Pulsating idle...bad fuel pressure regulator

Joetech34 · 11-04-2009, 12:20 PM

ok I have an 04.5 LLY that pulsates when your at a stop sign. Meaning it feels like you tap the gas when your sitting at a stop sign. Does this sound like a fuel pressure regulator? If a put additivies in the tank it helps out the problem but comes back after a while. What do you guys think?

Thanks

Joe

RedBowTies88 · 11-04-2009, 12:21 PM

any smoke coming out? maybe injector 7 wiring harness

Jscherbs · 11-04-2009, 12:23 PM

IDK, I put a lift pump on mine and the pulsating symptom stopped. I am curious to see what it could be and if it may reoccur down the line.

Joetech34 · 11-04-2009, 12:28 PM

I've had to fix both injector harness #2 and #7 but the problem still occurs

hans1986 · 11-04-2009, 01:23 PM

ya i fixed a guys truck who had the same thing and the fpr fixed the problem. but if you have diagnostic equipment there is a way to look at this. if you can look at the fuel pressure put it in a graph and it should be a smooth wave look. if it is spiking hi and low of desired it will need a fpr. good luck

kwbaum829 · 11-04-2009, 04:26 PM

I had a pulsating/surging idle too. Not noticable on TAC or EGT but you could definetly hear it. Replaced the FPR last month. I have not heard it again. Hope this helps. Check your warranty, stealership fixed mine for $80 deduct. I think if you buy the part yourself its somewhere around $200. Diesel Place has a DIY.

najones79 · 11-05-2009, 10:12 AM

Could be something as simple as a leak in your fuel system as well, though... I had the same symptoms, and it was a bad o-ring in my WIF sensor. I didn't see any visible fuel leaking out (particularly becaue it's right near the A/C dump spot) but it was only a $70 fix...

Just something else to check...

**Hondarider552** · 11-05-2009, 10:14 AM

How many miles are on your truck?

Jscherbs · 11-05-2009, 10:27 AM

Quote:

Originally Posted by Jscherbs

IDK, I put a lift pump on mine and the pulsating symptom stopped. I am curious to see what it could be and if it may reoccur down the line.

From Air Dog:

Rough idle results from the inconsistent injection timing due to the variation of air/vapor present in each idle injection. The delayed injections also cause the idle speed of the engine to drop below the desired RPM. Consequently the ECM then must increase the ammount of fuel injected to bring it back to proper idle. This adds more fuel than the engine can completely burn, if this continues for a consireable ammount of time, if the idle is not brough up by 800 to 1000 RPM, the excessive fuel washes oils from the rings and liners, contaninates the oil in the crank case and causes extensive engine wear.

Joetech34 · 11-10-2009, 03:51 PM

thanks for all your help, the truck only has about 80k