Search the Community

88 4.0, auto. I tried some things to get my fuel gauge to work, mostly playing with ground wires and cleaning the big c101 connector above the brake master cylinder, and the engine started idling high, about 2k plus. I let it sit a few hours, came back and cleaned out the throttle body that wasn't dirty, shot some carb cleaner into the vacuum lines, removed and cleaned the TPS and idle switch. idles a little rough but it always has, Still stalls when I press the throttle. It doesn't die completely but it's damn close before it catches up and revs. When it was idling high it was doing the exact same thing it did when I ran it with the EGR disconnected and the port open. It sounded the same, there was an audible sucking sound from the engine bay. I have to suspect the EGR again. If I take off the intake and just have the throttle body open and I pull on the throttle cable, I can hear the EGR briefly, and then the revs pick up. EGR or something different?

so i have an 87 manche 4.0 4wd with nv3550 that has been fairly reliable but has a high idle problem. when i first start it up it is good at only 1000 rpm but as it warms up the idle will drop down to 400-500 a few times until its finished warming up then it remains at 1000 constant. However once i begin to drive the idle at a stoplight is typically around 1600 way too high. Also i don't know if its related but it will occassionally stall on me but I have made no relations as to what happens the stalling seems to be a very random and intermittent problem. Any thoughts on what should be tested or what direction to move in first?

I have and 88, 4.0, standard. I put a new engine in 2 years ago (pulled it all by my tiny self, hence the self portrait in the left corner). This Comanche is truly a labor of love. It was running great afterthe new engine, but the honeymoon is over. I'm having trouble diagnosing the latest challenge. It started to kind of hiccup and/or stall while driving one night. Then completely stalled on the highway and would not restart. It had plenty of power to turn over but wouldn't completely start, though it valiantly tried. I guessed fuel issues so I had my son bring me a fuel filter... it was worth a try. I put it on and it started. Wow, did I actually fix it on the side of the road??? Well, no. It drove home then started to do it again the next day. I was almost on E, so I got gas and suddenly it drove great! It stayed running for a couple of weeks, so I figured I had gotten bad gas. Well, no, again!! it started doing it all over, and I had just gotten gas at Shell, the gas couldn't have been that bad, right? I did some goggling and tried replacing the MAP. Nope, didn't fix a thing. It barely wants to idle and the idle is all over the place like it's trying to figure out how much gas it needs to stay running, and will eventually die. Plus, it is very rough sounding, almost like a timing issue, but I don’t think that’s it. I bought a fuel pressure gauge and goggling tells me it should read 39-41 psi, providing I have MPI (I think I do?) I will describe what the fuel pressure gauge did because if I had to guess, I would have called in a priest for an exorcism. One friend actually suggested I park my truck in a church parking lot over night to see if that would help. Anyway, the gauge violently bounced from 35-40psi while it tried to idle, even after it had warmed up. I had my son try to hold the rpms at about 1500 and the gauge would drop to 30psi and be slightly more stable but not by much. Even when the throttle was held at 1500 rpms, there was still a lot of fluctuation like it was confused and unstable. Also, I have checked all the vacuum hoses and they are all in place as far as I can tell. My gut tells me it's some kind of sensor or vacuum issue. From what I have read here in some of the forums, I think I need to do a vacuum test next and I'm guessing again (I do a lot of that) that I need to buy another gauge. There is a lot of talk in these forums about valves and sensors like: Exhaust Gas Recirculation (EGR) valves, Idle Air Control (IAC), Throttle Position Sensor (TPS) and the Electronic Control Module (ECM). I hope it's not the computer $$$! I don't know where to start with these, is there an order to go in and can you test or clean them, maybe even bypass one or two? The last car I did a lot of work on was a 72 Cutlass with a 350 rocket, it was so simple, sigh... I could sit in the engine compartment with plenty of room for beer and tools. There wasn’t much in the way of electronics or vacuums. So if anyone can point me in the right direction with out kicking me in the a$$, I would be grateful. Many thanks in advance!