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So, it’s been a while since I’ve posted. My Comanche’s just come off a month long break due to coolant tank hoses and the tank itself being busted. Now that she’s back on the road, a few new issues have come up. The truck will now sometimes stall when on an incline or in reverse (Today was the first day I’ve driven it and it has done it twice, once while I pulled into my driveway and once when I reversed down it). It also stumbles and bucks under acceleration sometimes, though it isn’t consistent.

 

One thing to note is that I don’t believe my idle air control valve is working properly, as I’ve pulled the plug on it multiple times with no changes to my idle. Could this be the reason behind this? Any help would be appreciated.

 

1988 4.0 Liter w/ AW4

 

 

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no change then no worky. no biggie. I'm  leaning towards cps. does it stumble under load mostly? 

Yes, and in reverse gear. When it’s in reverse the engine RPMs pulse a lot.


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Try removing the vacuum line elbow from the EGR solenoid and plugging it with golf tee. That's next to the fuel pump ballast resistor in the photo. Drive for a couple of days. If the stalling, etc. goes away, next thing to look at is the EGR transducer.

20180911_192456.jpg

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Try removing the vacuum line elbow from the EGR solenoid and plugging it with golf tee. That's next to the fuel pump ballast resistor in the photo. Drive for a couple of days. If the stalling, etc. goes away, next thing to look at is the EGR transducer.
20180911_192456.jpg.3604d881b77132473af64be3f30de482.jpg

Thanks! I’ll try it and get back to you


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Okay, so I blocked off that elbow on the egr, but it still stumbles. That stumbling nearly got me into an accident yesterday when I tried to accelerate on a left turn. What else can I try? Could it be my IAC? I see no change when I unplug it, but I’ve replaced the IAC twice, so I’m not entirely sure. Is there a fuse or relay for the IAC or a grounding issue with it or something?

Way back when I got my truck, it did not run right, as it would sometimes die and not even start, but jogging and replacing all the relays by the diagnostic ports managed to fix it. Could it be a problem there? Because I know the fuel pump uses a relay there.

Also, on start up it struggles a bit and then hits 2000 RPMs. I don’t think this is normal and I think it may be related to the other issues.


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ohm test be about 5. volts i reckon  dunno.gif

Looked it up on cruiser’s site, (thank god a man like him is around) and it supposed to be .50 volts. Mine reads .248 volts so I guess I got a CPS to replace.
Any brand recommendations?

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Replaced the CPS, but it’s still no good. It’s reading .28 now, so I guess I gotta take it off and drill it out.

Also, another symptom I noticed is when I blip the throttle hard, when it comes back down, it hits around 200 RPM. Is this a potential symptom from the CPS?

When I look at the monitor data, it says an open egr solenoid code on the data list with a sorted code for a lean loop fault. How would I deal with the lean loop?

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how is your cps connector? sometimes they're issues with the plug itself and the fix was a direct connection per say. but the reading your getting seems to say your not getting enough juice to it, so hows your grounds and connections overall? 

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how is your cps connector? sometimes they're issues with the plug itself and the fix was a direct connection per say. but the reading your getting seems to say your not getting enough juice to it, so hows your grounds and connections overall? 

They way I’ve done it is unplug the CPS and stick the connector with probes. That’s how I get my reading, so I don’t have any external power from the truck itself


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At connector A in his diagram, which has the male end connector on the CPS, is where I stuck the probes in after I unplugged it from the harness.


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I just brought up my CPS to drill out the hole to 3/8 like cruiser says to. While I was under there I noticed 2 things: one, there’s a steel cable underneath that isn’t connected to anything, like it may be cut. It’s in a bundle wrapped in some brass foil. Also, I checked my oxygen sensor for the hell of it and found that the three wires in the connector have some white crap in it, both on the male and female side. Am I right I’m assuming this is some corrosion? (I’m a youngster so I haven’t seen much in the way of auto work and connectors yet). Would I have to go about replacing that?


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