Another Idling problem needs help badly(dont trust the dealer no more)

[Yimu]

Hey guys, sorry to bother u guys again, this stupid idling problem is just killing me.I recently replaced 2 injectors and all the hoses and Knock sensors on my 94Q, things didnt turn out good after they were changed. First, car would almost die on the road with bad idling. Also had black smoke from the exaust. Realized might be the TPS so switched back to my original one(shouldnt have changed at the first place), now the bad idle went away but still not normal. The idle will fluctuate from 200-800 and then stables after start up, but then might vibrate again. Could feel the car is shaking a bit. Went to the dealer today and they spent 4 hrs diagnosing it, and came out told me they dont know what exactly is the problem, but said they are guessing it could be that i didnt replace all the injectors. I ohmed all the injectors, the rest 6 were absolutely fine, and no engine light was ever on. U guys are my last hope, really dont wanna get in there and replace all the injectors, it's just a pain in the butt. Any ideas guys, TPS, MAF or even IAC?Seems to dealer these are all fine, hope to hear from u guys soon.ThanxRichard

[Yimu]

Just one thing to mention, there were never a rough idle before i changed the injectors, just a bit shaking, shall i start with a BG injector flush first?

plz advice

thanx very much

[sdkhalsa]

What you need to know first is whether the idling problem is local to a particular cylinder or systemic. If local, you are probably speaking of a coil or injector, possibly bad plug. The easiest way of doing this is with the consult diagnostic which can disable the cylinders one at a time. Similar results can be had by running test connectors across the injection wiring harness joint and then disabling them one at a time. A little side note, ohming the injectors is not a definitive test. You can have good wiring but fuel flow problems. Also, you can have injector harness problems. Did you ohm the coils also? How about checking plugs for deposits indicating non-firing? It is also possible to have a couple of tuning problems at once, typical of an older/high milage vehicle, so it is necessary to go about it a bit more systematically. If things are working on a cylinder by cylinder basis then you get to check out things like the EGR, MAF, etc. but I think that you have plenty to get you started.

[Yimu]

Thanx for the responseThat really seems like a lot of work!Plugs were new, coils were just replaced but are used, old ones were fine but replaced anyway coz i got into it already. They are all ohmed and seems no problemMight need to take cylinder bu cylinderI'll post the result when i get them tested

[maxnix]

I recently replaced 2 injectors and all the hoses and Knock sensors on my 94Q, things didnt turn out good...

Did you pinch one of the new O rings you installed with your new injectors?

Could cause all of your symptoms. Check to see if you have final updated MAF plug while you are at it.

[Yimu]

Thanks for the responseO ring were new, but might be placed a bit wrong coz was my first time doing injectors, however, didnt have any huge mistakes i suppose, i will double check that when i get a chance

Richard

[elwesso]

i agree on the O rings.

So to recap, all the injectors ohm fine, right???? I would definitely get in there, pull the fuel rail out of the car and replace the O rings.... Its at least a cheap start (for parts)....

[Yimu]

i agree on the O rings.

So to recap, all the injectors ohm fine, right???? I would definitely get in there, pull the fuel rail out of the car and replace the O rings.... Its at least a cheap start (for parts)....

Thanks for the replyActually all the Orings were new, just i did it myself so dont know whether did it perfectly or notAnd is there anyway to test whether a Oring is leaking or not?Thanks

[elwesso]

Hook up a fuel pressure gauge.. turn the car on and make sure you get 34psi or thereabouts, and then turn the car completely off, and if the pressure goes down, you have bad O rings.

[richardchen0530]

I

Hook up a fuel pressure gauge.. turn the car on and make sure you get 34psi or thereabouts, and then turn the car completely off, and if the pressure goes down, you have bad O rings.

Seems like hookin up a fuel pressure gauge is a cool idea, just wondering where shall i hook it up to? anywhere that i dont have to take off the Manifold?

ThanxRichard

[elwesso]

Youll hook it in right after hte fuel filte ron the passenger side, get a T fitting and T the fuel pressure gauge in.

[Yimu]

Tried some old fashion way today on the injectorsCalled dealer again just to make sure there were no code at all Run the car for like 20mins, open the hood, tried to sniff the two injectors i replaced, no sign of any type of fuel leak(my nose are extremely sensitive to fuel smell) Is this a reliable way or shall i still do a pressure test?I'm heading for a BG injector cleaning tmr, and if that still doesnt work, probably time to open the manifold again(really dont want that to happen at all)

And advice guys?

[goody90q45]

....or shall i still do a pressure test?I'm heading for a BG injector cleaning tmr, and if that still doesnt work, probably time to open the manifold again(really dont want that to happen at all)

And advice guys?

I went through a similar problem when I had my first (of 3) leaky injector o-ring. Rough idle, poor acceleration, bad gas mileage. All the symptoms. I paid $100 for a BG flush only to have the tech tell me he thinks I have a leaky injector o-ring since he noticed it was feeding too quickly. I think a lot of the flush went past the o-ring straight to the cylinder and I wasted my $$$.

Since the tech doing the flush has to tee into the same fuel line that we're telling you to check the fuel pressure at, why don't you ask him to check the fuel pressure before starting the flush. If it's lower than the pressures Wes quoted you then don't waste your money on the BG flush. Fix the leaky o-ring(s) first to get the full benefits of the BG flush later. Good luck.

[richardchen0530]

This is what i did the past 2 weeksGot a Fuel pressure gauge and measured the fuel pressure, pretty much normal, so no issue abt a fuel leak anymoreWent for a BG injector flush, right after the flush, car ran smooth, no fluctuating anymore, very happyHowever, 1 week later, car start to fluctuate again, this time even worse, sometimes it just reaches 100 RPM during start, but never diesNo light was on til today, engine light came on today for like a min,no clue wuts going on, started again, went away.Not going to read code anymore since dealer charges around 100bux just to read, had them checked twice without any solutionPlanning to replace all the other injectors beside the 2 i have just doneAny sugesstions guys?

[texasoil]

sounds like you got a tnk full of REAL crappy gasoline-loaded with lots of gum.

Since it ran well right after a good injector cleaning, I'd do it again. Lots cheaper than replacing the injectors--and get rid of the crappy gas.

[maxnix]

Yeah, buy only tier 1 premium from a station with high volume and new tanks.

You can buy lots of BG44K for what injectors cost.