95' 3.4 DOHC High Idle

[dlaroche]

Yeah you are correct I think. I decided to pull the intake off, and assess the gaskets. They lower intake gasket was shot! It was missing the rubber seal on two different cylinders. I had to order in the gasket set, and hopefully pick them up today. I am almost sure that this is the cause of the high idle now.

While I have the intake off is there anything I should do to the engine now?? Like the oil pump drive seal or anything? I think my oil pump drive seal may be developing a slow leak. Not sure though as I haven't really driven the car since buying it.

The car only has 124,000 miles on it, but I think the three previous owners were teenagers so I am sure they were pretty hard on it. I know they were at least to the exterior.

But the engine looks and sounds good besides the high idle. No knocks, ticks, or anything of that nature so I am sure it still has plenty of life left in it. Plus I only paid $350 for the car so not a bad deal in my book.

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[bbeck]

definitely do the distributor hole cap- mine started leaking with about that many miles pretty bad- right after I did the intake gaskets. It's embarassing the amount of oil that thing was leaving behind in driveways. might want to look into the doing the timing belt at the same time as well if it hasn't been done recently

[dlaroche]

Well, I finally got the lower and upper intake manifold gasket replaced. It did help the idle significantly. However, I ran into other issues now.

Now I get an intermittent check engine light, and the codes that are getting thrown are P1640 P1650, which both are related to the quad drivers in the PCM. The P1640 is the one causing the intermittent check engine light to come on. Sometimes the code is thrown, and sometimes it's not.

I went through Alldata, but couldn't find any information to what the quad A driver controls so I can troubleshoot them.Does anyone know what P1640 is related too??

[95SleeperAcheiva]

I have identifix, I'll check when I get to my shop and see what pops up. ETA 2 hours.

[95SleeperAcheiva]

Check the Brown wire at pin E of the transmission connector. If no voltage is present, then check the TCC fuse in the right underhood electrical center. If there is voltage at pin E of the transmission connector, check the wiring from the transmission to the Powertrain Control Module (PCM). Check for any signs that wires might be shorted around the AC accumulator.

If these codes weren't there before your repair it's something you did.

Trust me, I've been there. Had a bad yet running motor...rebuild it, then spent 3 days looking for why I had no fuel delivery, all because of a ground wire that was hiding behind the motor and didn't reattach.

[dlaroche]

Thanks for the info, I will get out there tomorrow, and check it out. I put the PCM back in today after cleaning it up, and inspecting it. It didn't appear to have any water damage or shorts on the inside. I am almost sure that it is a wiring issue, because the car did sit for a very long time, and I know mice were probably up in the engine bay going to town.

I will let you know what I find out.

[95SleeperAcheiva]

Moth balls in ziplock bags, poke holes in the bags, place behind dash and in crevices in engine compartment. It helps with the mice. :P

[dlaroche]

Hey,

I checked the brown wire/E on the transmission connector, and it it should a good voltage of 11.37 volts. I put the car up on some ramps today to hook the exhaust back up, and crawled all over under the engine looking for signs of wear on the wires, but did not notice any.

I did find a small vacuum leak on the vacuum line that connects the PCV valve and everything together. I patched it up with another piece, and noticed the idle quality is even better, however, it kinda surges at idle now. Not a major surge, but just a few hundred RPM fluctuates at idle. I am assuming this is probably due to a bad IAC valve, so I will be sure to pick one up. It checks out ok with TunerPro, but I understand that this is a moving part, and becomes caked with carbon. So I am assuming it is "working" but just not fast enough to maintain a consistent idle.

I did notice that the check engine light goes off and on now, instead of just remaining on all the time. I also noticed, that the low oil level light is on all the time until the check engine light goes off, and then it also goes off. From my understanding, this is associated with the P1640 code that I was receiving. So again, I assuming this is an intermittent short somewhere probably. I made sure to jiggle every inch of the wiring harnesses under the hood in case a wire was grounding out on something, but no difference.

Once my old laptop with the serial port charges up I will go back out, and see what codes are being thrown, and do another data log for later review. I will post the results once I get them.

Any other ideas??

[95SleeperAcheiva]

fluctuating idle brings me back to several things. MAP/MAF, TPS, EGR valve stuck a little open, another vacuum leak....you got a smoker or access to one?

[dlaroche]

Yeah, I understand that I now have sensor issues after fixing the intake gasket. The thing is, with the quad drivers acting up it only shifts from 1-2. So it makes road testing it very difficult. Also, I can be driving it, and the check engine light, and low oil level light will go off, and the car runs and shifts fine.

I don't have access to a smoke machine, but when I replaced the intake gasket I plugged and blew in each vacuum line to see if any had leaks. I did find one, but it got patched up yesterday. I think the vacuum issues have been resolved due to the fact that the engine now idles right, but just has a little fluctuation.

I really want to get this quad driver issues fixed first, because then I would be able to just drive it on the interstate to the dealership to have them start working on it.

Here is what I know about the two quad drivers that I am having issues with:

P1640/Quad A driver <-- This one is the intermittent one
-----------------------
1. It controls the #2 cooling fan, thus it doesn't come on at all.
2. Controls the EVAP canister purge valve. <-- This one may be energized too due to the error, thus creating a "vacuum leak"
3. There is another transmission controlled solenoid for this quad driver, but don't have Alldata in front of me to look.


P1650/Quad B driver
------------------------
1. Controls shift solenoids A and B
2. Controls the TCC solenoid
3. Controls the EGR solenoids <--- I disconnected the EGR for now, because with the quad driver throwing a code the computer responds by energizing the EGR which opens the #1 or #2 pintle.
4. Controls the AC Clutch

My plan for today is to pull every fuse and relay one by one, and test the fuse socket with a multimeter. I will first test for a good voltage by connecting the black lead of the multimeter to ground, and the positive to the incoming power side of that fuse or relay. If the voltage is OK, I will then hook the multimeter leads to both sockets of the fuse or relay holder to see if there is voltage present. If there is voltage present with the last test then I will know if the circuit is shorted to ground somewhere, and know what circuit to tear apart.

If the multimeter test passes I will then begin unhooking one by one each solenoid or fan from the circuit to see if maybe one of them is causing an internal short.

Beyond that, I really don't know what else to do except rip the whole harness out, and physically probe each wire for continuity, and resistance values. <--- I do NOT want to do this.

I wish I had a proper scan tool or knew the commands to send over TunerPro that would let me energize each circuit independently to see which one is acting up.

Also, I did print out some info from Alldata on how to test the PCM to see if the issue is internal. You remove connector A from the PCM, and then turn the key on. Then you probe certain pins of the harness to for the different circuits to see if they are returning 12 volts. This too should help narrow down which circuit/s is going nuts on me.

I will let you guys know what I find out after all this. I'm sure this should help narrow things down a bit.

If anyone else has any other suggested testing procedures then please let me know.