Today I checked for codes and I got 34 O/C/R and 44 R. Only other codes are 67, 52 and 77 but I didn't floor the pedal or move the steering wheel nor did I depress the clutch. Both EVP and EGR were put in this year in January. I tested the EVP sensor according to this thread and it tested OK. The EGR holds vacuum and visually seems to be working fine. When I unplug the vacuum line from the EGR I have no change in idle but I think the idle should increase, shouldn't it? What else should I check?

 

[QUOTE=minimalist;18731251] When I unplug the vacuum line from the EGR I have no change in idle but I think the idle should increase, shouldn't it? /QUOTE]

I don't believe the EGR operates at Idle, only @ cruising rpm.

 

With EVP the connector disconnected;
Have you checked the continuity/resistance of the EVP Sig wire to the ECA/computer connector?
Also, the SIG RTN/Ground wire ?

 

Check the voltage at the TAD & TAB solenoid connectors.
Check the resistance of each vacuum solenoid, with the connector disconnected.
Check the vacuum hoses leading from the TAD & TAB vacuum solenoids to the Diverter & Bypass valves.

 

I checked the voltage last night at the TAD & TAB solenoids and I got 13.5v with the truck running. Also checked the signal voltage of the EVP again and this time I got .78v running and with KOEO. I also removed the EVP and checked the signal voltage and got .3v KOEO. Am I correct to assume that this points to an issue with the EGR valve?

Later this week I will check resistance, continuity, and vacuum. A few months back I did change all vacuum lines. High possibility that I messed that up.

In case it matters I should mention that I checked codes because I am trying to eliminate the last issues with idle surging. When I got the truck last November it was really bad but now it only surges when I start the truck after it warmed up or when I brake hard in particular when the AC is running. AC is dealer installed ( I think) and brake booster was replaced with a re-manufactured one also 2 month or so ago.

 

Do you know the specs for these solenoids by any chance?

And thank you for taking the time and helping me.

 

Should be obvious that is the source of your Code 34 KOEO/KOER (EVP circuit above the closed limit of 0.67 volts.) and CM (EVP circuit has intermittently failed above the closed limit of 0.67 volts.)


No, the EGR valve preloads the EVP sensor when installed on top of the EGR valve. Perfectly normal for the output to drop a few hundred mV when removed. Many of the aftermarket EVP sensors have a shaft that is too long. If you are certain the EGR valve is fully closed then shave off a bit of the shaft until the closed value output is within range.

 

TAD & TAB 50-100 ohms.

EGR 65-110 ohms.

 

I took a look at that link above, probably not a complete test.

Check this one; Fuel Injection Technical Library » EGR Valve Position sensor (EVP)

You can also shim the EVP up by adding another washer or some spacer material under the screws temporarily until the voltage is in the closed range to see how much you need to shave off the shaft as Randy indicated.

 

Found some time yesterday and did test resistance of the TAD, TAB and EGR/EVR. All tested fine. Over the long weekend I will triple check the vacuum lines.

To test if the EGR valve was seated correctly I did a smoke test and if it wouldn't be seated correctly I would see smoke, wouldn't ?

 

That will usually verify if the valve is seated or not.Based on your results and troubleshooting it is probably okay.

 

Code 34 is gone after I shaved the shaft of the EVP. Still working on code 44.

I have been driving the truck a bit more over the last days to figure out a pattern when the idle surges. There are basically 3 things that trigger it:

1) Warm start. Typically the engines idles about 4 times before it settles into a stable idle around 750 RMP. This is worse when the AC is turned on. With AC the engine typically stalls right away.
2) Truck is running and warmed up and I turn on the AC. Again about 4 or so surges before it settles to a steady idle.
3) Slowing down. I have the habit of pressing the clutch pedal and putting the truck into neutral when approach a stop or a turn. The truck apparently doesn't like it and starts surging and occasionally stalls. In particular when the AC is running. If I just slow down and put the truck into neutral or change gears very late, looks like there is no issue.

Since it is worse with AC I'm going to get the AC checked but I don't think the AC causes the surging but rather amplifies the issue. The only common factor I see so far is engine temperature so I'm going to check the ECT as well. Anything else?

 

I forgot to mention I found my engine/emissions-diagnosis book that has some intensive trouble shooting for code 44. I totally forgot that I bought it a while back on ebay.

 

Many causes of a surging idle. Sticking/faulty IAC, bad TPS, sticking throttle cable, sticking throttlebody/shaft, vacuum leak(s). It's a process of elimination.

 

When I got the truck last fall it was really bad and the idle was surging all the time. The PO had changed the IAC but that didn't do anything. Since then I have changed all vacuum lines except brake booster vacuum hose which seems fairly new and the hose going to the vent actuator (not sure what the correct name is). The TPS is adjusted correctly and the throttle cable is not sticking. The ECT, EGR, EVP, distributor cap, rotor, and the spark plug cables were all replaced. I never checked the shaft on the throttle body though. Will do that hopefully next weekend. If I have time I will also take out the PCM to look at it. .

I have a feeling I am missing or overlooking something. The only time the idle surges is when the engine is warm and I either start the engine, turn on the AC when idling or when I slow down with clutch depressed. Most of the time the surging is not too bad but occasionally it stalls. Any pointers are more than welcome.