Stumbling at idle-down and to 2500rpm

MarcM · Post by **MarcM** » 11 Nov 2017, 09:55

So here I go again. Gave it hell yesterday morning getting thru a group of chuckleheads in the left lane going the same speed as the right. Got her to 110mph. (hehehe) I got to the stop light at end of highway where it ends and noticed the engine chugging. Thought "oops, another coil gone bad". I got it home that night and stopped to get another coil and plugs (figured they'd be fouled from raw gas). Now, this really was a mistake because as I'm driving realized "I'm dumping raw fuel into a cylinder causing stripping of the oil from the cylinder wall and putting raw fuel to the cat." The car idles terrible and runs rough up to about 2500rpm at highway speed. Seems the more in the neutral zone I keep the RPMs (not really accelerating nor decelerating) the more it runs like hell.
I did the coil connector pull test. #3. The coil I replaced last time a year or more back. I replaced the coil with the new one and the plug. Did a quick test and NOPE. I pulled the rest of the coils and replaced the other 4 plugs and inspected the coils. #5 had a crack right down the side (original coil). Pulled that and put the "it wasn't really bad" coil in to replace it.
I suspect #3 injector is plugged. Not finding information on searches readily here, I started my search to find out what the ohms are for injectors. All are 11.8/9 to 12.1. According to information gleaned... it's a 14.5 ohm resistance. 12 ohms is a little low, but could also be multimeter calibration (Extech) so will find another to double check. I also found OEM new injectors for $18/ea! I'm seriously considering buying, but "if it's too good to be true, it probably is".
I'm thinking that when I gave it hell, the full 30 lbs/hr and sucked something up through and into fuel rail causing a blockage of #3.
I've replaced the fuel filter twice (once because it was stock and 10yrs old, 2nd time because it's cheap maintenance).
Before I order these, I'm going to run to the local independent shop who can read my engine codes at least.
Recap for easier searching for people in the future:

Bosch Fuel Injector
Volvo / Bosch PN: 0280155831 or 9186340
Resistance: 14.5 ohms
Flow rate: 30 lbs/hr @ 43.5 psi

MarcM · Post by **MarcM** » 11 Nov 2017, 17:45

Interesting. Got the Bosch 1050 just to get the basics. Apparently 1-3 had misfires. Pulled coil #3 and nothing changes in stumble, so I definitely know which cyl it is on.

MarcM · Post by **MarcM** » 12 Nov 2017, 08:46

Pulled the fuel rail off. All the tips are broken or cracked, seals are gouged. When I first got the car, it had an overheating problem. The place I bought it from had a Russian states guy working on it. To get to the thermostat, he pulled the fuel rail. Did this several times. They're not designed to go in/out/in/out/in/out. Ordered 5 rebuilt injectors for $127 shipped. Hoping they're not junk.

MarcM · Post by **MarcM** » 14 Nov 2017, 18:20

Still an issue. Just installed 5 rebuilt injectors tonight and have the new plugs and new coil on #3 I installed on Saturday. 12.1v to Pin 4 on coil #3. Stumble no where near as bad and pulling coil control connector to #3 changes nothing whereas 1,2,4 & 5 will cause a more noticeable stammer.
Any suggestions to test for control signal to coil and control signal to injector #3 without using an o-scope? My multimeter does do Hz and AC.

MarcM · Post by **MarcM** » 15 Nov 2017, 18:25

Well, the injector was firing at 22hz. 1350rpm during the warm-up / vapor purge procedure. I moved into the coil. Engine ran down to "idle" as I was getting coil connector off. It was getting firing signal at 11hz (650rpm). All systems fine in that fashion (still glad I changed the injectors though). BUT... I decided to go to the absolute mechanical basics... ye olde compression tester. I removed fuse #11 & #20 (disable coils and fuel). Brand new spark plug was blackened. At startup and idle I'm getting <big sigh> 25 psi. Had someone rev it up until it smoothed out... 125psi. Still... 25psi? Stuck/bent/cracked valve, cracked head/seat... the list goes on in speculation. I love this car and don't have the proper tools (cam lockdown tool, etc) to do the job. Putting the cams into the "valve cover" is a good idea to save on engine height, but now the fun REALLY begins.

Post by **abscate** » 16 Nov 2017, 07:54

Probably sticking valve. do you have a dry place to work to pop the head off and get it reworked?

Cam tool available from me - connect in BOS area sometime to pass it over. I just finished with it!

MarcM · Post by **MarcM** » 16 Nov 2017, 17:51

Thanks abscate. I was considering just sending it down the road in Valhalla. SO much $ invested in it (steering rack, 2 new coils, rebuilt injectors (should have just done compression test first), racing rotors/pads, new front CV joints/ball joints/tie rod ends, etc. At that cross-road.

Post by **abscate** » 17 Nov 2017, 11:38

My 1999 is stumbly when cold if it sits in the airport parking lot for a week. It runs on 3-4 cylinders until the first minute of road. It may be it takes the cylinders a few miles to find good compression - in which case don't worry about it.

Compression should be measured on a warm engine for this reason.

Start with engine cold. Loosen plugs and then just tighten them enough to not leak. Start and idle to operating temperature.

Stop, remove plugs, good battery, open throttle, record pressure.

MarcM · Post by **MarcM** » 27 Nov 2017, 15:43

I'm currently working up a quote with SE Cyl Head in FL and need to get him more info for an accurate quote. Also working another angle to see the cost of swapping the motor out as a whole by an independant shop, and putting in a low mileage engine pull since I don't have a lift nor proper means of doing it myself. With the light ticking in the bottom end of the motor, I'm leaning towards the low mileage engine swap... but the head rebuild is cheaper. Stuck between a rock and a hard place in my decision. I'm upside down in the car as it is, but I love it and don't really want to part with it.
Most definitely a valve issue. Boroscope shows the piston head is fine with no obvious valve smacks, so I'm thinking partially stuck or burnt valve. I can't get the mirror on the boroscope to function properly to see exactly what's up, but I know there's an issue there.

Post by **abscate** » 28 Nov 2017, 05:09

These cars respond well to a head job so I would do that route of you have a dry place to work.

Do valve guide seals too of course,

Note how the misfire indicators aren't always reported correctly. I doubt you had number one and two proble,s but if the car is skipping the sensing of cylinders can be fooled