landlubber Posted September 6, 2012 Share Posted September 6, 2012 Hello all, I have been having problems for a while now with my engine, seems to be the worst when its under full load (WOT) or when it is cold in the morning just leaving my driveway. It seems like the throttle is ineffective when starting off in the morning, like you put it down almost an inch i'd say and it doesn't seem to do much. And say i do a few gear WOT pull from a light or something, something is not right, it goes fine till maybe 3ish, then it feels like its bogging out or definitely losing power in some fashion. It might be worth mentioning that is seems to be back-firing more than usual recently, when downshifting and down hills off the gas. It has a newer o2, within the last yearish New MAP sensor, seemed to help a little I started testing the tps, but nothing definite yet, i'm leaning towards it being the tps no vacuum leaks that I can tell, it idles same as usual The egr sheared a hose when I was putting my new engine in a few weeks ago, but I believe I plugged everything up. and finally, it was doing this with the old stock renix engine, I recently put a 95 engine in and the problem seems to be exaggerated. If nothing else, it is very annoying, I wanted to get some opinions before I start throwing parts at it. hopefully one of you can provide some insight. thanks in advance. Link to comment Share on other sites More sharing options...
mountainman Posted September 6, 2012 Share Posted September 6, 2012 Always start with basics. Id say replace the fuel filter first if its old, then do fuel pressure and volume tests first. Also throw a vacuum gauge on the engine and verify all is mechanically ok. Then if all checks out, move toward the known renix issues that are well discussed on this board. By the time your done dialing in all the known trouble areas, you will likely have fixed the issue. :wrench: Link to comment Share on other sites More sharing options...
landlubber Posted September 6, 2012 Author Share Posted September 6, 2012 new fuel filter also, had a vacuum gauge on it and it seemed normal. I don't have a fuel pressure gauge but will look into that. Link to comment Share on other sites More sharing options...
cruiser54 Posted September 6, 2012 Share Posted September 6, 2012 new fuel filter also, had a vacuum gauge on it and it seemed normal. I don't have a fuel pressure gauge but will look into that. Fuel pressure test is definitely the next thing to do. Link to comment Share on other sites More sharing options...
landlubber Posted September 8, 2012 Author Share Posted September 8, 2012 none of the shops around here rent out any fuel pressure testers, so its down to one of these. http://www.harborfreight.com/catalogsea ... e%20tester another interesting symptom to note, when driving normally it seems to lose power also. If I am in say 3rd gear with 60% throttle accelerating up a hill normally, it will feel like it is going 60% power, then suddenly, with no adjustment in the throttle, will drop to maybe 30 or 40% power. It has been doing this quite a bit recently, not necessarily on hills, or accelerating hard at all. Link to comment Share on other sites More sharing options...
mountainman Posted September 8, 2012 Share Posted September 8, 2012 Sounds like either no fuel pressure/volume... OR plugged cat. Also could have a possum in your air box...lol. Link to comment Share on other sites More sharing options...
landlubber Posted September 8, 2012 Author Share Posted September 8, 2012 there is no cat, and no possums either, haha. i'll test the pressure. Kinda sucks because it is supposed to have a newer pump. it kicked the bucket once driving and I rolled into a chain shop and had them fix it because it was there, way too much money. they said the wiring was like spaghetti, thanks the po for that. I wonder if they even put a new pump in. Link to comment Share on other sites More sharing options...
cruiser54 Posted September 8, 2012 Share Posted September 8, 2012 Well, if the new pump was an Airtex, be prepared for a failure. Link to comment Share on other sites More sharing options...
landlubber Posted September 13, 2012 Author Share Posted September 13, 2012 I tested the TPS, it has .67 volts at idle, and 4.3 volts (iirc) at WOT, would that be enough to kill power? Also, I pulled the floor mat and I got another few tenths on the meter. Link to comment Share on other sites More sharing options...
pilecenturyfarm Posted September 13, 2012 Share Posted September 13, 2012 mine was similar to that and my egr valve was opening and closing constantly. pulled the line and plugged it now runs like a champ Link to comment Share on other sites More sharing options...
marie Posted September 18, 2012 Share Posted September 18, 2012 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 :) Link to comment Share on other sites More sharing options...
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