Would injector problems show up on an Engine Dyno? ---

[alwayscode390]

I think I am having secondary injector issues.

I was told the injectors were changed. I got a bag of 15 stock injectors, and one new red/yellow Ford seconday injector. Haibeck stated in a thread that he hasn't heard of a Ford injector failing yet. I initially didn't want to think I was having issues.

The car drives great unless I am between 1/4-1/2 throttle at 3k rpms. I think the injector is stuck shut until enough pressure from 1/2 to WOT pulls them open.

I think this is why my Dyno run went so smoothly. There was no signs of any issues since it was a WOT run.

Normally, if you had issues on the Dyno ... wouldn't it show a lean/rich Air/Fuel ratio and a dip in the power ratio?

The car isn't throwing any codes, but if I hit 3krpm and only have 1/4-1/2 throttle down ... its a crapshoot whether it bucks on me from 3k-4krpm. I haven't had the gull to keep my foot in it when it starts bucking. Could I cause any permanent engine damage by driving it like this?

The car sat for the last year, not sure if I just need to get more drive time ... I haven't put many miles on it, its been snowing since I bought it pretty much.

THANKS :) ---

[boostedmaxPSI]

How about the TPS? It's possible it has a bad spot.

[alwayscode390]

Not sure ... whats the procedure to check that?

I really want to get it on video ... but its so intermittent that I don't want to be trying to film it all afternoon.

I will be driving it a lot on CRUISES soon since the weather is starting to turn. I will do more testing to see if I can get it to buck "on call" ... then I can snatch a video of it.

I also was reading that the Dual Mass flywheel gets noisier if there is injector issues? Mine makes quite the racket after the car is warmed up at idle. Once again intermittent, I tried to get a vid once and it was quiet as can be LOL.

Thanks for the idea!!! :) ---

[boostedmaxPSI]

Put a multimeter on the TPS, get the initial voltage and with the key on engine off, slowly move the throttle blade to WOT. The voltage reading should smooth and precise from the rest position to WOT. If you see a big jump in voltage while moving the throttle to WOT, then that's a problem.

Difficult to describe via a post.

[vilant]

The FSM says "a broken or loose TPS can cause intermittant bursts of fuel from the injector and an unstable idle, because the ECM thinks the throttle is moving." See if it has come loose. You could always ohm out the injectors too, it's pretty easy. That's how I found my injectors were bad.

[alwayscode390]

My idle is great actually.

I will search on the ohm out injector process too.

I appreciate it ---

[alwayscode390]

Is there any preferred "fuel injector cleaner" to use ... or does that stuff not usually help with our injector issues?

Figured I should try out the basic maintenance stuff first to see if that helps out at all. ---

[Paul Workman]

I think I am having secondary injector issues.

I was told the injectors were changed. I got a bag of 15 stock injectors, and one new red/yellow Ford seconday injector. Haibeck stated in a thread that he hasn't heard of a Ford injector failing yet. I initially didn't want to think I was having issues.

The car drives great unless I am between 1/4-1/2 throttle at 3k rpms. I think the injector is stuck shut until enough pressure from 1/2 to WOT pulls them open.

I think this is why my Dyno run went so smoothly. There was no signs of any issues since it was a WOT run.

Normally, if you had issues on the Dyno ... wouldn't it show a lean/rich Air/Fuel ratio and a dip in the power ratio?

The car isn't throwing any codes, but if I hit 3krpm and only have 1/4-1/2 throttle down ... its a crapshoot whether it bucks on me from 3k-4krpm. I haven't had the gull to keep my foot in it when it starts bucking. Could I cause any permanent engine damage by driving it like this?

The car sat for the last year, not sure if I just need to get more drive time ... I haven't put many miles on it, its been snowing since I bought it pretty much.

THANKS :) ---

Technically, it is the Air/Fuel graphs that are usually run along with the dyno torque/HP curves that tell the tale. I suppose indirectly those graphs could and do result from injector performance, but the AF ratio is by far the more direct (and accurate) approach, methinks...

All my dyno runs also have an AIR/FUEL ratio graph. This is a direct reflection of fueling. And, as a matter of fact, that is how I came to learn I had a fuel pump going south. Later, when Marc was tuning my "FBI 500" package, AF ratios would not respond to changes in the fueling tables over rpm. That lead to ohming out the injectors which produced some NOS injectors that had gone south.

If you are running with stock secondaries, those injectors can become fouled if you don't run the secondaries enough. If that is the case, perhaps some Techron or the like might clean them. Marc has a good article on his web page with instructions on what to do to minimize the injectors getting foulded.

