drscottsmith

also replaced the filters on the top side of each injector....!

Kiln_Red

Try the old cap and rotor.

soontobered84

Am I remembering correctly that it has not ever run on all eight cylinders since you've had it? Or am I just dreaming that?

drscottsmith

I was hoping the refresh would cure that. However, it was driveable in its prior state - I would say it was probably missing on one cylinder. Now it's missing on more than that.

docmirror

Usually we go back to what was touched last. But - in this case you were trying to fix a rough running engine to start with.

My best plan is to get rid of the easy stuff first. Rent a compr gauge and pull the plugs test for compression and make notes. leave the plugs out for now.

Next, remove the cap, and check the ignition routing by rotating the engine by hand, and watch where the rotor is on each firing stroke. You can find compression at TDC on #1 by putting your thumb over the plug hole and feel for pressure as the piston moves up. Then insure you follow the firing order and check rotor position and ign wire all the way to the plug well(you touched this last).

Also a good time to check the continuity of your plug wires using an Ohmmeter. inside cap contactor all the way out to the spark plug electrode. Some resistance may be present depending on the type of wires, and plug you have, but they should all be very similar, no outliers. If you get 55 ohms on 5 of the leads, and 950 or 1000 ohms on two, that's a problem.

Now you've verified compression and timed spark, the only thing left is fuel and air mixture. Noid light will help here. Also can measure the resistance of each injector since you washed them. Should all be similar resistance. If that checks out, then maybe find the cold cylinders and start moving injectors around to identify which isn't firing. If it follows an injector, there's the problem. If not, then start looking at the inj wiring, or even back to the ECU.

dr bob

On top of all the previous suggestions, chase down any vacuum/intake leaks. Dwayne's excellent intake refresh instruction is for S4+ cars, but includes how to use a homebrew intake pressure tester to verify that there are no leaks. His is made from home store plumbing parts, and needs an air compressor with a pressure regulator to do the actual testing.

vanster

Take a look at the wires that connect to the MAF and check if any are cracked as by now they are most likely brittle.

soontobered84

Always a good suggestion, but this wouldn't account for not running on 7 or less cylinders. This would affect all the cylinders.

drscottsmith

Ok - Have put the old distributor cap and rotor back on and engine has same symptoms. Plug wires are brand new from Roger as well - have not checked them for continuity as of yet.

My local Advance does not have a Noid set...I read Seth's post today about using an oscope to test fuel and ignition problems. I have read through the Bosch L-Jet manual and the WSM but am unsure of the setup to use my oscope to test injector pulses and plug firing. Can anyone walk me through the proper setup for that? I have a basic 2-channel 20mHz scope (from the dark ages) and a pocket scope that is full color as well.

Thank you all as always!

-scott

GregBBRD

Injectors.

Send them out and have them professionally cleaned, if they are not ruined.

drscottsmith

Quick vacuum-related question...

With the engine off, if I connect any vacuum line that attaches to the throttle body (e.g. the line to the advance unit on the distributor or the fuel pressure regulator) to my vacuum device and apply vacuum, what reading am I looking for? 15-20hg?

Greg - thanks! Indeed I hope I did not ruin them by jumping in and thinking I could do the injectors myself!

dr bob

There is no o'scope capability for checking individual injectors in service. The noid lights option is your best and easiest solution for finding failed wiring and connections. Absent that, you can LISTEN to individual injectors to make sure they are opening. Use a long screwdriver if you don't have a mechanic's stethoscope. Each injector clicks in service, all of them together, so you are looking for the one that isn't clicking. As far as individual injectors working correctly when open, you can remove and test them individually in a test fixture. But that's a chore at best, dangerous at worst. Best to pull them and send them to a specialist for cleaning and evaluation.

Detecting cylinder "misses" is a snap with even a cheap IR thermometer. Look at the exhaust port temps, for a cold one. At idle speeds from cold, your "missing" cylinder will be obvious.

drscottsmith

Updates -

Pulled the injectors and will send them off. Glad that I did as some new evidence is found:

Numbers 1-3 looked ok and had a little fuel residue on the bottom of the pintle cap around the nozzle. I am assuming this probably means they were working to some degree.

Number 4 - I must have gotten the pintle cap somehow caught on installation, as it was torn at the bottom of the cup and kind of smashed up on the side. Surely it was not working correctly if at all.

Number 5 - bottom of cap looked suspiciously dry - as if no fuel made it through.

Numbers 6-8 were like 1-3 and had a little bit of fuel on the bottom.

So they are going off to witchunter tomorrow. Also will rebuild several connectors while they are out. Should have the first time. All of the coils in the injectors measured around 2.7 ohms, save one - it was 2.3 (still in spec but definitely not as consistent as the others).

-scott

docmirror

Well, you went backward to my method. So, now is a good time to check that compression and do the continuity test from the inside of the cap copper to the tip of each plug electrode.

Mark R.

^^^ Definitely do the compression check while you're waiting for the injectors to return.
So easy to perform, and virtually eliminates all of the possible engine mechanical issues.
A total must to assess/confirm the health of any base engine (especially an unknown one).