93 4.0 expo rough idle power loss ((PLEASE HELP))

[toooofast]

Ok ill get right to it my expo has a idle like its miss firing likes to run better it seems when it cold out but it really picks and chooses when it wants to run right. Under load its very sluggish bad gas Mileage and power loss plus it seems to start going and the engine wants to just kick in and run better not always though. When in gear but at a stop light it some times drops down in rpm,s and kinda boggs and idles really rough. Checked the codes and they said EGR, 02 SENSORS but that's it. I can't figure it out. Any help would be very much appreciated.

Things replaced
Coil pack
Plugs and wires
EGR
fuel pressure regulator
fuel filter
Vac lines
02's
Cleaned MAF

 

[Roadrunner777]

Can you get a fuel pressure reading when it is running rough? Also, can you give us exact codes please?

 

[toooofast]

Pressure is fine. Codes are.

KOEO
335
10 not sure what this is
173
336
536

 

[toooofast]

Also these codes don't always come up it might be my reader but i can tell when its going to work i can hear the ECM come on and then the codes come up.

 

[Roadrunner777]

Ok, I'm going to let someone good with codes take over here, I'm away from my code books right now and sort of fighting another battle. Good luck!

 

[Spook]

Have you checked for vacuum leaks or loose lines?

 

[toooofast]

Yes i have replaced all vac lines.

 

[FLwireman]

Innova 3145 Code reader book says:

335 EGR sensor circuit (ckt) voltage higher or lower than expected.
10 Not a fault code- it is to signal the operator to perform Wide Open Throttle test.
173 HEGO (HO2S) sensor fault/lean
336 EGR sensor ckt voltage higher than expected.
536 Brake on/off ckt not activated during test.

This is from the book that came with my code reader. You can find the manual online for free. I read it before I bought the tester. $32 at O'Rielly's, because I ain't swift enough to read the blinks.

 

[toooofast]

Yes i have the same tester i replaced the 02 sensors and the EGR. Same problem didn't do a thing. But the wide open throttle does that mean i need a new IAC? Its just not idleing all crazy it goes up to about 1000 rpm's in park sometimes but hardly ever.

 

[Roadrunner777]

I wonder if this is a flakey throttle position sensor. Search around, there's a test for the TPS here somewhere.

 

[toooofast]

I thought of that to but its not throwing a code for it. Plus if it was that wouldn't it just go crazy on rpm's all the time. When my expo does jump on rpm's its only in park at idle like it has a choke it never does it when in drive and it hardly ever does that anyways.

 

[toooofast]

Or do you mean that may be why it through that code #10 for wide open throttle. Faulty TPS?

 

[toooofast]

Bump
Just need help

 

[benjammin97624]

fuel pressure can be fine and not volume. fuel pressure test conforms that the fuel pump works it don,t test how well the fuel pump works. you said you have replaced the fuel filter, pressure regulator, and other stuff. have you tried the air filter. if that's a mess it would cause those problems. loss of power and hesitation. when you unplug the vacuum line to the pressure regulator and see in there is vacuum. you don't want to see gas coming out the fuel pressure regulator. you also should notice a rise in rpm once the vacuum line is disconnected. try your gas cap as well. make sure its a vented gas cap. the system gets pulled into vacuum and cause the tank to colaps or suck its self in. also resulting in poor idle and fuel mileage. this requires more surgery but the injectors could be leaking. you can test that by a fuel pressure drop test. that's all i can think off the top of my head. i hope this helps. oh your tps will not throw a code necessarily if there is a dead spot all the PCM (brain) will think that the driver had let off the throttle than floored it. you can check that with a digital volt meter. of coarse connect to a ground with the black lead and the red lead into the signal wire. with no throttle you should get about .3 volts or more. slowly move the throttle and watch your meter. you should see the voltage increase

 

[Ageman]

After doing a lot of reading on the forum about rough idles I have to ask you to check your intake bolts. According to some forum members some bolts tend to loosen up and cause air to come in and can cause all kinds of code issues.

 

[toooofast]

Thank you all very much for your replays. I did change my air filter to a brand new one when i cleaned my MAF i also sprayed around the intake and changed all vac lines to rule out leaks. I will try the gas i know mine is vented but ill just replace it. Ill have to replace the TPS and the IAC to rule those out. I'm just hoping its not the injectors. Any other help or tips would really be appreciated.

 

[toooofast]

Still have the problem. Any more suggestions?

 

[SwaintaN]

maybe i missed it did you do a test yet on your fuel rail to see what your gas pressure is?

when you say power loss as in electrical or hg/torque

sorry if i missed it, long night.... i had the same problem, where the idle would drop way to low and didnt feel like it could pull its own weight, turned out to the the FPR, while changing it you might as well do fuel injectors... i can give you a link from the guy i got mine where you get all 6 for 100.00 w/ warranty

VERY RANDOM.. have you checked your Negative to your battery?
OR
After replacing everything did you clear the codes?!?

edit: what was your fuel pressure test readings??
edit 2: what plugs and wires did you use? did you gap them right?

 

[arcblue]

This sounds very similar to what mine is doing; I've just lived with it because I haven't found the problem and neither has anyone else I've taken the car to.

On mine, most of the time the idle is randomly rough in drive or neutral/park, with a slight miss noted. Sometimes I can detect a miss under acceleration too. Power seems to be slightly down and mileage too, though I also had removed the octane shorting block years ago to fix pinging.

After coming to a stop, while in drive, the idle will be about 800 rpm (or over 1000 if in neutral), then after 15-30 seconds, the idle will suddenly drop to 500 and then return to normal (625-650 in drive), but lumpy.

However, sometimes it will idle almost perfectly smoothly.

I suspect on mine, the FPR is going bad but haven't replaced it yet (I sometimes smell fuel, and sometimes I get a really rough idle after a hot start - but even these symptoms are intermittant). I've replaced the IAC, plugs, wires, battery, cleaned MAF (maybe I should replace it entirely?), checked vacuum lines, etc. with no change. No CEL and no codes.

I'll see if my problem continues after a new FPR but I suspect in both our cases, it could be the PCM. It seems to be the only thing left if you've checked everything else, and could account for the symptom being random. I have also read about several people replacing that and curing idle problems (although there have been many other causes too).

 

[SwaintaN]

i know this is random but umm check your voltage supply etc... wiring can cause some messed up issues.