Alright, ive been trying to find the cause to why my engine is running with a bad miss and is severely down on power. After searching through this site, i came across the concept of unpluging the injector clips to see a change in idle. Sure enough #4 and #6 showed no change in idle what-so-ever. So i then read about doing a test to measure the resistence of each injector. I was told that 16 was optimal while all shoud be above 12. Can anbody verify this? I ran the test and ALL injectors measured between 17.1 and the lowest was 16.4 hms. This seems abnormally high but what i really dont get is that the #4 and #6 put out 16.9 and 16.8 ohms. What gives? Does anybody know what this is telling me?

 

Rumple,

What your resistance test is revealing is that the injector solenoid coils are all good. 16 ohms is a nominal resistance reading, but Bosch injectors are serviceable down to 12 ohms or just below.

BTW - It always helps to know what model/year/engine you have, since it's a little tough to try to remember the data for all 21,000 + members. Not a BIG deal, but it saves a little time, and another post.

Since you have at least six injectors, I'll guess that you have some form of multiport injection, either MPFI on a V-6 or TPI on a V-8. Depending on the year, you may or may not have serviceable injectors. By "serviceable" I mena those worth repairing. If you have Bosch or Lucas injectors, they are worth sending off for cleaning and flow-matching. If you have Multec injectors from the early '90s, they might not be worth it.

I'm also guessing that since you measured no RPM change with a couple injectors unplegged (electrically), they are not delivering fuel correctly. That can either be a volume issue, where the injector doesn't flow at the correct rate, or a spray pattern problem, where teh injector drips or streams the fuel instead of spraying it into a nice, round cone pattern. Either can be caused by dirt, varnish, or fuel deposits. In either case, the cylinder(s) served by that injector(s) is not getting the correct fuel charge on every cycle.

Since your power balance test has detected at least two injectors that are not delivering fuel properly, you'll be wanting to remove and repair that.

So what year/engine is it?

 

its an 86 lb9 with the 77000 on the odometer. i am confused though b/c i am the third owner and it looks like i have a cold start valve. I dont understand how this can be. Its a plug thats in the back driver side fuel rail with a metal hose going in the lower part of the runner. any ideas? much appreciated.

 

You'd BETTER have a ninth injector on your '86. The cold start "valve" (as the factory called it) was a standard item on TPIs through 1988.

My injectors needed cleaning at 18,000 miles (after nine years use), so don't feel too bad about that. I think the long periods in storage were allowing the fuel to evaporate from the injectors and deposit lots of varnish and solids. I've since experimented and may have found a solution to the storage/injector plugging problem.

 

It all makes sense now. For some reason i was thinking that post-88 models had the cold-start valve. This car sat for roughly 6 monthes so that would explain it. Do i have to remove the plenum to remove the injectors? or can i simply lift the fuel rail up enough to get them out? How would you suggest i clean them or where should i send them to be cleaned? Would cleaning them solve my problem or do i need to look into getting new ones? thanks.

 

You have to remove the plenum and the runners to get to the fuel rail. There are a couple of tricky spots, but it's relatively simple.

Here's a good article to follow, I believe one of the torque numbers are wrong in that, so just follow the numbers in your service manual to be certain. Also, the article recommends using petroleum jelly or o-ring lube for the o-rings, but you can use a swipe of motor oil as well. Always replace the o-rings, just because it's cheap and better than having a leak.

https://www.thirdgen.org/newdesign/t...ctorswap.shtml

The trickiest part is the hard fuel line removal from the fuel rail, aside from the grueling gasket cleaning. My lines were a bit bent, so I had to remove the alternator completely, and the bracket support bolt, and twist and wiggle to get the lines out of the rail.

For cleaning, there are options, I think the best is to remove it and to send it to rich @ cruzin performance. http://www.cruzinperformance.com Do a search and you'll see lots of positive notes on him.

Before you send them off, I would check to see if any of the injectors are leaking first. Leaking injectors can't be fixed, you'll need to replace those. Underflowing injectors are probably clogged and can be cleaned.

Since you have the fuel rail off, reconnect the fuel lines to the rail, but don't plug the rail in to it's location. Place a paper towel under the injectors blue shop towels work good because it's easy to see. Prime your fuel pump, but don't start the engine. If you see drips under the injectors, you've got some problems there. If all's clear, take off the injectors (noting the clamp orientation), and send them off for cleaning and flow balancing...or take it to a local place for cleaning, your choice.