Wes...Your recommendation for injectors is ikely culprit...

[Dabizzo1]

Hey all, I've been doing my homework to figure out what is causing my lumpy idle. As of now, I've confirmed that my entire air system is free of clogging and gunk---been doing a lot of cleaning. My IAC is spotless and works perfectly, as does my EGR valve and the passages from the exhaust manifold to the plenum are now completely carbon free as well. The MAF and Harness are in proper working order also. The fuel pump is a month old (OEM NEW) as well. All of my injectors are new oem except for 3, 4, and 6. I was reading TEXASOIL's post with his injector problems and he made a statement that pointed to my problem perfectly. He said one of his cars had a high resistance injector that was good past 1500 rpm but dead at idle....I bet when I ohm 3,4, or 6, I anticipate that one of them will be slightly higher than spec which would allow it to still perform at speed but will fail to create proper spray at idle due to its higher constant resistance (as approaching infinity or open failure)being out of the range to create smooth idle. The lumpy idle I'm experiencing is after warmup and the car has a characteristic sputter in the tailpipe, indicating a missing cylinder at idle, however mild. I even considered the ignition timing to be out of adjustment but if it was, acceleration and engine operation at any speed would be awful. Performance at speed and acceleration is perfect, but I suspect that will degrade as the cuplrit injector or injectors progressively go south. I will ohm the injectors this weekend and find the culprit. This car was originally a north Dallas car (ethanol anyone?) so I wouldn't be surprised if the remaining 3 need replacing altogether. Gas here in New Orleans luckily has no ethanol, but given we have 100% humidity year round, ISO HEET will go in my car every tankful.

1 question though...when hooking up the ohm meter, should I connect the positive to the car battery (is that what was meant in the tutorial)? Just wanna be sure. As I've mentioned before, Wes, you da man and I wish Indy good luck this weekend VS. New England....Peyton deserves a Super Bowl shot. Hope to see you guys at the Super Bowl!! WHO DAT!!!!!!!!!!! GO SAINTS!!!!!!!!!!! Boris P.

[Q45tech]

You never apply voltage to an ohmeter! The multi purpose VOM confuses some..............never apply a voltage when you have selector set on OHMs!

An ohmeter uses its internal battery to measure ohms ...........most use 1.5 volts some use a 9 volt and measure the current flowing thru the external resistance to calculate ohms using OHM's Law.

On low resistance scales the current draw from internal battery is high so alway use a fresh battery when measuring low resistance.

[elwesso]

the way ive always ohmed the injectors is to put the positive terminal of hte VOM on the positive terminal on the battery and then put the negative terminal on the pin of the injector on that harness on the rear passenger side of the motor.......

[qsiguy]

You do that with the ignition on, right Wes, or does the + side of the injectors have power all the time? You are measuring the resistance from the negative side of the injector (which doesn't have a ground on it during testing because you've unplugged the harness) to the positive side. As long as the injector harness is unplugged you aren't applying a voltage to your ohmmeter.

Now if the harness was plugged in and the car was running your ohmmeter wouldn't like being wired like that.....

[elwesso]

no everything is off in the car!!

[Dabizzo1]

I took a reading before I went to work today from the harness pins using the ohm setting...positive to a pin on the 4 port connector...negative on port for injector 3...4 readings for injector 3 = avg of 26.4ohms...on its way out ....I'll post 4 and 6 when I get a reading...
Modified by Dabizzo1 at 9:12 PM 1/19/2007

[3Q Jay]

what is the 4 port? you unplug the 8 wire connector, and ohm the engine side, 1 wire for each injector. other end of the meter to positive battery....it works. be sure and do all 8. just reading #3 (even over 4 averages) won't tell you the whole story. need to see all the others to make sure 'tare' resistance is right and the degree of problematic on the suspect ones.

there may be other suspects for your lumpy idle--we'll see after you post the injector reads.

[Dabizzo1]

Hey all, I'm just gonna ohm each injector directly with the plenum off when cleaning tomorrow with a digital mulitmeter I have. I can't hook it up directly to the battery due to its internal power source when measuring ohms...I should just get an analog VOM...might just do that. i was reading the manual for my meter (Radio Shack 22-813) and the only allowable reading to take from an external power source is for amperage. An older post from FIRSTQ showed how he ohmed his injectors at the harness with the positive probe on one of 3 pins in a 4 port connector right next to the knock sensor harness and the negative probe on the respective injector pin in the 8 port harness (multimeter in ohm measure setting). I figured I'd give iti a try on injector 3 and I got a reading. Who knows if he was right but I'm gonna measure directly from the injectore because my harnesses aren't the best looking (99K) and I'm planning on replacing them anyway. i'll repost when I have conclusive results. I expect 3,4,and 6 to be high given they are the only originals left...all others are less than 2 months old. GO SAINTS!!!!!!!!!!!!!! Boris P.

[Q45tech]

The problem with analog ohm meters is the impossiblity of measuring 12 ohms to at least 1 decimal place.

The 10 - 14 ohm range is to avoid warranty claims [notice many things in FSM have extremely wide specs]. There is no reason that an injector should be more than +- 0.5 ohm from the MEAN if they are all measured at the same case temperature.

Identical wire with identical turns doesn't vary unless something is wrong.

I've measure a few hundred new and used injectors and they all show within +- 0.5 ohms, most within +- 0.2 ohms......................~~~2%

I would expect the actual manufacturing tolerance to be +-1% or 0.12 ohms

[Dabizzo1]

So I ordered 3 new injectors for my Q today from Joe along with new o-rings(lower and upper) and brake pads all around. I won't get them till next Monday but I plan to ohm all of my injectors this Sunday when I do my plenum. All of my injectors are new except 3, 4, and 6 which are originals. I expect 3 to definitely be fubar, but if 4 and 6 ohm ok, I'll leave them in until they cause an idling issue. Given this was a N.Dallas car all its life, 3, 4, and 6 will probably ohm way out of range...they are 13 years old afterall. I'll at least have their replacements on hand. My KS and harnesses are brand new as well so that's one less thing to worry about. I plan to at least try to clean the connectors of my FI harness but if they're too corroded, I'll just replace that too. My ultimate goal is to have this Q as original as possible, just like I fell in love with it. At the most I plan to install a catback SS Magnaflow system, Tokico blues, an aluminum radiator, and a transmission cooler and that's it. With this car's timeless lines, less is truly more. I just love the idea of a perfectly manicures sleeper in corporate clothing...especially if I feel the need to mess with a ricer on the I-10 sporting fartpipes akimbo Thanks for all of your input to this point. At the risk of being repetitive, the veterans of this forum rock. Boris P.


Modified by Dabizzo1 at 12:36 AM 1/23/2007

[3Q Jay]

if you are going to keep 2 originals, suggest you put them (move them) to 1 and 2. that way, you won't mess with the plenum again when they go. Make sure you have enough o-rings to replace the o-rings on the ones you move.

a well tuned vh45de is swweeeeet music. actually, to be fair, the vh41de sounds good, too just not quite the same scream at redline.