97 thunderbird 3.8L good idle, crap power above that - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-09-2011, 03:06 PM
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97 thunderbird 3.8L good idle, crap power above that

got a 97 thunderbird 3.8L

it starts idles great, but when you rev it up or try to drive it it stumbles sputters wont go no power, total crap junk

vacuum guage on it reads right in normal range and steady needle no movement, all fine with valves and timing and vacuum etc,

we put on new fuel pump and sock and filter and new many other parts including ign coil and FP regulator

MAF unplug it and it runs worse


no change at all otherwise with all the other parts replacements

new TPS also, no change, already been replaced once before is a new one already too

am at wits end with this junk *** ford

anyone have any ideas?

before i put a grenade in it?

wow..

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Old 07-09-2011, 03:31 PM
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check Fuel Pressure. Sounds like a weak pump. You need to check it as the symptom occurs to verify it. I dont recall the exact specification so check the repair manual.
Never assume a new part is a good part.
I had a 96 t bird with a similar problem , when you flogged it , it would just bog down, turns out the MAF was dirty, I cleaned it and then it would smoke the tires.No doubt it was a 4.6 and not the 3.8 LOL
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Old 07-09-2011, 05:53 PM
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Could very well be the MAF sensor.

I went thru a couple of those on my 94 'bird with a 3.8.
That car would chirp the tires on a 1-2 shift without even trying.

Also went thru a couple on my 97 'bird with a 4.6
one time it would not even rev up---idled just fine, but when you pressed the accelerator---absolutely nothing would happen -- it just idled

the other time---idle was fine----ran rough on the road.
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Old 07-09-2011, 06:55 PM
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MAF sensor another one changed nothing

[fuel pressure is fine when running

at key in run but not running its weak nothing really

we put in brand new pump and filter sock and all the other day

in which changed nothing at all

still no power wont go, junk


thanks for any further ideas
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Old 07-09-2011, 07:00 PM
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Is the check engine light on? did you check for pending codes?Current codes?
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Old 07-09-2011, 07:13 PM
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without hearing it run, I would be guessing at anything.
There are plenty of basic things to check that could cause an issue.
Ignition coil health- does it throw a hot blue spark?
Fuel Pressure- you said it was good
engine vacuum- a good indication of engine health- can also indicate a plugged exhaust.
Cats could be melted down, causing a restriction and very poor engine performance.
You can check for exhaust restrictions by unscrewing an o2 sensor to see if the condition improves. Also I check for a blocked cat by screwing in a fitting and hooking a vacuum / pressure gauge into the hole. Then rev the motor sharply. If the gauge indicates more than 1 psi the cats are plugged or plugging.
When you have 2 or 4 cats this is an easy wayto single out the culprit.
Keep us posted.
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Old 07-09-2011, 09:52 PM
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oh, well its not the cats- i forgot that we also took cats off and hollowed them out totally

check engine is on

i scanned it and three codes other than the old TPS one

egr circuit something something
fuel vapor recovery something something

and idle air control valve something


what do i need to exactly?


whats the most likely culprit if its one of the above things?


and what do i need to remove to pull any parts that need to be, according to above codes/items?


reiteration of what its doing how its acting:

it starts right up easily no problem there

idles fine but maybe a slight light miss at idle kind of


falls on face totally sputtering and a pretty long delay in revving up(a normal rev up, not a big rev up, not trying to rail it or anything like that)
and totally not driveable will not pull itself at all


not using water or oil,
no exhaust smell,
no smoke of any type in exhaust,
no leaks,
normal temps,,
no moisture in oil or foam or anything else at all,
no ticking or clicking or tapping or anything,
no backfiring or coughing

and according to vacuum guage check it is good timing and no valves or camshaft other problems like that


thanks again

Last edited by fast68; 07-09-2011 at 09:57 PM.
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Old 07-09-2011, 11:06 PM
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take off the iac and clean it
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Old 07-09-2011, 11:07 PM
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i may be mistaken but doesnt' that have o2 sensors before and after the cat? if so that could be the problem. with no cat the rear sensor is sensing that the car needs to be leaned out because nothing is cleaning up the emissions
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Old 07-10-2011, 06:41 AM
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Quote:
Originally Posted by badknuckles
i may be mistaken but doesnt' that have o2 sensors before and after the cat? if so that could be the problem. with no cat the rear sensor is sensing that the car needs to be leaned out because nothing is cleaning up the emissions
The downstream sensors only measure the health of the catalytic converter. Thats all.
Upstream O 2 sensors could cause a similar problem, unplugging them would put the car in open loop , if the cars trouble pretty much cleared up, then you found the trouble.It is a possibility, anything is worth checking as it is all basic stuff.
When a cat plugs up it confuses the readings pretty badly, so a scanner may not help.
Lack of exhaust flow confuses the O2 reading, the fuel trims,raises engine temp which causes it to run leaner...etc.
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Old 01-08-2013, 08:56 PM
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Same problem with 1996

I have the same problem almost exactly with my 1996 3.8 Tbird. Starts a bit slow but makes ok power until the engine heats up. Checked MAF, TPS, replaced CPS, good regulated fuel pressue, does not show any codes except ones I create. Blue spark at >0.75" (30kv) at all plugs, EGR seems to work normally. Can't find any leaks. It seems like a timing issue with spark or ignition.

I have heard some issues about checking timing with timing light, any issues or concerns with using an inductive light ?

If you ever solve this problem I would really appreciate a post and I will do the same. My father has been as Ford Mechanic for ~ 50 years and he shakes his head. Need to get a real time analyzer hooked up but i don't have one and his is 1300 miles away.
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