94Q- Engine running rough

[goody90q45]

On the way to work last week the engine began to run rough. I have not been able to find the source of the problem. Here's the status and some of the things that I have done:- Pulled codes from the ECU 3 times. Only code coming up (all 3 times) is knock sensors.- Ohmed knock sensors. I get no reading on one and 560K ohms on the other. I got the same reading a month ago and the car was running fine.- Ohmed injectors. All are reading midrange except #7 which is 27.6. It measured open when I checked it about a month ago.- This problem has not activated the CEL- Cleaned MAF and wiggled connector, no improvement. No black smoke.- Cleaned throttle body (even though I'd done it about a month ago).- Replaced the spark plugs today (That was 3 hours of fun). Big improvement but still runs rough.- Cleaned EGR a few weeks ago. It wasn't clogged or really very dirty.- Cleaned PCV valve.- I put a new injector (#1) in about a month ago and have noticed a gas smell since and a decrease in fuel economy. It is not a fuel line leak. Makes me think that I might have done something wrong when installing it although I don't know what it could be.

The car had been running fine with one bad injector and a dead knock sensor. It had a very slight rough idle after the engine warmed up but still had plenty of power. The rough idle I have now is similar to what I felt when there were two bad injectors but the ECU was also throwing an injector code then.

I haven't checked the crank angle sensor yet and will do that tomorrow. I know I can take the car in and get it diagnosed with a consult or power balance test but wanted to try and diagnose the problem myself (with a little help from NICO). Any suggestions are appreciated.

[maxnix]

Well, not to be too obvious, I would replace the failed parts and then try to diagnose any misbehavior. Compounded faults are difficult to sort over the internet via text.

Maybe you pinched the O ring on injector 1? Don't work for Morton Thiokol, do you?

Can't believe it was running fine with dead injector and dead KS.

[3Q Jay]

All are reading midrange except #7 which is 27.6. It measured open when I checked it about a month ago.

Mike- i would start here. yoiu might also ohm them over temperature. get it hot, measure, then every 1/2 hour or so during cool down. sometimes the flakey injectors will show up more clearly when the data is mapped over a range. bad ks, while should be fixed won't cause the ruough idle.

[3rd Q]

Goody,The gas smell may be due to the #7 going bad - I notice the raw fuel smell when they start to go. Could also be as Brian surmised- #1 with a pinched o-ring. #1 is easy to check as you know- no need to pull plenum to remove it. #7 requires a plenum pull and is the toughest of all to get to.I'd pull #1 and check it first since it is so easy to get to.

Paul

[goody90q45]

Thanks to all for your replies. I will pull #1 injector tonight and reseat it. I had been delaying doing this since I didn't have the o-rings but I found the spare set I ordered from Joe on my workbench when cleaning up yesterday.

I forgot to mention that when I changed plugs 7 of 8 were finger tight and the 8th wasn't much tighter. Also, the plugs were Autolite brand (a NICO no-no). I noticed a big improvement in my test drive yesterday but still have the rough running engine. When I finally get her running smooth again she's going to be a beast.

I'll report back after the injector check.

[maxnix]

I found the spare set I ordered from Joe on my workbench when cleaning up yesterday.

Your workbench eats parts too?

[goody90q45]

It fell out of the zip lock bag I'd put it in for safe storage and I knew it was on the bench somewhere. It just took a while for it to resurface.

Any tips on reinstalling the #1 injector? The first time I lubed up the large o-ring, got it seated level in the fuel rail, and then tightened it down by alternating tightening the two bolts on the cap.

With enough lube, should I be able to fully seat the injector prior to bolting on the cap? As careful as I was the first time I must have gotten the injector a bit crooked during bolt down and pinched the o-ring.

Finally, does anyone know if the injector o-rings correspond to a Parker o-ring number. We have a huge supply of every o-ring imaginable at work if I can match it up to the Parker #.

[goody90q45]

I'm still having major problems with a rough running engine. Got about 9 mpg on the last tank of gas (Usually get 15) and the smell of raw gas is present. I've quit driving her for now. Runs better at high rpms but you can still feel the roughness. I took it in for a BG flush, thinking I may have plugged injectors but no improvement. I also swapped in a good MAF and no change. Plugs and CAS connector cleaning helped but still running rough.

So things are pointing more and more towards injectors. The shop measured the fuel pressure at 34 psi. I failed to ask if they plugged into the line past the filter and turned on the pump only, or teed into the line and checked with the engine running. What is the correct procedure and what kind of pressures should I be looking for? I thought I read that the pressure should be in the mid-40's so 34 psi might mean something. Based on your responses I'm going to go buy the setup tomorrow so I can check it myself .

Another thing I'm confused with is the term "leaky injectors". Are they not holding pressure internally? Leaking internally from inlet to outlet? Or does it mean that the small o-ring is not seated and the gas is pouring in through the fuel rail. There are no external leaks from the large o-rings and no hose leaks either. Or, does the injector fail electrically in the open position and let gas pour in.

Finally, what injectors can be taken out easily without removing or grinding the plenum? I ordered some from Joe and might get lucky and find the one that's leaking.

I guess I'm asking these questions because I am having a hard time understanding why only one injector with a reading of 27 would cause all these problems. Something else must have gone wrong to cause my current issues.

I've got her parked for a while since I was in an accident last week and she's going to the body shop on Thursday ($3700). I don't want anyone to see her all banged up. I'm going to listen to the injectors with a long screwdriver tomorrow and check the fuel pressures.

Looking forward to your input to help me with what I need to know to pass Fuel Injectors 101.

[goody90q45]

!!! PROBLEM SOLVED !!! I did some searching last night (great thing, the SEARCH button) on spark plugs. Went back and dug mine out of the trash and looked at them a little more closely. All looked the same except #8 which was black and sooty- cylinder running fuel rich.

I removed # 8 fuel injector this morning (never had it out before), cleaned up the port, replaced the o-rings, lubed it up and reinstalled. Engine fired right up and runs great. The bottom o-ring must have come unseated (swelled?) and let fuel seep by. The o-ring didn't come out with the injector and I had to fish it out of the fuel port. Unfortunately I dropped it under the plenum so I wasn't able to examine it.

Great to have the Q running good again. She really likes the new plugs and fuel rail flush and I learned a lot about her in the past week.

[3Q Jay]

you know you are going to take some ribbing for not examining old plugs on removal......that's great to hear that you are up and running though! glad it was #8 as #7 is much more questionable r&r unless you pull plenum. I'd still keep an eye on #7.btw, i've used vaseline on the injector o-rings. i'm sure someone will flame me for that.

[maxnix]

Good thing you knew which plug it was. Did you cross index the O ring to the Parker number?

[goody90q45]

Yeah, I went through all the trouble to label them as I took them out but never compared them side by side. I used vaseline also, they pop right into place. I've got more new o-rings coming from Joe. I'll take a set in and see if I can match them up to a Parker set.