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Rough idle


chrisser

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Hoping you guys can help me out...

Have an '87 Ranger 4x4 with 2.9 MT.

It's never run all that well. When I first got it, I put in new plugs, wires, cap, rotor and pickup. Drove it most of the winter.

Few months ago, it would occasionally stumble at low RPMs and then suddenly recover.

Pulled the codes, had 31 and 32. Replaced the EGR valve.

Drove it a few months more till the weather improved.

Earlier this week, pulled the codes again. 31, 32 and 41. Replaced the EGR solenoid valve and the EGR sensor. Ran a vacuum to the EGR valve while idling and the engine died. Also replaced the coil.

Now with the engine off test I get 11 for current and 32 for history.

When running, I get 22, 41, 32 and 25. It idles really awful now. This is without the brake vacuum line plugged (see below) - I'm going to go plug it and test it again while running to see if that affects the 22 and 41 at all.

When I ran it around the block to heat it up before testing this last time, I noticed hissing when applying the brakes and the brakes don't have much assist all of a sudden. I think the vacuum assist diaphragm is probably leaking. Plugged off that vacuum line, but the idle still sucks. Will occasionally stall at a stop and is very hesitant from a start unless you wind up the RPMs and then it's fine.

I'll post back in a few when I test again with the vacuum line plugged off, but I suspect that 32 will at least be there.

Anything else I should be checking?
 


chrisser

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So, plugged the brake vacuum off.

Ran the codes will running - same set.

So, I grabbed the vacuum gauge. Plugged it into one of the ports at the back of the manifold. Reads about 5mm HG although fluctuates as the RPM wanders.

Then I plugged it into the port where the red line to the EGR solenoid goes. Took a few seconds but the vacuum slowly rose to 18 and became dead stable. Idle improved dramatically. Better than it's ever run.

So I guess the next step is probably to check the vacuum lines to the EGR solenoid.

But it makes me wonder. This truck is old enough to be emissions exempt. Is it worth just disabling EGR altogether? Is that even possible? I'm all about keeping this truck simple - MT, crank windows, no A/C, etc. If I could take the EGR out of the equation, it would make things simpler.
 

chrisser

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I tested the red and green vacuum lines for the EGR. They were fine.

Pulled a vacuum on the reservoir under the air box. Held fine including what appears to be a check valve in there.

The thing idles great when I pull the vacuum line off the EGR valve, essentially disabling the EGR. I've left it that way for now to see how it drives.

I've also pulled the brake booster and replaced it with one from the parts store, which came bare metal so I had to spend some time priming and painting it. While it was drying, I took the master cylinder apart. It was a gunked up mess. After about an hour completely disassembling it and cleaning everything, got it back together and then hit it with a coat of paint too.

My fluid reservoir was oddly chalky and deteriorating. I had picked up a spare from the junkyard a few months ago, so I cleaned it all out with laquer thinner and blew it out with compressed air. Lots of grunge came out.

So it's all back together. Now I have to put it up on jacks and bleed the brakes. Then I'll take it for a ride and see how it runs w/o the EGR for now.

As a side benefit, I need parking brake cables and they appear to depend on the rear drum diameter, so I can see how big those are while I have the wheels off, and also see if there's any parking brake hardware in the drum assemblies to attach to the cables when I get them.

Unfortunately, it looks like my stash of brake fluid finally ran out. Had just enough to use for assembly fluid for the M/C. So another trip to the parts store...
 

chrisser

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Brakes are bled. Since I have it up on jacks, I picked up some new shocks over the winter, so I'm putting them on.

Front ones look like they're the originals, so hopefully it'll ride better. Got the rears on before I ran out of daylight.
 

ab_slack

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I have some similar things on my 87. I get a 33 code on my KOER test and that is it. I believe that is saying the EGR is not closing completely.

I am pretty confident the EGR is closed. With gauge on it, I don't see any vacuum pulled on the EGR vacuum line under any circumstances. I think with no vacuum the ER is closed. If I pull some vacuum at idle on the EGR the engine stumbles which is what I would expect when the EGR opens.

The 88 do not have EGR. I have heard that one can disable/delete the EGR and swap in a computer from an 88 for it to run properly as non-EGR.

If I recall correctly too the 87 has larger ports in the throttle body than the 88s and that because of that there is some other advantage picked up going with an 88 computer. I haven't tried this myself however. Just been focusing on getting it running the best as it was built.
.
 

chrisser

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Finally got it back together. Discovered a worn tie rod end while I was putting the front wheels on. Looks like it was the original as it was a PITA to get off.

Started it up and it had a wandering idle with the disabled EGR. Took it for a drive. At first it was very slow to accelerate. After a few minutes, it was fine. Runs better than ever and idles fine.

I'm going to let it cool down again and take it for another drive after a cold start to see how it behaves.

Checked my computer and the part number appears to be for an 87; E7TF-12A620-BJ1A. Found conflicting info on the web as to whether or not this it the right one for an 87 4x4 MT. One site said it was CA emissions. An ebay auction said they pulled one out of an '88 Bronco, but the E7TF should indicate '87 if I understand the part numbering correctly.

I may pick up an 88 or 89 ECM just to see how it performs.

Depending how it runs tonight, I'll probably drive it to work over a couple of days and see how it behaves before making a decision on what to do.

Does look like I have 9" drums in back so I can order up some parking brake cables.
 

huh?

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Hoping you guys can help me out...
looks like you took the bull by the horns and got everything under control.

a couple of years ago my sister bought me an isuzu pickup that idled like crap and smoked a wee bit. this was after her friend adjusted the carb so it would at least stay running. it drove(and stopped on command), so i didn't really dig into it. just took a look under the hood for a few minutes every day or so. finally after a couple of weeks of cruising i openned the hood to try pulling a couple of vacuum lines to see what might happen. the moment i pulled the second vacuum line i heard a loud "clack" and the engine started racing somewhere around 2,000-2,500 or so r.p.m. turns out the egr was open all the time and when i pulled its vacuum supply it slammed shut. i turned down the idle to a more appropriate level and that engine ran pretty cherry til i killed it a couple weeks later(oops).
 
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chrisser

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I ordered an '89 ECM off ebay this a.m.

Will probably get it later in the week.
 

chrisser

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Put the '89 ECM in last night.

Runs significantly better, but still not great. Sometimes the idle wanders and it bogs at low throttle. Once it warms up, it's much better.

Drove it to work today. I'll see if it's thrown any codes when I get home tonight, then go from there...
 

freedom5

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Put the '89 ECM in last night.

Runs significantly better, but still not great. Sometimes the idle wanders and it bogs at low throttle. Once it warms up, it's much better.

Drove it to work today. I'll see if it's thrown any codes when I get home tonight, then go from there...
I had similar problems - changed the EGR and almost everything else. I finally found a split in the EGR tube which caused it to pull ambient air into the system instead of recycling. I could not find a replacement through any auto parts outlet. The split was hard to find and not discovered until it blew a hole in the insulation. I sealed it with JB Weld and a thin piece of sheet metal reinforced with two small hose clamps. That was a year ago.

Freedom5
 

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