Other than that, ohming them out after they're hot might turn up a problem, OR a wideband O2 rig too, if you have the capability to tune on the fly (referring again to Marc or Dominic or =Jeff= or Pete for help with that.

[alwayscode390]

I totally forgot I have Datamaster on my P.C. that I need to download to my laptop. Now is as good of a time as ever to get it working. I cant figure out a way to drive and take a vid with my current camera LOL.

To Ohm them out do I need a voltometer?

Thanks for the lead on Marcs injector fouling tips ... I think that will help me out a lot , its the first I have heard of this issue ---

[alwayscode390]

This is definitely intermittent ... I drove the car lastnight and got on it twice with ZERO issues ... its always fun to fix stuff that decides to be a ghost once in awhile LOL ---

[Paul Workman]

My idle is great actually.

I will search on the ohm out injector process too.

I appreciate it ---

After a shop gave me back my 95 LT1 Vette, with a note that said, "No problem found", I bought an AutoXray scanner.

The scanner was able to report status of 42 different items, but the one thar really pulled off the fix was the "event" capability. I drove the car in the manner where the problem usually occured, and when it did, I pushed the button resulting in several seconds of data before and after the "event" was triggered. This allowed me to find an intermittent problem (with an O2 sensor, in that case). Since then, that scanner has paid for itself many times over - not just on the LT1 Vette, but once or twice on the ZR-1 as well (diagosed some connector problems for me!).

I keep the scanner in my "cubby" storage box behind the passenger seat...Just in case!

P.

[alwayscode390]

Awesome!

I drove the car this morning. I got it to "shudder" in the same problem spot but ONLY when I am not in the throttle enough.

It seems like its dumping a lot of fuel when the secondaries open, and if I don't have the throttle open enough or the rpms climbing quick enough it cant burn all the gas... and it shudders from it being too rich for that second.

As long as I am driving it aggressively enough there isn't a single issue.

Now, I have noticed irratic starting behaviors ... BUT the weather here has been so up and down (70 one day , 30 the next ... seriously) I am not sure if its connected to the temperature , or if its another clue to an injector issue.

When its cold outside it seems to take 5 seconds to start ... when its hot outside it starts the instant I turn the key which freaks me out because it takes 2 seconds for the oil pressure to rise when that happens, and its running with 0 pressure in that time frame.

Just figured I would throw that out there in case it points to another issue or confirms anything :) ---

[vilant]

You will need a voltmeter (never seen one without an ohm test on it) to ohm out your injectors. Here's a post that someone gave me when I needed to do mine. Great post, made it easy http://www.zr1.net/forum/showthread....7299#post17299 (http://www.zr1.net/forum/showthread.php?p=17299#post17299)

[alwayscode390]

Now that's what I am talking about. Thanks a lot Joe! Sometimes I need that motivation to get to work :) ---

[Hib Halverson]

An injector problem likely would show up on the dyno if you were taking air/fuel data

That said, injectors don't "stick" until "enough pressure from 1/2 to WOT pulls them open. "

First of all, at WOT there is no pressure other than atmospheric in the intake manifold so there's no "pressure" to "pull them open".

My guess is is there is a hesitation it's some problem with port throttles. Either they are slow to open or they're late to open on one side...something like that.

It's also possible the mixing and matching of injectors is a problem.

Never thought I'd see the day when someone would mix/match 15 stock injectors with one aftermarket unit. But then...fact is always stranger than fiction.

[alwayscode390]

OK, thanks.

I was given 15 stock injectors and 1 new aftermarket in a bag ... Im worried they re-used one of the original ones for some reason. ---

[Paul Workman]

OK, thanks.

I was given 15 stock injectors and 1 new aftermarket in a bag ... Im worried they re-used one of the original ones for some reason. ---

I'd be concerned if the 15 were NOS injectors built before 93. I can tell you from personal pain that NOS injectors before 93 are good for something less than 3 years before they start going south (on 10% ethanol).

Hope you didn't already install them if they're the older injectors... Are they, do you know?

p.

[alwayscode390]

The 1 new secondary injector I got is a yellow/red Ford aftermarket.

The 15 others were black/gray OEM.

I hope they bought 1 too many injectors , but its looking like they either forgot to use the 1 Ford leftover , or it had issues so they reused the 1 best OEM.

Just checking ... but you cant see what injectors are installed until the plenum is taken off, right? ---