Fuel Pressure & Injectors

[CarGuy]

I am tracking down a problem with my car idleing high sometimes. After working with the base idle, ICA, and TPS I feel I have those eliminated. I thought I may have leaky injectors so I bought a pressure gauge to check the fuel delivery. After taking the readings I believe I may be right about the injectors. On the KOEO (key-on-engine-off) test - the pressure went to 37psi and then dropped slowly. With the engine running it stayed at a steady 37psi. Can anyone else tell me anything about these results? If I should replace the injectors - what should I go with. My car is mostly stock with a boost controller. I got a few I was checking up on:

Local Auto Parts: Borg Warner rebuilts - $46 each.
ATR Performance: Delphi injectors - $40 - any size sugg?
Tiny Avenger: Lucas 36lb - $57
Tiny Avenger: Lucas 42lb - $60
Tiny Avenger: R.C. 42lb - $80
Local Auto Parts: MotorCraft New - $104 each

Any tips on installing them - Is it possible to remove the fuel rail and injectors without removing the intake manifold?

Thanks

[Gator]

How fast does it bled down...Couple seconds...? One minute..? two minutes..? ten minutes...?

It is normal for it to bleed down over time.

When your car idles high, have you ever tried to turn the key back and forward ( as if to turn the car off then turn it back on instantaneously..? ) If the idle goes back to normal, it should not be the injectors.

In anycase, if your not going the "performance route" I would select none of the above, take the injectors out and have them sent to RC Engineering for cleaning and re-balance. $ 25 a piece.

[Pat_in_L.A.]

NY eric has mentioned a great source for injector refurbs. Check the search feature.

[CarGuy]

Thanks Pat & Gator for the reply

The pressure starts to bleed down immediately. I would say the pressure drops about 5 psi per 10 secs.

When you talk about turning the key back - do you mean turn the car off - then restart it immediately? I can get it back to normal idle by just tapping the pedal.

I plan on adding performance items to my car - so I'd like to get nice injectors that can be utilized now and down the road.

Thanks

[Gator]

Originally posted by CarGuy
When you talk about turning the key back - do you mean turn the car off - then restart it immediately?

Not completely, just turn it back and forth in a heart-beat....just enough to break the cir for the computer to re-set itself.

If it idles normal afterward, i would start over at the IAC and TPS.

I plan on adding performance items to my car - so I'd like to get nice injectors that can be utilized now and down the road.

How fast or how much HP do you plan on...?

42's are pretty big for just bolt-on parts. If you dont plan on porting the head or going with the ESS Alum, I would just get the 35lb'ers rebuilt and buy an adjustable fuel pressure regulator ( which you will need anways if you buy the 42's )

[CarGuy]

Thanks for the replies.

Mike - would stuck fuel injectors cause high idle? The car is an 86 model and I have changed the TPS. I ran a code scanner on the car to see if it would tell me anything. System checked fine on the KOEO - but gave me code 25 on the KOER (key-on-engine-running) test. The book I had said it was the knock sensor not giving signal. I working on that issue too

Gator - I'll try the key turning

Thanks

[GAboySVO]

I had a similar high idle problem in my 86. It would come and go as a problem. Went through the whole IAC, TPS thing and would still idle high. My problem turned out to be related to the EGR valve. If the diaphram has a hole in it, it will suck in unmetered air. Also, I had to use a screw drive to punch through the carbon build up in the EGR port.

You might try misting some water over suspect areas under the hood with a spray bottle to check for vacuum leaks.

[CarGuy]

Mike - My problem is exactly like you say. Some days it happens none stop. Other days it may not happen. I'll check the EGR valve - Thanks

[SVOeric]

here's a couple of more ways to check -- to find out if the problem is your fuel pump --- connect a pressure gauge to the fuel filter - -- turn the key on, and see what the pressure does, it if starts dropping imedialty, then your porblem is the pump, (or check valve)

your code 25 is because you didn't tap the engine durring the test. it was waiting for you to knock on the intake, so don't get too worked up on that one.

[CarGuy]

Originally posted by SVOeric
your code 25 is because you didn't tap the engine durring the test. it was waiting for you to knock on the intake, so don't get too worked up on that one.

Please tell me you are joking

Well - I was thinking along those lines - I didn't know whether the sensor would send a signal regardless if there was pinging. So are you telling me I wasted $30 on a new sensor?

[svoman2300]

I also had the same problem after screwing with the TPS a bunch of times and cleaning the IAC I never solved the problem. Trying to fix a different problem I replaced my throttle body with another one and I no longer have that problem. It idles smooth and the same rpm all the time. I was thinking maybe the seal was bad on the throttle shaft and it was sucking air in through that.

[CarGuy]

The car ran fine today (I didn't drive much) so I couldn't try the turn key thing. I'll look a little more into things before I change the injectors.

svoman - I did changed out my TB because I got a nice deal on a larger one - and still have the same issue. I guess a leak could come from the TB-to-intake gasket - but it would seem a lot of air would be leaking to make it run steady at 2k - right?

Thanks again for the replies

[Eyelawdoc]

Check your TPS wiring VERY Carefully! If there is any sign whatever of cracking or broken insulation or bare wires replace it with soldered and heat shrink splices. As these cars get older this is becoming more of a problem. There is a length of the loom for the TPS that passes directly over the turbo and elbow area underneath the intercooler where I have seen exposure and heat damage to the wires on several SVO's.

[GAboySVO]

Wasn't there a post by LonChair a while back that when you install a larger TB that you have to add some sort of restrictor plate between the IAC and the TB to control the idle?

ANybody who has installed a larger TB please chime in.

[CarGuy]

Mike - I had the restrictor plate on the old TB that I carried over to the larger one. I also tried it without the plate - nothing changed.

Eyelawdoc - The TPS and harness were the first things I tackled for solving this problem. I replaced the old TPS with a new motorcraft and set it to the correct voltage. The harness did have a few exposed wires which I cut, resoldered, and then wrapped.

Again - the car ran fine today however I did try the turn key thing just to see how it worked. With the car idling just under 1k, I flipped the key back as quick as I could - the engine stuttered and then jumped up to 2k - then slowly dropped back down to 1k (just like a cold start). I really wasn't expecting those results. Question - If I did the turn key trick while my car was idling at 2k - wouldn't the stutter disrupt the idle? I figure the car would probably do the same thing as when it was at 1k. I mean when the car is idling high - the slightest tap of the pedal brings it back to normal.