Tough Troubleshooting Problem
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New User
Joined: Apr 2005
Posts: 9
Likes: 0
From: Austin, TX
Thanks Stuart, will try that tomorrow. Didn't have any carb cleaner, been using brake cleaner for everything lately. Maybe that would have the same effect?
EPNCSU2006: You had said Throttle position sensor .9v to 4.8v thru range. I read the wrong sensor when I said that's what I get. I actually get .2v closed to 3.4v WOT. Is that okay?
Codes I got tonight
KOEO Hard codes, pass, Continuous codes, 34 (EVP voltage above closed limit) or (Exhaust pressure high, or defective PFE/EPT sensor)
PFE(Pressure Feedback EGR sensor)
EPT(EGR valve pressure transducer)
Don't think I have an exhaust pressure feedback EGR on '90 302. Only one port and one exhaust line to EGR
Running Test
25, Knock not sensed during dynamic response test (I think that's the least of my problems at this point)
44, Thermactor air system or secondary air injection system inoperative.
By "secondary air control" do they mean my Idle Air Control Valve? I do smell gas in my exhaust (since putting my advance at 10). Since my stumble occurs at light throttle maybe the IAC isn't opening soon enough?
EPNCSU2006: You had said Throttle position sensor .9v to 4.8v thru range. I read the wrong sensor when I said that's what I get. I actually get .2v closed to 3.4v WOT. Is that okay?
Codes I got tonight
KOEO Hard codes, pass, Continuous codes, 34 (EVP voltage above closed limit) or (Exhaust pressure high, or defective PFE/EPT sensor)
PFE(Pressure Feedback EGR sensor)
EPT(EGR valve pressure transducer)
Don't think I have an exhaust pressure feedback EGR on '90 302. Only one port and one exhaust line to EGR
Running Test
25, Knock not sensed during dynamic response test (I think that's the least of my problems at this point)
44, Thermactor air system or secondary air injection system inoperative.
By "secondary air control" do they mean my Idle Air Control Valve? I do smell gas in my exhaust (since putting my advance at 10). Since my stumble occurs at light throttle maybe the IAC isn't opening soon enough?
Lead Driver
Joined: Nov 2002
Posts: 9,555
Likes: 40
From: Concord, NC
The TPS reading seems a bit low to me. Check between the orange wire and the black wire to make sure there is a steady 5V signal there. Other than that, look around for any grounding points and try cleaning them a little bit. The engine computer grounds through a bolt on the drivers side fender. Make sure that one is solid and making a good connection. The secondary air control is the air injection for emissions controls. That shouldn't be related to your problem, unless for some reason the diverter valve is sending air to the heads all the time. That would likely make the computer try to run the engine more rich than it should be.
Guest
Posts: n/a
TPS IS low. From center wire to ground with key on /engine off, should be as close to .999 VDC as possible. if you loosen the 2 phillips screws holding the TPS down, you should have a slight amount of adjustment available. If not enough, you can get a small round file and elongate the holes a very slight amount.
Adjust with a goal of .998 vdc in mind (with the throttle resting at idle position).
(This may not solve the whole issue but you will be surprised at the difference it will make.)
Keep chipping away and by the time you find the base problem, you'll have 'er finely tuned.
BTW, once you get it running "right", try bumping the initial timing up to about 13 deg BTC....or as close a possible without "pinging" (should be able to go to at least 12 deg and maybe 14 deg depending on several factors), you'll feel the difference. In any case, 14 deg (if possible) is about as far as you can go and get any notable improvement.
HbL
Now:87 (91 5.0 HO FI/AOD) Ranger STX 4X4 + 7" lift and 33's.
Then: 89 (Pro-Street) Mustang 5.0 FI/5-speed coupe....high 12 sec et's on street tires
Adjust with a goal of .998 vdc in mind (with the throttle resting at idle position).
(This may not solve the whole issue but you will be surprised at the difference it will make.)
Keep chipping away and by the time you find the base problem, you'll have 'er finely tuned.
BTW, once you get it running "right", try bumping the initial timing up to about 13 deg BTC....or as close a possible without "pinging" (should be able to go to at least 12 deg and maybe 14 deg depending on several factors), you'll feel the difference. In any case, 14 deg (if possible) is about as far as you can go and get any notable improvement.
HbL
Now:87 (91 5.0 HO FI/AOD) Ranger STX 4X4 + 7" lift and 33's.
Then: 89 (Pro-Street) Mustang 5.0 FI/5-speed coupe....high 12 sec et's on street tires
Thread Starter
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New User
Joined: Apr 2005
Posts: 9
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From: Austin, TX
Stuart1, my fuel pressure is 32 psi, 40 with vacuum to regulator disconnected. This is what it is supposed to be.
I have steady 5V to TPS, and I noticed when I ohmed it out it started low, went up then down a little then up. So I changed it out with a new TPS but that didn't help.
You know the vibrating is in such a narrow band of RPM (1100), immediately after shift point, that I'm going to have a tranny guy have a listen.
I have steady 5V to TPS, and I noticed when I ohmed it out it started low, went up then down a little then up. So I changed it out with a new TPS but that didn't help.
You know the vibrating is in such a narrow band of RPM (1100), immediately after shift point, that I'm going to have a tranny guy have a listen.
Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
after changing these electrical components have you been disconnecting the battery letting the ecu power down , then reconnecting and driving for 30-45mins in various driving conditions like WOT and stop/go traffic an such. this allows the ecu to relearn and clears the garbage out
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Thread Starter
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New User
Joined: Apr 2005
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From: Austin, TX
kemicalburns: Yes, but more like 10 or 15 miles.
I finally found the problem. Low compression #8 cylinder. I guess the new looking plugs when I bought it fooled me into thinking cylinders were at least ok. #8 dry and sooty now. I will NEVER do anything before a compression test again!
I want to thank everyone who helped me with great troubleshooting suggestions. Great forum!
I finally found the problem. Low compression #8 cylinder. I guess the new looking plugs when I bought it fooled me into thinking cylinders were at least ok. #8 dry and sooty now. I will NEVER do anything before a compression test again!
I want to thank everyone who helped me with great troubleshooting suggestions. Great forum!
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