91 engine running like crap lately

[kendem]

Ok, I admit it has been some time since I have done any maintenance on my car except for the occasional oil change.

So here are the symptoms;

1) It is difficult to start, sometimes I have to press the gas pedal. On cold mornings however it seems to start right up.
2) My idle is rough expecially when the car is warmed up.
3) When accelerating there is hesitation and loss of power, kinda like maybe the engine is misfiring. However when the engine is above a certain rpm it seems smoother with less hesitation.
4) There is also a strong smell of exhaust (not gas) when I am driving on the freeway with my windows open. If I close my windows I do not smell the exhaust.
5) finally my gas mileage sucks.

The last time I checked the ecu (before things got worst) it was throwing a fuel injector code.
Last weekend I checked all the injectors resistance and all were 11 - 11.2 ohems which the fsm says is good.


So I know this could be a ton of different things
so this weekend I am going to change the following;

plugs
plug wires
cap and rotor
fuel filter
air filter
O2 sensor

It's probably none of the above, but I going the change them regardless.


And if this does not fix the problem
Then I am going to;

Inspect the exhaust system for leaks
check for vaccuum leaks
check timing and set if needed
check fuel pressure
check leaking fuel injector

Probably a few other things that I can't think of yet.

Any suggestions are welcome
Thanks

[PapaSmurf2k3]

You've got a pretty good list going there.
I think when you pull the plugs, you can inspect them to see if they are running rich (black) or lean/hot (white). Post pictures of them if you can.

If you don't find any vacuum leaks, try inducing one to see if it improves the condition or makes it worse. Should point you in the next direction to go.

[kendem]

papasmurf2k3,
I took photos but have no idea how to upload them to this forum.

Anyhow...
Well I changed the cap, rotor, plugs, plug wires and fuel filter Saturday. I noticed the plugs were white. THIS IS BAD!
So after changing those pieces I then checked the ECU
it was throwing 32 (EGR), 33 (O2 circuit) ,34 (knock sensor) and 45 (fuel injector) error codes.

I decided to pull the exhaust manifold heat shield off and noticed the exhaust manifold was also white. AGAIN THIS IS BAD!
So I performed the O2 sensor test in Mode II per the FSM and there were no blinks coming from the CEL.
(It's supposed to blink at least 5 times every 10 seconds.)

The FSM says to checked for continuity on pin 19 of the ECU to the O@ sensor wire and that was good. So back the the parts store for a new
O2 sensor and then amazingly the car ran like new but was still starting hard.

Finally I checked the fuel pressure while engine running and it was 36 PSI, the FSM says it should be around 34 but I think 36 is close enough.
Also checked the fuel pressure regulator and it was also good (when applying vacuum the fuel pressure drops accordingly).
However when I turn the engine off while my fuel pressure gauge is still connected I noticed the pressure dropped slowly.
Even if I crimp the fuel return line the pressure still drops. So I can only conclude that fuel is leaking from one of the injectors.

So I then immediately starting removing each spark plug to see if any were wet and sure enough, plug 3 was wet with fuel.
Removed injector 3 and discovered the small o-ring near the nozzle was cracked.

Ok now back again to the parts store for an o-ring kit (only 6$, cheaper than a new injector). Replace the o-rings and retested the fuel pressure and
it now holds at approx, 34-36 psi after the engine shuts off. Now the car starts up immediately and runs like new and no check engine light.

This cost me about $100 and around 8 hours of my time (but it was fun).

[PapaSmurf2k3]

Here's how you would mostly go about posting images:
https://community.imgur.com/t/posting-p ... rums/21454
You'll have to sign up for a 3rd party image hosting service (many of which are free. Don't use photobucket) and then post them here.

That's some solid diagnostic work you did there. Good job man! Glad it all worked out in the end.

[kendem]

Unfortunately my check engine light came back on yesterday. Codes 32,33 and 45 again just like last night coming home from work. What's amazing is the car runs like new, it idles so smooth you don't even know it is running. Did the O2 test again and that checked out ok. Then the check engine light turned off. If I remember correctly turning the screw on the ecu back and fourth clears the codes.

So I must have something else going on that is re throwing those codes. I wouldn't care except I have a smog test coming up in a few months.

BTW what is the best way to find a vacuum leak. Normally you can just hear it. I'm not to keen about using the spray can method.

[PapaSmurf2k3]

I've always done the can of ether or other propellant method. You could always use a little propane tank or something too if you don't actually want to be spraying anything.

[kendem]

was thinking of getting this...
http://www.evaporativesmokemachines.com/
Can also use it to find exhaust leaks.

[PapaSmurf2k3]

Oh yeah! I've used a cigarette too to see where the smoke goes. Totally forgot about that.
Just be careful you don't burn any wiring or anything while trying to get it in those tight nooks and crannies.

[kendem]

I think this might be safer than the cigar or spray can method. I'm thinking of removing the brake booster hose on the intake collector and reattaching a hose to it and then feed in the smoke that way. Their website mentions attaching their hose to a Schrader evap port. This must be something on new cars?
You can also run that hose into your muffler pipe and see if there is an exhaust leak. Still not 100% certain about buying this. After resetting my ecu the cel has remained off for 2 days now. But i'm sure it will come back on.

Funny thing, 2 years ago I passed the smog test with flying colors, then when I was leaving the smog shop my cel came on 5 minutes later. What's even stranger is my cel light had been off for several months (year maybe) prior to the smog test. Is this luck or did the smog test cause it to turn on? I didn't care cause I didn't have to worry about it for 2 years.

[PapaSmurf2k3]

The only schrader valve I'm aware of on cars is for the AC system.

Might have been luck with your CEL, or maybe they snagged a wire or harness or something as they were monkeying around with your car.

[macgiver]

mac, a little about engine codes , which are a great starting point , I remember prior to OBD what we had to do ! 3 weeks ago I had the typical "hesitation" - marginal/OK idle , sluggish off idle ,
weak power (under any kind of attempted throttle -up) , very slow weak climb to 2800 RPM when finally a semblance of power ( it's got the hydraulic intake VVT advance kicks there too ) . So , it gives a "coolant temp SENSOR" code + KNOCK SENSOR code + "L. O2 SENSOR" code . I meter Ohms on coolant sens. (as it cools ,to "map proper " readings) OK! I meter both O2's , as comparison - both OK. Now for the Knock sens. ,tested infinity= "Open" -Ohms ) it's INSIDE the motor Because I knew this I previously purchased one when I found "brand new" at a decent price 8 years ago. Now - there's a FIX for not having to remove intake manifold/Valley where it's located. A mount on pass. side on block or plenum is shown on youtube - but I didn't like that location for NOT being symmetrically "distanced" to R & L heads . So I looked under that Goofy engine cover and found that one of it's mounting holes (threaded) is very much centered I got the sensor tightly "sandwitched" w/beefy washer on top and re-check base timing - was OK. Engine ran like a champ - no more codes of any kind , seems all was do to Knock sensor and it's EFFECTS on OTHER componants !!