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Rough idle/hesitation/pinging?


cp2295

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Truck idles kinda rough (got a 99 3.0... Bought it and the head stamp indicates non flex fuel, however the vin indicates it is..hmmm) anyways it idles rough, and kinda hesitates when it's idling. Good power though when I go. But when I go up a hill and put it under a load it starts pinging. I replaces the dpfe sensor just about an hour ago and drove it.. Nothing seemed to really change and it still pinged (however I only drove it up one hill and for about 3 minutes, not enough time for computer to think?) any suggestions other than dpfe sensor? O2? Some other egr sensor or some weird emissions thing.. Thanks!
 


RonD

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Yes, if it has an EGR system then EGR problem fits the symptoms.

EGR valve slightly open at idle will cause rough idle and hesitation when starting off, exhaust gas is fouling the idle fuel/air mix.
EGR valve not opening all the way under load will cause pinging, exhaust gas helps cool the cylinders under load, pinging is from cylinders being too hot and fuel is pre-igniting.

Might be worth pulling off the EGR valve and making sure it isn't fouled with carbon.
You can test the EGR valve first, with engine idling, remove it's vacuum line(there should be no vacuum on this line at idle), put a longer vacuum line on it and suck on that line, EGR valve should open and engine should stall, or almost stall.
If that doesn't happen, or you get a mouth full of exhaust, lol, replace(mouth full of exhaust) or clean EGR valve.
Also make sure EGR tube isn't blocked or restricted, this won't cause the symptoms but if valve is dirty the tube will be as well.

A vacuum leak could also fit the symptoms, but you didn't mention a higher idle speed, which would usually be present with other symptoms, so EGR is probably the issue.

When replacing a sensor, or changing anything really, you need to unhook the battery for 5 minutes, this will remove power from computer, and just like any computer it will reboot when power is restored, this will cause it to relearn any new changes you might have made.
So when you see "Step 1. Disconnected Negative battery terminal", it's not just for safety reasons anymore :)
 
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cp2295

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So I did the egr test and it would start stalling.. However I had to suck pretty hard and i couldn't get it to die.. All it did was lower the rpms by about 200 id say (just from listening).. Is that an indication the egr is going to die soon or is it working properly? And If it's working properly what's another thing that could be causing this?
 

cp2295

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Also another thought, I unplugged my iac valve while the truck was idling and the rpms would drop, however it didn't die.. Isn't it suppose to die when you do that?
 

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Engine should really run rough and usually die if EGR valve is open all the way, reads like it would be worth while taking it off and having a look inside.


No, unplugging the IAC valve won't always lower the RPMs enough to stall the engine, most throttle plates have a set screw, on the cable side bottom, and that is set for about 500-600RPMs.
This is set more for the TPS(throttle position sensor) as the "foot off the gas pedal" setting.

The IAC valve raise the RPMs by letting in air, so a "controlled vacuum leak", when you unplug it, the vacuum leak is stopped, so idle drops to whatever the throttle plate is set at, which should always be lower than 600 RPMs, and above 500 rpm so engine won't stall.
 
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dino360

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I had a similar situation, kinda bogged down under hard excelleration especially up Hills and would ping. turned out to be the fuel pressure regulator.
 

cp2295

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Okay I replaced the egr valve and the dpfe valve.. I switched to some 92 octane and that took the pinging away (the other gas was just crap I think) but the idle will still bounce around, only when it's in neutral and in motion, if I come to a stop it will still bounce around for a couple seconds but then straighten out.. What could it be??
 

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My Ranger exhibited those problems when my DPFE sensor went bad (DPFE going bad = common on the 3.0 engine), so that's something you may want to check into.
 

cp2295

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My Ranger exhibited those problems when my DPFE sensor went bad (DPFE going bad = common on the 3.0 engine), so that's something you may want to check into.
Already replaced that..
 

cp2295

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Also my truck has been stalling.. Not every time I drive however, I've noticed it a few times after I put it under load and then put it in neutral
 

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Vacuum leaks are one of the more common causes of a rough idle. The EGR systems are vacuum controlled, so a vacuum leak, or defective EGR controller could be causing both the idle issues, as well as contributing to your pinging problem.

It could also be two unrelated symptoms. The 3.0 loves to ping even if there is no other issue at hand. The head castings are rough, and trap lots of carbon, which can cause preignition (pinging). This problem is made worse with low quality fuels, poor spark plugs and a lack of maintenance. If you'll be changing spark plugs anytime soon, I'd run a decarbonizer like Seafoam through the brake booster line to clean the carbon out. It can foul plugs though, so do it just before you change the plugs.
 

cp2295

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So you just spray the sea foam through the brake booster intake line and then plug it back in and run the engine?
 

cp2295

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Whoops, I missed that in your original post. Sorry 'bout that.
All good haha I'm thinking tomorrow in the daylight I'm gonna try the cigar vacuum leak finder trick.. Don't know how well that will go with the fan blowing air everywhere.. Any other suggestions other than vacuum leak.. Evap stuff??
 

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Have you checked your PVC valve to make sure it isn't plugged?

If your fan is blowing too much air for a cigar then use a can of starting fluid and spray around your vacuum lines... the starting fluid will make your engine's RPMs increase if it gets sucked into a vacuum line leak.

Another option to reduce pinging is to install a 180* thermostat.
 

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