bought it from didn’t know what has been done besides it having a cam. Once I got the car I did the normal tune-up with new brakes, spark plugs, wires, oil, oil filter, and bought a new MSD distributor capand rotor. Anyway the car was running fine till it started to pop under acceleration; the car did have some backfire at high RPM when off the throttle. I checked the codes and only came up with a bad EGR valve, and a fault 02 sensor. Checked the sensors and one had a cut wire that I fixed and cleared the code up. I tried to use a timing light and rotate the distributor thinking this would clear up the popping under acceleration. Timing showed a retard degree of 10 so I slowly advanced to BTC of 10 degrees which is what the manual called for. This helped a lot and was able to drive for about a month. Till an exhaust leak arose and found that what ever the previous owner did to plug the “thermoreactor pipe”, smog pipe off the rear of the heads, decided to blow off.

Hurricane Florence hit and the car sat till today which I bought plugs and closed up the exhaust leak.

Went for for a drive and noticed that at idle I was barely at 500 RPM and struggling to not stall. I have to over accelerate to not stall to get moving and once going I can feel a lack of power as if not getting enough fuel then all of a sudden the car would surge as if all the fuel built up then decided to slam into the engine.

Sorry for for the long post but wanted to give everyone all the info and any advice would be must appreciated. Just want her to run smooth.
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Old 09-19-2018, 03:43 AM
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dawson1112
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So what your describing sounds an awful lot more like a bad connection somewhere in the ignition harness. Either in the salt and pepper shaker plugs, or even possibly a bad PIP in the distributor or TFI module on the side of the distributor. Try moving the 2 black/white plugs around while idling and see if the idle picks up or decreases. If the idle changes with shaking those plugs around, then you need to Clean them out really good look for any sign of corrosion if cleaning them and applying a bit of dielectric grease doesnt solve it, disconnect them and insert a small pick or thin pointed tool into the prongs of the male side to open them up just a little so they make better contact inside the female plug. The TFI module on the distributor can be taken in for testing, but they have to run the test about 3 or 4 times. As for the PIP inside the distributor, you can replace that but you have to fully disassemble the distributor to get it out. Dropping in a known good distributor will aid in diagnosing problems with the distributor.
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Old 09-19-2018, 03:51 AM
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dawson1112
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Also check all connections and wiring around the distributor. Including the spout and wires to and from it.
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Old 09-19-2018, 07:34 AM
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HarshFyasko66
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I forgot to add that I had just replaced the TFI module.
I will try the connections today and see what happens. Thank you for the advice. I will let you know what happens
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Old 09-19-2018, 09:21 AM
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HarshFyasko66
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Cleaned out the salt and pepper connectors and had to zip tie them shut since the clips snapped right off. Checked all connections and wires by the distro. I let the car warm up and took it for a quick spin and seems to have cleaned up the issue. Will drive again a little later to see if it sticks. I know that disconnecting the battery and resetting the EFI can “temporarily” fix most ignition issues. Will update with status of car after a good drive
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Old 09-19-2018, 01:34 PM
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Took the car for a longer drive and still no issues have arose!!
thank you again for all the help and advice.
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Old 09-19-2018, 05:53 PM
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So did some more driving and the car is starting to act up.

when I give throttle it hesitates then catches up then hesitates. Sometimes it will bog down and or somethings it’ll just pick up and drive along.

i should also mention that I feel a decent amount of power loss.

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Old 09-19-2018, 08:42 PM
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HarshFyasko66
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Ran the code reader again and got the following codes

KOEO
67 AC input high= which I think may be from the AC Removal from the previous owner
KOER
41 HEGO (HO2S) sensor voltage low/ system lean
91 HEGO (HO2S) sensor voltage low/ system lean
I believe 41 means passenger side and 91 means drivers

33 EGR valve not opening properly

any tips to fix these issues?
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Old 09-24-2018, 08:01 PM
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Make sure the vacuum hoses arent reversed on the evr solenoid.The evr solenoid is the component mounted on the passenger strut tower(rear),with two vacuum hoses connected to it.Make sure the hose connected to the lower port on the evr solenoid is coming from a vacuum port on the upper intake(rear)
Make sure the hose connected to the upper port on the evr solenoid is coming from the egr valve.If these hoses are reversed,the egr valve will be held open anytime theres vacuum present at the intake.This will act like a vacuum leak and trigger the o2 sensors to read lean,which triggers the ecm to falsely richen the fuel mixture.If the vacuum hoses are routed correctly at the evr solenoid,remove the hose from the egr valve,plug the hose then test drive the car to see if the symptoms disappear.
If they do go away,the egr system should be checked.In most cases,the egr valve will be stuck open either because its dirty or defective or because the evr solenoid is bad.The egr valve is only supposed to be open during part throttle/cruise conditions,so if its open during idle,it will trigger a rough idle. The rubber diaphragm on the egr valve has also been known to tear or develop a pinhole leak in it,which will also trigger a vacuum leak.Be sure to check the vacuum hoses themselves for leaks too because vacuum leaks are the #1 cause for lean o2 sensor codes,like youve currently got.The following link details trouble shooting for lean/rich codes.

(Code 41/91)
http://sbftech.com/index.php/topic,29771.0.html

When you done a timing adjustment,did you remove the spout plug from the tfi harness before you aimed the timing light,took a reading and rotated the distributor?? If no,your timing is off.
The stock/oem setting is 10° btdc,with the spout plug removed, & advances to 20-24° as soon as the spout plug is reconnected.The base setting can be moved up to 12-14°,if high octane fuel is used & pinging doesn't occur.If you left the spout plug in and rotated the distributor until timing was at 10°,its retarded way too much,so you'll have to readjust it again,but correctly this time.

When you run the koeo/koer tests,the shifter needs to be in P or N(aod) N(manual),the ac switch needs to be off & the clutch pedal needs to be floored during both tests,otherwise code 67 will be present.If you ran the tests with everything above done correctly,but code 67 is still present,trouble shoot the nss/clutch safety switch & wiring to id whats triggering code 67 because that code being stored as a OD code can/will trigger idle surging,rough idle & stalling when coming to a stop.On a manual setup,the ecm needs to know when the clutch pedal is down and when the transmission is in neutral.Idle issues will occur if the ecm isnt able to id a "In Neutral Condition".So its important that you figure out the cause of this code,so you can get rid of it.The following link explains a little more.
(Code67)
http://sbftech.com/index.php/topic,29824.0.html



Last edited by wbrockstar; 09-24-2018 at 10:44 PM.
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