marie

@ 1987 Comanche, the scenario I described with the fuel pressure gauge included the engine being warm. So, the pressure gauge reading didn't change with the engine warm. I will try it again tonight to be sure. It has happened randomly, I can't force it to happen. It got progressively worse and is undrivable now. I could try to drive it around the block a few times, it would require a lot of nursing it along and leave the pressure gauge attached at the rail to test it as you described. How do I check the flow? @ Cruiser54, I did not check the fuel pressure gauge with the vacuum hose disconnected from the pressure regulator. I will do that tonight when I recheck the reading. I don't have a voltmeter and have never used one, but I am willing to get one and engage my brain if you can give me a few hints. FYI, at idle the throttle is all over the place. It goes from almost stalling to revving and will die if you don't tap the gas pedal when it starts to die out. thanks for the replies!

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!

While tire balance can be an issue, I had a death wobble and it was from other issues. My Comanche is an 88 4.0 4X4. I did have tire balance checked as my first option. Next I went with the track bar because it had obvious wear. Moved on to the steering damper as it was leaking. Then the center link and what looks like a tie rod end on the center link near the pitman arm. I also replaced the tie rod end that attaches to the middle of the center link at that time too. My friends at Napa were a little stumped at this point too. They even came out jacked it up and looked themselves. The next suggestion was the steering shaft from the firewall to the gear box, still no luck. I decided to go for the tie rod end at the wheel. As I crawled under the truck and was spraying the rusty old nuts with WD, I looked further up into the engine compartment. I noticed a missing bolt and three with the nuts half off. Two of the loose nuts were for the motor mount. The one missing bolt and the third one that was loose, were what held the mount for the track bar to the bottom of the motor mount. Finally resolved! But, before you start thinking "dumb girl thinking she can work on her truck and isn't strong enough to tighten bolts properly....." There is only one part in this whole process that I did not put on myself, and you guessed it, it was the track bar, the part that came loose. I’m not blaming anyone, it just wasn’t me. I have a couple of lengths of pipe that are my equalizers. I am a master of mechanical advantage. :chillin: Anyway, that’s my story on death wobbles. If it doesn’t help you hopefully it will help someone else going through the forums.

Hey, I have a similar problem but a little different. I have and 88 with a straight six 4.0, long bed. 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, 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 it 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 $$$! I don't know where to start with these, is there an order to go in and can you test or clean them, maybe even bypass one or two? The last car I did a lot of work to was a 72 Cutlass with a 350 rocket, it was so simple, sigh... I could sit in the engine compartment with plenty of room for beer and tools. There wasn’t much in the way of electronics or vacuums. So if anyone can point me in the right direction with out kicking me in the a$$, I would be grateful. Many thanks in advance :)