Surging on cold start

[velacreations]

I've got a 94 F250 7.3L idi turbo. Overall, it is a great truck. There are a few little issues with it (like the AC), but in general things work fine.

Recently, it developed a problem where on cold starts it surges/revs and drops. revs and drops. It doesn't hold up at 1500 rpm like it used to. Once it warms up, it is fine.

It does have a stutter, and I only ever notice it at lights or when idling. It is very faint, but almost like it is missing. I ran out of fuel a few weeks back, and the stutter was really noticeable, so I bled the fuel lines (post IP), figuring air was in there, and that really helped a lot. It still stutters, but ever so slightly, you wouldn't notice it unless you were really paying attention.

It smokes just a little bit on a cold start, just for a second, some grey smoke, and then no more smoke, ever.

It has 250K miles on it, and I don't think it has ever had the injectors or IP changed. The injectors were serviced a year ago, right before I bought it, and they did change out one injector. I am planning to get a set this year, and maybe go ahead and change the glow plugs while I am at it. It starts fine when cold, so I don't think they are weak. Usually turns over for 1-2 sec, and it's up and running.

So, my question is, what do you think is going on with the revving on cold startup? Is the cold start solenoid bad? or maybe the IP advance?

And the stutter at idle? does that sound like a weak injector to you guys?

 

[velacreations]

Also, what's a good price for a new set of Delphi injectors? I found a set for $312 plus shipping, but they are G code.

 

[dgr]

My new to me but old stock rebuilt pump did that. A big dose of diesel clean took care of it. You can empty the fuel filter, fill with diesel clean or atf, run for 30 seconds or until the engine gets quiet and shut it off. The next morning, it will hopefully run better.

 

[velacreations]

I've added ATf to the diesel periodically. I'll try filling up the filter with it and see if that helps.

 

[riotwarrior]

Perhaps you will want to do a PURGE of the fuel system.

This is a superior method of cleaning injectors and IP than just filling the filter with ATF or diesel klean.

You will run a closed loop from the lift pump and return line with 2 or 3 bottles of Diesel Purrge.

Closing the loop, means running the product in it's own separate container that the lift draws from and the return line flows back into that same container.

You run the setup and it cleans the IP and injectors far longer and better than a fuel filter full of cleaner.

Take a look here for the basic idea of this.

http://www.dieselgiant.com/injectorcleaning.htm

Once it's run through quite a bit one could shut it down overnight like others suggest with diesel klean or ATF, let sit over night and fire up in AM again continuing untill the product is completely gone....

Others far more experienced than I will chime in and offer their thoughts too I'm sure...

JM2CW

Al

Oh, and for shitz n gigglz I'll be doing this particular method very very soon, PRE winter tune up...so to speak... and I'll as a matter of SOP be doing a Pictutorial of it as well.

 

[velacreations]

do you think that would address the issue of the surging on cold start? just crud in the system?

 

[riotwarrior]

do you think that would address the issue of the surging on cold start? just crud in the system?

Well for the cost of two or three bottles and a couple of filters on a en engine with 250 K would it hurt to try?

I cannot say for sure if it would help or not but I doubt it would hurt any....

Just saying...wait for the Guru's to chime in and post their thoughts....

 

[dgr]

Perhaps you will want to do a PURGE of the fuel system.

This is a superior method of cleaning injectors and IP than just filling the filter with ATF or diesel klean.

You will run a closed loop from the lift pump and return line with 2 or 3 bottles of Diesel Purrge.

Closing the loop, means running the product in it's own separate container that the lift draws from and the return line flows back into that same container.

You run the setup and it cleans the IP and injectors far longer and better than a fuel filter full of cleaner.

Take a look here for the basic idea of this.

http://www.dieselgiant.com/injectorcleaning.htm

Once it's run through quite a bit one could shut it down overnight like others suggest with diesel klean or ATF, let sit over night and fire up in AM again continuing untill the product is completely gone....

Others far more experienced than I will chime in and offer their thoughts too I'm sure...

JM2CW

Al

Oh, and for shitz n gigglz I'll be doing this particular method very very soon, PRE winter tune up...so to speak... and I'll as a matter of SOP be doing a Pictutorial of it as well.

Over achiever ;p Good stuff there. It is creepy how quiet my engine runs on diesel clean

 

[velacreations]

yeah, I recently changed my fuel filter, so it's pretty new. I know it wouldn't hurt the engine to run a bit on it. I doubt I can find Diesel Purge here, though I will check with Auto Zone. I assume ATF will work, too.

It just doesn't seem like that would cause the issue with the cold start surging. I suspect it has to be the solenoid or something associated with the high idle system.

 

[Wyreth]

yeah, I recently changed my fuel filter, so it's pretty new. I know it wouldn't hurt the engine to run a bit on it. I doubt I can find Diesel Purge here, though I will check with Auto Zone. I assume ATF will work, too.

It just doesn't seem like that would cause the issue with the cold start surging. I suspect it has to be the solenoid or something associated with the high idle system.

The solenoid for the high idle normally isn't strong enough to overcome the throttle spring. On mine I have to tap the throttle before starting to let it set, otherwise no high idle. So it shouldn't be able to cause an idle surge.

A good cleaning is a really good place to start.

After cleaning it, (either with the filter method, or with the closed loop) if it's still doing it. Look for air. Try replacing the line from the fuel filter, to the IP with clear fuel line. Then while it's surging look for bubbles in the fuel on it's way to the IP.

 

[velacreations]

The solenoid for the high idle normally isn't strong enough to overcome the throttle spring. On mine I have to tap the throttle before starting to let it set, otherwise no high idle. So it shouldn't be able to cause an idle surge.

A good cleaning is a really good place to start.

After cleaning it, (either with the filter method, or with the closed loop) if it's still doing it. Look for air. Try replacing the line from the fuel filter, to the IP with clear fuel line. Then while it's surging look for bubbles in the fuel on it's way to the IP.

yeah, I have to press my throttle to get it to engage as well. But, what I was thinking is that it just doesn't hold it at 1500 rpm, like it should. It drops to 1000, up to 1500, back to 1000, etc. The truck never acts like it is going to stall or anything, and no smoke is visible. It just won't stay up on the 1500 high idle.

the clear line is a good idea. I will try that. I mean, once it warms up, it runs pretty normal, so I don't know if it is air or not. Maybe it is. It seems like it would continue to run rough even after warming up if it was air getting in, but that's a simple way to rule that out.

For doing the closed loop clean, I will have to look where it is convenient to pull off the intake and return lines. Maybe back by the fuel tank...

If I can't find Diesel Purge, s there anything else I can use to do that clean? will ATF work? or another product that might be common enough that even I can find it? I live in a very rural area of a 3rd world country, so some products are not always easy to find

 

[riotwarrior]

Over achiever ;p Good stuff there. It is creepy how quiet my engine runs on diesel clean

What the heck is that supposed to mean? Over achiever?huh????

 

[riotwarrior]

I get Diesel Purge at my NAPA dealer, he can carries it, after I suggested bringing it in. Now the Manager is sold on it. He's waiting for me to do the closed loop so he can pinch my bottle lines to do his own....rofl!

 

[dgr]

What the heck is that supposed to mean? Over achiever?huh????

Nothing other than a compliment. You always give 100 % to this community.

 

[velacreations]

we don't have a Napa around here, but there is an auto-zone. There are also a few diesel shops, so I will check with those.