4.3 CPI Stalls in gear

[Sinful7]

Ooookay... So tonight's diagnoses provided a potentially interesting symptom change:

-The vehicle will maintain idle indefinitely in gear when the EST (Electronic Spark Timing) wire is unplugged thereby preventing EST adjustment.

-The vehicle will idle in gear from startup until the temp gauge has reached 200 degF.

From reading the FSM, it says,

"Controlled idle speed is always specified for normal operating conditions. Normal operating conditions are: coolant temperature in normal operating range, the A/C OFF, auto trans in Drive."

I'm wondering now if the IAC is stuck? Should I be able to manipulate IAC position by hand? How far out should the IAC pintle be when it's fully extended?

I wish a dealer service was in the budget.. Bah!

[randolphtpr]

broken record.....temperature sensor.....only $17 and 15 minutes.....it just sounds so similar to my symtoms....a cap and rotor and replacing the soaked spark plugs didn't hurt.....your temp gauge can read normal but the other temp sensor may not be working....it's right down by the egr...

[Sinful7]

Originally Posted by randolphtpr

broken record.....temperature sensor.....only $17 and 15 minutes.....it just sounds so similar to my symtoms....a cap and rotor and replacing the soaked spark plugs didn't hurt.....your temp gauge can read normal but the other temp sensor may not be working....it's right down by the egr...

Ok, I'll give that a shot. I thought a temp sensor would throw a code or something. I also found a dude on eBay selling the IAC, TPS, EGR and MAP for $29.99 so I hit that just in case! I'll replace the temp sensor tonight and report back!

[old_master]

The ECT sensor will not set a DTC unless it's output is out of range. It's entirely possible for it to be out of calibration and still be within range.

If the ECT indicates a lower than actual temperature: The ECM "assumes" the ECT is indicating the correct temperature provided it is not out of range. The ECM will adjust fuel mixture, idle speeds, etc etc, based on the signal it receives from the ECT.

[Sinful7]

Well, the ECTS is replaced with no effect. Good idea though!

I just really hope this isn't a short in a sensor wire.. that would suck. Hopefully shortly I'll be getting some used emissions controll equipment that I can try swapping out. If I get time soon, I'll remove and clean the EGR. To be continued!

[randolphtpr]

geez....what is the idle speed now???....this is another notion i thought was my problem .....i checked vacum at the brake booster and thought for a second that maybe the booster leaked....it was not the case but it was something that never occured to me...brakes ok???......what about a neutral switch either shifter or tranny???....my God man....what have you got....?

[Sinful7]

Originally Posted by randolphtpr

geez....what is the idle speed now???....this is another notion i thought was my problem .....i checked vacum at the brake booster and thought for a second that maybe the booster leaked....it was not the case but it was something that never occured to me...brakes ok???......what about a neutral switch either shifter or tranny???....my God man....what have you got....?

LOL! Yeah, hence bringing forth the problem to the community.

I guess I haven't measured the vacuum yet, but I have conducted the 'spray test' with carb cleaner to find any leaks around the upper plenum and attached lines.

I also don't have a very precise tachometer- just the one in the digital dash. I've had this truck for 14 years though, and I would know if something sounded amiss.. Nothing does.

[randolphtpr]

i'll keep checking in but i'm at a lose right now...sorry....you have me going though and thanks for that..

[Sinful7]

Last night I replaced the IAC to no avail. I'm gonna head out to the garage and try replacing the egr.

[randolphtpr]

oh please let that be it...i think the egr would make it act the way it has been...i'm praying for ya!....it will be a nice thing to be thankful for...please post results

[Sinful7]

Unfortunately I have not had an opportunity to check/clean/replace the EGR since my last post. (I'm on night shift all week and my sleep patterns are all whacked) I did however, manage to remove the UIM/Plenum and observed not only washing in the RH dish, but also a small puddle of oil within the plenum interior!

Now, I'm not really sure how this oil got in there as the area should be sealed of by the plenum gasket. I'm also not certain the washing is indicitive of a fuel pressure regulator failure - I've replaced the CPI Spider thrice in the past years, and I've never seen a re-accumulation of carbon on the RH side.

Next item up for replacement is, of course, the EGR. However I will also attempt to R&R and clean the spider ball valves and recheck the fuel pressure stability.


One more observation of interest - When I replaced the IAC, the new pintle was fully extended. After flunked testing of the replacement, I removed the IAC to check its position and found it to fully retracted. This obervation, combined with previous (that opening the TB allows the engine to run), tells me that the ECU is indeed attempting to control the idle and is simply unable to adjust the A/FR appropriately.

[old_master]

Fuel on the passenger side indicates a leaking fuel pressure regulator. Check back to post #4... Check fuel pressure and leakdown when the engine is cold. Pump running engine off pressure must be 60 to 66psi. After the pump shuts down, pressure must remain above 55 psi for 3 to 5 minutes.

[Sinful7]

Originally Posted by old_master

Fuel on the passenger side indicates a leaking fuel pressure regulator. Check back to post #4... Check fuel pressure and leakdown when the engine is cold. Pump running engine off pressure must be 60 to 66psi. After the pump shuts down, pressure must remain above 55 psi for 3 to 5 minutes.

OK! I finally had a second to check the FPR and EGR:

FPR-
Pump running - 61ish PSI.
Pump off - 57 PSI.
3-5 Min Leakdown - 55PSI (holds steady indefinitely, I watched it for 10 mins).

I performed the leakdown test three times. The first time, I got 61/57/54. The second time I didn't relieve fuel pressure prior to testing and I got 61/57/57. The third time I did relieve fuel pressure to yield the above results.

EGR-
No visible blockages.
Valve moves freely, no reason to suspect clogging or failure. Clean and reinstall.


EDIT: After I posted this, I went back out to the truck to compare the EGR movement with the used replacement EGR I have and to visibly inspect CPI poppets to confirm none are stuck open. None were. For sh*ts and grins I flipped the ign on to check the FPR one more time- a true 'cold test' as I've let it sit for more than 5 mins a 0 psi. The result was:
Pump on- 61PSI
Pump off- 57PSI
5 Min leakdown - 52PSI.

Is it possible I'm experiencing an intermittent FPR failure? Are my testing procedures above just incorrect?

I'm considering ordering the Linder Tech FPR replacement. Anyone have experience with this product?

[old_master]

Fuel pressure is good, the regulator is what determines the 61psi that you have been getting. It is not adjustable, whatever the spring pressure is in the regulator...that's the pressure you'll get. The (cold) leak down you're experiencing is very small...and will be difficult to pinpoint. The fact that it leaks does not tell you where the leak is, only that there is a leak. To determine if the problem is the pump, regulator, or an injector, you need to isolate the fuel pump after the system is pressurized. The only way to do that is with a shut off valve installed in the fuel pressure line between the fuel pump and the pressure test port. After the pump pressurizes the system, shut off the valve and watch pressure for leakdown. If it holds, the problem is the fuel pump, if it drops, the leak is under the plenum.

[Sinful7]

Argh! The very last thing I want to replace it the fuel pump, yet again.

Let me see what I can come up with for a FP shutoff valve.